PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

Fuel Trims

Old Dec 19, 2024 | 08:22 PM
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Default Fuel Trims

LS3 with small cam. 218/226. Local dyno tune with hp tuners and wide band. Still feel like it’s running rich. High negative fuel trims have me worried.
LTFT -17 idle to -22 WOT

STFT 0 to -9



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Old Dec 20, 2024 | 08:32 AM
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If those are your LTFT's then the fueling is WAY off.
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Old Dec 20, 2024 | 11:07 AM
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this is at idle and then at WOT. Truck had 36lb and now has 54lb injectors.
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Old Dec 20, 2024 | 12:58 PM
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I would take it back...thats horrible. +-3% is what I normally shoot for.
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Old Dec 20, 2024 | 01:14 PM
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TWO ways to adjust: Quick and dirty: simply input HIGHER injector flow rate ( I'd go plus by 2/3 of your LTFT- so basicly multiply injector flow rate by 1.11 or so )
Again, that's quick n dirty, no one said it was right, but it'll get those trims down quick.

The RIGHT, way, which take s more time, is to massage the VE table.
Drive it around, log AFR, and grind that fuel table straight.. Cell by cell - Baby.
NOBODY is going to take DYNO time to do that, unless you are a billionaire.
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Old Dec 22, 2024 | 12:01 AM
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He did did a few small runs to dial in the base tune then did 2 dyno runs. It was done in about an hour and a half. Trying to communicate with him to street tune and the drive. I feel it’s way rich. Exhaust alone is extremely black.
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Old Dec 23, 2024 | 08:53 AM
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From: Brenham
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Originally Posted by Full Power
TWO ways to adjust: Quick and dirty: simply input HIGHER injector flow rate ( I'd go plus by 2/3 of your LTFT- so basicly multiply injector flow rate by 1.11 or so )
Again, that's quick n dirty, no one said it was right, but it'll get those trims down quick.

The RIGHT, way, which take s more time, is to massage the VE table.
Drive it around, log AFR, and grind that fuel table straight.. Cell by cell - Baby.
NOBODY is going to take DYNO time to do that, unless you are a billionaire.
I dont hit every single cell in a ve table but I can hit a good majority of them on the dyno using the eddy brake (load cell) in less than 1/2 the time it takes driving around. Can also hit cells that are really hard to hit by driving around.
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Old Dec 23, 2024 | 02:50 PM
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I’m worried I may of had a vacuum leak at the valve cover pvc line or at the valley plate line. Not sure if that would have thrown things off. I do get considerable bucking at low speed now. Have about 300 miles on the tune and 100 mines on the 4.10 gears and truetrac.
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Old Dec 26, 2024 | 07:12 PM
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You said u changed to larger injectors. Was it tuned for these or the older ones? If not thin thts your issue with the richer trims. It needs correct injector data to respond correctly.
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