how much to adjust PE? running rich
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
how much to adjust PE? running rich ok checked my o2's after header install and knocked donw the PE a little bit. ran the car a while today with a few WOT runs and now they are both reading 945 on the dot. how mcuh should i reduce the PE to take out about 20mV?
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
ok i just got back i droped it down about .75% and looks to be at about 935. im gonna ride and check that out some more through the week. i figured take my WOT fuel voltage, 945 times .01 (1%) and thats about 9-10mV just didnt know if thats how it works but seems to be about right.
With the Predator, I recall about 20mV per %PE adjust.
Once you get closer to the 13:1 the mV/%PE will get
more sensitive. I'd just keep on going with incremental
PE decrease until you get to a consistent 900-920mV
ballpark and then nudge timing to its KR onset limit.
Once you get closer to the 13:1 the mV/%PE will get
more sensitive. I'd just keep on going with incremental
PE decrease until you get to a consistent 900-920mV
ballpark and then nudge timing to its KR onset limit.
TECH Senior Member
Joined: Nov 2001
Posts: 9,246
Likes: 3
From: Troy, AL
Keep in mind that these O2 sensors are not at all accurate at WOT. They weren't designed to be. They vary for different reasons, one being sensor temp. You can see .945 on one run and .935 on the next with NO changes. Even changing from .945 to .915 with no changes wouldn't be uncommon and it may or may not mean that your actual mixture has changed.
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Verdad Gallardo Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
well see i took 4 runs and they both read dead on at 945, i ride the car for about one hour before i check them so the exhaust gets nice and hot so it would read more consistent. i wanna get a wideband hooked up and see how close i have it haha i have been researching and doin all kinds of stuff to get it dialed in and i think i have it down pretty good where i can get it close off the o2's, between hearing detonstion, seeing knock and just the feel and sound of the motor. hell imight be way off but we will see haha
Don't try and kid yourself, you're playing with fire to tune by those stock O2 sensors! Don't reduce your PE by any more than 4% until you get a wide band on that thing. I'm not kidding; I didn't realize how far off they can be until I got wide band myself. You won't be laughing if you burn a hole through a piston.
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
o yeah i know it man, but 945 seems high and im not gettin any knock or detonation and i am eating up a lot more gas. this was right after the header install. trust me i know i have to get a wide band so im leaving the numbers at 935mV. i only went down .75% i wasnt gonna go 4% but thanks for the imput, im pretty sure me and u pmed back and forth a while ago about fuel by the o2s and all your points were well taken thats why i dont plan on leaning it out anymore, thanks 
The most important thing to get right first is the L-terms.By installing headers they probly went into the +'s at WOT.Your trying to adjust by the PE table which will change in different weather if the L-terms are not fixed first.I've found that the 02's can be accurate if you do a wideband to get what voltage ='s the A/F you want.Of coarse each car is different,so you can't go by what works on somebody elses car.With my A-tap and my car the voltage is .900 for 12.6-1 A/F.
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
well my fuel trims are at 0% at part throttle and no matter when i punch it, even if they are off like -5 or +5 they still go to 0 at wot, but ill double check. i feel safe with mine at about 900-920 i have no ping or anything but il think ill try to stay in the 920 range for now, thanks