Generation III External Engine - Ported mass air = Faster car. Why worry about Ltrims?

I have a bolt on 00 Z28 that picked up 10 rwhp on Thunder's chassis dyno with a ported stock mass air meter. I've been reading all this talk about L trims, and wonder why people are paying attention to this. With the ported mass air meter my ltrims are around -10 or so at cruise.

So i have a couple of questions:

If the ported mass air meter makes my car faster while skewing the Ltrims what difference does it make?

Are the changes that I could make to my Ltrims via a MassAir Translator effective and worthwhile?

Could i concievably negate the ported mass air meter with Ltrims inside the factory range?

Should i think about any of this stuff?

What were the LTrims at wide open throttle? That is what counts. <img src="gr_stretch.gif" border="0">

ERic

At WOT, I was under the assumption that the L-trims have no input. The O2's are what you want to be concerned about at WOT. <img src="gr_images/icons/wink.gif" border="0">

[quote]Originally posted by Palm Beach Z:
<strong>At WOT, I was under the assumption that the L-trims have no input. The O2's are what you want to be concerned about at WOT. <img src="gr_images/icons/wink.gif" border="0"> </strong><hr></blockquote>

Actually, L-trims do count when they are positive. But the L-trim will be locked, and they will just add more fuel. If L-trims are negative however, they do not do anything and will not take away fuel.

If the ltrims are negative just prior to going wot, then the wot ltrims are set to 0. If they are positive prior to wot, then they remain that way. The idea is to not lean it out any under wot, even if it does at part throttle.

O2's are what have no input at wot. They are only useful in diagnosis (to a certain extent).

[quote]Originally posted by AzzHauler:
<strong>

O2's are what have no input at wot. They are only useful in diagnosis (to a certain extent).</strong><hr></blockquote>


huh? why do we look at O2's?

Positive LTrims can affect lock up with your TC during daily driving. Most of the time it accurs when you install a cam without tuning.

Mike as long as your o2s and timing look good i would not worry about it. That's a pretty good gain with a ported MAF. I did not dyno mine after i removed the screen but picked up a .1/1MPH during a T&T sesion at RRR by swaping a stock MAF out with a descreened MAF.

[quote]Originally posted by AzzHauler:
<strong>If the ltrims are negative just prior to going wot, then the wot ltrims are set to 0. If they are positive prior to wot, then they remain that way. The idea is to not lean it out any under wot, even if it does at part throttle.
</strong><hr></blockquote>

My ltrims are 100% negative except at WOT (where they are +2.3 and +1.6). Any ideas? This is immediately after a PCM reset if that matters.

[quote]Originally posted by The Underdog:
<strong>


huh? why do we look at O2's?</strong><hr></blockquote>

Because the o2's still have a reading. We can still see what's going on by looking at them, even if the computer isn't.

[quote]Originally posted by sross:
<strong>

My ltrims are 100% negative except at WOT (where they are +2.3 and +1.6). Any ideas? This is immediately after a PCM reset if that matters.</strong><hr></blockquote>

Well as long as you mean they are always negative, not actually reading -100%, then it's fine for them to go positive. It just means that as your making the transition to wot, the pcm thinks it needs to richen it up a bit. Your numbers might change once it relearns though.

[ March 13, 2002: Message edited by: AzzHauler ]</p>

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by AzzHauler:
<strong>
Well as long as you mean they are always negative, not actually reading -100%, then it's fine for them to go positive. It just means that as your making the transition to wot, the pcm thinks it needs to richen it up a bit. Your numbers might change once it relearns though.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Sorry, that wasn't very clear. They are in the -3 to -7 range except at WOT where they are +2.3 and +1.6. Would you just shoot for lower (-8 to -10) ltrims?

This post might help you decide:
http://www.ls1.com/forums/showthread.php?s=f39613476cec8d0eb0980c461b2bf165&threadid=58902

L-Trims are used to determine A/F ratio at idle and cruise only. -10% l-trims means that you are running 10% rich. You would adjust your MAFT to 10% lean...repeat the process until the l-trims are as close to 0 as possible.
For WOT, you would record several runs and take the average O2 reading from fuel table 22 only...let's say it came out to .965mv (rich).
Ideally you would like to be around .88-.91 with the smaller number being leaner than the larger. You want to run as lean as possible without KR, or the point where you make most power at WOT (around 12.9:1 A/F).

If you're running 10% rich with ported ends...the MAFT would let you gain more power by leaning out the mixture to the ideal ratio. Rich is safe..but lean generally makes more power...unless you are getting knock retard or detonation.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Mike Hoffpauir:
<strong>I have a bolt on 00 Z28 that picked up 10 rwhp on Thunder's chassis dyno with a ported stock mass air meter. I've been reading all this talk about L trims, and wonder why people are paying attention to this. With the ported mass air meter my ltrims are around -10 or so at cruise.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">2 major issues. First of all, the instant you go to a new part is not the best time to dyno it... the computer, when you first install a ported MAF will lean out the mixture, thus adding more power. However, after a short while of driving the car around, usually, the computer learns out the gains you have just seen. Second, ported MAF's have a BAD HABIT of causing Knock on motors, especially in the heat, due to causing a lean condition. My best long term results BY FAR have been using the Stock MAF with a MAFT to tell the computer what I want it to know. Stock MAF with custom tuning is probably even a notch above that. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />