MaxxAction

Hey Guys..

I just finished my LS1 300zx conversion, and am trying to get it dialed in.

I am running a return style fuel rail with adjustable FPR, and am curious what the fuel pressure should be set at?

The z motor was 38 lbs of pressure at idle, and I am wondering if that is adequate, or if I need to crank the pressure up because I read that the regulator in the stock configuration LS cars maintained 54 pounds all the way form idle to WOT.

Any input is appreciated.

Mercier

iTrader: (15)

At startup my return-style 5.3 (2002-earlier) setup runs almost 58. The vacuum signal to the on-rail regulator modifies it somewhat. High vacuum(idle) seems to give me about 48-54 and when I induce a low vacuum situation (quickly open TB) it spikes up to almost 58. This is measured by a Harbor Freight fuel pressure gauge on the test port so don't take these numbers as exact but that's the neighborhood. I suppose if you have a proper tune the lack of a vacuum-referenced FPR wouldn't matter much but that's how the stock return-style deal works, at least on a truck LS. In theory, since you have aftermarket adjustable regulator and would need a tune, you /could/ set it at whatever you want and make the tune work it out by adjusting pulse and such. At any rate, I think 58 is the number you are looking for.

I believe later LS all went to returnless and I guess would have semi-constant rail pressure.

Good luck!

MaxxAction

Thanks Mercier...

The AFr's during cruise conditions are almost perfect, and that may be because I am vacuum referencing the regulator. So under less vaccum at cruise, the pressure goes up, so the AFR is closer to balanced. But I am fighting like hell to get a steady idle.

I can make it idle fine at about 1000 RPM, but I want a lower idle. If I close the butterfly or the IACV to bring it down, then it starts hunting. I am thinking fuel pressure may be the culprit.

I been messing with motors and cars since I was about 8 yrs old, but this is the first one that I have had to electronically tune on my own. I got a lot to learn.

Mercier

iTrader: (15)

At cruise and idle you should have high vacuum and low(er) pressure..stomp the throttle and vacuum goes down and pressure should go up. Have you checked for vacuum leaks? High/hunting idle points there first. #2 is bad or malfunctioning /dirty IAC or IAC port in the throttle body.

Hopefully some of the guys that tune their own stuff can help more.