SR20DET, AFR's not changing while in boost. - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Thomas0zero · 08-23-2014, 08:39 PM

99% Stock Redtop SR20DET in an S13.

I was running STUPID rich, 10 at idle and cruise, maybe lean out to 11.4 in full boost at redline. Replaced the bad maf pigtail, cleaned maf and fixed the terrible leak between the turbo and manifold. Now the car ran 13.7-15 afr's idle, cruising and in full boost. It has since leaned out and holding 15.7, in and out of boost. Car runs amazing and feels strong, but these lean AFR's are no good.

I dont think it is a clogged fuel filter because the AFR's good at redline before i changed anything.

Things to know.

Boost leak test/vacuum leak. System held 14psi without problems and without any real leaks.
ECU Code 55, all good.
Vacuum lines consist of, FPR, BOV, Gauge, Wastegate and vacuum booster.
Stock boost, Greddy BOV, AEM Wideband, stock injectors, FMIC.

Ive searched quite a bit with no definitive answer. I honestly cant figure out whats going on at this point. I really appreciate your help guys

Thomas0zero · 08-24-2014, 08:16 PM

No one?

Kingtal0n · 08-25-2014, 07:40 PM

It got lean when you messed with the maf.

Mafs are cheap, go grab several KA24E mafs from anywhere and try them, one at a time, until you find one that gives the a/f you like.

Took me 3 tries to get mine. Some go stupid rich. Some stay lean. They are old...
Its easier to diagnose a lean issue than rich. Lean is very straightforward: you need more gas, which is directly driven by the maf at those pressure ratios.
and worst case scenario, you play with the fuel system (fuel pressure / pump / filter)

Thomas0zero · 08-25-2014, 08:01 PM

Quote:

Originally Posted by Kingtal0n

It got lean when you messed with the maf.

Mafs are cheap, go grab several KA24E mafs from anywhere and try them, one at a time, until you find one that gives the a/f you like.

Took me 3 tries to get mine. Some go stupid rich. Some stay lean. They are old...
Its easier to diagnose a lean issue than rich. Lean is very straightforward: you need more gas, which is directly driven by the maf at those pressure ratios.
and worst case scenario, you play with the fuel system (fuel pressure / pump / filter)

Ill give it a try and let you know what happens. Thanks

Kingtal0n · 08-26-2014, 01:12 PM

it could also be an enormous vacuum leak before the turbo (after the maf)

Thomas0zero · 08-26-2014, 02:57 PM

No leak before the turbo. We are running hard piping.

08-23-2014, 08:39 PM	#1
Thomas0zero Leaky Injector Join Date: Nov 2012 Location: Pryor, Ok Posts: 65 Trader Rating: (0) Feedback Score: 0 reviews	SR20DET, AFR's not changing while in boost. 99% Stock Redtop SR20DET in an S13. I was running STUPID rich, 10 at idle and cruise, maybe lean out to 11.4 in full boost at redline. Replaced the bad maf pigtail, cleaned maf and fixed the terrible leak between the turbo and manifold. Now the car ran 13.7-15 afr's idle, cruising and in full boost. It has since leaned out and holding 15.7, in and out of boost. Car runs amazing and feels strong, but these lean AFR's are no good. I dont think it is a clogged fuel filter because the AFR's good at redline before i changed anything. Things to know. Boost leak test/vacuum leak. System held 14psi without problems and without any real leaks. ECU Code 55, all good. Vacuum lines consist of, FPR, BOV, Gauge, Wastegate and vacuum booster. Stock boost, Greddy BOV, AEM Wideband, stock injectors, FMIC. Ive searched quite a bit with no definitive answer. I honestly cant figure out whats going on at this point. I really appreciate your help guys

08-25-2014, 07:40 PM	#3
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	It got lean when you messed with the maf. Mafs are cheap, go grab several KA24E mafs from anywhere and try them, one at a time, until you find one that gives the a/f you like. Took me 3 tries to get mine. Some go stupid rich. Some stay lean. They are old... Its easier to diagnose a lean issue than rich. Lean is very straightforward: you need more gas, which is directly driven by the maf at those pressure ratios. and worst case scenario, you play with the fuel system (fuel pressure / pump / filter) __________________ 5.3/4l80e/turbo 240sx playthrough: https://tinyurl.com/turbo240

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08-24-2014, 08:16 PM	#2
Thomas0zero Leaky Injector Join Date: Nov 2012 Location: Pryor, Ok Posts: 65 Trader Rating: (0) Feedback Score: 0 reviews	No one?

08-26-2014, 01:12 PM	#5
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	it could also be an enormous vacuum leak before the turbo (after the maf)

08-26-2014, 02:57 PM	#6
Thomas0zero Leaky Injector Join Date: Nov 2012 Location: Pryor, Ok Posts: 65 Trader Rating: (0) Feedback Score: 0 reviews	No leak before the turbo. We are running hard piping.