Playing with my new MAFT, and my LTFT's average +0.2 in fuel cells 1-19 using +10/+0. They drop to -4.x using +15/+0. I was under the impression you want it as close to zero as possible and have it negative.

So, is -4.x close enough? I'm going to put some more miles on it tonight to see if it gets any better at +15 base.

 

OK, ran it some more last night and the LTFT's dropped to -6.9 average. So I changed the base back to +10, and after a 90 minute trip it's back to an average of 0.099. O2S1B2 is consistently ~0.035 higher than O2S1B1.

O2S1's & LTFT's: How close should B1 & B2 be to one another? What's a large difference and what can cause it? I've heard having LTFT's slightly negative is better than exactly at zero. But is -6.9 too far below zero?

TPS: Should idling while stopped always have this value at 0.0%? I've seen it intermittently going to 0.4% and 0.8% while stopped & idling.

Timing: My timing doesn't seem to be fantastic for a '98 H/C/I car. How much timing should I be seeing over which RPM ranges in both closed and open loop? I presume the only way to now get more timing is further PCM programming?

KR: How close to zero is considered not worth the hassle to tweak? What's each degree of KR worth from a performance standpoint?

[ January 30, 2002: Message edited by: JimMueller ]</p>

 

[quote]Originally posted by JimMueller:
<strong>OK, ran it some more last night and the LTFT's dropped to -6.9 average. So I changed the base back to +10, and after a 90 minute trip it's back to an average of 0.099. O2S1B2 is consistently ~0.035 higher than O2S1B1.

O2S1's & LTFT's: How close should B1 & B2 be to one another? What's a large difference and what can cause it? I've heard having LTFT's slightly negative is better than exactly at zero. But is -6.9 too far below zero?</strong><hr></blockquote>

The difference in B1 and B2 you see isn't anything to worry about. After my Heads and Cam I was seeing 2.xx difference in banks.

If you run your LT's at Negative 6.9 you are running it rich and the computer is correcting. I got good results tuning it either way, rich or lean no more than 5.0 - 7.0, so you're okay. Just don't leave them off in the high teens, that's alot of correcting by the PCM, but you don't have to get them to 0.

[quote]<strong>Timing: My timing doesn't seem to be fantastic for a '98 H/C/I car. How much timing should I be seeing over which RPM ranges in both closed and open loop? I presume the only way to now get more timing is further PCM programming?<hr></blockquote></strong>

This really depends on if you see any KR, and some other stuff, what numbers are you seeing at WOT?

[quote]<strong>KR: How close to zero is considered not worth the hassle to tweak? What's each degree of KR worth from a performance standpoint?<hr></blockquote></strong>
This is where I would be very ****. I luckily never got any KR except for when i had the case of y-pipe banging. I read before, but cannot verify that each degree of KR will take something like 4hp off a stock car. I believe this number changes though when more is take out, do 2 degrees of KR would be >8hp.

I do know that some people have false knock, but I don't know what mods you have, so we can't even begin to talk about that and how to diagnose it.

Maybe someone will correct me if I'm wrong on this.

[ January 30, 2002: Message edited by: HalfMoon ]</p>

 

Thanks for the reply...

Mods:

FTRA, FRA, FRA2, K&N 33-2118, Whisper Lid, Whisper MAF Ends, LS6 intake manifold, CNC cylinder Heads 2.02/1.57, Comp Cams 218/226 527/535 112, NGK TR55's @ .050, Grotyohann headers/Y-Pipe/CarSound cats, Flowtech 3" cutout, Ed Wright tuning, SPEC Stage II clutch.

My timing is 23-25 for short bursts at WOT. Haven't had a chance to wind out a full gear.

KR: Logs indicate random single instances of 2-4* of KR, typically around 5K or below 2K. However, I intermittently hear what I think is audible detonation above 5K. How much KR would it take to make it audible?

 

The LT's seem to have stopped at around -2.3/-5.5. The O2's are averaging .937 & .904, so I'll need to lean that out. Should I be more concerned about the average of the two being near a certain value, or just having both values within a certain range?

Ed Wright told me most LS1's make the most power on the dyno at 13:1, but like 12.9:1 on the track due to additional loading. What's 12.9:1 approximately equal to on our O2's? .87-.88?

However, all the online documents indicate 12.5-.6 make the most power. Whom do you believe?

 

Lean is mean.

I tune for 13:1 AF and feel that the pcm will adjust for the real world load conditions of being at the track.

I messed around with my BASE and WOT with the MAF T last week at the track. Regardless of the settings, I still saw 28-29 degrees of timing is what my pcm is programmed for...

I have been told that best performance is get the Ltrims to zero or in that ballpark... +/- 5%.

I also tune by ear sometimes... And I also have an AF gauge.

I'd go .870's.