Fuel system help.
Thread Starter
Intermediate
Joined: Nov 2019
Posts: 37
Likes: 6
Fuel system help.
I have a 1999 C5 with the FPR / fuel filter combo by the tank and am wanting advice on line size for the system I'm building.
Car is twin turboed and has a forged 346 that runs on 93 pump and 50/50 water meth. Shooting for 15ish lbs of boost and 700whp. I already have a racetronics pump in tank and a hot wire kit installed.
My plan for the fuel system is;
install a 98 fuel filter.
Add a -6 Y block and braided line under the hood from the factory feed line connection to my 99 fuel rail.
Install a 340lph secondary fuel pump that will activate via Hobbs switch at 5psi and tie it into the Y block with a -6 line as well.
Tap the tank and run a -6 feed line to the secondary pump.
add a check valve where the secondary pump ties into the Y block so fuel doesn't backflow when the secondary pump is not on.
On my 99 fuel rail from the -4 connection with the Schrader valve in it I will remove the Schrader and use a -4 to -6 adapter to run -6 line to a 1:1 regulator that will be vac / boost referenced.
From the regulator I will run a -6 return line back to the factory connection by my tank that was the original return from the 99 FPR / filter combo.
Thoughts? Is -6 feed / return line big enough to support a little over 700whp? Should I tap the tank for the -6 return line as well instead of having it go back into whatever size that factory return line is?
And last. assuming none of my lines are on an exhaust pipe, is a system like this prone to issues with fuel getting too hot or should this make fuel pressure more consistent vs my factory set up and say a BAP or something along those lines?
Car is twin turboed and has a forged 346 that runs on 93 pump and 50/50 water meth. Shooting for 15ish lbs of boost and 700whp. I already have a racetronics pump in tank and a hot wire kit installed.
My plan for the fuel system is;
install a 98 fuel filter.
Add a -6 Y block and braided line under the hood from the factory feed line connection to my 99 fuel rail.
Install a 340lph secondary fuel pump that will activate via Hobbs switch at 5psi and tie it into the Y block with a -6 line as well.
Tap the tank and run a -6 feed line to the secondary pump.
add a check valve where the secondary pump ties into the Y block so fuel doesn't backflow when the secondary pump is not on.
On my 99 fuel rail from the -4 connection with the Schrader valve in it I will remove the Schrader and use a -4 to -6 adapter to run -6 line to a 1:1 regulator that will be vac / boost referenced.
From the regulator I will run a -6 return line back to the factory connection by my tank that was the original return from the 99 FPR / filter combo.
Thoughts? Is -6 feed / return line big enough to support a little over 700whp? Should I tap the tank for the -6 return line as well instead of having it go back into whatever size that factory return line is?
And last. assuming none of my lines are on an exhaust pipe, is a system like this prone to issues with fuel getting too hot or should this make fuel pressure more consistent vs my factory set up and say a BAP or something along those lines?
Melting Slicks
Joined: Jul 2014
Posts: 2,356
Likes: 359
From: Virginia
Factory return line is 5/16"(I think, may be mixing it up with the jet pump line) but you should be fine just running the 6AN into that, the -4AN fitting on the rail will be a restriction before the 5/16" hardline.
I'd do dual 6AN feeds into a Y block with a single 8AN feed to the rails personally but you may be able to get away with 6AN. Hose and fittings are not cheap so you don't want to have to do it twice.
Run all your new lines through the rocker panel and drivers fender, no heat issues there. Yes, this setup should give you much better fuel delivery.
Also, ditch the 50/50 and just run pure meth.
I'd do dual 6AN feeds into a Y block with a single 8AN feed to the rails personally but you may be able to get away with 6AN. Hose and fittings are not cheap so you don't want to have to do it twice.
Run all your new lines through the rocker panel and drivers fender, no heat issues there. Yes, this setup should give you much better fuel delivery.
Also, ditch the 50/50 and just run pure meth.
Last edited by Turpid porpoise; Nov 27, 2019 at 11:14 AM.
Thread Starter
Intermediate
Joined: Nov 2019
Posts: 37
Likes: 6
This is what i had drawn up. Unfortunately there is zero room for fuel lines in the rocker panels since the turbo charge pipes run through them to the intercooler. (Rear mount TT set up) So the lines would have to go up next to the torque tube.. exhaust is heat wraped from manifold to the turbos though. No cats either. Not sure if the would still pick up too much heat there or not.
