Gavins 1st gen MX6 DSP autocross build - Mazda MX-6 Forum
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post #1 of 37 (permalink) Old 5-25-08, 17:06 Thread Starter

 
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Gavins 1st gen MX6 DSP autocross build



Well, I guess I have some explaining to do.

Clearly the autocross car is in some state of completion (finally got it going this past march). Id been starting and stopping with a build writeup to chart my progress, but the car is now running..no more "buildup" for the time being, so Ive been pretty uninspired to get that finished. Some people have spoken to me and mentioned that it would be nice to see what it took to get the car to this point so Im giving it a go once more.

So here it is....what it took to get from there....



to here....




AKA: Gavins SCCA DSP autocross build.

Youll have to bear with me while I attempt to do this writeup as itll be a bit unorthodox. Ive been building the car for the last couple years with a huge push in the last year to get things done. Except for a few folks who knew what I was doing with the car, Ive been keeping things under my hat and keeping the nose to the grindstone. Because of that Ive done a fair amount of things to the car without documentation and to do one big writeup is a bit daunting(maybe one of the reasons I just didnt have the energy to do this before).

The build process was very "organic" as one component choice affected the effectiveness/choice of other components. But I dont think I would be able to make the whole thing make much sense if did a "point a>z" explanation and it would be a mess to try to connect all the dots. With that in mind, Ill be doing the writeup in installments, going from component to component eating the elephant in small bits (so to speak). I think this will focus things a bit better than me going for the whole thing and hoping that it will all be cohesive.

So what am I doing?

PURPOSE:

to build an autocross car!! (well duh)

Ill be building what would be considered a “built to the rules, nationally competitive” 1st gen MX6 to be campaigned in SCCAs SOLO. The car will be prepped for competition using the ruleset in “Street Prepared”. The car itself is grouped with other cars with similar performance attributes in D-street prepared. The SOLO2 rulebook will be my guide in the cars .

http://cms.scca.com/documents/Solo_R...Solo_Rules.pdf this is 2009.

A couple things that should be understood about the reading of the SCCA SOLO rulebook. The rules are allowance based (telling what you can be done) and not restriction based (telling you what cannot be done). It’s a very important distinction in the reading of the rules. Simply put, if it doesn’t say you can, then you cannot.

As with many preparation levels there are limits to what can be done. Street Prepared is a lower prep category (compared to Prepared or modified). The limits can seem restrictive, but for me, I actually like the guidelines. The rules force you into a “box” where you have to be a good reader and then be clever enough to get the full worth of the rule all while being rules compliant.

Another thing about the classing structure for the cars…SOLO2 gives every car a place to play. It does NOT guarantee competitiveness. Got a Renault Fuego ?...theres a place for you to run, but don’t expect a national trophy anytime soon. In any given class theres @2-3 top contenders (1st tier cars) then a small midsection of cars that are close to but not as fast as the 1st tier cars for whatever reason(tires, gearing, whatever), and theres “the rest”. A mass of cars that are either too unknown/unpopular/slow/etc. Trophy fodder in other words.

When building a car for a class, theres 3 types of builders.

1:Theres the ones that look at the existing top leading cars and build one of those. No reason to reinvent the wheel, go with a proven performer.
2: You have people who want to try something different and look for something they believe will “shake up” the status quo (and possibly change perceptions about what the car for the class is). Theres a risk to this as what looks good on paper sometimes doesn’t translate well in actuality. You have more of a chance for a dud than a winner.
3: Finally theres people who build the car they have/like. Generally, not a good idea if you are looking for a “national competitive” car.

Im somewhere between the second and third categories.

THE PAST:

You are going to have to do a lot of reading here(sorry), because Im not going to try to rewrite all of this (Gavin = lazy), but heres the links to what has been done to the car in the past.

1st effort stuff:
https://www.mx6.com/forums/1g-mx6-oth...sion-mods.html (original suspension buildup, illuminas, cusco camber plates, ground control springs, urethane bushings)
https://www.mx6.com/forums/1g-mx6-oth...elocation.html (battery relocation)
https://www.mx6.com/forums/1g-mx6-oth...-endlinks.html (solid swaybar endlinks)
https://www.mx6.com/forums/1g-mx6-oth...t-savings.html (sunroof removal, seat replacement, weight reduction efforts)
https://www.mx6.com/forums/1g-mx6-oth...-rx7-rims.html (3rd gen RX7 wheels and fitment)
https://www.mx6.com/forums/1g-faq-eng...tallation.html (MSD igniton install)
https://www.mx6.com/forums/1g-faq-eng...atch-cans.html (dual catch cans)
https://www.mx6.com/forums/1g-mx6-oth...-swaybars.html (swaybar calculations)

2nd effort stuff:
https://www.mx6.com/forums/1g-mx6-oth...treetable.html ( koni suspension, mazdaspeed camber plates, delrin suspension bushings, suspension geometry)
https://www.mx6.com/forums/1g-mx6-oth...lternator.html (lightweight alternator)
https://www.mx6.com/forums/1g-mx6-oth...heel-post.html (16x9” CCW wheels, fender flares)
https://www.mx6.com/forums/1g-faq-tra...lots-pics.html (GURU torsen diff install)


That’s all of that past. Ill be updating things to get to the present by doing individual chapters and breaking things down a bit. Again, by doing things in smaller chunks, I hope that things wont be too jumbled and confused. Itll also give me time to focus better on those subjects.

Next installation will be about what my competition looks like.

Gavin

Last edited by gavin; 2-15-11 at 22:30.
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post #2 of 37 (permalink) Old 5-27-08, 20:11 Thread Starter

 
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THE COMPETITION

Im lucky to live in an area where the local competition in DSP is well represented. I will have well prepped and well driven cars in my class to compare the cars potential/performance with.

The class leader in DSP is the E36 chassis 3-series BMW. BMW makes an interesting car. Although its performance potential isnt as transparent as a Porsche, when prepped for competition they are excellent handling machines that are much more than the sum of their parts.

This is one of those cars.




Gordon Whites Edge Mortorsports "RED"

Its main strength is that er…it works? Well balanced chassis. Responsive to performance upgrades. RWD crunchy goodness dynamics. Ability to run wide/tall tires without adverse penalties to the driving dynamics(285/30/18s F/R are the hot ticket for the car). Wide range of rear end ratios to use. 2.8l I6 is a smooth, powerful and torquey engine that responds well to bolt ons. Massive go-fast knowledgebase from BMW community.

The Bad?…. its not light. Low 2800lb to high 2700lb weights are whats to be expected out of a prepped E36. RWD can be a hinderance on some surfaces (low grip asphalt/rain).


So far for the last 4-5 years this has been the car to beat.

The contenders…

Subaru Impreza 2.5l RS.




The Good: AWD grip*. Boxer engine is pretty torquey. Can(has to?) run 285s.

The Bad: Struts all around(struts suck), short gearing makes 2-3shifts necessary, not light (@2800lbs fully prepped?). Non-turbo engine doesn’t like to rev high.


*(This is important as the lots we use are low grip asphalt and the new surface of the national championships site is a low grip, sandy, asphalt surface. The old nationals surface was high grip concrete which equalized the differences between drivetrain configurations..IE: everyone had grip.)

Locally the De-Los Rios brothers have been showing the way to the front and currently lead the local point standings in DSP with numerous 1st place finishes.

DC3 Acura Integra RS/ITR



A recent change to the rules has added the Integra Type-R to the previous listing for the integra RS. Basically owners can mix and match parts between both chassis. The decision was made because all of the things that made the ITR a superlative stock car compared to the RS (engine, diff, chassis mods) were all negated by SP rules anyway
.

The Good: Light weight (2300lb weights?), Honda engine that’s powerful and a screamer, Honda aftermarket, Honda knowledgebase, real working suspension.

The bad: Low torque, wrong wheel drive.

Locally there isn’t a DSP integra that I can compare to. There was a fellow in the past but the Acura curse struck and his car was stolen. There is another fellow in the northeast that’s currently building an ITR for the class that I am watching carefully (his local competition is the current 2 time national champion who has a BMW).

E30 BMW 3-series…..see “E36 BMW”




Lighter than the E36, but with a “worse” rear suspension.

Alex Shchipkov has been runner up with his car at the nationals for the past 2 years and 3rd 3 years ago. Its not a slow car. Unfortunately theres no one locally with a car to compare to.

