Engine/Transmission (1994 - 1998) Fuel line size for 400hp CTD

[bluthndr]

I know there are a few posts on here about this, but nothing specifically for what I'm looking for. I am replumbing my gas fuel system for the diesel swap, and I see that the fuel line is 3/8 into the pump with a 5/16 return.



Is that plenty of fuel (volume) for a 400 - 500hp Cummins, or should I be trying to put in 1/2" supply and 3/8" rtn. The reason I ask is because even if I run 1/2" supply, arent' I still limited to the 3/8" supply inlet at the pump (on the engine?).



Along those lines, have any of you guys running bigger turbos or twins had to change the stock fuel line size(s)? I understand that 1/2" would be plenty, but it would be a hassle to make all the step-up/step-down connections at the sender and the pump - especially if it's not necessary.

 

[Joseph Donnelly]

stock fuel feed lines @ 633. 8 hp on the Dynojet.

 

[Jim Fulmer]

Stock system does good but there is a limit and it depends on what you want to live with, most of the time and on a dyno as they are no a big load the fuel pressure drop is no issue, if your at 500 HP and doing a high MPH pass or racing and your pressure is dropping from say 30 to 15 or lower then there is an issue but there is no need in changing out the hole system, keep the stock system in place and buy or build and aux system as a helper, I have one and it works just like I want it too keeping fuel pressures up high at all times the switch is on and no they are not expensive.



Jim

 

[illflem]

I don't know how much fuel a 5. 9 is rated to use at full load per hp but here's simple way to look at it that is far from scientific but gives a good comparison.



100ft of 3/8 ID hose will flow 1gpm(60gph) water (diesel is probably more) with less than 1psi of pressure drop.

So if you were getting 1 mpg you could travel 60 miles or 60mph.

Carrying this out to 5 mpg you could go 300 mph.

So even with very poor fuel economy of 10 mpg 3/8'' hose will supply enough fuel to go 600mph.

I think 3/8" hose/tubing is plenty big especially when you consider less than 10 feet is used in our application. This doesn't take into consideration any restrictions such as elbows, filters, lift pump capacity (crummy 24 valve pump only does 47gph, not sure of 12valve pump), etc but still leaves plenty of room for extra fuel.

1/2'' hose is rated at 3. 6 gpm (216gph) with less than 1psi drop/100ft = enough fuel to go 216mph @ 1 mpg or 2160 mph @ 10mpg. Now you're talking racing a F-15.