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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > Negative -15LTFT?



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      04-28-2021, 08:16 AM   #1
zohaibrose
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Negative -15LTFT?

Kinda weird how this n55 has such a high negative fuel trim, when I rev it goes down to -12 but at idle itís at like -15 and sometimes even goes to -18 if it idle long enough, when you cold start it idles so rough but once it warms up it drives just fine

Stock tune, jb4 disconnected, new plugs and Delphi coils, ignition advancements was all over the place. Tried doing a smoke test and the only place that was smoking was where the charge pipe from the intercooler meets into the turbo.

It kept smoking from there the oring in it is new and itís a vrsf charge pipe so I donít think itís cracked. I pushed it in all the way idk why smoke keeps coming out there. Is that normal?
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      04-29-2021, 01:11 AM   #2
TunafishE93
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I would start where you are leaking.. Replace pipe between turbo and intercooler since it is leaking. They have known to crack. Then go from there.
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      04-29-2021, 10:15 AM   #3
NRigs
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A leak at the charge pipe would allow excess air in which would make him go lean, not rich.
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      05-04-2021, 10:03 PM   #4
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So what do you suspect .. A leaking injector?? Or you just want to be mr correcto? I would would always start with what you know is wrong .. Leaking from anywhere after turbo to intake is a issue.

I think i am still right though. . in a direct injection turbo engine if there is a leak then there will be less air (less boost) but same amount of fuel making car run rich... The lean condition you are think is a traditional leak when there is only vacuum taking fuel and air in..

Last edited by TunafishE93; 05-04-2021 at 10:14 PM..
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      05-06-2021, 09:03 AM   #5
zohaibrose
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Quote:
Originally Posted by TunafishE93 View Post
So what do you suspect .. A leaking injector?? Or you just want to be mr correcto? I would would always start with what you know is wrong .. Leaking from anywhere after turbo to intake is a issue.

I think i am still right though. . in a direct injection turbo engine if there is a leak then there will be less air (less boost) but same amount of fuel making car run rich... The lean condition you are think is a traditional leak when there is only vacuum taking fuel and air in..
Ok so I just forgot to note that I just swapped another engine into this car and I did not code the fuel injectors In to this ecu, itís the same ecu as before but not the same injectors from the old engine so I can only assume thatís the culprit.
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      05-10-2021, 08:06 AM   #6
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Quote:
Originally Posted by zohaibrose View Post
Ok so I just forgot to note that I just swapped another engine into this car and I did not code the fuel injectors In to this ecu, itís the same ecu as before but not the same injectors from the old engine so I can only assume thatís the culprit.
Yes, this is likely the culprit if you have everything signed, sealed, and delivered.

There are correction values on each injector - coding AND the DME both adjust fueling.

If yer feeling lazy, just adjust the fueling table in MHD.
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      05-11-2021, 06:00 AM   #7
zohaibrose
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Quote:
Originally Posted by anjuna View Post
Yes, this is likely the culprit if you have everything signed, sealed, and delivered.

There are correction values on each injector - coding AND the DME both adjust fueling.

If yer feeling lazy, just adjust the fueling table in MHD.
How to code them
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      05-11-2021, 10:56 PM   #8
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