The Dark horse


Ben Martinez has a gift for car control and loves german Fords (for some odd reason). He has finished as high as 3rd nationally with his 1974 v6 Capri. With a recent change in the rueleset regarding the relaxing of turbo restructions, he has changed to this car to something he believe will take the fight to the BMWs…a 1986 Merkur XR4Ti. 2.3l Turbocharged I-4, RWD, strut front and semi-trailing arm in the rear. Suspension wise its basically a Ford(of germany) BMW 3 series.

The good: 2.3l lima engine is built like a brick outhouse(solid aftermarket as well). T3 turbo power. RWD. Light weight (2600lbs?) for a RWD car.

The bad: small front wheelarch means difficult fitment of 285s in front. Big T3 is laggy off boost. Not as many rear end ratios as BMWs. Limited front castor on front struts.

Ben is fast, the car is fast and promises to get faster.

Theres other cars for the class, but those are the current top contenders.

EDIT: Ill add another possibility...The Rookie



Mazdaspeed Protege.

This is Jeff Wong who works in southern california for Tri-point engineering (The same people who used to run the Speed World Challenge Proteges and now the Mazda6s...they also do the work on my struts). Jeff recently started autocrossing and has moved his car from street tire class (STX) to Street Prepared (DSP). He is in the same boat as I am as no one really has attempted a national competative build of a MSP. The car has a lot of potential though and Jeff is a quick learner.

The good: Most modern/refined F-series engine that likes to rev. Small/quick spooling turbocharger using modern technology. Long legs from transmission. Doesnt hurt to be working in a race shop with knowledgable people.

The bad: struts all around. limited update/backdate means its kinda heavy for FWD. G-type transmission doesnt like heavy shock loading.




And then theres the 1988-1992 Mazda MX6 GT



The Good: Im pretty sure I can get mid 2400lb weights out of the car legally. 2.2l F2T is pretty bombproof. Tons of torque. Turbocharger equals easy power gains. Small turbo is pretty lag-less in autocross setting. Strong H-type transmission.

The bad: Tons of torque in a FWD car is a lot to ask of the front tires. Not the lightest FWD car of the bunch. Engine doesn’t like to rev/low redline. Short gearing means 2-3 shifts. Struts all around. Limited aftermarket/knowledgebase.

The plan naturally is to work with the cars advantages and minimize the limitations. Its not as light as the Hondas but is much more powerful in the lower RPM regions. Struts aren’t ideal, but that means the car is no worse off than the Subaru or MSP. Its much lighter than the RWD cars(and arguably with more torque potential as well).

There have been three new changes to the rules and a change in tires that (I hope)will beneft my car as well.

-Boost controls have been released on turbocharged cars. With the advent of ECU controlled boost on newer cars and an existing rule that allowed for aftermarket ECUs, it became problematic to verify stock boost levels. Instead of fruitlessly chasing electrons the rule was changed to allow open boost controls in the STOCK turbocharger(stock turbo can be easily verified by something as simple as a set of calipers). Its become known as the “unlimited boost” rule.

-Adjustable cam gears have been allowed to cars that have no electronic or mechanical means to alter cam profiles (IE: vario-cam, VANOS, VTEC). Theres no way a static adjustable cam gear can be as effective as an infinetly variable intake/exhaust double VANOS, but it’s a way to bridge the performace gap a bit.

-Alternate bypass valves have been allowed. Under the old definition a bypass valve was considered to be part of the turbocharger and not a part of the intake system(which was free to be changed). A recent change in the rules interpretation has the bypass defined as a part of the intake system and thus can be altered.

-Lastly a new crop of tires have been released by Hoosier in response to calls for a wide 22” diameter 15” tire and a wide 20” diameter 13” tire.

Without these rules and tire changes I believe the MX6 wouldn’t really have a chance to compete, especially with the previous restrictions on turbocharged cars. Now that changes have gone into effect…and love for ones car notwithstanding (its easy to fool yourself into believing that your car of choice has some innate superiority)…think that the car has a legitamate chance of being close to the top. Can it be top dog? Maybe not, but I think it can get close…close enough to be a real handful.

Anyway, lets go on to what Ive done so far.

Gavin

Last edited by gavin; 5-28-08 at 21:29.
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post #3 of 37 (permalink) Old 5-28-08, 17:29 Thread Starter

 
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First things first

I wanted to do things "right" and in my mind that meant that I had to find a way to get the car out of daily driver status. You dont treat your daily driver like a racecar and you dont treat the racecar like a daily driver. horses for courses.

Theres a lot of people who get pride in the "daily driven" moniker, but Im not one of them. You get half the drivability/comfort, half the performance potential and all the cost of maintainance. I dont see much sense to that, but thats just me. (In truth I think the "daily driven" thing is a hoax anyway, because the cars tend not to be really daily driven anyway. A trip around the block every year doesnt equal daily driven to me. Meh..whatever)

After the initial build of the car I did actually daily drive it for a while. The car was a handful on the streets. Its suspension was stiff and the roads were not the best of shape. It made for long braking distances and twitchy handling in the rain is always a thrilling experience. There was also much wear and tear on the car as bushings needed to be regreased constantly and spherical bearings needed to be replaced in short order.

Those issues were simply annoying for the most part. The thing that really got to me when I started the second stage of the cars life was the potential for loss while driving the car.

It really got to me that all of what I was doing could be lost in an instant because of a mistake on the road. I dont know how things are where everyone else lives, but the drivers here in california arent the best. What would happen if I were to be in an accident? What would insurance pay? Whatever it was it wouldnt be able to pay for all that I had done to the car. I had custom this and custom that, discontinued this and discontinued that. Id worked had to get quality parts for cheap that if they were lost I couldnt pay full retail value for them a second time around.

In other words, I couldnt afford to replace the car for what it really would cost at full value.

I *never* thought of the possibility of trailering my car when I started. A trailer seemed too expensive, out of my league, too ostentatious.... but faced with the (very real) possibility of a catastrophic event with the car....the cost of a trailer to preserve my investment was looking like the most sensible thing I could do.




A local racer was upgrading to a 20ft enclosed trailer and needed to sell his old open bed 16ft texas bragg. I was lucky that I was up late at night when he posted it on the local autocross forum.

16ft low boy (it had the axles flipped so it was taller to clear driveways better), dual axle, closed steel bed, welded castors on the rear, hand winch added, spare tire, removable drivers side fender with handles, new electric brakes, new hubs, wheeled front casor, manual dolly.......$850(!!!)

5min later he had a PM, email and phonecall to his cellphone. I was at his house the next day to put a check in his hand(he mentioned he had 50 other offers by that time).....I didnt even have a truck in my disposal. i figured it all out later, but there was no way I could pass this opportunity up.



I borrow a friends Ford F150 to tow the car to events. He has a Spec Miata and a truck, but no trailer and I have my car and trailer, but no truck. We swap back and forth with the rig and this arrangement has worked out for both of us. I have more events than he does so if there is a schedule conflict he gets the trailer. I figure thats fair since there will always be another autocross the next week.

My thought on all of this trailer nonsense? Its fully worth it.

If theres anyone out there who has thoughts of a "full build" anything I highly reccomend getting the project vehicle out of daily driving duties ASAP. Working yourself to death on weekends to get the car back in shape to get to work on monday will get old fast. Get a new daily driver (I did).

Is a trailer the answer for everyone? Maybe not. For me it absolutely was. I can tweak the car to its limits and can go to events with the confidence of knowing that if something goes wrong(engine, transmission...plug in the exhaust manifold blowing out because of EGR pipe removal..this did happen) I can still get home.

Gavin
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post #4 of 37 (permalink) Old 5-30-08, 22:02 Thread Starter

 
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suspension part 1

SUSPENSION

Two things that matter the most to an autocross build(and for a road-race build as well), suspension and tires. Ive worked on this portion of the car since the beginning. The prior links should explain the bulk of it, but here are some changes and explanations for some of the pervious changes..

