I am tuning a heads/cam car currently, and the fuel curve is perfect till ~4800-5000....it maintains the exact A/F I want. At 5000 or so, it goes dead rich (~11.5:1) and stays there. Now I have changed the WOT RPM multipler from 1.x all the way down to .001....and it doesn't change the A/F at all.......it still goes down to 11:5:1 like clockwork. I even made it a negitive number(-.50), and it would hicup really bad. How much does this multipler really effect the a/f???? I can't seem to find a happy medium at all. HELP!! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Chris
AMS Racing

 

hmmm..it works for me. Since PEvsRPM is not working for you, can you change the maf flow rate in that region? Or could it be a maf limit problem?

 

Do you have an autotap log of one of the runs? What did the MAF and Pulsewidth's look like during the event?

 

I changed the ported meter out for a stock one, and redid the tuning. Gained power and smoothed the curve way out. Something was just funky with that meter setup.......I dialed it in really easy with the stock one. Thanks for the suggestions guys!

Chris
AMS Racing

 

Chris....to bad I'm late, but I noticed the very same thing last Saturday. I did about 15 dyno pulls, and was trying to adjust using the PE vs. RPM table all the while. I wasn't having much luck leaning out the tuning.

IMO, The first step should always be to get the LTrims as near to zero as possible. This is why:

I am running an 85mm SLP MAF with LS1 tuning. This was resulting in +LTrims around +10 to +15. With these LTrims, the PCM was trying to add fuel across the spectrum to compensate for lean condition. All the while I was trying to lean the WOT power enrichment, they were just cancelling each other out.

Afterwards, I reset all my work and went to work on the LTrims using the MAF table. Used the multiplication feature to increase the MAF setting by about 7-8% across the board. This got the LTrims to zero and a little on the rich side even (0 to -2).

With the LTrims averaging near zero (or a little rich), it was much easier to lean out the WOT tables because the WOT wasn't fighting the computer's need to richen (based on the LTrims).

Anyone else see this?

 

Yep, ported meters can be funky at high rpm - their seem to progressivley loose precision as the airflow rate increases.

Reckless: Yep - if your l-trims are positive then you will have incosistent/excessive WOT fueling. The computer will always make sure you are rich, so if you are lean at part throttle and adding in fuel to maintain stoich it will use one of these correction factors at WOT also.

It will not ever pull out fuel on it's own at WOT, so as long as your l-trims are negative (or 0) then you will have consistent and tuneable fueling. I normally shoot for -4 to -5 on the l-trims to make sure they don't go positive.

Chris

 

Darn it! I'm finally getting the hang of this stuff <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
Todd

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by ChrisB:
<strong>Yep, ported meters can be funky at high rpm - their seem to progressivley loose precision as the airflow rate increases.

Reckless: Yep - if your l-trims are positive then you will have incosistent/excessive WOT fueling. The computer will always make sure you are rich, so if you are lean at part throttle and adding in fuel to maintain stoich it will use one of these correction factors at WOT also.

It will not ever pull out fuel on it's own at WOT, so as long as your l-trims are negative (or 0) then you will have consistent and tuneable fueling. I normally shoot for -4 to -5 on the l-trims to make sure they don't go positive.

Chris</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Chris, you feel that L-Trims that are -4 (rich) are better than having like +4? Can you explain that for me? Thanks <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

 

With negative l-trims at WOT you will default to 0 for l-trims - regardless of where exactly the negative trims where. This allows for consistent fueling at WOT - which you can then tune with PE vs RPM.

With positive l-trims the computer can default to a positive fuel enrichment value at WOT - what this value is depends on the l-trims it is seing previous to WOT, etc. This leads to inconsistent fueling at WOT. You can't tune it properly because conditions are changing.

 

Chris, would this apply to MAFT tuning? I should have stated that this is what I was refering too. With 30 lb/hr injectors I have LTrims of 3-4 and WOT O2's of .92 (I spray). Just wanting to make sure I'm on the right track <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

TTT

 

TTT

 

ttt

<img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" />

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by NastyC5:
<strong>Chris, would this apply to MAFT tuning? I should have stated that this is what I was refering too. With 30 lb/hr injectors I have LTrims of 3-4 and WOT O2's of .92 (I spray). Just wanting to make sure I'm on the right track <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Whoops, somehow missed this <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

I would say it applies to just about any tuning - with a maft you would use your base curve to achieve the desired l-trims and then the WOT curve for tuning.

As for stock O2 values - no comment <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Chris

 

Ok, I'll tune the base to around -1 to -2 and then set my WOT. Sound like a plan? Thanks.