Lesson learned

[odd boy]

I posted (http://forum.efilive.com/showthread.php?t=8141), that was for tuning a big cam (610 on 98 Camaro). I faced a problem which is getting the car rich all the time, even when I reduced the VE numbers by 60%. After looking here and there I found that the injectors were too too too big for that application, in a way that the car never gets the right idle, never reaches the commanded AFR. I found the following:


1. At WOT, the duty cycle was around 55%.
2. At idle (when the throttle is closed and the car is not moving), the duty cycle was 1~2%.

My personal recommendations are: at WOT and high MAP, duty cycle should be greater than 70% and not exceeding 80%.

Don’t accept duty cycle less than 3~5 % at idle. Really, small sizing mistake made the tuning too difficult.

Looking forward to hear your valuable comments.

[odd boy]

like no one likes it

[TFZ_Z06]

like no one likes it

If you put injectors on, you gotta set those up first. Do it using STFT at IDLE. You can use RTACS feedback or whatever, but once you achieve a neutral fuel trim, you are good to start tuning other areas. To tweak the top end of the fuel inject curve, set PE to your desired A/F, then cross check w/wideband until they match. Adjust injector slope on opposite end of injector curve until they match. At that point, do a linear intepolation of the injector data between IDLE and WOT and you are done.

I did this with 36lb/hr inj.

[odd boy]

Thanks, STFT is not applicable on this case because my friend has removed the O2 sensors forever and forced the car's PCM to be in OL all the time. Not only that, due to the rail pressure (60 psi) the injector size becomes 42lb instaed of 36lb (it is rated at 45psi) !!!!!!!