0rion

iTrader: (1)

Car 98 H/C vette TR 230 cam on a 112lsa

I'm just curious what side effects would be caused by high fuel pressure? The guy bought the car used and it already had mods. I checked the fuel pressure on the rail and at idle it was 68 psi. I think the previous owner did that to keep from replacing the injectors?? That's the only reason I can think of. The drawback is the car is rich at idle and low rpm cruising. I'm just making sure that my theory is correct.

bigredexpress99

iTrader: (15)

yeah, a rich idle and no load/cruise situation sounds like what would come of that. Anyhone else?

txhorns281

iTrader: (12)

That's pretty much it... At a higher rail pressure, your injectors are flowing more than they are expected to by the PCM's calculation. Thus, the window that the injectors are open for are allowing more fuel then needed and causing your richness and surging. The fix:

IFRs

0rion

iTrader: (1)

Thanks for the replies. I think the first thing I'm going to do is put his fuel pressure back to 58psi and see where his injectors are at and maybe have him buy new injectors. I already know he's going to need some. I figured his injector duty cycle and even with the high pressure he was right on the fringe at 80%. Lower that fuel pressure by 10 psi and those injectors are no longer cutting the mustard. Since it's a 98 he has the 28 lb/hr injectors. How much difference would there be between those and 30 lb/hr? I know 2 lb/hr but I mean as far as his duty cycle. Will 2 lb/hr be enough?

txhorns281

iTrader: (12)

You can still run 68 psi, but you just need to refigure your IFR (Injector Flow Rates) to accurately reference the type of flow the sotck injectors would see at that pressure. At 4 bar (58 psi) they are rated to 28#s, well at 68 psi, they will definitely flow more like 30#s or so, so you need to tell the PCM that they are flowing XX.XX lb/hr.

0rion

iTrader: (1)

Thanks for the info. So I shouldn't mess with taking everything back to stock and starting over? Just figure the IFR table at the low RPM's and be done with it?

txhorns281

iTrader: (12)

refigure the IFRs, and from there, if you need to retune anything due to ill trimming or whatnot, then go through the VE tuning process again and all will be well.

Black02SS

iTrader: (36)

I had the same problem with my car after I added my fuel pumps. I have scaled my IFR table by 3% and found out that after I got my VE table dialed in and smooth, the psi went back to a solid 62-64 psi. This is with a inline and intank 225lph pump on stock 28lb inj. I have since fixed the rich idle, smell, and other problems.