I would like to know why this happens? I mean shouldn't the car COMPENSATE???????????????? and go back to 14.7:1?

Shouldn't the car be set to go and get this AFR at certain rpm and the computer itself will get there through corrections or so?????

 

When in closed loop the PCM will adjust the pulse width and maintain 14.7. The reason you adjust the pulse with is aftermarket injectors have significantly different open times than the stock ones. If the difference is great enough the PCM can not adjust the pulse width enough to maintain 14.7 taking in to account the stock injector offsets. At idle this can be a real issue since the injector offsets make up a large portion of the pulse width. If you adjust your injector offsets so your idle BLM's are close to 128 the you are set for the rest of the RPM range.

 

Not what I was asking but a good point to take into consideration for my tunning which I had overlooked... SO THANKS!!! I just killed 2 birds with one shot

The question about the constant was the injector constant ie 30#/hr etc.

 

Yes the pcm will and does compensate in closed loop, but it can only compensate so much. If you make modifications that effect A/F you may have to make changes to certain constants and tables to keep the BLM in range so that the pcm can control the A/F properly. I try to get as clpse to 128 as possible in the cells used most often.

The other issue is open loop (initial start up and wot). The o2s are not used here so you need to make changed in constants and tables to tune for major mods that effect A/F.

 

If I'm understanding the above question correctly namely why your AFR has to be realigned with you changing paulse width to maintain the desired A/F ratio (that normally be controlled by the engine vacuum (stock FPR) and the paulse width via the PCM (the others answered it initially) but how are you adjusting the AFR to compensate? If you significantly increased injector size and paulse width, you're fuel lines or fuel pump may not be keeping up with demand. If lines are stock and your fuel pump is not matched to your injectors, your spray pattern could turn into droplets rather than misting fuel (from going lean). If your fuel rail size is increased and your fuel pump can't keep up, you will have a pressure drop @ WOT rather than an increase in fuel pressure. I don't know what you're running or how much fuel you're supplying (or the duty cycle and size or your injectors) so I may be shooting in the dark here...

edit: (if nothing in my answer is making sense, I've just awoke and a little cloudy in the thinking department)

 

I thought at WOT the car is in closed loop?

 

Your correct in that once the pcm goes into closed loop when you go WOT the pcm goes into PE mode and the o2s are not used. Good catch.

 

Didn't understand that!
At WOT is the PCM in Closed loop or Open loop.

 

Open loop (which means that the O2 sensors are not used in the fuel calculation).

Rich Krause

 

Rich ,Datamaster does report as being in closed loop at WOT once the pcm has entered closed loop ....I know that PEmode does not use the o2s.....is it just a glitch in Datamaster or is this the reason the pcm has a PE mode.