Struts:

Quote:
15.5 C :Any shock absorbers may be used. Shock absorber mounting brackets which serve no other purpose may be altered, added or replaced, provided that the attachment points on the body/frame/subframe/chassis/suspension member are not altered. The installation may incorporate an alternate upper spring perch/seat and/or mounting block (bearing mount). The system of attachment may be changed. The number of shock absorbers shall be the same as Stock. No shock absorber may be capable of adjustment while the car is in motion, unless fitted as original equipment. MacPherson strut equipped cars may substitute struts, and/or may use any insert. This does not allow unauthorized changes in suspension geometry or changes in attachment points (e.g., affecting the position of the lower ball joint or spindle)




European 2nd gen Koni single adjustable strut inserts (revalved by Tri-Point Engineering) with ground control coilover sleeves. Theres no better combination for the money in terms of performance. Factor in servicability, adjustability and the vast knowledgebase and things get even more lopsided. There was an outside chance that I would go with KW and their variant3 setup for the 2nd gen, but with limited knowledgebase in the US and questions about revalving services and turnaround time I went with the more well known konis. Ground Control has been making coilover sleeves since the dawn of time and are the US distribution point for Eibach race springs.

I have shock dyno charts for the work done to the konis. Ill have them scanned one day and include them. Suffice to say I have more than enough rebound damping to deal with the spring rates I intend to run.

The european 2nd gen fitment is about 2" shorter than the 1st gen struts. Ill be using a spacer to bring the rear struts to within 1" of stock length. As the car will be running on smooth surfaces I simply do not need that huge amount of downtravel like the stock length struts. The fronts will be 2" shorter than stock. The shortness will be to accomodate a modification made to the geometry in the upper mounts. The overall downtravel when assembled will be within 1" of stock. Uptravel will not be affected mainly due to the high spring rates.

Springs are 7" 500lb fronts (with 50lb/in tender springs) and 7" 650lb rears (with 50lb tender springs). Its marginally a two-stage setup(as seen in the 2nd and 3rd pictures). The main springs do the bulk of the work. The tender springs are there to extend the strut to the ground and keep traction if I find myself in some silly cornering scenario where the wheel otherwise would be off the ground.

These will not be the final struts the car has. I am currently working on the successor to the konis.





These are Penske 8760 series triple adjustable remote resevoir struts. They were originally made for a 993 Porsche RS-R GT car. The owner of the car had two full suspension sets to sell (Porsches use struts in front and shocks in the rear). I bought the two front sets of struts. I took a guess on the struts as I didn’t know their dimensions, but as it turns out the body lengths are close to that of the stock MX6 front struts and the strut shafts are similar to the stock MX6 rear shafts. Theres a bit of work to do to convert them for use in my car. Ill have to lengthen one pair for the rear of the car, remove the stock Porsche mounting ears and replace with new ears that fit the mazda. One of the pair of shafts will need shortening for the front and then theres misc seals that need replacement. Then Ill figure out valving.

Did you know that all of Penskes piston valves are/were patented? Its mindboggling to try to figure out the different permutations of what can be done with their pistons. It seems that they can do anything. In any case, Ill be sorting the car out on the Konis. When the car is set and I feel Im ready(3 knobs?), Ill make the change to the Penskes. They should be the last strut Ill ever need to install on the car.

(on to part 2)

Gavin
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suspension part 2

Camber plates:

Quote:
15.8 F. The following allowances apply to strut-type suspensions: Adjustable camber plates may be installed at the top of the strut, and the original upper mounting holes may be slotted. The drilling of holes in order to perform the installation is permitted, but the center clearance hole may not be modified. Any type of bearing or bushing may be used in the adjustable camber plate attachment to the strut. The installation may incorporate an alternate upper spring perch/seat and/or mounting block (bearing mount). Any ride height change resulting from installation of camber plates is allowed. Caster changes resulting from the use of camber plates are permitted.
I used a combination of the mazdaspeed camber/castor plates in front and the custom rear plates made by long time ago board member Adamturbo.




I wanted as much castor as I could possibly gain from the car. To do that I designed an offset castor spacer to be used in tandem with the mazdaspeed plates. The spacer offsets the camber plates 1" further towards the firewall and relocates the camber plate 3/4" lower. Camber adjustment is still on the top. Castor adjustment is done under the fenderwell. The new result is a max of -4.5 camber and a max of 5.5deg castor.








Why so much castor?

The camber curve (amount of negative camber gained in compression) for struts is almost nothing. Id roughed out the camber curve calculations for the front of the 1st gen at @.97 to 1 and the rear at @.98 to 1. Basically youll be seeing about -.03deg to -.05deg of camber for every inch the suspension compresses. This isnt completely linear for the full range of motion(things actually start going back to positive camber at a certain point), but for the important bits youll be lucky to get -1deg total camber at full compression. So whats the big deal about that?

Since the car wont gain negative camber when the suspension compresses, I have to “pre-add” a fair amount of negative camber to the car to keep the tire patches flat when the car is trying to roll in a corner. However, because of the angled contact patch, when the car is going straight acceleration and braking are negatively affected since the full width of tire isn’t touching the ground completely. In an ideal world one would have the tire flat to the ground when accelerating/braking and gaining negative camber when the car rolls in a corner. The tire patches would always be optimized for maximum grip. This is generally what happens with a double a-arm (wishbone) suspension....but I dont have a double a-arm suspension like a Honda/Acura, I have struts...and struts kinda suck in this regard.

Because of this issue, the traditional solution to get struts to work is….prevent them from working!(no, Im serious). Up the spring rates high enough that the suspension doesn’t move. If it doesn’t move then you never have to deal with the camber gain issues. This ,however, poses issues as well. Mechanical traction goes out the window. Off line traction will be abysmal, the car will “work” the tires harder and because of the lack of compliance in the system you will have handling issues on less than smooth surfaces.

The biggest help in this is castor. When viewed from the side of the car, castor would be defined as the angle at which the strut top points towards the firewall. For me, the more I can get the strut tops moved to the firewall, the better. Castor has the effect of adding “dynamic” camber when the car is cornering. The more castor I can run, the less static camber I need to affect the same performance in the corners.

Nothing comes for free though. Castor has a self straightening effect (think about the front wheels of a shopping cart). There are plenty of RWD vehicles that have strut fronts and lots of castor (BMWs, Mercedes) without issue, but in general FWD vehicles tend to run low amounts of castor to get away from the self straightening effect on the powered front wheels. Basically, youll get heavy steering as the car tries to just go straight.

There will be increased steering effort from the "jacking" effect of high amounts of castor… but this is actually something that I want, heres why. Looking at the strut on a side view, you see two planes. One plane is the surface of the road where the wheels sit. The other is the axis defined by the castor angle. If the castor angle is 10deg in a turn the wheel (since it is no longer pivoting perpendicularly with the surface of the road but instead at a 10deg angle) will at a certain point be pivoted above and below the roads surface. The “jacking” effect. I want this effect because of what it does for the inside wheel. If the car is making a left turn, it is now rolling to the outside right.. the inside wheel is running left and is now being pivoted outwards and DOWN into the roads surface keeping contact and traction to be maintained longer.

If a car was running lower castor angles the same action would have the wheel being pulled off the surface and wheelspin/lack of traction would be the result. Id need heavier springs/swaybars to prevent the car from rolling and maintain that traction, but that only works so much (as mentioned above). With a lot of castor I can have the inside wheel produce more forward traction longer than with low castor angles. I hope that will allow me to run reasonably stiff spring rates without having all the penalties that come with overly high spring rates.

Suspension Bushings:

Quote:
15.8 C. Suspension bushings may be replaced with bushings of any materials (except metal) as long as they fit in the original location. Offset bushings may be used. In a replacement bushing the amount of metal relative to the amount of non-metallic material may not be increased. This does not authorize a change in type of bushing (for example ball and socket replacing a cylindrical bushing), or use of a bushing with an angled hole whose direction differs from that of the original bushing. If the Stock bushing accommodated multi-axis motion via compliance of the component material(s), the replacement bushing may not be changed to accommodate such motion via change in bushing type, for example to a spherical bearing or similar component involving internal moving parts. Pins or keys may be used to prevent the rotation of alternate bushings, but may serve no other purpose than that of retaining the bushing in the desired position.


Custom machined delrin/UHMW polyethelyne.




Effectively these may as well have been machined out of steel, they are that hard. The UHMW is a litle softer and springier than the delrin and thats to give a bit of motion to the rear arms. The rear arms do not move in single planes. They instead move in wavy arcs that require bushings that give a wide range of motion. Rubber is the ideal material for this. It is durable, long lasting, weather/contaminant resistant, an excellent isolator of noise/vibration, compliant to absorb shocks to the cab.

