Idle PW and VAFPR

[whatif3387]

Can anyone offer me any incite on what an acceptable minimum pulse width would be. I'm currently at 15 psi with 80# injs. I just recently realized I don't have enough fuel pressure to achieve less then 85%dc at wot so I'm going to have to increase fuel pressure and redo my VE tables. I have yet to increase my pressure and start redoing my VE learns because I'm unsure if I should invest in a VAFPR first. My engine idles perfectly smooth at about 12-12.5:1 AFR in openloop. Once it goes closed loop I begin to have issues with stalling. This was much much worse before I greatly reduced my PROP gains tables. Adjusting them has helped a ton. I've noticed when it idles closed loop it trys to lean out the AFR to 14.7:1 the PW drops to .9 and it almost stalls and catchs it self and AFR drops to 12:1 then on its way back up to 14.7:1 it almost stalls or stalls. I know I could just run an openloop idle but I'm currently trying to get everything squared away so that I can get through my states emissions testing. I've read there are things that can be done with the tune to work around this issue. But if I can save myself headaches by adding a VAFPR I will likely purchase one since in the future I plan on having to increase my pressure even more when I add a larger cam, better intake, and possibly better heads.

[PJG1173]

sounds like you have a big lumpy cam. what code/computer are you running?

[whatif3387]

Sorry I guess I should of mentioned it in my post I need to make a signature. It's a 1995 c1500 I swapped my old 5.7 tbi engine for a new GM vortec L31 5.7. I'm running the GMPP TBI vortec intake manifold with a bored 5.7 TBI with 80# injs at 15 psi. The motors 100% stock besides the 1.6 roller rockers I added along with long tube headers Y pipe 3" exhaust and flowmaster 10 series as well as electric fans. The truck came with a 7427 ecu which I still have but I'm only using it to control my 4l60E. I have an EBL flash piggy backed to control my motor. I realize this is the wrong section for the EBL but from what Ive read I believe most of the code is based off of the 7427 and 7747 ecu's. So I'm not really looking for advice on what parameters I need to look at to fix my problem as I believe its related to having to low of a PW at idle with the 80# injectors causing an erratic idle. I'm wondering if this is something people with a similiar setup has experienced and tuned around and If the addition of a VAFPR would help. With the VAFPR I could turn up my fuel pressure for what I need at WOT and have the pressure down to whatever I need to maintain a good solid idle with a larger PW.???

[PJG1173]

I doubt a VAFPR will help. that us usually used to compensate for pressure differentials involved with injectors exposed directly to manifold vacuum. I did have a similar issue when I put headers on my vortec 350. I have a long duration cam so I run open loop idle. I've tried simulating a NB with my wb and changing the idle lean/rich o2 voltage table with little luck.

[1BadAction]

Idle and off-idle target o2 voltages need to be adjusted higher so it's not trying to lean the piss out of the engine at idle and off idle. (and for anyone else reading this) Depending on the cam/compression/heads, you may need to go lower or higher than stock with these numbers. It all depends on how much "air" the overlap of the cam is pulling into the exhaust at idle.

Screen cap of the 7427 parameters below.

http://i.imgur.com/XC80SbG.jpg

[whatif3387]

Idle and off-idle target o2 voltages need to be adjusted higher so it's not trying to lean the piss out of the engine at idle and off idle. (and for anyone else reading this) Depending on the cam/compression/heads, you may need to go lower or higher than stock with these numbers. It all depends on how much "air" the overlap of the cam is pulling into the exhaust at idle.

Screen cap of the 7427 parameters below.



http://i.imgur.com/XC80SbG.jpg

That is very helpful thank you I'll give that stuff a look this week.