Magman

iTrader: (6)

I recently installed a fuel pressure gauge w/isolator inside the car and have been paying close attention to it moving around. It ranges from: 46 PSI at idle, 42 PSI during decel, and up to 50 PSI at WOT. VAC readings of 11-12 Hg at idle in Park. In an attempt to increase Idle VAC and drop fuel PSI at idle, I have changed the timing, re-adjusted the IAC and TPS, only to learn the IAC keeps re-opening to maintain engine idle at 900 rpm (hence, vacuum leak). I cant get the IAC counts any lower than approx 56, or at least don't know how to...yet.

I'm thinking... at idle, the VAC should be the highest, at part cruise it should lower and WOT should be zero. Is this right?

Also, how does everyone get IAC counts down so low? I've read to set IAC at zero, 10, no more than 30??? Like I said, mine won't go below 56.

Car is a 1990 IROC, 383 w/6"rods, Cam has 230/236 dur and 544/555 lift, AFR Al heads and Ive been tuning the 730 via TPRT.

Thanks in advance!

rx7speed

get rid of the motor and put a 2.8 in there. it's the only way to make power.


sorry I had to.


just curious though if you had a system setup for fairly high rpms. lopy cam, big heads, nice exhaust manifold, huge intake, couldn't that cause this?

might also want to check to make sure the IAC has full movement and isn't gunked a tad bit. vacuum leaks doubtfull but hey worht a shot I guess. and does your car have a idle speed screw seperate from the IAC?

Magman

iTrader: (6)

You've obviously been engaged in other posts regarding a 2.8 spinning it's tire and tons of power!

Yeah, guess I could take the IAC apart for cleaning but since I havent noticed any discrepancies with it I never have.

The CPU controls the Idle speed through the IAC dependent on the positioning of the throttle blades, a change to one, changes the other. I've reached the max adjustment on my idle RPM screw at the throttle blades so maybe I'll start over after I clean the IAC. It's running great, but I'm always looking for ways to impove it and maybe even find some more power!

Sonix

iTrader: (1)

230/236 in a 383 should give 14" vacuum or so....

highest vacuum is during engine braking 20+
then cruise 16
then idle 13
then WOT 1

those #'s are total guesses, but that's the ballpark idea.