E85 on stock turbo - Mazda MX-6 Forum
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post #1 of 28 (permalink) Old 10-16-12, 18:40 Thread Starter
 
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E85 on stock turbo

My set up: colt cam, chipped ecu, 440 cc injectors, mbc @17 psi stock turbo, intercooler/pipes.
My main question is running e85 benefiting me any on the stock turbo?
I know scaling injectors is a crude form of "tuning" for e85 but the car idols fine and runs good in and out of boost.
I don't have a wideband either.. Practicalities of being a poor college student, I guess
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post #2 of 28 (permalink) Old 10-21-12, 4:27
 
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There is no such thing as a stock chip ecu running great on 440cc injectors and stock turbo, maybe running extremely pig rich. if thats your case then the e85 might in fact help lean you mixture out and makes the car better/ easier on fuel

1990 mx6lx 13.5@102.9 on 87shot
1989 white pgt 486whp 543wtq@29psi..dynoed 11-9-13
1991 probe gt 373whp at 24psi
1988 mx6gt 461whp @32psi
1990 mx6lx 348whp@ 18psi slipping clutch
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post #3 of 28 (permalink) Old 10-21-12, 23:05 Thread Starter
 
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I understand what your saying about being rich from the larger injectors but how would the e85 lean it out?
I have noticed surprisingly good mileage which seems to contradict the fact that I should be getting less on ethanol. I typically get around 20-25 mpg in town depending on how heavy my foot feels.
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post #4 of 28 (permalink) Old 10-22-12, 0:01
 
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Because E85 has a lower stoich' ratio, it actually takes roughly 30% more E85 to maintain the same gas A/F ratio.

So by changing to E85 without anything else touched you AF ratio will go from say 10:1 to 13:1.

BTW 17psi on the stock turbo is asking for trouble, you'd be better off upgrading your turbo and running a little less boost.
You'll make more power, hold torque longer, have less valve bounce, have less driveline breakages, etc, etc.

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post #5 of 28 (permalink) Old 10-22-12, 5:22 Thread Starter
 
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I understand that e85 stoich ratio is lower and that more fuel is required, and that's why my injectors are roughly 30% larger.
I'm mainly wondering if I should throw the stock injectors back in and run premium or keep running e85 as it runs good without any hesitations in the chance that I'm making more power from it. Also wouldn't e85's cooling properties help with the terrible effiency of the stock pea shooter at higher boost levels?
@mxmasta What's valve bounce?
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post #6 of 28 (permalink) Old 10-22-12, 6:55
 
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Ahhh sorry I didn't get that you were already running E85.

E85's cooling properties don't affect compressor efficiency, it does however produce cooler exhaust temps, in theory meaning the turbine side can flow a little better.
Or the flip side that same cool exhaust temp results in measurably slower spool.

Valve bounce is a form of valve float.
Valve float falls into 2 general categories; valve loft and valve bounce.
Valve loft is the valve not following the profile of the cam due to excessive or sudden valve acceleration combined with valve springs that are too weak to control it.
Valve bounce is the valve leaving (or bouncing off) it's seat when it meant to be closed, this is primarily caused by high exhaust manifold pressure combined with valve springs that are too weak to overcome it.

Both forms are not good things to encounter but valve bounce in particular results in the engine failing to gain hp with rpm as the torque falls away the more you rev.

Do you have a dyno plot you could share?

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post #7 of 28 (permalink) Old 10-22-12, 14:03 Thread Starter
 
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I haven't had it dynod nor do I have any form of tuning.
I have noticed that after straightening out my vaccuum line problem the car seems to lag slightly more but carry the power well up to 5200ish.
I usually have full boost by 3000ish and holds the power up past 5k.
Could someone please tell me the general spool characteristics of the stock turbo?
Maybe it's the cam in combination with e85 but it doesnt seem too lose power as rapidly as other members have stated as the stocker should.
It also maybe that the stocker is taking a dump as the turbo has spiked over 23+ pounds before, but wouldn't that equate to less power overall? Second gear is still useless as soon as it reaches 17 psi.
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post #8 of 28 (permalink) Old 10-22-12, 17:57
 
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I would look seriously at getting a wideband. At least you can have an idea of what your engine is doing. They are not that expensive either; check on ebay for innovative wideband they are good, without breaking the bank.

If your too cheap to do that then at least take your car to a local 1/8 or 1/4 mile track and do a run on different days one on just e85 and one on 93 octane. at least you will have an idea of power difference. My local 1/8 mile track charges $10 or $15 to run as many times as you want.
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post #9 of 28 (permalink) Old 10-22-12, 19:50 Thread Starter
 
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Good idea on going to the track, dark.
I definitely need a wideband but being in school without any source of income at the moment prevents this.
I was just wondering if anyone had any experience with ethanol on the stock turbo? I'm also curious about the stockers boost characteristics just to give me a baseline to compare too.
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post #10 of 28 (permalink) Old 10-22-12, 22:05
 
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I have a busted bone stock probe gt that i put 1/2 a tank of e85, ran fine. Does that mean its good for it? No idea. My wideband got sold with my white mx6. I should have ripped that thing out.
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post #11 of 28 (permalink) Old 10-22-12, 23:34 Thread Starter
 
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Yeah, I Definetly need to get some form of monitoring and a tune.
@dark. Did you notice any difference in power or turbo lag when you tried the half tank ofe85?
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post #12 of 28 (permalink) Old 10-23-12, 2:06
 
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Not really, I pushed it hard through the gears but it just felt the same. With a tune it should make a difference.

Edit:

the exhaust smelt kinda sweet though.

Also I don't think you needed bigger injectors. The car already goes pig rich under boost, your still on the stock turbo.

I was running rich on my tbird with no fuel mods at 14psi 93 octane. with ethanol it would have probably been fine with no modifications.

Now what i would be worried about is everything before full throttle (like driving up a hill at say 40mph). at partial throttle you may have problems. you really need a wideband to know.

Now the question is what would i do? well I have extra engines in my garage so changing one out is no problem. I would boost on a tbird with e85 and stock fuel, but then again I'm a little crazy.

But don't ask when was the last time i've really worked on a project. My sig basically says it all. it really ended up being a still born project. I will get it done eventually, after college I guess. Its still sitting in my garage.

Last edited by DarkMx-6; 10-23-12 at 2:17.
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post #13 of 28 (permalink) Old 10-23-12, 19:06 Thread Starter
 
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That's where things get screwy, the car has much more power at 1/2 throttle and spools quicker than when going wot. Infact, if i push the pedal to far it'll buck and lose power but at around half throttle she pulls like a freight train.

Obviously that isn't right but could it be from being insanely rich with the 440's?

If I were to run e85 on stock injectors wouldn't I run lean considering it takes about 30% more fuel to reach stoich with e85?
Unless our factory maps are close to 30% richer than they should be.
Does anyone actually know HOW "pig rich" the factory fuel tables are?

I really need a wideband.. Any donations? : p
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post #14 of 28 (permalink) Old 10-24-12, 4:49
 
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Usually 10:1 every car is different.

But that is under full boost where it ignores most sensors and just dumps fuel. Its not going to be at 10-1 when your just cruising. It will probably be close to 14-1. The ECU in Riches fuel as it's needed.
That is why it can be very possible to lean out under partial throttle.
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post #15 of 28 (permalink) Old 10-24-12, 12:45 Thread Starter
 
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Hmm interesting..
Why do you think my car only runs properly at 1/2 throttle but not full throttle?

Sorry if my questions are kinda application specific I just am not very educated on ecu's and tuning. By the way, I bought the car setup how it is now.
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