Rubber is pretty awesome, but in a performance application its benefits work against it. Because of its compliant nature it tends to be vague and lacks the crispness needed for precision driving, thus the change to the rules compliant(no pun intended) hard-as-steel delrin. Its a pain in the arse as they transfer every bump in the road to you but its precice.

When you have the tires that I am currently running and have limited clearance, precision is what you need or things start banging into each other. The tires are next.

Gavin

Last edited by gavin; 11-6-08 at 1:34.
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wheels/tires part 1

Quote:
15.2 A. BODYWORK
Fenders and bumpers may be modified for tire clearance. This includes the portion of hood which serves as a fender/wheel well, where applicable. This does not permit modifications to the chassis or bodywork inboard of the vertical plane of the hub/ wheel mounting face (at rest, with front wheels straight ahead). Flares may be added although tires may extend beyond the bodywork. Replacement of complete hood, flared fenders, or quarter panels is prohibited. Plastic and rubber wheel well splash shields may be modified for tire clearance and for installation of fender flares as allowed herein.
Quote:
15.3 TIRES
Tires must meet the eligibility requirements for Stock Category with the following exception: the list of non-eligible tires in Section 13.3.A is replaced with the following list, which may be altered at any time by the SEB upon notification of membership.
(section 13.3A goes on to describe the eligability of tires available (when they can be available for purchase, in how many sizes available, non-zero measurable tread depth, etc)
Quote:
15.4 WHEELS
Vehicles may only exceed the allowances of 13.4 as specified herein.
A. Wheels of any diameter, width, or offset may be used. Aftermarket wheels may be modified to install OE tire pressure sensors.
B. Wheel spacers are permitted. Wheel studs and knock-off wheel drive pegs may be changed in length and diameter. Wheel bolts may be replaced with studs and nuts.
Effectively the three above rules allow me to use any DOT (Department of Transportation) certified tire (IE: DOT race-compound tires), any wheel width/diameter tire and flaring to fit them. The harder part is figuring out what the best combination will be for the application since tire size will change gear ratios. Since I cannot change gearsets or final drives, changing tire diameter is an effective tool to changing gear ratios.

In autocross (much like drag racing) the fewer shifts one has to make during the run the better. Typical speeds in autocross is in the 60mph range. Ideally one uses 2nd gear for the majority of the run with no need for shifting. A car needs to have enough bottom end grunt to get out of slow turns without having to downshift to 1st while having enough legs to get to @60mph in the faster sections without needing to upshift to 3rd. Its a lot to ask of an engine and transmission, but cars that can do this are usually a leg up on the competition.

The 1st gen MX6 has an abundance of low end torque so the need to shift to 1st in slower sections wont be necessary. The nature of the engine and transmission gearing however have it a bit close at the high end reaches of 2nd gear.

Heres a couple nifty tools to sort all the numbers out.

Gear ratio calculator http://www.f-body.org/gears/
wheel/tire size calculator Wheel / tire size calculator / comparer - RIMS-N-TIRES

And heres the gear ratios for the GT transmission.

1st: 3.250
2nd: 1.772
3rd: 1.194
4th: 0.926
5th: 0.711
Rev: 3.461
Final:4.105

The stock tire size for the GT is 205/60/15. This tire has an overall diameter of 24.7". Assuming a 6000rpm redline and plugging in the rest of the numbers into the gear calculator chart, youll see that the top speed in 2nd gear will be at 61mph. Not bad at all. Looks like for my purposes Ill need a tire that has a diameter of 24.7".

There are two top tier DOT R-compound manufacturers that have proven themselves to be perennual winners. Hoosier tire and Kumho tire. Their best offerings are as follows.

Hoosier A6


Kumho Ecsta V710


In general, the Hoosier is the tire that gives better feedback because of its sidewall construction. Its a "snappier" tire that turns in well. The compound is also a bit grippier than the Kumho giving better braking and acceleration. Its a more expensive tire (sizes being equal) and the softer compound wears much faster than the Kumho. The Kumho on the other hand has a high tollerance for high slip angles than the Hoosier (you can slide it a bit more without completely breaking traction).

I need a tire thats 24.7" and nets me the most rubber I can stuff under the tire wells(and beyond since I can flare the fenders). The best candidates for this are the Hoosier 245/45/16 (24.6") or the Hoosier or Kumho 285/30/18 (24.8"). Initially I chose the 245. Heres why.

Theres actually more factors in choosing a tire for a car than diameter. The tire width also has an affect on the car. The wider the tire the wider the car becomes overall. In a game of inches you need a car that is the narrowest it can be to navigate the course without needing to turn the steering wheel as much. The more steering angle needed, the longer the distance travelled. Imagine the difference between a corvette and an elise navigating a 6 cone slalom. Use the centerpoint of the cars to draw a line through the course as they make their way through the slalom. Because of the sheer width of the corvette, the line it needs to make it through the slalom will be further away (and ultimately a longer line) from the cones than the line of the much narrower elise. Longer distance traveled equals slower time.

The 285s while a lot of rubber will make the car very wide. Add to that the cost of wheels to fit the tires (18x10.5 or 18x11"), the amount of spacing needed to have adequite clearance in the fender wells and finally....with the car to be in the 2400lb range thats not a lot of weight to generate enough heat int he tires for them to be at maximum effectiveness.(theres no warmup lap in autocrossing, the tires have to be up to temperature in a couple turns). The BMWs and other rear driven cars can make use of this tire, but in general they have more weight and upon acceleration transfer that weight to the tires, not so in a FWD car where the weight shift will be to the undriven wheels. There is such a thing as too much tire, at least in this case. The 245s, while not as much rubber as the 285s, seemed the better choice.

This was the first go at things.







The flares were for datsun 240/260z cars. The wheels were 16x9" CCW 3piece wheels using a 1" spacer and 245/45/16 Hoosier A6s at all four corners.

A funny thing happened while I was in the middle of finalizing this setup, but first a trip down memory lane.

on to part 2..

Gavin
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wheels/tires part 2

In the past Kumho had two top contenders the V700 victoracer and the Ecsta V700. Hoosier countered with the A3 series culminating in the brilliant bias ply A3S03. In the Hoosier vs Kumho tire wars, its always been a Hoosier advantage. The Kumhos are Good, but if you wanted that extra tenth of a second and you were willing to sacrifice cost/wear it was always the Hoosier, no questions asked.

At the same time many Subaru owners were looking for a wider tire than the 245/45/16. Kumho had a 255/45/16, but (while good for their short gearing) made the cars too tall, raising the already tall CG. With a lage ownership and online community they petitioned both Kumho and Hoosier for a shorter, wider 16" tire. Something like a 265/40/16 (24.3"). With the subarus being strut suspended cars, I was hopeful that they would be successful with their petition as I could also use such a tire. Unfortunately their requests fell on deaf ears. The consumer car market had long since gone past 16" wheels as standard fare...17"s, 18"...even 19" were more commonplace. Kumho, being primarily a passenger tire maker couldnt see a 16" race tire on their radar. Hoosier is a race tire maker and is smaller and more flexable, but with a barrage of championships and tires that worked, an oddball 16" size wasnt at the top of their list of things to do.

A couple years passed and a few things happened. The Subaru WRX STi came to the shores of the USA. The previous folks who had non-turbo and WRX model subarus graduated to the new car and left thoughts of 16" wheels in the past. Kumho introduced the Ecsta V710 to replace the aging Victoracer. Hoosier introduced the new radial A3S04 to replace the old bias ply S03....it was a disaster for Hoosier. The grip was actually worse than the S03 and the tire wore like soft cheese. Many stock class cars went to the cords in mere runs. The V710 however was proving to be a success. The grip was phenominal and the wear seemed impossibly low. Its didnt hurt that the tire was cheaper than the Hoosier offering as well. Hoosier sales stumbled a bit while Kumhos stock rose. Hoosier countered the next year with a revised offering the A3S05. It had improved grip, better construction and more rubber in critcal areas that tended to cord quickly. Still, it wasnt the answer to the V710. The hoosier still wore quickly and was too easy to run to the cords in fast order. Finally with new construction and compounds, Hoosier introduced the A6 series. This was the answer hoosier was looking for. It was still more expensive than the V710 and still wore faster, but it had more traction than the V710 and the cording issues were finally solved....but the damage to hoosiers reputation was already done. Once there was no question to hoosiers superiority, but with 3 years of solid V710 performance their stock had slipped a bit.

