One thing I've never really understood.
As long as you are getting the afr you are shooting for, what does it matter where they lock at? Does it help the car to consistently hit the afr you are shooting for more accurately?
One thing I've never really understood.
As long as you are getting the afr you are shooting for, what does it matter where they lock at? Does it help the car to consistently hit the afr you are shooting for more accurately?
Yeah, but why does it matter if you are still hitting your desired 11.5-7?
My SSEi has a range of 0 to +3.1 at WOT. I've been running the same dialed in MAF curve for 3 months now. I quit chasing "0" trims and found that the carried over fueling adjustment does not have a significant impact on my WOT fueling. My average Commanded AFR vs. WB AFR is within +/- .1 AFR regardless of locked in LTFT (0 to +3.1 LTFTs).
From my experience, as long as your Commanded AFR is within the accuracy specs of your WB AFR, you should be ok. (At least that what I found that works for me and my car.)
Last edited by TommyGloves; 03-21-2010 at 11:15 AM.
fuel trims are an O2 error correction based on end exhaust gasses, its a percentage of the commanded injector duty cycle.. if its + its adding fuel to whats commanded by the constant if its - its telling to cut down on the fuel injected,
if your o2 is of age, it gets slower, bosch have detailed writeups on this but by the end of its life it "sees" the engine running as lean, adding fuel. a built in failsafe if the sensor were to fail prematurally.
now comes to fuel trims the main ones to deeply consider are your long term trims. if theyre out, look at the relevent cells, coordinate to the appropriate tables and make the adjustments needed to bring the corrections as close to 0% as you can
Beached as bro!
Thanks for the comments everyone. I've been tuning for a few years, and I realize what is going on when the trims are either positive of negative. I can understand the benefits of getting the trims close at cruise. But, I still see no benefit of getting them to lock onto 0 at WOT as long as you are hitting your correct AFR. Anyone know why this has become a standard?
x2. It is more important to tune PE with a wideband, not trims. I stopped trying to get an exact lock on trims as well since it does not impact AFR. I also have found that my trims don't always "lock" in PE. I have seen instances where the trim will start around -5 in PE, then jump up to -1, then back to -5 right before exiting PE. AFR stays flat throughout.
2000 Regal GS | Twin-Charged T72 | HPT Pro + PLX Wideband | 12.55 @ 110 on 15psi | Now running 20psi on E85!
1998 5.9L Durango | Powerdyne supercharger @6psi | Mesa Headers | Gibson Cat-back | 1.7 RR's | Tuned PCM | Ported Heads | Custom TB & Intake | Custom fuel rails | Rebuild coming soon...
Cool. I've never seen them move while in PE, but don't doubt it. I usually try to get them close, especially during cruise, but I never really understood why they needed to lock onto 0 as long as you have the correct afr. Thanks for the info.
If multiple learned cells are experienced under PE, multiple learned fuel trims could be seen.
If our cars use fuel trims in PE, it is something potentially serious..
Say you command 12:1 AFR with a 0 trim and hit 12:1 actual AFR.. Great.. Next run you have a fuel trim of -1 (percent).. That mean you are now really commanding 12:.99 (about 12.12:1).... Go a bit further.. -5 percent... 12:.95 = 12.63:1....
97 Grand Prix GTP (not going to bother listing mods in detail) 1 messed up 97 PCM with about 30-50% of a 2003 calibration and parts of a few others.
i've wondered this forever. why does it even help in cruise??
Bilemke.
if you command 12.1 and get 12.1 with no fuel trims. Why would you get a fuel trim of -1. sorry but your post totally lost me
2001 3.8 v6 camaro, T5, ford 42lb green top injectors, grand national .63 a/r turbo. 8psi. stock motor, ngk tr6 plugs (one step colder) 91 octane.
2001 4.3 zr2 s10. daily driver, 31" tires, 4x4, cat! and exhaust. looking for mpg.
Using the STFT Maf histogram you can easily get your LTFT's within 1% at idle and cruising which will should give you a LTFT of Zero in P/E every time. I have tuned a handful of 3800's this year using the histogram and the LTFT's stay between 0 and 0.8%.
If you have a LTFT that is something other then zero in P/E then you are not tuned.
Regards,
Brian Turner
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1988 Ford Mustang GT INCON Systems TT
331 Cubic Inches - Corn - 808 RWHP 918 RWTQ
97 Grand Prix GTP (not going to bother listing mods in detail) 1 messed up 97 PCM with about 30-50% of a 2003 calibration and parts of a few others.