LTFT and O2 problems

**ASCStinger** · 10-12-2010

I got ahold of the VCM suite a few weeks ago, in order to tune for the 3.29 gears in my TEP tranny and to try my hand at tuning for my few mods.

Right now the PCM is pretty much stock on the engine-side with COT disabled, stoich and PE tables modified for E10 (stoich at 14.16, PE target afr multiplied by 0.96). Also torque management has been disabled.

Initial scans are showing a -9.4 ltft part throttle (fuel trims were reset and relearned). The one time I went up to 66% tps and entered PE, 02's were hovering at 850 and ltfts were -8.6. I got 5 degrees KR so I stayed out of the throttle after that.

My mods are SSAC Headers, Gen V w/ 3.6, Open Cone, TR55's and Edelbrock 9.4mm wires, 185 thermostat.

I'm going to have a bung welded in my crossover for a wideband so I can do a proper MAF tune next month. Is there anything I can do with my tune right now to fix my LTFTs and 02's and try to stifle that KR?

**GAFF** · 10-12-2010

Are you maf tuning?

**ASCStinger** · 10-12-2010

I will be once i get the wideband, which is in about a month or two, is there any MAF tuning I can do on the narrowband or am I stuck? Sorry if I didnt make it clear, I just wanted to know if theres anything I can do while I wait for the wideband.

**GAFF** · 10-13-2010

On my DHP I tune my maf with no wideband.. got my ltfts pretty good..

**ASCStinger** · 10-13-2010

Do I adjust the MAF based off of the LTFT %'s then? I've looked all over and all the guides I find for MAF tuning all involve using a wideband

**Zalfrin** · 10-13-2010

Do MAF tune with narrowband to get your fuel trims closer to 0. Once you have the wideband adjust fueling in PE so commanded AFR = actual AFR. In the mean time you can probably get in the right ballpark by looking at how your MAF curve changes for the cells you can hit outside of PE and applying that same change to the higher cells (eg: you end up with about a 7% change to MAF values, apply that same 7% to the upper cells).

Eddie's table modifier is what powrtuner guys use to tweak the MAF based on LTFTs. HPT guys can use histograms, but I can't help you there. The table modifier DOES support HPT scan exports so you could use that. Table Modifier - The Scan Data Thingy

**01gpgt01** · 10-13-2010

850 WOT 02's is low, you need about 3 percent fuel added on the 7K-11,500HZ. Without seeing a scan on the cruise maf range its hard to tell you what you need there. Remember to feather in when adding or decresing maf values. you dont want a suddun lean or rich spike

**Silver GTP** · 10-13-2010

Create a histogram that logs LTFT vs. MAF Hz. This will tell you what percentage your MAF Hz are off at idle and cruising speeds. When you go into PE mode, it will command an AFR and calculate how much fuel to add based on that AFR and what the MAF settings are. For now, you can adjust your commanded afr in PE mode down to a lower number and get your O2's up to around 930-940, but you will be able to tune it much better once you get your wideband in. Once you have the wideband, then set up a histogram that logs AFR error % against MAF Hz to tune the upper range of your MAF. Once I got my MAF table tuned in top to bottom, I set my commanded AFR in PE to 11.3 for E10 and zeroed out my PE add vs. rpm vs. time table. I am still fine tuning things a little bit, and bringing up my WOT timing, but I am knock free and it's running strong.

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