Toy4Bob

I didn't buy gauges just for looks, but need some education on what the heck I am looking at. I did a "fast" record today on both scan gauges at the same time, and what you see below are in sync with each other. Some questions come to my mind, hoping you all can advise.

I understood that while under heavy acceleration/boost, the fuel pressure should be up over the idle or cruising reading of my normal 39. Seems here it dropped into mid/hi 20's under acceleration, and went up when letting off the gas. Did have a few times that it was up, but a couple quick glances at the A/F gauge thru the run showed lean, I did catch a reading of 12. While i wasn't watching fuel pressure last week under some runs, I was watching the A/F and thought most times under heavy acceleration it went toward the rich side, and lean when I let off. so, should I be concerned?

Notice the 500+ HP readings. While I know this Saleen SS kit should not be over 500, I will say that running the gauges all last summer before i went FI, I never saw the gauge read over 300.

And one more, a boost question. I am guessing my gauge is not reading correctly, since I saw close to 9 psi, and Brenspeed said I should see 6.5 to 7 at most. If I turn the ignition on without starting the car, it does read zero though.

If it matters, it was about 20 degrees F today.

Left gauge---------Right Gauge
Boost--------------Pedal Position %
Fuel Pres-----------HP

BruceH

.......

Jersey Stang

did you go with BAP or GT500 pumps? sounds like either one is not working properly. that would give you the low fuel pressure. After my install, i noticed the same thing where fuel pressure would drop during acceleration and pick up after i let off the gas. It turned out I forgot to adjust the BAP to max. that quickly solved everything.

Toy4Bob

No upgrade to pump at all, Brenspeed doesn't add anything to their kits until you get to a stage 3 on the Saleen, and when I asked them about it said it wasn't needed. The car seems to run fine, just had concerns that in the long term it could be causing a better chance of engine damage.

Toy4Bob

Thanks for the info Bruce, will check it out.

Jersey Stang

brenspeed said you don't need a BAP on 9psi? that's strange. I have the stage 3 that puts out about 9-10psi and I use a BAP. I think at the very least, a BAP is recommened over stock pumps

moosestang

I'm not sure what is going on there, but the fuel pressure dropping doesn't seem right. I've recorded my fuel pressure using the aeroforce gauge and it steadily increases and then jumps to 70 for a split second when I let off.

Did Brenspeed do the install? What is your vacuum at idle? I would contact brenspeed about the fuel pressure, it should not be that low at wide open throttle.

moosestang

Are you an auto or manual? Did you get the car dyno tuned?

The most HP i've recorded is 549. Next time record your MAF lbs/min. I record my MAF readings and got 63.23 lbs/min and 543hp, that's the highest MAF reading i've seen on my car.

tx_zstang

Yeah it would seem the fuel pressure should stay up there until you let off the gas, and it could then spike up afterwards. Seeing your fuel pump duty cycle would help tell us if your pump is getting max'd out, too (just a suggestion).

moosestang

+1 on recording the duty cycle, but I think there's a vacuum problem or a problem with the stock fuel pressure sensor.