Its my opinion that at this time Hoosier needed something to regain the marketshare it lost...but how? Hoosier and Kumho both had similar size offerings. Hoosier is a smaller and more flexable company, it could make up the difference in "tweener" sizes, but which ones? The subaru voices had dimmed down as time had moved them to STis. Right about this time a fellow by the name of Craig Wilcox started a campaign for a tire that would benefit his Mini Cooper S for Street prepared. He wanted a wide 15" tire, something like a 245/40/15, a tire neither manufacturer had to offer. Its,again, my opinion that Hoosier saw this opportunity to regain marketshare by making a tire that only it offered. They went to their factory and added a spacer to the mold for their 225/45/15 tire and created a 275/35/15.

Gavin

Last edited by gavin; 6-3-08 at 22:58.
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wheels/tires part 3

The 275/35/15 is a 22.6" diameter tire. A full 2" shorter than the size tire I needed but with the width I had wanted. My inital feeling for this was "thanks for nothing Hoosier!".....and then I thought about it a bit.

Truth of the matter the 24.7" diameter tire was barely keeping the car up to speed. Yes, the numbers seemed to work, but only at 6000rpms. Frankly the drop off in power after 5500rpms left the car out of breath. The loss of power at high RPMs in 2nd and a very strong 3rd gear(shifting to 3rd from 5500rpms drops the tach in a good portion of the torque curve) found me in between gears a lot on course. Too long in 2nd gear and not long enough in 3rd. It wasnt ideal. I was airing my frustration of my gearing woes and my annoyance of the new 275 tire and got a unusual suggestion.

If the car is in between gears now, why not completely go for 3rd gear? (Damned the torpedoes and full speed ahead). Go for the 22.6" tires and instead of using 1st and 2nd gears, the tire will dump the gearing so I could use 2nd and 3rd as the primary gears.

With a 22.6" tire 2nd gear will top out at 55mph @ 6000rpm. 3rd gear tops out at 82mph. Thats a bit much for my needs, but 55mph in 3rd is @4000rpm. I could short shift 2nd and still be in fhe fat of the torque curve in 3rd, which pulls to 68mph @5000rpm. Still a bit too much, but better. Im liking this.

A 22.6" tire also means that the car automatically drops 1" in height and CG without the suspension geometry being comprimised. 15" wheels will be lighter than 16" wheels, the tires will also be lighter leaning to lower unsprung weight (the struts will have less work to control the weight on the hubs of the car). The smaller diameter will also shorten the gearing of the car leading to improved toque multiplication and acceleration. Sure more torque could lead to tire spin...but 275/35/15 is a LOT of tire. That lot of tire will be an asset to a front weight biased FWD car. The weight per sq/in of tire on the road will be less leading to less worked tires. Except for the need to do a 2-3 shift, everything seemed to be an improvement.

The E36 BMW wasnt always the dominant car for the class. It was classed in DSP for many years and wasnt a top contender. It was too heavy and too under tired (245/45/16 were the best tire for the car at the time). And then a miracle....Kumho introduced the Ecsta V700 in a 285/30/18 size. It took a while for the BMWs to adopt this new tire, but it was the catalyst that catapulted the car from 2nd best to top of the heap in short order.

Many people looked at the new 275/35/15 offering and wondered if this was the answer that could also make a difference for their car like the 285 had done for the E36. I thought It was definetly worth the risk to find out.

I sold the 245/45/16 setup and redid the tire/wheel combo. The king is dead...long live the new king.






The wheels are custom made by Kodiak racing wheels. They are 15x10.5" and 15x9" 3-piece wheels. Forged outer shells and billet CNCed centers. 5x114.3" bolt circle with a 60deg taper, 5.5" backspace, 69mm hub center holes, non-hubcentric(I wanted them that way). The 10.5s are @12lbs apiece and the 9"s are @10lbs.

The rear tires are 225/45/15 Hoosier A6s. I had mentioned before that one of the reasons for not going with the huge 285s was the lack of weight to generate heat in the tires. Well the same applies here. The weight of the car is biased to the front about 75/25%). I can make use of the 275s in front as theres enough weight to generate heat and grip, but the rear of the car lacks that weight. Theres no sense in me using the same size tire in the rear as I believe the tires will not get to temperature and generate decent grip. Hot front tires and cold rear tires doesnt sound like a good setup. I went with 225s because I feel that thats "enough" tire for the rear of the car to get heat in them. The theory is that both ends of the car come up to temperature about the same time. So far this seems to have worked out well with a 15deg split in front and rear temperatures.


I did have to redo the rear flares of the car. Well, I didnt "have" to, but the old rear flares were big for even the 245s as they were made for a RWD car that sees the larger tires in the rear. With the new staggered setup I was to run, the flare simply looked silly, too big for a tire that small...like a beach umbrella covering a toddler. The wheelarch was already cut so I simply went for smaller flares made for a toyota corrolla.





Drivetrain next?

Gavin

Last edited by gavin; 6-4-08 at 3:19.
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Drivetrain part 1

Good to see that I have people riveted to this series. Positively unable to respond it seems


Quote:
15.10.Q. Limited slip differentials are permitted. This permits locked differentials, either by design, welding, or mechanical means. Differential cases, internal differential parts, and axle stubs may be machined as required for clearance and installation to the extent that material may only be removed, not added, and the exterior of the case may not be altered in any way. This machining may serve no other purpose.


This is pretty straightforward.







Installation was challenging. But after a few tries it seems as if I have gotten the preload correct. The Guru Motorsports torsen works brilliantly. Between the choice of tires and the ability to have traction at both wheels, the car can make full use of the torque produced. I have a bit of concern about the load the transmission gears will take because of this. Its been my observation that torque tends to break things. Its been said that the H-type transmission of the GT is the strongest FWD box that mazda has made. I hope this to be the case.





The axles are From Raxles of Florida. I cant say enough good things about the product. The cups and associated hardware are NEW and not remanufactured. The axles run about $125 per item and there is a lifetime guarantee. Both of my cars have a set on them.

Quote:
15.10.O. Any metal clutch assembly, metal flywheel or metal torque converter that uses the standard attachment to the crankshaft may be used. Non-metallic friction surfaces (e.g. clutch disks) are permitted. Dowel pins may be added. Any hydraulic clutch line may be used. Minor repositioning of the clutch slave cylinder is allowed to accommodate the alternate clutch, but the unit may not be relocated and the repositioning may serve no other purpose. This allowance does not permit the substitution of slave cylinders or the use of non-original methods of clutch actuation (e.g. pull type versus push type).


Again, pretty straightforward in what is allowed. Initially I went with a conventional route.



11lb fidanza aluminum flywheel and a stock exedy/daiken clutch disk and pressure plate. This was a very easy bolt on change. The stock flywheel was 23lbs so the aluminum flywheel shaved a good 12lbs from the rotating mass.

While I had the transmission out of the car to check on the torsen diff, I looked at the clutch assembly I had. I felt I could do better and started looking at competition multi-plate racing clutches. They are compact, lightweight, durable, rebuildable and hold a stunning amount of power for their size. The only issue (naturally) is no one makes a fitment for the 1st gen MX6 and no one has previously attempted to have one fitted (even in the old IMSA support series where the MX6 competed used full face clutches). I thought I could engineer a solution so, I would (again) have to do this myself.

On to part 2

Gavin

Last edited by gavin; 11-6-08 at 1:47.
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drivetrain part 2

I looked to different companies who offered multi-plate racing clutches. Theres 10,000rpm, Tilton, AP racing and Quartermaster clutch. I went with Quartermaster Industries as they seemed to be the most flexable and willing to work with unique applications. Quartermaster has been around the racing industry forever and has supplied clutches to circle track and road racers racers across the country(world).

They make a variety of clutches in different sizes. 8.5”, 7.25”, 5.5” ,4.5”. They have single, double and triple plate combinations of organic, sintered and carbon friction material for most models. I wanted something small, but had “enough” friction surface to absorb some torque. after a bit of back and forth with the engineers at QMI I settled on the 7.25” V-drive model.

This is a Quartermaster twin plate V-drive 7.25” clutch. Heres how I got it to work.




