Fuel line supply and return size needed for TII swap
 

So the time has come to pull the turbocharged 12a and replace it with a streetported TII. I'm curious what size fuel lines I should be running. I've red on here that -8 or 1/2 supply and -6 or 3/8 return is ideal. Just curious what others are running. Thanks guys!

I have a 13B-RE with single turbo, and I'm running 3/8" or -6AN supply and return. This size is common for motors making up to 500HP. I was curious what the actual pressure drop was, so I ran some calcs. The value here is more comparative than absolute, since I had to take liberal assumptions because I'm doing this on my phone between flights.

Assuming a 10ft run of aluminum tubing, 0.35" wall thickness, 75 PSI pressure, 20LPH, the 3/8" tubing yields a pressure drop of 0.75 PSI, while the 1/2" tubing only drops 0.15 PSI.

The flow resistance is much lower, but even if the real resistance is 5x what I listed due to connectors, bends, rubber hose, etc, it isn't significant enough for me to change.

Ive been running the stock 1st gen feedline with another stock 1st gen feed line for a return for 10+ years with no problems.This setup is an easy install since the curves all fit.These sizes copy the stock FC fuel line specs.
I have a Supra TT fuel pump in the tank and a streetported S5 TII engine with 550-800cc injectors and around 15-17 psi of boost.
Stock ECU relay/resistor pack,stock fuel rails,filter and regulator.....Id guess in the neighborhood of 350 crank HP for the last 50-60K miles.The factory stuff is pretty capable,Im convinced that a lot of people "upgrade" things that really dont need it,either due to misinformation,fear, or the need for shiny stuff under the hood.

http://img.photobucket.com/albums/v2...y/DSC02020.jpg

I have had quite a few FBs over the eyars and a RX3. On all of them that had any level of work done, I needed to upgrade to a 1/2 inch feed line.

The biggest issue I ran into was fuel starvation when autocrossing, road racing, or track days. The issue was the float bowls draining out, even when adjusted properly.

In the end the solution I found to work best was a holly blue fuel pump, or equivalent, and a regulator set at 7 psi, with 1/2 inch feed line. THis will keep a well tuned, emission stripped, ported, nikki carb fed well. The 1/2 inch fuel line had enough volume available at that pressure to keep the bowls filled when under high demand.

Now translating to a turbo FC engine, you will need to change that thought pattern. You need high pressure as well as the volume of fuel. And all the thought processes of the 2nd and 3rd gen crew come into play.

Run the larger lines, with your preference of FI fuel pump. Remember the FB doesnt have a in-tank pump, so you will need to find an alternative. And the GSL-SE external pump wont cut it. I had a FB with a S4 engine in it, and the GSL-SE pump would run out of gas around 5500-6000 in 3rd gear. So you will need to look at options for external FI pumps. If you are gonna be making bigger power.. then consider something like an aeromotive or SX.

Rule of thumb:
1/4" OD / 0.180" ID / -4AN for 165hp pressure or 110hp suction
5/16" OD / 0.243" ID / -5AN for 300hp pressure or 200hp suction
3/8" OD / 0.319" ID / -6AN for 500hp pressure or 335hp suction
1/2" OD / 0.444" ID / -8AN for 1000hp pressure or 675hp suction
The return line can be the same size or smaller than the feed line.

Also see the Aeromotive Power Planner:
http://aeromotiveinc.com/power-planner/

I hear about people over running the stock fuel pressure regulator with a inline walbro, is this really true? Line size dependent? I have a GSL-SE tank and lines for the swap. It's roughly 3/8" feed, 5/16" return. I suppose it might be easier to run the 3/8" return as well and re-use the stock 3/8 that's already there.

soooo...this is why the cartech kit came up for sale....wow...once you get a taste for boost. Good luck with your new set up. Although its been said already I have always seen 1/2" feed on all the better set ups.

Got a deal on an s4 I couldn't pass up