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Motor is built, bunch of stuff has changed and I'm in the middle of tune with Dave.

 

AFR's are fine at idle, under low load and vacuum they are fine, when I'm transitioning from vacuum to positive pressure (say around 0 or 1psi) the AFR's go lean to 15.5 or 16. I can feel the hesitation.

 

Imagine cruising the freeway in 4th or 5th gear and you ease into it, boost starts to build and then the AFR's go to 15.5 or 16. You can get through it by pressing the gas a little bit more.

 

Things I've done:

• Pulled fuel pump and put in new a o-ring, made sure the pump 'set' into place.

• Installed a fuel pressure gauge and monitored fuel pressure while this was happening. Pressure is steady.

• Boost leak check.

• Starter fluid boost leak check.

• Changed out MAF sensors, reset ECU.

 

Maybe there are some parameters to log to get an idea if something is haywire?

 

Any thoughts appreciated.

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1st revision power tune.

 

Already completed break in tune with Dave, had problems over boosting but that has been resolved.

 

The weird thing is there has to be a slight load in a certain throttle position for it to happen.

 

Seems to be getting worse too, I hit 17's in 5th gear on the highway yesterday.

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If I were to log MAF voltage, would it tell me anything?

 

I did change out MAF and nothing changed.

 

Some mods:

 

Cobb Intake

Perrin Inlet

TGV deletes

Radium rails and FPR

ID 1000's

ID fuel lines

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I would let your tuner finish the tune before you try to fix things, 1st revision is still very early on, thus I wouldn't expect to be be right yet. I would mention the leanness to him and supply the logs.

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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Sounds like it's occurring during the closed-to-open-loop transition (log CL/OL switch to confirm). If so, that indicates MAF scaling as a likely culprit. Like covertrussian said, let Dave take care of it in the coming revisions.
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Been talking with Dave and he has checked his end of things and they all are good, and he doesn't want to resume tuning until this issue is resolved.

 

Found a list of parameters from a Rom Raider forum that targets fueling, gonna do a cruise log and send it off to Dave and see what he says.

 

• A/F Sens 1 ratio

• A/F correction 1

• A/F Learning 1

• Calculated load

• Inj pulse

• Inj duty

• Inj latency

• CL/OL fuel switch

• Tip-in enrichment

• MAF

• MAF voltage

• RPM

• Throttle position

• TPS delta

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That's odd since that really sounds like the tune, but lets say it's a stock intake tune (no need to change MAF scale), then it would be a hardware issue.

 

You might have a boost leak too, what are your learning view values?

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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That's odd since that really sounds like the tune, but lets say it's a stock intake tune (no need to change MAF scale), then it would be a hardware issue.

 

You might have a boost leak too, what are your learning view values?

 

I had a shop do a smoke test and a leak down, everything was good. If I did have a post MAF-before turbo leak, wouldn't the lean condition happen throughout the rpm range? Also, when the torque-converter kicks down and revs climb it goes away.

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I had a shop do a smoke test and a leak down, everything was good. If I did have a post MAF-before turbo leak, wouldn't the lean condition happen throughout the rpm range? Also, when the torque-converter kicks down and revs climb it goes away.

 

 

No, only in open-loop. In closed-loop, the car would sense that the fueling is off and correct it (A/F #1 Correction). If it continues for an extended period of time, it will start updating the values in the AF Learning table. That said, you would almost certainly see skewed values in your learning tables if you have a leak AND the MAF sensor is scaled correctly.

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Yeah a lean condition such as he is seeing would cause a huge hump in the maf scaling if that was the root, im guessing its a leak, bad sensor or possibly something being caused via fuel resonance/delivery/pressure. We should never see that drastic of a lean spike as long as the maf scaling is smooth, it would be a continuous lean condition if the scaling was off in openloop.

 

Im happy to review any further data you collect as well like i mentioned.

 

Thanks

 

Dave

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Providing unmatched customer service and a Premium level of Dyno/E-tuning to the Community

 

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Dave, I'm gonna try and send you a cruise log tonight with some different parameters, maybe they can show us something.

 

covertrussian I'll try and get a learning view tonight after work.

 

Thanks for the input guys.

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Turns out I'm not the brightest bulb in the pack.

 

Accessport V3 does not do learning views like I thought. Memory snapshot does not equal learning view.

 

I did send a fueling specific log and video to Dave, so that is something. :)

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It seems weird it only comes up at certain throttle position and I can pedal out it pretty easy. Even when the TC kicks down it goes away.

 

So is the ECU is adding fuel (positive number)? If those were negative numbers the ECU would be cutting fuel?

 

 

 

I love vacuum leaks, especially pre-turbo.

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A and B is fine, C is little high. It's positive which means ECU is detecting unaccounted air and adding fuel to correct it. So yes you have a vacuum leak someplace, or could be a faulty O2 sensor or MAF.

 

Another thing is rear O2 corrections, if you don't have a cat or O2 behind a cat, these cars will use rear O2 for fuel trim adjustments and it will be skewed due to bad readings, but I'm sure Dave would have disabled that.

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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It seems weird it only comes up at certain throttle position and I can pedal out it pretty easy. Even when the TC kicks down it goes away.

 

So is the ECU is adding fuel (positive number)? If those were negative numbers the ECU would be cutting fuel?

 

 

 

I love vacuum leaks, especially pre-turbo.

 

 

What can you "pedal out" that "goes away?" What's TC mean in this context?

 

 

If you're talking about a stumble in power, that's probably learned knock correction, and extra pedal is changing the engine load to push it to a different load range (that may have less/no pulled timing). I don't know/remember an easy way to get those "learning" tables directly from the AP, but if you have AccessTuner Race you can get them pretty easy by connecting to the ECU and looking at the "Fine Learn Knock Correction" table.

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What can you "pedal out" that "goes away?" What's TC mean in this context?=...

 

If I adjust the gas pedal it seems to help, usually step on it more.

 

"TC" refers to the torque converter unlocking, which bumps the revs up, which in turn gets it out of the lean condition.

 

My idle has been funny lately also. AFR's swing up and down a bit.

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