MrJ

Lately, I've been reading that the stock TPI PROM has these cars running rich from the factory. I am using a quarter to bump the fuel pressure up by approx. 5 psi. What the actual pressure is, I don't know. Should I set the FP back to stock for now? I am running an almost completely stock engine, the only mods are a fully ported TPI setup and catback exhaust w/ high flow cat. One reason I had thought of this is due to the fact that when it is cold out, say 30 degrees, the car runs like an animal compared to when it's warmer.... like I'm talking what feels like a half second in the 1/4 mile faster.

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91 Trans Am WS6
Bright White
5.0 TPI auto
Flowmaster 3" 2 chamber catback
Trans Go shiftkit
2000 stall converter

Built on Wednesday

The ODB

I would.
I ran mine as lean as it would go before lean-misfire set in. It got faster up until that point.
If you want more accurate fuel correction for the outside air, then just move your MAT up into the plastic air duct.



[This message has been edited by The ODB (edited February 25, 2001).]

theformula

Go back to stock. Glenn Matus can tell you how rich these cars already run from the factory.

Re-located MAT is not something you want by the way. I have a detailed email from Glenn about the harmul effects it has on performance.

As for the fuel pressure, the car feels faster in colder weather due to the air being denser. Denser air, means more air is able to cram itself in.

I too believed high FP meant higher HP. But after all the different FP settings I've run and butt dyno tests.... stock always felt faster. I ran 47psi for a long time I think because I felt bad about spending $66 on an AFPR



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91 Formula
305 TPI 5speed
1LE/G92/WS6

Paxton SN92 polished kit, SLP airfoil, ported/polished plenum, March pulleys, Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL,MSD boost-master,Holley 9mm wires,Ac delco R43ts plugs,custom chip,Ford SVO 24# injectors,Bosch O2sensor, Bosch in-line pump(w/stock pump), SLP 1 5/8" headers,SLP catback,short shifter,3:73s w/Auburn posi,170* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

Darrell

iTrader: (1)

So what you are saying is stock pressure (approx. 43psi) is better?? I have mine set to 48 psi with the mods listed below.. I know in a few of the books that I have they gave their horsepower and torque increases and showed that more was a little better. Also would this increased gas flow affect milage much?
Darrell

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1991 GTA L98
K&N Filter, Subframe Connectors, 3.73 Gears, Hypertech Airfoil, Ported Plenum, Underdrive Pulleys, Flowmaster Catback, no cats, Hypertech AFPR, Fastchip.

theformula

The company that stresses to run higher FP and shows dyno increases is TPIS. As far as I'm concerned, they are in it to make money. They sell other companies products for 25% more to us. Not to mention, their TPIS insider hints book is basically a huge subliminal message saying "BY OUR STUFF." Hell, I found their free catalog I just received more useful then TPIS insider hints.

Higher fuel pressure will affect your mileage negatively, it will also decrease the life of your regulator and fuel pump. That is why I also chose 24#injectors, so I can run relatively low FP while retaining normal life on my fuel system.
With the mods listed, your fuel pressure is set way too high. You want to be as lean as possible without detonation. That is where optimum power is made. Set your fuel pressure back to stock. If you really want to see results, get into PROM burning and slowly lean yourself out.

Some other ramblings.Another "mistake" mod that makes cars run richer (as I was taught by a friend) is the low temp t-stat. Since I run a blower, I wanted the extra insurance. My car makes more power with a 195* and stock (rt45)plugs because I have actually experienced a 160* stat before. I would have this setup right now if I did't have a blower. Thats why I run plugs two stages colder and run a Ac delco 170* thermostat. I recommend this stat because it actually runs at 176*. Which I find to be a happy medium. However, if I was not blown..I'd be running a stock T-stat and hotter plugs.

I also see you have a Hypertech chip. I don't know about the chip you have, but the stage II chips require a lower t-stat right? I have figured out that this is a type of "insurance" chip companies use to prevent you from blowing up the motor. All those chips are, is just more aggresive timing curves. (another thing I learned from a friend)


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91 Formula
305 TPI 5speed
1LE/G92/WS6

Paxton SN92 polished kit, SLP airfoil, ported/polished plenum, March pulleys, Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL,MSD boost-master,Holley 9mm wires,Ac delco R43ts plugs,custom chip,Ford SVO 24# injectors,Bosch O2sensor, Bosch in-line pump(w/stock pump), SLP 1 5/8" headers,SLP catback,short shifter,3:73s w/Auburn posi,170* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

[This message has been edited by theformula (edited February 25, 2001).]

F22Raptor

What's the stock pressure on a '88 350.
Rick

Darrell

iTrader: (1)

Hey theformula..actually I have the Ed Wright Stage 1 fastchip and the 160 degree thermostat. (I just cleaned my signature a bit so should be more clear.
Darrell

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1991 GTA L98
K&N Filter, Subframe Connectors, 3.73 Gears, Hypertech Airfoil, Ported Plenum, Underdrive Pulleys, Flowmaster Catback, no cats, Hypertech AFPR,Ed Wright Stage I Fastchip, and a 160 Thermostat.

Darrell

iTrader: (1)

Hey theformula..actually I have the Ed Wright Stage 1 fastchip and the 160 degree thermostat. (I just cleaned my signature a bit so should be more clear.
Darrell

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1991 GTA L98
K&N Filter, Subframe Connectors, 3.73 Gears, Hypertech Airfoil, Ported Plenum, Underdrive Pulleys, Flowmaster Catback, no cats, Hypertech AFPR,Ed Wright Stage I Fastchip, and a 160 Thermostat.

theformula

Definitely set your fp back to stock then