Hi All,

I read the tech pages regarding the dyno runs on the AFPR with L98. The results were stunning to say the least -- an L98 seeing in excess of 50lb torque gains by increasing fuel pressure to 50 lbs ?!?!? There must be something up with this info ?

I was wondering if anyone could substantiate the numbers from the graph ? (See tech pages under engine/exhaust/induction).

Has anyone installed a 50lb afpr and seen any results ?

thx, RP.


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'91 Formula Firebird G92,WS6,5-speed,3.42 a ton of fun to drive.

 

Hey, I just finished wondering the same thing myself. From what I've read, it's not possible to gain that much in the stock application like the FAQ says. Do a search and you should turn up some info. I'll try to link some now though...

https://www.thirdgen.org/messgboard/...ML/000763.html

https://www.thirdgen.org/messgboard/...ML/007375.html

I haven't added the afpr myself, so no personal expirence. I'm sure someone else will come along and spread more light on the subject though.

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Stock 1991 L98...for now.

 

Only if the L98 had severely low fuel pressure or mods requiring more fuel but did not have the proper eprom.

FYI, stock TPIs tend to be overly rich as they are. This is all caused by the eprom. Yes, higher fuel pressure does help with atomization, but if your eprom is not adjusted to compensate for the additional fuel (if it's a stock engine), then you will most likely run overly rich @ WOT and most likely go slower.

If you can alter the eprom to give a shorter pulse width, then the higher fuel pressure can have some nice benefits...but not 50 lb/ft of TQ by itself.

In the "good old days" before eprom burning was popular and "available for the masses", raising fuel pressure as a tuning tactic to correct for modified engines that NEEDED extra fuel. Today with eprom burning, that is the route to go and setting your fuel pressure to 46-48 psi to get good atomization. But the extra HP is from the mods and tweaks to the eprom. The actual gain from the higher fuel pressure is not a lot.

On a BONE STOCK engine, extra fuel pressure will help with your "throttle response" at part-throttle. But this is just like giving your engine a "bigger Pump Shot" via the eprom. So it's a "false placebo", as you generally hurt performance on a bone stock engine because "lack of fuel" is not the problem with these engines. "Lack of air" is...or should I say, the inability to move a lot of air when your rpms > 4,500 rpm.

 

I see you've read the TPIS propaganda too. Its got to be a typo or a misprint, but they've never corrected it.

I cant remember anymore, but I think I did do a fuel pressure test on one of my engines way back when. I went from 42 to 46 to 50 PSI, and I think I gained all of 7 HP and 5 TQ at the rear wheels.


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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH (2.10 60')
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

 

Well you guys pretty much made it clear then. Whatever the circumstances were of the AFPR dyno test it would be hard to replicate in 'real life'. For what it is worth it didn't make sense to me that you could see 40+hp and lbs torque out of a simple increase in fuel pressure ?

Somebody ought to remove the article from the tech pages because it is misleading.

RP.

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'91 Formula Firebird G92,WS6,5-speed,3.42 a ton of fun to drive.