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SuperG
04-03-2006, 11:06 AM
What fuel pressures do you guys typically see during boost, say from 4-8 psi?

When my booster pump (T-Rex) was running, I saw up to 60 psi and the car ran really strong. The T-Rex has since failed, so going with the recommendation from Vortech and many Cobra owners, I had a Walbro 255 lph fuel pump installed to replace the stock fuel pump and the T-Rex. However, the installers kept the lousy T-Rex inline, so I see absolutely no gain in performance. I will remove the T-Rex, but what fuel pressures should I expect from the Walbro?

Thanks for any help!

tcrews
04-03-2006, 08:47 PM
With the stock setup you probably have an 8:1 FMU as well (or did you go with larger injectors?).

Either way....you want to see the same pressure if that is what your original tune had. The only time you'll want a pressure drop is if you move to larger sized injectors that can deliver the same fuel "volume" but at a lower fuel "pressure".

I remember on my stock kit I saw over 80psi FP at 8psi boost with the 24# injectors, 8:1 FMU and 255lph intank and T-rex inline pump.

With the 42# injectors, 4:1 FMU, Bosch 390 inline and KB boost-a-pump I was seeing around 60 psi FP @ 16 psi.

tcrews
04-03-2006, 08:51 PM
However, the installers kept the lousy T-Rex inline, so I see absolutely no gain in performance. Just an FYI you should never see a gain in performance from changing out your fuel pump. You'll either have a better fuel delivery setup (doesn't have to work as hard) or you'll have the ability to deliver 'more' fuel that with more boost (powerpipe, smaller pulley, etc..) you could tune more power in.

SuperG
04-04-2006, 07:46 AM
Just an FYI you should never see a gain in performance from changing out your fuel pump. You'll either have a better fuel delivery setup (doesn't have to work as hard) or you'll have the ability to deliver 'more' fuel that with more boost (powerpipe, smaller pulley, etc..) you could tune more power in.
Tom, thanks for your replies to both of my posts! That helps a lot! What I meant about increased performance is that without the T-Rex working, I cannot get high enough fuel pressure/volume at higher boost levels, thus I believe I am running lean...when I got the T-Rex running it was like night and day under boost. And you're right...with the stock fuel pump, that booster does scream like a banshee!

I also have the 8:1 FMU and stock injectors. Next round of upgrades will certainly include bigger injectors, but until now, i did not even think that I might want to change out the FMU.

For now, i will remove the booster pump and see what happens. If pressures aren't where thet need to be, I'll get another booster. Thanks again!