Help with new fuel line size.

I just added a Vortech Supercharger to my car EFI and am now dealing with the fuel system. I originally plumbed the car with 5/16" line and now am thinking that is too small. I will be running 2 in-line pumps. I plan on connecting a canister filter from the tank then a y to split the line to each pump and then a y back to make one fuel line to the engine. I don't think that 5/16" will be enough to support my 500 hp (hopefully). Should I step up to 1/2" or just stay with 3/8"?

Thanks,
Darreld
 
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Most guys end up going with 1/2" feed and 3/8 return (-8AN/-6AN). That is the next step for my '95. The two parallel pumps and Y is a stellar idea. Make sure your canister filter can support the needed flow.

Running the numbers on a 500hp car (using 600bhp), you'll need 60lb injectors to maintain a 20% safety margin and 265lph pump capacity with a 30% safety margin. This is at 39 base fuel pressure and 0.65BSFC.

What fuel rails are you using and what is your setup now?

Wes
 
I am running stock fuel rails (weak point of the system), 42 lb injectors and 5/16" return line which may be upgraded if needed. I have an MSD and T-rex in-line pumps.

It sounds like I should just do 1/2" lines. Later I may have to upgrade to better flowing fuel rails it sounds like. What do you think? Can I get by with just doing the supply line?
 
The SN95 fuel rails get taken to >500rwhp without any problems (Search supercharger forum on Corral to find a good deal of discussion and verification from a couple qualified, professional tuners).

I put an Autometer 2246 fuel pressure sender on my rail and datalog the fuel pressure. If you can datalog MAP pressure as well, you will see the fuel pressure and supercharger pressure increase in a 1:1 ratio.

For example, your base fuel pressure might be set at 39psi (stock). With 10lb of boost, that fuel pressure will measure exactly 49psi instead of 39. If you see it drop off then you know something in the system is slacking off.

Another quick and easy test is to pull the return line and run it into a graduated container. Set your fuel pressure regulator to the maximum PSI you will see (49PSI in the example above). If you don't have an adjustable regulator, apply pressure to the regulator via an air compressor with adjustable regulator. Jumper your pumps to run (you can do this at the service connector on EEC-IV). Run it for a minute and then multiply it out measure how much flow you were getting.

FWIW, my 42s at stock fuel pressure at 14PSI boost on stock 95 5.0 longblock was right at 83% dutycycle (running 11.8:1 AFR). Putting down about 380rwhp through a 4R70W automatic. With the addition of heads and ported intake, the 42s are nearly tapped out. 60s are up next if i decide to swap the cam (left stocker in to keep HP down so the block doesn't split. I've got a 255lph pump and a Trex about to go on when I get motivated to lay down in the driveway and run it. :)

Wes
 
Call me crazy but I say you are fine... Lots of new cars have 5/16-3/8" fuel lines running aftermarket superchargers. If you look at some of the pumps out there like a Walbro 255, they have 3/8" outlets. Aeromotive carb pumps (less pressure but same volume) are capable of 700hp on 3/8" lines. The a1000 does 1000hp on 1/2"... I think you are fine where you are.
 
I am taking the car to a tuner in about 1-2 weeks. I guess I will wait on replacing the 5/16" line until I see what kind of power I am putting down. I may run into problems since I have AFR heads and a E cam. Not a radical combo buy may put me in a lean position at upper rpm's. In a way I hope the tuner will tell me to upgrade the line but if they do that means I will likely be shopping for a new shortblock some day. Thanks for the help guys.
 
On cars in the shop making 500-600 horse I like to run the following. I use the Aeromotive A1000 pump with 10an line up to a Y block and split it into two 8an lines through the rails and to the regulator, I use a 6an return all the way back to the tank. We also use anywhere from 42 up injector sizing depending on the combo. I think your injectors will work o.k. but you will have some pump/line problems once dynoed
 
You guys have talked me into putting on a 1/2" supply line. Do I really need to redo the return line or can I leave the 5/16"?

5/16 should flow enough for the return..just going to depend on what pump you are running. The more it pumps and you dont use, the more you need to feed back. While extra fuel running to the fuel rails is good, a lot of time its excessive. I think a 1/2" line will be more than enough for supply.

Im really seeing how people like to over do stuff these days... never realized it until recently.


Found this...seems to cater to carb setups though
http://www.centuryperformance.com/fuel.asp

The reason Im saying 3/8" will be enough is because my Dodge truck (diesel) was running about 400rwhp (after a HUGE driveterain loss) using a Walbro 255 pump with a 3/8" line with a return. That return was spitting a lot of fuel back into the tank. This was running about 22psi after going through 3 filters

ok, you got me really researching this... If you look at mallory's website fore the efi pumps, you will see that the 160FI pump will do 150gph at 50psi. Your fuel consumption according to the formulas above will be about 45gph. The pump is recommended with a 1/2" -8an fuel line. With that logic, that fuel line is flowing 3x the amount of fuel you need. We also know flowing more fuel is important because you dont want to go lean. So, 1/2" should be more than enough. I really think 3/8" is plenty.

Ok after reading a thread on a local board, a well respected mechanic/tuner was saying 500rwhp on stock lines (fox body and up) was fine but fuel rails should be upgraded. This guys REALLY knows his stuff. He was asked (and went to) to work on the Prince of Dubai's cars and their friends cars. The stock lines I believe were 5/16". A 255 inline pump will work great. One thing to consider also is the pickup of the tank. If its a 5/16" pickup, it doesnt matter how big of a fuel line you have, its not going to put out more fuel than a 5/16" line can.
 
On most 400 horse cars I agree that the stock p/up and lines can remain just add a 255 intank and your bigger injectors and mass. You will prolly also need an adjustable reg. to tweak it a bit but yeah that will fly I do it every day. Why are you running two inlines on y's?
 
All good advice, what I've come down to is I would rather have a bit more capacity than I need. 30% safety on the pumps and 20% safety on the injectors are the magic numbers I shoot for.

In all your calculations make sure you are figuring in the pump flow under boost where the fuel pressure is increased. (They flow less at higher PSI) Measuring your fuel flow at the rail is a great way to be sure you are not hitting a snag anywhere.

Above all, figure out a way to monitor the fuel pressure and AFR while tuning (or have your tuner do it). Every car is different so why risk it on advice from random people on the Internet on what "should" work? (myself included) They won't be around to pay for broke parts. Calculate out what you should need, add a safety net and see if that is what you have, if not, throw more money at it. :)

Wes
 
Above all, figure out a way to monitor the fuel pressure and AFR while tuning (or have your tuner do it). Every car is different so why risk it on advice from random people on the Internet on what "should" work? (myself included) They won't be around to pay for broke parts. Calculate out what you should need, add a safety net and see if that is what you have, if not, throw more money at it. :)

Wes

probably the best advice yet :nice:
 
I decided to run a because it will give me a little peace of mind if one of the pumps go out it won't take the other out with it. My system will be like this (all within 2' of the 3/8" tank outlet). 3/8" line to canister pump (good for 140 GPH) to a Y block that feeds 2 pumps (3/8" inlet and 5/16" outlet) then a y back to a single line up to the engine. I have an adjustable regulator on the engine and plan on having the car chipped.

Great advice guys! I appreciate the help.