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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Fuel trims real high then real low in the same pull



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      11-29-2012, 10:31 PM   #1
TenshiWingusu
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Fuel trims real high then real low in the same pull

Hey everyone, got my PROcede back from Vishnu yesterday, plugged it in and it runs great. Loaded the 9-10 Aggressive Stage 1 maps on and started playing around. Kept maxing my fuel trims +34% so I eventually took the start boost back to 15% and my OL fueling up to 100% and this was the result... My fuel trim goes high but under the threshold and then throughout the pull it drops negative just as high as it was positive... I searched around and couldn't find anyone else's logs that showed it going negative? My AFR looks a bit jumpy as well... Any thoughts? I'm probably going to switch to the 7-29 auto tuning maps but I figured this was showing an underlying problem that i cant seem to figure out yet.
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      11-29-2012, 10:36 PM   #2
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Raise OL fueling for those midrange cells (and perhaps lower it some on the top end) and it will be more flat.
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      11-30-2012, 09:02 PM   #3
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Quote:
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Raise OL fueling for those midrange cells (and perhaps lower it some on the top end) and it will be more flat.
OL fueling is almost maxed in those sectors. The aggressive maps have a sharp OLFC gradient into the boost curve. The autotuning maps max my trims at OLF 100% as well, but since the map has a lower fuel correction table i hit 34% fuel trim immediately and my AFR goes to 20... Knock much?
It appears that my fuel pressure is ok because its higher at the trouble spots than it is at 6000rpm does that make sense?
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      12-01-2012, 02:15 AM   #4
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Quote:
Originally Posted by TenshiWingusu View Post
OL fueling is almost maxed in those sectors. The aggressive maps have a sharp OLFC gradient into the boost curve. The autotuning maps max my trims at OLF 100% as well, but since the map has a lower fuel correction table i hit 34% fuel trim immediately and my AFR goes to 20... Knock much?
It appears that my fuel pressure is ok because its higher at the trouble spots than it is at 6000rpm does that make sense?
The OL fueling map isn't maxed-out unless it reads 100 in those cells which is likely doesn't. If you don't have the flash, I had my OL values (map, not global) in the 60's to keep the trims from maxing, but that comes with some trade-offs. The flash fixed all that, for the most part.
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      12-03-2012, 11:30 AM   #5
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Quote:
Originally Posted by The Ghost View Post
The OL fueling map isn't maxed-out unless it reads 100 in those cells which is likely doesn't. If you don't have the flash, I had my OL values (map, not global) in the 60's to keep the trims from maxing, but that comes with some trade-offs. The flash fixed all that, for the most part.
Right, but that only seems to be a band-aid to the problem, its hard to see from that AFR plot but bank 1 on my more recent logs has been consistently over a point higher than bank 2. It looks like I have a couple bad injectors and possibly some wearing O2 sensors
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