All one needs to have one of these clutches work is to have the disks mate with the stock input shaft of the transmission splines, a flywheel that bolts up like stock and has the appropriate diameter friction surface. Then youll need the correct throwout bearing to mate with the new clutch fingers………right. Since we have none of that, I had to be creative.


The input shaft of the H-type transmission is 1” diameter with 23 teeth. As it turns out there is an application for the ford 2.3 lima (pinto) engine that uses…….a 23t on 1” diameter shaft. With millions of circle track applications for the pinto engine there were tons of suitable friction disks available for use. Excellent, this means the clutch unit itself is a simple enough proposition…well sorta. There was a lot of measuring to be done with the stock flywheel/clutch combination to find the correct heights and clearance available in the transmission bellhousing. Many trials were done to get the right offset and backspacing.

Since no off the shelf flywheel with a 7.25" friction surface is available for the F2T, one solution would be to get a custom flywheel made. A custom aluminum flywheel would have cost me $3000 for a small production run of 4 units. Quartermaster likes to keep extra examples on hand for replacement if one breaks, or for another car. Besides, the economies of scale say that the cost of making only one flywheel is the same as making four. This all makes sense, but I didn’t have the funds for that. There had to be another option.

After a bit of searching I found that, when the manual flywheel size and the automatic flexplate size are the same, its not uncommon for many circle trackers and road racers to use the automatic flexplate as the "flywheel". A friction surface “button” is machined which bolts to the flexplate(shown in the 2nd of the above pictures). Its used in situations where the max rpms do not exceed 7500rpms and is a much lighter assembly than using an aluminum flywheel(for high RPM applications the aluminum flywheel is the preferred choice). This seemed to be the solution I needed. The buttons are pre cut for the different sized clutches. All that would be needed would be (as mentioned) measurements from the stock clutch and bolt pattern. The button would them be machined down to the new application. The machining costs were nothing compared to that of making a flywheel. I sent a flexplate to QMI for them to take measurements from…… There was a large hurdle to overcome however.




The manual flywheel for the H-type transmission is 116t. The automatic flexplate is 112t(as is the manual flywheel for the G-type transmission). This was a significant shortcoming. Going this route would have the starter not mesh with the outer ring gear. I needed either a bigger auto flexplate or a bigger pinion gear for the starter. Unfortunately none of these solutions seemed viable. I also couldn’t modify the transmission case to reposition the starter as there is no allowance in the rules for that.

Quote:
15.9.D. Any starter, generator or alternator may be used in the original position. An alternator or generator must have an electrical output equal to or greater than the original equipment unit. Any generator or alternator pulley and belt of the same type as standard may be used (see 15.10.Y).
I cant modify the transmission case, but that doesn’t stop me from modifying the starter case(“any starter”), and that’s exactly what I did. There is just enough clearance between the engine block and transmission for the starter to be repositioned.




I cut one of the original three ears off and had it repositioned and rewelded so the pinion gear of the starter meshed correctly with the smaller automatic flexplate. This loses one of the mounts as it no longer lines up correctly, but I believe that the starter has enough strength to manage with just two mounting ears.


Finally I needed a throwout bearing that would mate with the smaller clutch fingers. The bearing also needed to be round faced and not square faced. The stock mazda throwout bearing happens to be round faced and have enough clearance so the clutch fingers don’t “hang” on it when its released. Unlike the stock pressure plate where the bearing face rests on the edges of the fingers, the stock bearing rests a bit further from the edges on the QMI pressure plate. The net result is less leverage on the clutch fingers and a somewhat heavier clutch pedal. Overall though, its not that bad and WAY better than some of the “heavy duty” pressure plates out there that Ive felt.

Probelms with the installation? Yes, naturally.

One of the first issues I found was there was interference with the transmission input shaft and the friction plate splines. The output shaft “teeth” don’t run the full length of the shaft. The overall height of the mating surfaces of the friction plates was too high leading the the splines on the shaft “bottoming out” on the friction plates. When the transmission was finally connected to the engine block the input shaft squashed the friction plates together damaging them and leading to the clutch being unable to release. QMI redid the setup to have friction plates that had thinner, hardened interfaces with the output shaft. This provided the clearance needed.

I made a mistake somewhere in all the calculations of the height of the clutch assembly and where everything was in space. I was off by about 1mm and the entire assembly ended up a bit too tall. That had the bolts that hold the fingers of the pressure plate hitting the inside of the transmission case. I had to shave the bolts down by just a bit for clearance.



Lastly…it’s a royal pain in the arse to try and get the two plates lined up well enough to get the input shaft of the transmission to go through both plates. You cant force the matter either or youll wind up bending the friction plates. This was by far the most difficult part of things. I also do not have a transmission jack…or any other heavy tools for that matter. This was all done with jacks and jackstands in an uncovered driveway.

The end result? A clutch/flyweel(flexplate) combination that weighs <14lbs complete. More than that is the mass of all that weight is very centralized to the crank so there is a very small moment of inertia. With so much weight off the crank, the engine spins incredibly freely. I wont say like a motorcycle, but this, without a doubt is the freest revving F2T Ive encountered.

The clutch is not easy to modulate. It grabs incredibly hard, doesn’t slip much(or like to be slipped much because of the small friction surface) and the low weight on the crank means its like a tripwire (the first trip around the block netted 32 stalls, I counted…thank goodness the battery was charged). Ive gotten a bit used to it with time and practice, but its not exactly the most streetable thing out there(which is fine by me as the car is trailered) . But the weight and freedom on the engines ability to rev is more than worth it.

It has transformed the engine drastically. Ive seen the high side of 6500rpms in very quick order. The interesting thing is that the engine doesn’t seem as strained at those high revolutions any more. With less mass on the crank to accelerate and decelerate, the engine seems more eager and willing to spin at those levels. Ill have to see how things hold together at those sustained higher RPMs.

on to part 3

Gavin

Last edited by gavin; 4-2-09 at 6:54.
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drivetrain part 3

And finally, the last bit of things.

Quote:
15.10.Y. Any accessory pulleys and belts of the same type (e.g. V-belt, serpentine) as standard may be used. This allowance applies to accessory pulleys only (e.g., alternator, water pump, power steering pump, and crankshaft drive pulleys). Supercharged cars are excluded from this allowance. Alternate pulley materials
may be used. Idler pulleys may be used for belt routing in place of items which the rules specifically allow to be removed, such as smog pumps and air conditioning compressors. They may serve no other purpose.


It’s a lightweight crank pulley from performanceprobe(in bling-bling gold no less). I had a thought to install it after the (long in the future) engine rebuild. But I decided that it didn’t really make too much difference since I had reduced the weight on the crank by so much with the clutch.

Yeah…I know, not too exciting as it just bolts on.


Turbo maybe?

Gavin

Last edited by gavin; 6-6-08 at 15:10.
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Turbocharger/Intercooler

Quote:
15.10.C.3. As utilized only on engines originally equipped with forced induction, induction charge heat exchangers (known as “intercoolers” or “charge air coolers (CACs)”) are unrestricted in size and configuration. Air-to-air CACs and radiators for air to-liquid CACs must be cooled only by the atmosphere, except for standard parts. Body panels, fascias, or structural members may not be cut or altered to facilitate CAC installation.

15.10.C.4. Turbochargers and/or superchargers (“forced induction”) may not be added, changed, or modified (this does not allow ceramic coating of turbochargers). On vehicles originally equipped with forced induction:

a) No hardware changes or alterations to turbocharger(s) or supercharger(s), in size or number, are permitted. Turbochargers or superchargers may be updated/backdated
only in conjunction with the accompanying complete engine unit.
b) No changes are allowed to waste gate(s) size, number, or location. No changes are allowed to variable-geometry turbine (VGT) hardware.
c) No changes are allowed to supercharger drive system pulleys. Belt tensioners may be added/changed to reduce belt slip.
d) No changes are permitted to blow-off/pop-off valves.
e) Compressor bypass valves (CBVs) are considered part of the air intake system, and may be replaced or updated/ backdated independently of the other components of a
forced induction system.
f) Boost regulation systems, either electronic or mechanical, and electronic fuel cuts referencing boost pressure may be altered or modified except as prohibited herein. Boost pressure changes resulting from authorized changes are
It’s a lot to absorb, but the crux of this is that I can use any intercooler(as long as its cooled by the atmosphere), any bypass valve and have any means to control the boost on the stock unmodified turbo.

