had FP at 20 lbs to fuel adequately at WOT. had issues with idle quality as injectors had problems with getting BPW small enough. results evident on WB with significant fluctuations of A/F super rich/super lean with corresponding IAC activity to prevent engine dying. this was more evident when engine fully heat soaked and temp at 200F.

i set commanded idle speed to 650 and manually set idle stop screw to idle at 750 with 0 IAC steps. that was a faillure. no help.

dropped FP to 17.5 lbs. idle quality improved. seems relatively stable on WB at 900 rpms. did not check WOT A/F yet for 17.5 lbs.

BLMS went from 126-130 right to 136-150 accross the board. so a small(??) change in FP made a large change in tune.

i am thinking the cam and injector size and CID may be over the edge to enable a decent tune with satisfactory drivability?

 

Ron,

You may seriously want to look at upgrading to an 8625 PCM.
Part of the problem you're experiencing comes from a VE table that is just plain too coarse. There isn't enough resolution to properly maintain the AFR. You may be able to get to an adequate AFR at a lower FP, but the DC% will be too high. I started out at 10.5 psi and idle was great. ben73 is running 90# injectors at 20psi and seems to be having little problem with idle. His 383 may allow him to have a PW sufficiently long enough to avoid the issues you and I have experienced. Try running O/L idle. That seems to be working best for me. If you'd like, send me a copy of your bin too.

 

thanks Dom. i did run OL for a week before i upped FP to 20. then i had to go CL and reconfiqure my VE for the FP change. i noticed when in OL idle was much improved however that tune was running 12.5/1 at idle and around maybe 12.50 to 13.50/1 at cruise speeds. i was concerned about fuel mileage(50miles a day) so went back to CL. i will get VE optimized and try again OL. time to research that 8625! car runs great till i get to drive thru at McD's !

 

i will send bin after i work it over a bit. i am certain it has some shortcomings!

 

Ron,

If you have a 7.4L bin, you'll see settings for running O/L Idle.
I have mine set so that it goes C/L once I get past 10mph or 1400rpm. Once in C/L, my AFR is in the 14.7-15.1 range for cruise. That's why this is a bit frustrating because it runs great otherwise. My O/L Idle is in the mid 13's. One thing I have found is that AFR from the WB doesn't necessarily track with the BLM's.

 

was not aware of that feature in a 7.4L bin. i may need tunercat to modify my program. they have added other parameters for me before. i suspect that may be all i need to conform my currrent bin. in fact i think i am using the one you provided (yours) a while back.

 

The 7747 can control the idle with some luck and good advice.

I made significant gains in my idle this week by following Rbob's advice in his IAC article. When engine is completely warmed up to 180, IAC count is 10 in gear and 5 in p/n. I lowered timing at idle and raised the delay setting as per the article. I now have a good idle between 775 and 825 in p/n and a steady 650 in gear. I'm going to level out the VE table at idle to see if I get further improvements.

Low speed drivability has greatly improved now.

 

Look in the hack for something like this;
"AE - IAC opening additional bpw" I don't know for sure if it's in the $42 code but I bet it is.
Notice how the title says additional bpw. Increase your fuel pressure and you'll want to decrease this value a LOT. Do it at least proportional to the injector flow rate. Sorry I don't have the location for the $42 mask but it shouldn't take long to find it. Maybe somebody'll have some time on their hands and find it, if not, I MIGHT get around to it later.