loosing fuel pressure up top?
10-19-2007, 02:31 PM
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loosing fuel pressure up top? well, I finally got the t/a tuned, and afterwards the guy told me that I was loosing fuel pressure around 5k, and it shows on the dyno results. peak power is right around 4.5 k, then it starts to drop. before the tune i was making max power at 5.3k, and with the tune it makes the same power at 5.3. the fuel pump is 15xxx miles old, as well as the filter. i replaced it when it ran out of gas. the car has 75xxx miles. what should I check first? any of you guys run into this problem? my mods are in the sig, just bolt ons, so i shouldnt need bigger injectors.
10-19-2007, 09:25 PM
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Could be the regulator is going bad - in the tank on the fuel pump holder assembly. When you say filter, do you mean the sock on the pump when you replaced the pump? Did you replace the canister filter under the car as well?
10-19-2007, 10:20 PM
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Could be a weak pump. Even though your peak power is at a lower rpm you still have to feed a larger volume of fuel to the injectors as rpm increases because you combustion cycle rate is increasing. Basing your assumtion directly off of the max HP point may not be a correct assumption.
10-20-2007, 07:38 AM
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what i was saying is that I thought that the drop right after peak power was due to the loss of fuel pressure. i would have thought that peak power would be somewhere between 5k and 5.5k
10-20-2007, 08:57 AM
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The difference is because before the tune, it was leaner throughout, but made it further in the pull before getting really lean - now the tune likely richened it up early on (which it needed to be) and its getting really lean earlier - so the power peak moved back. There is a certain lean threshold where it starts to drop power - that was moved with the tune. Make sense? But the main issue is still that you need to get the fuel issue straight and get it retuned!
