What fuel pressure on a minor bolt-on car?

Base fuel press

DaveB said:

I've had a slight over-heating problem since I did a big round of mods in the summer

-BBK LT headers
-Dr. Gas offroad x-pipe
-ASP Smog pump eliminator
-new plugs/wires/cap and rotor

Right after I did that round of mods, my car would run really hot. A couple times on the highway it got as high as the L in normal . And thats cruising at 2k rpm. If the car would just idle, it wouldn't go above the R. FWIW I have ASP pullies, but they never gave me a problem until after that round of mods.

I took the car to my mechanic, who said it was the car running lean (FWIW, the car has never had detonation, even when the temps were sky-high). He suggested I put in an AFPR, which I did. The instructions (Aeromotive) said to set the pressure at 47 psi. This helped a lot. But the temps will still get up there if Im messing around a lot.

But anyway, whats everyone's fuel pressure set at? The other mods that I have besides those listed above are:

-14* timing
-Densecharger intake
-ASP pullies
-Dynomax Catback

Last time I got an oil change (Im due for one soon), my mechanic said that if I lowered the fuel pressure, I would richen it up a bit, and the car would run cooler temps. Next time I go there, Im having the pressure lowered, but I was wondering to what. I've done a search and see people ranging from 40-44 psi. Should I just try 42? Thanks.

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Typically you can get away with 40psi (vac off) with 24# inj. I assume you're running the stock 19#s. One thing that may be causing the lean condition is the long tubes. With them installed the O2 sensors or now farther back in the exhaust flow causing erroneous readings to the EEC.

Do a search for Long tubes and PM some of the guys who have them. I also know that depending on whether they are ceramic coated makes a difference too since they run cooler.

Wayne

If anything the longtubes should cause you to run richer not leaner. What happens is the O2 sensors cool off a bit (they need to be at 600+ degrees to read accurately) and as they cool off they give the EEC a false lean condition, which it corrects for by adding fuel. This tends to only be a problem at idle, during cold (40-50*) weather. Anything warmer than that, or at higher engine speeds, and the O2's stay nice and warm.

Now, there is also some difference in the tuning because of the distance of the O2 sensors, which isn't related to their temperature or accuracy, but I can't see it causing you a lean condition.

I don't think any of the mods you've listed are likely to be the culprit, it's probably something unrelated. "L" on my car is unheard of, even on 100* days with the A/C on. Stock fuel pressure is 39 psi, and adjusting your fuel pressure is strictly a short-term solution anyway -- the EEC will adjust fuel trim based on O2 sensor feedback. By setting it at 47 psi, you effectively make the injectors act bigger than 19#. That'll throw the EEC off for a little bit and you'll run richer, but the EEC will figure it out and adjust for it (within limits -- plus or minus 25%).

What do your plugs look like now? If it's running lean, they'll be white. And if it's lean enough to cause your car to run *that* hot, they should be snow white. I'd check cooling system related stuff, thermostat, radiator, water pump, etc.

Dave

I'd tend to agree with Dave....I don't see a link between the LTs and your cooling issue, no doubt its there and your seeing it on your gage. you could be way way lean and that would do something, but you say you set your FP to 47...thats alot of fuel..I run 38 lbs at the moment..

They aren't the most accurate gages, but your car can run up to 200+ before the fan kicks on. Does it stay at the A or L ?? or come down...

Try this out...its seems crazy but works on my car when it gets to doing what your sayin, i have an Autometer and the factory gages to...Next time it gets up there in the A area, flick the fan on High....watch your gage, within a few minutes it should drop right down..I can do this one mine and it'll go from 200 to 190 in minutes, i run a 192 stat...When i see it running high, i flick the fan on 2, it cools it down..i shut the fan off...try it...I would really like to see if it works for others....

Did you say you changed the temp sensor on the intake too??

What method did you use to lengthen your O2 wires? Perhaps if it's ghetto style, you may have bad readings due to electrical issues. I seem to remember someone saying that he spliced random wires in himself, and had problems. Did you use a manufactured harness?

Rick

Dave, I just reinstalled my LTs along with a Performer intake. No overheating here. Ive got an AFPR set at 40 (no vac)

QUOTE "Perhaps if it's ghetto style."

I like that one. Have to remember this.