tuning question....

[gsxr141]

hey all. i recently installed my aem ems and have begun tuning.
i have it up and running, but i'm having a few problems.....
it is running lean above 4500 rpm. i installed a new wally 255, fuel filter and i'm running fic 630 injectors. the injector duty cycle is only at 60%.
also, i'm running a 60-1 ct26, bic ddp and full 3" exhaust.
no matter what i've done, it still leans out.
does anyone know of anything i should be trying?

 

[Nick M]

More info.

What is lean? Under a heavy load, partial load, no load 4500 rpm?

 

[gsxr141]

full throttle in 4th gear. it stumbles going through 2500-3500, clears up nice, then goes lean at about 4500. it goes from 10-11afr's on up as the rpm's get higher. i'm actually going out right now to do some more tuning.

 

[supranewbie]

full throttle in 4th gear. it stumbles going through 2500-3500 What is the AFR at this point? Is it lean here too? Is this a separate issue?, clears up nice, then goes lean at about 4500. it goes from 10-11afr's on up as the rpm's get higher. i'm actually going out right now to do some more tuning.

I imagine you've studied your maps through the RPM ranges you're having trouble with?

 

[gsxr141]

IT APPEARS RICH DURING THE STUMBLE. also, there seems to be a misfire. here's the kicker........ we tuned out this problem and got the car to go through the rev range without stumbling. BUT, as soon as i went to leave his shop, it was doing it again. also now, at 2500rpm in 5th going about 65mph it started missing real bad.
right now i have iridium ngk's gapped at 28thou. i'm going to try some autolite 5503's and gap them to 20 thou.
as far as the upper rpm lean issue..................... we tried bumping up the injector duty cycle from 60% to 80% and nothing changed. also this is at 11psi. at 17psi the lean spot comes on earlier. my tuner said it looks like we're running out of fuel.
i was under the impression that having the 255 in there would be enough. do i NEED to do the fuel pump wire mod? do i need to run bigger fuel lines?
any and all help is greatly appreciated.

 

[gsxr141]

I imagine you've studied your maps through the RPM ranges you're having trouble with?

at the stumbling point the car was tuned rich.

 

[super51fan]

I would change the spark plug first before any more tuning. Get several sets of plugs to change out while tuning. A fuel fouled plug may not look to bad but will cause drive ability problems that is caused by the plugs. .020 is to small of a gap for you airflow ability, IE spark blowout. IMO. People always concentrate on the complex and dismiss the basics. Good luck

 

[Suprapowaz!(2)]

I used to run Autolite coppers and I was having problems with break up. I went through two sets, and someone suggested going with NGK or Denso coppers. I went with NGK's and haven't had any break up issues since.

 

[Nick M]

it is running lean above 4500 rpm. i installed a new wally 255, fuel filter and i'm running fic 630 injectors. the injector duty cycle is only at 60%.
also, i'm running a 60-1 ct26, bic ddp and full 3" exhaust.

That is not nearly enough air to run out of fuel on that large of a fuel pump.

as far as the upper rpm lean issue..................... we tried bumping up the injector duty cycle from 60% to 80% and nothing changed.

And that isn't possible. Either it was not changed, or the readings are wrong. And .028 is too small.

 

[gsxr141]

i changed the plugs but the breakup is still there. the old ngk iridium's were gapped at 35 thou, definitely too much. it looks like i have bigger issues now though......... there's tons of smoke coming out of the catchcan filter, and exhaust. it would appear that the motor is somehow hurt.