overly rich condition on highly modded car... ?

G

gixxer750

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My supra was dyno tuned. Tune was perfect, so there must be something else wrong.

I haven't boosted for a while, and then I did. Car maintains perfect 11.7 AFR all the way to 5000 rpm. When it gets to 5000, wideband goes full rich, and the car starts rich misfiring and won't go past five. This is only @ WOT....

What could have gone wrong. I haven't modded the tune in any way since the dyno. All signals on emanage Real time display appear normal
 
Nick M

Nick M

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Do you have a clamp on fuel cut for overboost? If so, an intake leak will make you pig rich eventually, with out hitting fuel cut.
 
G

gixxer750

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I'm running such big injectors that I don't have to run the clamp because I'm scaling the signal so much. 720 CC with lex afm....

I'm running an emanage blue, and I have checked for boost leaks. I didn't figure it was one, because AFR's stay perfect until 5000, where the problem starts.

The only thing I changed before this happen was switching back from NGK 3330's to autolite 3923's. Had both plugs gapped to .028. I just changed to autolite racing 3932's with a .025 gap.

5000 rpm may be around peak cylinder pressure... I'm thinking maybe it's spark blowout?
 
suprarich

suprarich

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Try switching the plugs back. So it only does it under boost? Runs fine if you free rev it rast 5000? If you blowing out your spark, you should feel the stumble. Usually if you have a stumble under boost, caused by the plugs, it will go away when you turn the boost down.
 
Nick M

Nick M

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If you haven't clamped the signal, then pull codes and make sure 34 isn't there. Based on your symptom, I don't think it will be.

Then pull that number one plug and look at it.
 
G

gixxer750

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they were all clean. the 3923's were installed about 2 days ago. I pulled them out today to swap AR3932's in.

The electrode, ground strap and insulator were clean, the base had some soot residue from running stupid rich at 5k.

No code 34 present :(
 
G

gixxer750

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another bad ECU I think. TPS wire shows 1.65 volts constantly... emanage is always reading 30 percent throttle. need a new ECU I guess, since it still shows same voltage with TPS unplugged.
 
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gixxer750

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not a boost leak. I tested my entire set of harpipes to 35 psi.... thats what I thought at first too.

Nick: 1.71 volts constant measured there with a DMM, TPS plugged in or unplugged results in the same.
 
Nick M

Nick M

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What about with the throttle depressed? Does it go up? The idle voltage should be just under a volt.

I don't think this problem is contributing to your symptom. You would go lean.
 
Nick M

Nick M

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No, the TPS voltage being stuck at 1.65 volts. OEM tune up parts only, to prevent electrical misfires from mismatched parts.

I know there is a point at which people need a different plug, such as doubling the factory power.
 
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gixxer750

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I'm at over double the factory hp...

The reason it goes rich is this Nick:

In the emanage, for pump gas, I have the AFM scaled back about 30% based on throttle position

I then add fuel back in on a pressure based map from the emanage pressure sensor. The emanage thinks that the tps is always at 30%, and in that particular block, it is pulling 15% fuel. That seems to be all fine and good when the 02 feedback is controlling everything. The problem occurs when I start to hit boost, and that pressure based map starts adding massive amounts of fuel back in via additional injection(adding pulsewidth to the injector signal) completly bypassing the ECU for the addition of fuel.

The voltage does not change upon depressing the throttle. I'm sure the TPS is fried also at this point, but the constant 1.65 volts has me thinging that for some reason the ECU is back feeding voltage into that circuit.

Thoughts?
 
Nick M

Nick M

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gixxer750 said:
I'm at over double the factory hp...

The reason it goes rich is this Nick:

In the emanage, for pump gas, I have the AFM scaled back about 30% based on throttle position

I then add fuel back in on a pressure based map from the emanage pressure sensor. The emanage thinks that the tps is always at 30%, and in that particular block, it is pulling 15% fuel. That seems to be all fine and good when the 02 feedback is controlling everything. The problem occurs when I start to hit boost, and that pressure based map starts adding massive amounts of fuel back in via additional injection(adding pulsewidth to the injector signal) completly bypassing the ECU for the addition of fuel.

The voltage does not change upon depressing the throttle. I'm sure the TPS is fried also at this point, but the constant 1.65 volts has me thinging that for some reason the ECU is back feeding voltage into that circuit.

Thoughts?
Click to expand...

I haven't used the eman, only read about it. Why did you scale the airflow back 30%? For overboost? That is what I meant by clamping the signal. If you ran this way before and it satisfied the fuel trim monitor, then something may have gone wrong mechanically, such as the intake leak you say you don't have.

When you are in open loop, the oxygen sensor is not used, as you already know. So the ECU corrects for the setup. My guess is that the set up is wrong. Are you on the Lex housing or Supra housing?

Each day is another day since I have done this type of work. It is amazing the small detail you don't remember. I haven't seen the car myself and other than the settings you are using or mechanical problem would be what is wrong. Somebody that is fresher or has access to the info can better help at this point.
 
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