Return Fuel System and Fuel Pump Duty Cycle?

[devilish64]

I recently installed a return fuel system in my 07 gt500 so i could run E85. After I got the car running i was checking parameters on my Aeroforce gauge and the FPDC would hover around 29-30% at idle. I assume this means that the car is usnig 60% pump capacity at idle which seemed way high for twin 465lph pumps. The FPDC will go up to 100% duty cycle when getting on it a bit. Both pumps are running so i dont think I have a bad pump.... Is the PCM going to correctly read FPDC when the pumps are being triggered @ key on with relays from my Lethal wiring kit? How is FPDC calculated? I need a bit of insight on this.... im not sure if i have a problem or not:bash: THANKS

 

[Phantomhalo]

You may need a fuel pump booster if you don't already have one. My pumps were doing the same thing although they aren't as big as the 465's. I'm running ID1000's and 340lph pumps and mine were maxing out at around 4200-4500 rpms. HTH!

 

[devilish64]

i was under the impression the 465 pumps were good to 700 hp each on gas... so around 1000hp on E85. I dont think I should be maxing them out yet.

 

[Speedboosted]

I didn't think the car correctly reads Duty Cycle with a return system through the factory parameters.

 

[devilish64]

I didn't think the car correctly reads Duty Cycle with a return system through the factory parameters.

Thats what I have been thinking today.... i dont really see how it could read it correctly if the pcm isnt controlling the pumps anymore. the car runs great and the fuel pressure and air fuel ratios look good.

 

[Phantomhalo]

i was under the impression the 465 pumps were good to 700 hp each on gas... so around 1000hp on E85. I dont think I should be maxing them out yet.

I dunno but if it's maxing out then I'd check with your tuner and see what they say. I thought I was good too until the datalogs. Definitely don't want to run out of fuel at the top end.

 

[RedVenom48]

Possibly seeing duty cycle as it pertains to regular fuel and not E85? Remember you're flowing and using more than pump gas.

 

[69b302]

If your using external wiring to trigger the pumps, your PCM will not show correct values. A return system typically runs at a constant voltage and uses a regulator, to control pressure vs a returnless which modulates pump voltage. Duty cycle from the PCM is meaningless for a return system. You want to monitor FRPS to ensure adequate fuel supply.

 

[devilish64]

If your using external wiring to trigger the pumps, your PCM will not show correct values. A return system typically runs at a constant voltage and uses a regulator, to control pressure vs a returnless which modulates pump voltage. Duty cycle from the PCM is meaningless for a return system. You want to monitor FRPS to ensure adequate fuel supply.

OK cool thats what I was thinking.... i will check it out. Car seems to run great but those duty cycle numbers scared me.

 

[VNMOUS1]

I didn't think the car correctly reads Duty Cycle with a return system through the factory parameters.

This. It doesn't read correctly. I run the same system.

 

[ViperRed91GT]

Why would you not just run the pumps 100% all the time, regulate the fuel pressure, then let the injector duty cycle let you know how close you are to running out of fuel?

 

[biminiLX]

Twin 465s will take you a long way but you don't exactly just add each pumps individual limit, there's a percentage loss.
Has anyone found the limit of the twin 465 return systems with an E85 GT500?
-J

 

[VNMOUS1]

Twin 465s will take you a long way but you don't exactly just add each pumps individual limit, there's a percentage loss.
Has anyone found the limit of the twin 465 return systems with an E85 GT500?
-J

I can tell you it's at least 900+ wheel.

 

[Blackmax]

Justin at Fore Inovations has all the data for these cars.