I haven’t made the maximum of all of these allowances as I am currently using the stock unchipped ECU and stock boost control solenoid. The main reason for this was I had been working on many other complex projects and wanted to keep one thing in working order without having worries about reliability. Things will change, but for the time being the engine works and Ill refrain from mucking with it.

This doesn’t mean that Ive left everything alone however. I have made some changes to the ancillary hardware.

Intercooler piping.



I had been collecting a fair amount of intercooler pipes from a variety of cars that I thought could be use to make my own intercooler pipes, but I managed to pick up a used HKS kit from a local fellow who was selling his car for a WRX. I took this opportunity to see if I could assemble full hard pipes for the remaining upper intercooler pipe. With the other pipes I had been collecting, I figured this wouldn’t be too hard.



Lets see, going clockwise from the bottom that’s..Volvo 760 elbow with bypass connections, 760 elbows without bypass connections, silicone/coupler setup for a 240?, a full silicone elbow from a 242, a trio of Izuzu intercooler pipes and an intercooler bend from a Volvo.

The Volvo elbows were 2” diameter pipes. I took the aluminum elbows without the bypass ports and the small coupler to make hardpipes for the upper intercooler.



at the bottom naturally

Youll see in the picture that there is a mitsubishi bypass valve. With the new upper intercooler hardpipe there would be no place for the stock bypass valve.

I had the mitsubishi bypass for a while now and modified the lower intercooler pipe from the HKS kit to house the mitsubishi flange and bypass valve.




While this came together nice and tidy, I did change one final thing. I recall there was a lot of talk abut the Forge Motorsports bypasses and how much better they were than the stock applications they would replace. I decided to look into it and found that they did make a direct application for the DSMs. I quick check on e-bay found a brand new unit for sale. At $70, the change was made.





That all done, I looked to the intercooler.




Yes, it would be really nice to pick up one of AREs items for the 1st gen. As a direct drop in I could use the stock intercooler pipe routing (which is pretty short and tidy). I went in another direction however. I modified the stock intercooler.

The stock intercooler, in my opinion, isn’t a bad unit. Its fairly large for the engines HP output, has a decently thick core, and (again) makes pipe routing easy. The only major oddity that I notice is the somewhat abrupt direction change air has to make going in the endtanks. This wasn’t a dealbreaker for me however. This is an autocross car. The intercooler needs to chill the air well for short amounts of time, be light and not be terribly restrictive. I can deal with whatever heat soak may occur between runs with a water sprayer.

To that end, I used the Volvo elbows with the bypass ports to make new in/outlets on the stock intercooler.


I figure going from @1.65” OD to 2” OD cant hurt in terms of restriction. Another benefit of doing this was that It made getting silicone coupler fitments a breeze.


The end result.





All the original couplers from the HKS kit were changed for new items from Hose Techniques and everything is tied together with stainless steel t-bolt clamps from a local pipe supply shop.



I haven’t had the car on a dyno yet, but theres clearly more boost available. As mentioned Ive seen full boost (@8psi) in 1st gear and for the first time encountered boost cut in 2nd gear. I am unsure how much of this effect is from the lightweight clutch or the piping (especially since the clutchs effect will be more prominent in the lower gears). One day, Ill find out with a proper dyno run. For now, Im pleased with the end result.

Odds and end next?

Gavin

Last edited by gavin; 6-16-08 at 15:21.
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post #13 of 37 (permalink) Old 6-27-08, 20:07 Thread Starter

 
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MISCELLANEOUS part1

DRIVETRAIN

Quote:
15.10.P. Any mechanical shift linkage may be used.
Wheeee. I get to use a short throw shifter.

This isn’t that exciting, but it allows a bit of comfort for me. The stock throws ate direct and precise if not a bit long. Since I was strapped in the race seat I actually preferred the throws to the a bit shorter than stock. I purchased a PRD unit. It was steel with a pined delrin ball for smooth operation and was well built.

The first thing I noticed was that it made all of the shifts offset to the right. The PRD shifter is the same for the 1st and 2nd gen cars. The 2nd gen has no “left kink” to it but the 1st gen does. This has 1st gear in about the position for 3rd, 3rd winds up at about 5th and 5th winds up with you punching the passengers leg…..hard.

This would not work so I added the stock “kink” into the PRD shifter using a vice and a hydraulic press.



With the first issue sorted there was another to contend with. The length of the unit.

While a short throw shifter doesn’t need to be physically shorter than the stock unit the PRD(and frankly, pretty much all STSs) is. Two things happen with this. First one has to grab a lot lower than one is used to to find the shift knob. Kinda silly in my opinion. The other issue that arises is that you reduce the leverage even more from what you already have when repositioning the fulcrum point to get those shorter throws. One needs more effort to shift from one gear to the other. Its not as bad as some of the cheap civic shifetrs or the pacesetters that I have sampled, but its still an annoyance.

I want the shorter throw, but have no interest in the grab at the ankles and shift with all your strength nonsense..so I fixed that as well.



Its an aluminum shifter extension. This was an item for a Honda that I retapped. They can also be found for miatas with the correct thread pitch (cheaper too). A couple people have taken to calling it the “rally shifter”. It’s a bit goofy, but it works. The longer length give me plenty of leverage and makes shifting much more effortless. The overall distance the shift knob moves is still just a bit shorter than that of the stock shifter. All in all much more comfortable for me.

BRAKES

Quote:
15.6.A. Any brake line, single or dual master cylinder, vacuum brake booster, or brake proportioning valves may be used. This does not allow multiple separate cylinders, but does allow for any single,
dual-circuit cylinder. “Safety brakers” and units such as the “Brake Guard System” are permitted. ABS braking systems may be disabled, but not removed; brake boosters may be removed or added. Air ducts may be fitted to the brakes, provided that they extend in a forward direction only, and that no changes are made in the body/structure for their use. They may serve no other purpose. Backing plates and dirt shields may be modified or removed.
B. Cross-drilled and/or slotted brake rotors may be used, provided the replacement rotors have the same dimensions as standard rotors and are of a standard-type construction and of ferrous
metallic material. This does not permit the use of a two-piece hat/rotor assembly unless the standard configuration is two-piece.
I wont go much into this for reasons that will remain unsaid, but despite the allowances above, the braking system in the car is currently almost fully stock and uses stock components.

I while ago I did an experiment with a larger master cylinder from a 2nd gen on the stock brakes(see links in first post). The test was to see if I could modulate the brake pedal better using my left foot(left foot braking) using a M/C that displaced more fluid per pedal stroke. Left foot braking is a technique that’s been used to good effect on turbocharged cars to keep a load on the turbo while still braking for a corner. The load on the turbo is kept high to eliminate turbo lag exiting a corner. This seemed like a tool that I could use so I gave it a try.

As it turned out the setup was a failure and simply did not work for me at all. (whats interesting is no one has really asked me about the results of that experiment and have just continued to repeat that the replacement of the stock M/C with a larger M/C is an “upgrade”. Nothing could be further from the truth…. but no one asked so there you have it). Brake modulation was extremely difficult(for both left and right feet). The threshold for locking the brakes was very small and too easy to exceed. Add inconsistent/wet surfaces and it was just too much to be bothered with. Besides, the combination of the stock turbo and the availability of torque in the lower rpm ranges rendered it all pointless…almost.

When I redid the wheel/tire combination the net result was the need to shift to 3rd gear. Going back and forth to 2nd when needed was a possibility, but the idea of LFB came back as a way to keep the car in gear longer, keep the speed/torque/boost up. Less shifting meant less chances of errors. In the end, this seemed worthwhile to pursue again….but with the stock master cylinder.

Ive been running with this configuration for a while and have been using the new technique as well. Its very unusual to have ones foot to the floor and brake with the left while the right foot is still depressing the accelerator, but the times show that it works. I can only get better with more time and practice.

The rest of the equipment is as bland as can be.....

