Well i have my wideband on my car and ive noticed a problem only above 5K and only in 3rd gear.

It seems that the car goes lean, Really lean like higher than 18:1. Thats only as high as i let it go before i got out of it. I tried a couple more times just to make sure im not crazy and as the revs would climb only in 3rd above 5K it would progressivly get leaner. I get out of it before it pings or detonates because thats all i need to do is kill my engine.

In first or second gear is a little rich (11.4:1) but i dont mind that as much as the lean condition only at the top of 3rd. I dont know what would cause this and its bugging me a little. I have yet to check my fuel pressure but im not sure thats the problem because it only goes lean in 3rd gear.

any suggestions of what i could change in my tune?

Thanks for any help,
T.C.

 

Still have the stock fuel pump?

 

oops sorry no i dont. its a new walbro 255 in tank pump. and i know i have enough injector for the 383 because im running a relatively small cam and 42lb/hr lucas style injectors.

 

If you want to, send me the bin file and I can take a quick look at it.

 

sure just pm me with your e-mail address and i will send it to you.

Edit: i just sent it to the e-mail you listed in your profile.

thanks,
T.C.

 

I had the same situation in mine. All mine needed was more fuel at WOT. My reasoning is that since third gear is much longer than 1st and 2nd the PCM actually has more time to read the MAF values and figure stuff out, unlike 1-2 gears where you're basically on it for just a small amount of time before shifting up. I added fuel at WOT and it was just fine after that.

 

My car was the opposite.

Before the converter, it was leaner in 2nd, than in 3rd. 13.5:1 in 2nd, and 13:1 in 3rd (as indicated by my wideband sensor).

After the converter, it was 13.5 across the board, so I added some fuel to it and it appears to be fine now.

 

well i checked the fuel pressure and its perfect at wot in 3rd gear @ 45psi and stays steady when it starts to lean out so im leaning towards adding fuel in the pe tables.

BTW the pe table that i need to change is % change to AF vs rpm at wot right?

how much should i add to the values.

since it leans out above 4000 ish rpm how much should i add to the values above that?

 

another question... which way do i have to modify the tables to make it richer at wot?

make the values go down or make them go up?

Thanks guys for the help!!!!

 

Add to the values in the tables to add fuel. I usually add about 2-3% (multiply the values by 1.02-1.03) at a time and drive it to make sure I didn't add too much.

 

in which table should i add values?

 

I've heard that adding 10 to the cells lowers the AFR by 1 full number.

So if you have a 5 in a cell and the car runs at 14:1, making it 15 in that cell should take it to 13:1.

You'll add it to % change vs RPM (tunercat) or PE vs RPM (LT1 Edit).

 

I've found the same.

 

well i wanted to post a follow up to everyone thats helped. i know its been a while but hopefully i may help someone else out.

for some reason my wideband reading was becoming skewed and it was showing the wrong readings. when i put it on the dyno to tune it myself their wideband showed a much different number.

I added fuel before going to the dyno but it didnt help the lean in 3rd condition.

the dyno's wideband had something else to say. WAY TOO RICH.

i was around 9:1 in all gears.

after all was said and done i ended up taking out a buttload of fuel and adding some timing on the big end. i picked up 30 horse and 30 lb/ft.

thanks for the help guys.