ITB NA FE3 Miata/MX5 thread hidden from us! ;-)

[moebius]

Excellent idea, you'll have to be careful, a potential problem with a variable position servo is speed..

How fast can engine rpms change, and how fast can the ITB be adjusted?

Most of the variable intakes from manufacturers (thinks like VICS/VRIS from mazda) are valve based... one or more sets of runners..

They do that for reliability, cost, and simplicity.

Your idea with the variable length runners will definitely work. You'll probably need more than 5-10 points in the end, but it sounds like a great start.

[egonn]

Originally Posted by moebius

Excellent idea, you'll have to be careful, a potential problem with a variable position servo is speed..

How fast can engine rpms change, and how fast can the ITB be adjusted?

Most of the variable intakes from manufacturers (thinks like VICS/VRIS from mazda) are valve based... one or more sets of runners..

They do that for reliability, cost, and simplicity.

Your idea with the variable length runners will definitely work. You'll probably need more than 5-10 points in the end, but it sounds like a great start.

finally some feedback!.. thnx a bunch.. i have thought a bit about that and i've been thinking of a RC-servo from a RC-monstertruck or something similar.. maybe same kind as in a Radiocontrolled sailingboat with a pullpower of aprox 12kg.. (monstertruck-servo about 25kg).. I'm guessing the speed it can pull 100mm of travel for the runners is quick enough in comparison to revving-speed.

i haven't thought that much about reliability.. some about interferance and friction/wear in the tubes sliding in and out but my resolution is that i have to try and see..

[moebius]

You bring up a good point - Distance-- Is 100 mm of travel enough to make a difference? May need some mechanical linkage to increase the distance...

Take a look at tuning intake runner lengths - GoFastNews.com - All Racing News All the Time!

Specifically:
http://filebox.vt.edu/users/jalee5/F...n%20report.doc

Originally Posted by some guy

the Engelman’s Electrical Analogy rearranged to calculate
Length instead of RPM as in the .DOC file
looks like this equation=>
also in English Units instead of Metric

L = ((77 * S * ((CR - 1) / (CR + 1)) ^ 0.5) / N) ^ 2 * (A / V)

' Helmholtz formula
' where L= length, S=Speed of sound,
' CR= compression ratio, A= intake area,
' V= cylinder volume

S = 1160 'FPS 100.3 deg f = 12.360"
CR = 11 'guesstimated
N = 9167 '= (9000 + 9000 + 9500) / 3 Data Points
A = 1.43 ' OD in inches
V = 9.153 ' Cubic Inches

'Speed_of_Sound_FPS = ((459.67 + TempF) * 2402.625624) ^ 0.5
'1116.319772 fps @ 59 F
'.55 Mach = 613.9758744 fps
'Speed_of_Sound = ((459.67 + TempF) * 1.4 * 32.174 * 53.34) ^ 0.5
'Speed_of_Sound = ((459.67 + TempF) * 1.4 * 1716.567377) ^ 0.5
'and the easiest equation is
'Speed_of_Sound = ((459.67 + TempF) ^ 0.5) * 49.02
'TempF = temperature in degrees Fahrenheit
'459.67 = Rankine degrees

Originally Posted by egonn

finally some feedback!.. thnx a bunch.. i have thought a bit about that and i've been thinking of a RC-servo from a RC-monstertruck or something similar.. maybe same kind as in a Radiocontrolled sailingboat with a pullpower of aprox 12kg.. (monstertruck-servo about 25kg).. I'm guessing the speed it can pull 100mm of travel for the runners is quick enough in comparison to revving-speed.

Originally Posted by egonn

i haven't thought that much about reliability.. some about interferance and friction/wear in the tubes sliding in and out but my resolution is that i have to try and see..

Well.. that's something to be worried about for the second design.
It'll have to be some sorta twin tube design, and make sure there are no vaccuum leaks.. vaccuum leaks would wreck havok on this hole thing..

The other question - how are you going to meter the intake charge?

If you go with a variable length runners (which is very very interesting)..

you'll have to move the whole intake manifold somehow.. ugh.
(remeber.. tapered intake manifold.. )

[egonn]

Originally Posted by moebius

You bring up a good point - Distance-- Is 100 mm of travel enough to make a difference? May need some mechanical linkage to increase the distance...

Take a look at tuning intake runner lengths - GoFastNews.com - All Racing News All the Time!

Specifically:
http://filebox.vt.edu/users/jalee5/F...n%20report.doc









Well.. that's something to be worried about for the second design.
It'll have to be some sorta twin tube design, and make sure there are no vaccuum leaks.. vaccuum leaks would wreck havok on this hole thing..

The other question - how are you going to meter the intake charge?

If you go with a variable length runners (which is very very interesting)..

you'll have to move the whole intake manifold somehow.. ugh.
(remeber.. tapered intake manifold.. )

Thank you!.. I'm gonna look into that document as soon as i possibly can.. looked really interesting.. without beeing that good at math.. still..

i heard of helmholtz harmonical calculations but using the means i have i've thought of measuring the harmonical intervalls with a broadband lambda / AFR .. to see where the mixture leans out and maybe be able to do it without big and timeconsuming calculations.. (wich is also a bit over my head).. since it's a complex calculation including VE etc. (is this what you mean with intake charge?)
I have gotten some directions in what vicinity the lengths should be.. and between 300mm-400mm as i wrote.. and there is a guy/company here in Sweden that has built this before but not adaptable just 2-stage runners with 2 settings one for the low rpms and one for the higher ones..

