WTF - PE vs RPM doesn't do squat?!
Thread Starter
Joined: Nov 2001
Posts: 3,160
Likes: 663
From: Chandler, AZ
WTF - PE vs RPM doesn't do squat?! I ran an autotap log to log my O2s during a WOT blast. They were a bit rich all around .925. So what I wanted to do was start to lean it out around 4800 RPM progressivly to redline. So what I did was at each interval I leaned it out 4% more than the last. I eventually got to cell 6400 RPM at which it was adjusted down a total of ~20%. I thought this was a good starting point. Well was I wrong. After I programmed it to the computer I drove around a bit to let it learn some. Then I did a WOT blast and the O2s were identical to before! What is going on here, isn't this how you adjust WOT A/F ratios?
Re: WTF - PE vs RPM doesn't do squat?! So did you check your LTrims before hand? If not, that may be where your problem is. If you are running lean at part throttle, then the PCM will try to add fuel at WOT regardless of what you do to the PE tables.
If you are rich on top, you need to get you LTrims to just under zero at part-throttle cruise. Then your car will not try to add fuel at WOT because it thinks you are running lean. After you do this, you should see significant differences.
If you are rich on top, you need to get you LTrims to just under zero at part-throttle cruise. Then your car will not try to add fuel at WOT because it thinks you are running lean. After you do this, you should see significant differences.
Thread Starter
Joined: Nov 2001
Posts: 3,160
Likes: 663
From: Chandler, AZ
Re: WTF - PE vs RPM doesn't do squat?! I already tuned for my LTRIMS, they are -4 on avg and at WOT they kick to 0. They did this on both runs (the before and after PEvsRPM changes) and the O2 sensors were identical both times. How much should I have to change the PE vs RPM table to see changes from say .925 to .895? Any guesses?
TECH Addict
Joined: Nov 2001
Posts: 2,207
Likes: 0
From: College Station, Tx
Re: WTF - PE vs RPM doesn't do squat?! You can't really get reliable feedback from your stock O2's.
Here is a typical O2 response curve - notice if your O2's were at slightly different temps you can have *large* flucuations in the corresponding A/F ratio for a particular A/F ratio - not to mention the inherent steepness of the transfer function itself
www.slowcar.net/shared/o2_volts.xls
Here is a typical O2 response curve - notice if your O2's were at slightly different temps you can have *large* flucuations in the corresponding A/F ratio for a particular A/F ratio - not to mention the inherent steepness of the transfer function itself
www.slowcar.net/shared/o2_volts.xls
Thread Starter
Joined: Nov 2001
Posts: 3,160
Likes: 663
From: Chandler, AZ
Re: WTF - PE vs RPM doesn't do squat?! Wow, I didn't realize that exhaust heat and O2 temp made that much of a difference at anything other than stoich. OK, so I do realize that at WOT my O2 sensors are not very accurate, but how much of a change on avg does it take to go from say 12.5 A/F to 13.5 A/F in the PE vs RPM table? I just want to know if me changing my 1.24 to a 1.05 in the PE vs RPM table is going to make any difference whatsoever on the wideband dyno or am I way off and need to make much larger changes like -12?
<small>[ April 05, 2002, 01:16 AM: Message edited by: Nic00Z28M6 ]</small>
<small>[ April 05, 2002, 01:16 AM: Message edited by: Nic00Z28M6 ]</small>
Re: WTF - PE vs RPM doesn't do squat?! Mine did exactly the same thing....nothing. My ltrims are LOCKED at zero by Ed Wright, Yeah the o2s are inaccurate at different temps blah blah blah but i tuned my car with the o2s at the track with a maft and fuel pressure and got to the dyno. The wideband showed me at 11.5:1 Just what I had expected...a little rich for a FI car. You can get a/f close with the o2s once you reference them on a wideband. .915 is 12.5:1 on my car. I put in new injectors...entered the correct injector numbers into ls1edit. tried getting my o2s down from 990-1000 with pe/rpm and nothing i did made a change. Maybe we are missing something here as it works for some
Trending Topics
Thread Starter
Joined: Nov 2001
Posts: 3,160
Likes: 663
From: Chandler, AZ
Re: WTF - PE vs RPM doesn't do squat?! Yes, coolant temps were around 185-190 both runs. Everything was identical when I ran both WOT runs, the only thing that was changed was my PE vs RPM table. I know the O2s aren't accurate, but with me only changing stuff above 4800 RPM, the O2s should somewhat go down after that point. It just looks like it doesn't do anything. Are my adjustment too small? Do I have to make significant changes like by ten instead of 10 percent (ie 1.24 goes to -11.24 vs scaling the cell 90%)? This is very frustrating.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0
Brett Foote