-Rotors are from Centric. I get them from the online store at tri-point motorsports they are cheap and are priced per PAIR. No slots, no holes, no gimmicks, just straight blanks. I could pay more for all of that and get less performance and a lighter wallet…but why would I do that?
-Pads are from porterfield racing. I am using the R4-S compound. It’s a high performance street/autocross compound. Again, no carbon/ceramic/whatever the new gimmick claim is…they just work. I could have used the full race compound R4, but I needed a pad that could get to temp fast and with the lower weight of the car there wasn’t a need for the R4s capabilities.
-Brake lines are from corksport. I took a chance on these since my last pair was from Goodridge. The goodridge lines were longer and were able to be routed under the car better. The corksport lines were a bit shorter and more difficult to route as well. Bottom line..both work well and are very inexpensive. After many years theres no reason not to change the stock brakelines for new items. I would include getting new rubber lines as well, but the price compared to the braided SS offerings make them not really an option. This really is a place where the aftermarket does a better service.
-Fluid is ATE super-blue racing. There are “better” fluids out there in terms of maximum boiling point (wet/dry), but the cost of those items is much more than that of the ATE. Some of those items are also more succeptable to absorbing moisture and need to be flushed regularly(like weekly, or in some cases after every track/autocross session). The more moisture absorbed, the less effective the fluid. The ATE has a very high boiling point, readily available, and is inexpensive enough to do regular flushes without driving me to the poorhouse.

This is an important bit. Regular maintainance is what keeps a high level of performance. If you cant afford to keep a vehicle regularly maintained because you’ve specced out some very pimpy but expensive-to-keep-replacing-at-regular-intervals fluids, you wont be likely to keep your regular mainainance intervals and overall performance drops.

That’s pretty much it, no magic, the brakes just work and continue to do so.



Bear with me for a moment as Im going to take some liberties with this soapbox available to me, im going to say a couple things about “brakes” that isn’t part of the autocross cars build……

on to the soapbox

Gavin

Last edited by gavin; 6-27-08 at 20:22.
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post #14 of 37 (permalink) Old 6-27-08, 20:14 Thread Starter

 
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MISCELLANEOUS part2 (the soapbox)

“The stock brakes on our cars suck”, “big brakes are the best way to get better performance from our cars”, etc, etc. How many times have you heard this repeated ad nauseum? Guess what?… This is absolute crap.

Its my opinion and observation that about 99.99% of the brake complaints about our cars is the direct result of crap pads, crap brake fluid, crap hardware , junk rotors and just plain substandard maintainance.

I bought the RED car with frozen rear brakes, raybestos something pads on the front and brake fluid from the paleolithic era. Didn’t stop worth a damn (Im serious about this). Id be better off opening the doors and dragging my feet. You really had to anticipate when you had to stop because it would take a long while for the car to come to a halt from speed.

“our rear brakes don’t do anything”

More crap. Replacement of the rear frozen calipers yielded a car that would now stop in an acceptable fashion. Yeah..they actually DO do something after all.

"Brake fade"…this has to be one of the better internet rumor/urban legend myths of the last decade and its taken permanent residence here on MX6.com.

I intentionally took the RED car to a track event to check this for myself. Brake fade is the result of more heat than the braking system (rotors,pads, fluid) can take. Heat has to be absorbed and released into the air before the system gets oversaturated. The heat from the rotor bleeds to the pads and then to the fluid which then boils(which is why you dont want water in the fluid) and you end up trying to slow the car by compressing water vapor instead of incompressable brake fluid.

Cooling the brake system is an easy way of reducing this possibility, venting, removal of splash shields, ducting..…. I went in the other direction on my track event, keeping the stock splash guards(or heat shields if you want to call them by another name) and using the stock monobloc wheels (which have very little ventilation). I basically made a mini brake oven that would trap as much heat as possible. I used Porterfield R4 race compound pads, ATE fluid and stock blank cheapie rotors.

I had six 20min sessions with an extra added. My instructor,s car lost a turbo manifold gasket so I offered my car to be used for his session. That had the car doing three 20min sessions back to back.

This was the result.


These were brand new pads at the beginning of that day. Oh yes, I intentionally did my worst to get them to fail. There was no fade, there was no loss of performance, there were no issues. My instructor commented on the excellent feel of the brakes and how firm they felt in his session (his normal car is a turbocharged miata, lots of suspension, race-compound tires, willwood brake kit, etc, etc)

Ive repeated this test two more times with the same result. I had a friend who had a track event but his car was in a state of disrepair and couldn’t make it. I loaned him my car so he wouldn’t miss his date. His comment about he brakes was that they were strong enough for him to outbrake a fair amount of vehicles out on track with him.

Now either my $500 car is some miracle of engineering that defies the brake fade that people say it should be having…or you’ve been fed a load of crap.

Crap pads- carbon what? Pass on the gimmicks. If it doesn’t have the same compound front AND rear, pass on it. EBCs suck, KVRs are like glazed donuts (there I said it and Ill say it again). Street pads are not autocross pads. Autocross pads are not racing pads. Street pads on a racecourse is dangerous and borderline retarded.
Crap fluid- the minimum id use for a “performance” fluid is valvoline syn-power. Its pretty decent and on every parts shelf in the northern hemisphere. Its not even expensive. Whats the excuse for less? Anything above that is a bonus.
Crap hardware- torn piston boots? Leaky calipers? Stock brake lines? Sticking slider pins?…Are you kidding me??? Replace that stuff.
Crap maintainance- fluid brown? 1mm of pad left? 19mm of rotor thickness left(minimum allowance is 20mm for those checking)? You changed the fluid in the resevoir but didn’t flush the lines? Yeah….good job.

And that’s pretty much all I have to say about that.

Next…the future of the car?

Gavin

Last edited by gavin; 6-27-08 at 20:21.
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post #15 of 37 (permalink) Old 7-8-08, 14:24 Thread Starter

 
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The future part1

THE FUTURE

While the car is in running condition, at this point I consider it to be about 80% built. There are still quite a few things to be done and even on things that have been done, there is still some “massaging” needed.

They say that you are truly never “finished” when you have a racecar. There will always be a neverending path of repair or replacement(with better/efficient components). Just as an example the newest addition to the car is a revised catch can system.




The old system worked well, very well actually. The reason for the change was that, because of the higher cornering forces of the car more oil gets forced to the cylinder head and then evacuated out to the catch cans(esp the one on the intake side). The existing catch cans were too small a volume and quickly filled. When that happened the oil was then pulled into the intake tract, intercooler and then the combustion chambers. Made a big mess. The new catch can is larger and vented to the atmosphere (so the system isn’t under constant vacuum any more). For now this is fine as the bigger question is how to keep the oil slosh under control.

Itll always be a cycle of review, renew, improve.

But before all of that, theres the rest of the 20% of the build that’s still undone. Some of it is simple, some multi-layered and complex.

The new catch can was placed in the spot where the charcoal filter was.

Quote:
15.10.F. Emission control devices may be modified or removed. This permits the oil filler cap to be modified or substituted, but does not allow valve covers or cam covers to be altered to install a breather or for any other purpose.
Removing the charcoal filter was pretty simple, but removing the rest of the emissions control systems without the stock ECU going berserk will take some doing…like complete removal of the stock ECU.

Quote:
15.9.A. Any ignition setting, adjustment, or system may be used, subject to the requirements of 15.10.D. This does not prohibit the use of ‘two-step’ rev limiters used when the car is stationary
Aftermarket engine control.



I will be using the Electromotive TEC3-R system. It’s a powerful and incredibly capable device which should give me that ability to really see what the F2T is capable of.

I know that some looking at this will ask the question “why not megasquirt?”. Couple reasons actually, but the main one is that Its been a long build and Im a bit tired. I have no interest in picking up another long term project that has the potential of major downtime for the car. I searched for local tuners and found a couple. Most were more focused on drag racing (which isn’t necessarily a bad thing). 034 motorsport are VW/Audi tuners primarily (they do the work on the World Challenge StaSSis Audis). They at least have a notion for turbo engines that need to have a solid flexable powerband and excellent controls at the ragged edges.

I settled with Vic Sias of Siastuning. Vic is a local autocrosser (multi nationals championship winner) who has tuned many other national championship winning autocross cars (and also does tuning on some World challenge cars as well). His specialty is Electromotive systems...this is the unit I purchased.

At this point in the build for me, (since I plan not to do this myself...today at least) I feel that its worth it to get a “box” that a local tuner is completely familiar with, hand them the keys to the car, hand over cash and then return a week later and have a perfectly running car. I want minimal downtime and an excellent tune. The system is only as good as the tuner I have been told. I believe this is true and this is the path that I took. Your mileage may vary.

On to Part2

Gavin

Last edited by Zach; 7-9-08 at 19:25.
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