JPM

The text describing the main theory of "why change the length?".

for the vakumleak-issue i have thought of making a sleeve of very thin rubberhose-like .. as they use on dirtbike forks. wich can flex and ar fixated airtight in the ends..

about lenght/travel:

I think.. *ehmm*.. according to swift runner-length calculations the 2nd and 3rd harmonic wave (the two pulse strongest) .. using this for direction=> Optimum Intake Runner Prediction

for the ease of use and to work with i'm gonna try this with plastic tubes at first.. perhaps i'll choose aluminium later on but for now.. it's cheap and easy to modify..

[gtx510]

Rowland Manifolds M015

Products: Intake Manifolds
Manifolds 250 usd

[mazdafreaks]

My hood is only intact because I shimmed the subframe ~7mm.

Do you have a pics of this mod, i are also doing a fe3 swap for my miata, but i do not wanted to work on my hood, i want it to look like oem, I are using a kia sportage oilpan, whitch im lowered max, I are also using the hayabusa irtb, but im will start my projekt with custom inlet,,

[M2cupcar]

I didn't take pics because there's not much to see. Just cut a metal piece of flat stock that's about the same size as the foot or "landing pad" at each mounting point. The four studs at the front (two on each side) are just long enough to work with a 9-10mm shim. What you do is loosen all eight studs with a jack at the center of the front subframe. Also unbolt the shock hats (or shock rods).

I can't remember at this point what I did next. I can say you'll need longer bolts for the rear four mounting points. And do NOT tighten anything up until you have ALL nuts and bolts threaded. I did manage to get the front shims in position without disconnecting brake lines. Hope that helps.

Are you building a new IRTB manifold to replace the mani in the photo?

[mazdafreaks]

Im gonna make new manifold with hayabusa later, but i want to get it easy first to start, and i have a pal who can weld alu, so i sent him the oem fe3 inlet and ask him to do something fast, and he came with this, I think it will work.. Fm said my link ecu and irtb is not a good thing, so i need more money before the irtb, so i can buy something els of ecu,, maybe the HYDRA..

[egonn]

Originally Posted by mazdafreaks

Im gonna make new manifold with hayabusa later, but i want to get it easy first to start, and i have a pal who can weld alu, so i sent him the oem fe3 inlet and ask him to do something fast, and he came with this, I think it will work.. Fm said my link ecu and irtb is not a good thing, so i need more money before the irtb, so i can buy something els of ecu,, maybe the HYDRA..

Why wouldn't your Link-ecu be sufficient for the irtb-setup?.. You need a throttle-position-sensor that is compatible with it and a vacuum-buffert, which you need anyway to get the vaumsignal for your fuel regulator stable enough.. I connect all my outlets to one hose and directly to my fuel regulator.. although not optimal it still does work.. but you want break-vacuum/help. :P

[mazdafreaks]

I dont really know why the flyinmiata told me that the link ecu are bad with the irtbs, but they designed the link ecu and know that the link ecu are.. Maybe they just want to sell me a hydra ecu,, The link are controlled by a map sensor and not the lmm, so i think i can use the irtbs with link ecu, i will have to try later.

[eraezer]

Originally Posted by moebius

Excellent idea, you'll have to be careful, a potential problem with a variable position servo is speed..

How fast can engine rpms change, and how fast can the ITB be adjusted?

Most of the variable intakes from manufacturers (thinks like VICS/VRIS from mazda) are valve based... one or more sets of runners..

They do that for reliability, cost, and simplicity.

Your idea with the variable length runners will definitely work. You'll probably need more than 5-10 points in the end, but it sounds like a great start.

I don't think speed will be any problem, he just needs a good/fast enough RC car servo.
We have a varible intake for our KTH Racing engine which we are controling with VEMS (badly). But we have a curcuit that is looking at the tach. out from VEMS and then feed the servo a current for a period of time to get it where we want it.

[M2cupcar]

I'll venture to guess that FM's comment was regarding the 1.6 LINK's inability to take advantage of a variable tps - which IMO is critical for an optimal IRTB setup.

[egonn]

Originally Posted by eraezer

I don't think speed will be any problem, he just needs a good/fast enough RC car servo.
We have a varible intake for our KTH Racing engine which we are controling with VEMS (badly). But we have a curcuit that is looking at the tach. out from VEMS and then feed the servo a current for a period of time to get it where we want it.

cool!.. it's nice to know that more ppl have done this before, then it's more probable that it'll work

how far does your runners adjust?.. do you have any drawings or pix on how you solved it?..

I was hoping to get an adjustment of ~100mm of length.. but we'll see if it's "possible".

[egonn]

Originally Posted by M2cupcar

I'll venture to guess that FM's comment was regarding the 1.6 LINK's inability to take advantage of a variable tps - which IMO is critical for an optimal IRTB setup.

I had a discussion with fred about that issue in which he presented a problem reading the map-signal on boost from ITBS .. and i can see the average-signal/compression of ratio calculations but still not convinced that a single mapsensor with vakuum/pressure-buffer tank wouldn't solve the issue..

Well.. i had the discussion while ppl where constantly calling for my attention here at work so maybe i missed one or two factors of the equation but i'm probably not going to combine turbo and ITB's so it won't be that big of an issue for me.

[M2cupcar]

I think it's both- the variable tps AND the single map. Neither are optimal for the IRTB, and even tho it may work, it'll never work proper IMO.