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Running lean in open loop, STOCK ECU

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Spoolin92GSX

10+ Year Contributor
491
2
Oct 4, 2011
Inland Empire, California
Okay, I've tried searching for several hours and can't find a thread with my problem, let alone one that answers my question.. I'm on stock ECU (no Link, no SAFC, no tuning at all), stock MAF, stock injectors, stock fuel pump (rewired), stock FPR, stock turbo.
Car runs fine in closed loop, but as soon as it hits open loop and I start to build boost it runs way leaner than the stock fuel maps, and leaner than is recommended on a proper tune. At WOT it will start out around 11.5:1 and as RPM's rise it will lean out more and more, as far as 12.2:1 OMG
I tried pulling my MBC and running WG pressure to see if I was pushing my fuel system too much, and exactly the same behavior/AFRs. I've done so many boost leak tests I can do them blindfolded, tested alternator voltage, messed with spark plugs/gaps, lowered boost, reset the ECU, checked/swapped MAFs, everything I can think of.
ECU is perfect repaired from ECMTuning, MAF is known perfect working condition, o2 sensor is MTX-L wideband running narrowband sim, TPS is verified 100% accurate, throttle body is freshly rebuilt..
Can anyone point me towards what the hell could be causing this!?
 
I would check the intake pipe to make sure that there are no air leaks between the maf and turbo. IT is also possible that you are leaking fuel inside the tank from the o-ring where the pump seals to the sending unit.
 
Okay, I've tried searching for several hours and can't find a thread with my problem, let alone one that answers my question.. I'm on stock ECU (no Link, no SAFC, no tuning at all), stock MAF, stock injectors, stock fuel pump (rewired), stock FPR, stock turbo.
Car runs fine in closed loop, but as soon as it hits open loop and I start to build boost it runs way leaner than the stock fuel maps, and leaner than is recommended on a proper tune. At WOT it will start out around 11.5:1 and as RPM's rise it will lean out more and more, as far as 12.2:1 OMG
I tried pulling my MBC and running WG pressure to see if I was pushing my fuel system too much, and exactly the same behavior/AFRs. I've done so many boost leak tests I can do them blindfolded, tested alternator voltage, messed with spark plugs/gaps, lowered boost, reset the ECU, checked/swapped MAFs, everything I can think of.
ECU is perfect repaired from ECMTuning, MAF is known perfect working condition, o2 sensor is MTX-L wideband running narrowband sim, TPS is verified 100% accurate, throttle body is freshly rebuilt..
Can anyone point me towards what the hell could be causing this!?

I was going to suggest BLT but I see you have done this already. Did you calibrate your o2 sensor before installing?

What Bryan says makes sense. Pre turbo leak, More air is being sucked in then metered. I had the same problem because of a bad coupler design. I since installed a 2.75-2.25 reducer coupler and problem went away. You could try the BLT on the intake inlet by removing the filter and spray some soapy water and check for leaks.
 
Yeah, calibrated o2 sensor per Innovate's directions, runs perfect in closed loop. I'll have to admit defeat and get the exact size coupler I need, hopefully before the 14th >_<
 
Figured I would give somewhat of an update here.. Wideband unit took a dump a few days ago, so who knows maybe it was reading wrong. New coupler installed along with the 16G :D So once I get the gauge back from Innovate we'll see what happens.
 
On board, Does ytour car build boost? I'm experiencing the same thing, only I can't get more the 4 PSI on a 16G, the boost gauge ought to be trying to turn around backwards because there is no line attached to the WG. I got an LM-1 WB did you just send it back, and they fixed it?
 
On board, Does ytour car build boost? I'm experiencing the same thing, only I can't get more the 4 PSI on a 16G, the boost gauge ought to be trying to turn around backwards because there is no line attached to the WG. I got an LM-1 WB did you just send it back, and they fixed it?

Yeah it builds boost just fine, if you're only boosting that much WOT you could either have a massive boost leak or the wastegate isn't closing all the way. I sent the wideband back almost a week ago, just go on their website and fill out the "RMA request form" their turnaround time sucks to be honest: minimum 10 days!? Once I get it back I'll be able to see if that inlet coupler was the culprit.
 
Yeah I thought if I had a boost leak, it'd run massive rich. But I have seen it up to 18:1 on the WB, that can't be a boost leak.
 
Yeah I thought if I had a boost leak, it'd run massive rich. But I have seen it up to 18:1 on the WB, that can't be a boost leak.

I would be VERY careful if you're running that lean. If you're going lean and not building boost I would lean towards the wastegate not fully closing, along with a pre-turbo leak. Also a possible exhaust leak on one or both sides of the manifold causing the low boost. I don't know how much troubleshooting you've done already, just throwing out suggestions.
 
I've tried everything I can think of, I even blew the fuel lines out with compressed air to make sure they weren't clogged.
 
Just checked your mod list, you may just need a mild tune to dial in the injectors/MAF since it says you're also running a translator.. Just the 560cc injectors and 2G MAF should keep you close to where you need to be, but I'm not familiar with a translator for the 2G MAF.
 
Just checked your mod list, you may just need a mild tune to dial in the injectors/MAF since it says you're also running a translator.. Just the 560cc injectors and 2G MAF should keep you close to where you need to be, but I'm not familiar with a translator for the 2G MAF.


It may need to be tuned but it was running fine last week, then all of a sudden, it won't even run with a load on it. Even with the MAFT removed same result.

Oh, the MAFT is a GEN II, basically same as an Apexi AFC, just more options.
 
Damn that's rough. My ECU *should* be OK since I just had it gone through 100% by ECMTuning, and all my sensors are in good working order.. We'll find out once I get my wideband back if I'm still running lean, hopefully this week.
 
Hey spoolin, I had the same issue last fall running lean. Was even on WG pressure for a bit. Had started off with 12/1 then eventually i was seeing 13/1. Messed around with the car for about a month till i replaced my fuel pump. Problem solved. I was seeing below 10/1 after the new pump. So i was seeing the stock fuel maps for the first time since ive owned the car. It is possible for the pump to slowly die. Thought id just throw that out their for an idea.
 
That's very possible.. Since my wideband has been out I've installed a 255lph HP pump and AFPR, so we'll see what happens in the morning when I get my wideband hooked back up (FINALLY).
 
Alright, got my wideband put back in and I'm pretty sure the fuel pump upgrade did the trick! It reads a little lean (exhaust leaks) but WOT pulls already look a lot better reading in the mid 11:1 AFRs :)
 
Figured I would give a final conclusion on this, for anyone that might have been following. After getting my Ostrich set up and getting a base tune going, I realized my MAF took a LOT of scaling and compensation. "Hacking" the 1g MAF effects your airflow a lot more than you may think, by the time a 16g is pulling enough air for 14psi it'll skew AFRatios as much as 2 full points :notgood:
 
Well I'm glad you got it figured out! Now if I could just get mine figured out....In open loop does the ecu tune from the stock o2 sensor?...
 
Do you know anything about MMCd? I noticed the FL 0 section has a bunch of letters in it. the other has F, B. Alternating. is that for the boost solenoid, and the Fuel solenoid?

:EDIT: NM figured that one out. after a search...

Oh, according to MMCd, the air flow is all outta wack. Even floored It'll never go over 1000hz. and cruising around I'm getting 30-31* degrees of timing???... it used to be 36-38*
 
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