#68071, "RE: PocketLogger Questions" In response to Reply # 0 Feb-09-04 02:55 AM by XtremeRS
Originally posted by WickedESi Is long term fuel trim the air/fuel ratio? IE: long term fuel trim of 11 means 11:1 fuel ratio? Also, What should the primary o2 sensor read at idle (what does the reading mean, the higher the voltage the more o2 or the more fuel)?
No, your fuel trims are basically telling you how the ECU is adjusting fuel over a short time frame(STFT-almost real time), and LTFT- what the ECU has been doing with fuel over a longer time frame. The main perameter to look at is the STFT, as this is what the ECU is doing to the A/F ratio in real time. When the STFT is at 0, this means its at stock tuning. When the number goes into the postitive, this means that the ECU is adding fuel over the stock fuel map(running a bit too lean). When the numbers go into the negative, this means the ECU is trying to cut back fuel, to keep it closer to the stock fuel map. You have 25% of correction in either direction, so the closer you can keep it to 0, the better. BUT this does not mean you are running rich/lean, its just saying how much the ECU is adding/subtracting fuel. ONce you peg 25%/-25% then you are running lean/rich. LTFT is telling you what the ECU has been doing with the STFT over a longer time frame. Its perfectly normal to see the STFT go from around 5 positive, to 5 negative for stock fuel tuning. The longer you can keep your numbers looking like this, the lower you can get the LTFT closer to 0. I run the 30 lb injects, and its usually in the higher negatives, because its trimming fuel more than its adding fuel(a higher -LTFT number). This is perfectly fine.
If you ever have the STFT and LTFT pegged at -25%, you will get a too rich CEL. So lets say you have a -20% STFT. You are not running rich, but you only have -5% left to trim fuel, until the ECU has no more room to adjust. Make sense?
13.5 @108 MPH-2.2 60ft(stupid FWD!) S16G @ 18 PSI/FMIC/Running on MegaSquirt II (Now with sequential fuel injection) My webpage: http://eclipsed4evr.home.comcast.net -1998 Mitsubishi Eclipse RS-T- "Toy" -1992 Plymouth Laser Turbo AWD(SOLD) -2000 Honda CR-V(daily)
#68076, "RE: PocketLogger Questions" In response to Reply # 1
Yeah, good explanation, thanks!
What should the o2 sensor read at WOT?
I'm getting a cel 43, I just recently installed a screamin deamon coil (and flat pin style coil harness) and crane 8.5 MM wires, and I'm trying to see if my Upstream O2 is bad. (Should my downstream 02 be reading about the same as my upstream since there is no cat there anymore?)
Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician
#68096, "RE: PocketLogger Questions" In response to Reply # 4
When you say fluctuate, do you mean slowly change or rapidly change as you were making your tuning run? If it slowly changes, it just means you need to smooth out your A/F curve by changing your settings slightly. If it changes rapidly, mayby your O2 sensor is going out, maybe things are just fine and your fuel system just isn't adjusting that quickly (can't expect a rising rate FPR to adjust perfectly with a kit on our cars, that's why you usually aim to tune a hair rich, 0.92v or so, for safety).
#68097, "RE: PocketLogger Questions" In response to Reply # 5
If you are running 5 psi, then shoot for o2's in the .94-.96 range. If you are running 8+ psi, you need to run around .97-98. I get about .98-1 at 13 psi. Yes, it needs to be that rich
13.5 @108 MPH-2.2 60ft(stupid FWD!) S16G @ 18 PSI/FMIC/Running on MegaSquirt II (Now with sequential fuel injection) My webpage: http://eclipsed4evr.home.comcast.net -1998 Mitsubishi Eclipse RS-T- "Toy" -1992 Plymouth Laser Turbo AWD(SOLD) -2000 Honda CR-V(daily)
#68100, "RE: PocketLogger Questions" In response to Reply # 6 Feb-09-04 02:44 PM by WickedESi
Opps I didn't mean to mislead you guys, I'm not turbo yet (it was just a joke ).
I did another run it's reading .93 for my primary o2 sensor, w/ a constant 0 STFT (stoich mix?). What does this mean? I'm non-turbo.
I have noticed me getting a CEL 43 too since I've put in my screamin deamon coil (and soldered a flat pin style coil harness), 8.5 mm crane wires, and NGK-BKR5E's (1 step hotter) spark plugs gapped @ .065 like the directions for the screamin deamon coil said.
Ok the exact CEL 43 I'm getting is a PO300 which isn't a specific cylinder misfire.
Multiple cylinder misfire* Ignition coil / Spark plugs / Ignition circuit / Injector / Upstream HO2S / Compression pressure / Timing belt / Crankshaft position sensor / Air intake / Fuel pressure / Crankshaft position sensor circuit and connector / Bad tuning
I'm thinking since I'm gettina a constant high LTFT (around 11), w/ a 0 STFT, and a high o2 sensor reading (because doesn't the reading get higher/richer as your o2 dies), and that code above ^, and also that my testpipe isn't throwing a code, that my primary o2 sensor is almost dead. What do you think?
Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician
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