need help with fuel system in a big way.

[azkkn]

i just finished the build up of an lt1. i used a vortech v-2 s/c kit and the injectors that come with it, along with the fuel pump that they give you. the motor also has new forged pistons, a pretty good sized cam, hooker headers, borla exhaust, lt4 intake, afr 210cc heads, lingenfelter 58mm tb, and a crane ignition system, with timing retard for the boost. i dynoed the car yesterday, if you ease into the gas it rips, if you floor it it back fires and sputters. the FMU that vortech gives you is not working, so i know i need to get a new rising rate FPR. the car made 386 hp at the wheels and 425 ftlbs of tq. with 7~8 lbs of boost. what do i need to do with the fuel system? also its in a 1992 vette, with a prom style computer, wich is still stock. just need a little help

[Squat13]

remember that the Injectors and pump with the vortech kit are for installs on a Stock motor with a stock cam. That maybe your problem. It just wants more gas. I would increase the fuel pressure as much as I could until it runs better, and if that doesnt work, your going to need new injectors or a sick pump.
Edit: or did you let vortech know you were using a Big cam when you ordered the kit?

[fastTa]

Sounds like you are still getting too much timing advance and/or too much overall timing. What size injector did Vortech include with the kit? When you had the car on the dyno what was the duty cycle of the injectors? How was the a/f curve on the wideband?

The FMU's that come with the Vortech kits and even the Procharger kits are not regarding as very good by most.

Did you verify the fuel pressure on the dyno at the FPR and output of the fuel rail? Did you compare the change in fuel psi to MAP values?

Standard adjustable FPR's use pretty simple and straight forward fuel maps to control the fuel trim, but when you get the rising rate FPR, you will have to program the fuel maps with the appropriate rising rate ratio in accordance with the MAP readings.

Another thing you should do is determine how much flywheel HP you should be able to make with this motor at 7-8 psi. Then multiply that HP # by a BSFC (Brake Specific Fuel Consumption). It will usually be .55 - .60 for FI applications. Then take the number of injectors that will feed from the rail and multiply them by a target duty cycle of 80% (this will leave you some room for additional enrichment just in case ). Then divide your first answer (HP*BSFC) by your last answer (# of injectors*80%) and this will give a close idea of the appropriate injector flow rate you should have.

For example:

1. 500hp x .6 = 300
2. 8 x .8 = 6.4
3. 300 / 6.4 = 46.88 lb/hr

This equation assumes a stable fuel pressure differential of 43.5 psi.

Here is an online calculator:

http://www.mindspring.com/~steveflye...ector_size.htm

[Squat13]

Man the moderatos need to write a book. Id buy it........but then I would never need to go back to this site