question on upgrading fuel lines - difficult to remove stock lines?
 

i'm planning on upgrading my fuel lines to stainless braided ones, and was wondering how hard it is to replace the hard lines that go under the car and in the engine compartment. are the oem supply and return lines somehow linked together under the car? is it a simple unbolt and remove affair? i currently have a parallel fuel setup with an intank and external pump and i plan to upgrade the oem supply line after the "Y". Can i simply replace the supply line and leave the return line in place if i decide to keep the stock return line? i plan to upgrade to 8an supply. i will be running an aftermarket fuel rail and regulator.

I'm going to ask for my own fuel system sticky soon...

1) There is NO reason to use ANYTHING bigger than a -6 feed line. Period. I'm currently making 790WHP on E85 with -6 Feed line, stock regulator, stock return line. Buschur DP W/modded 255's supplies it. I started to see the stock fuel feed line becoming a restriction at around 700whp, and the -6 feed line TOTALLY solved that.

2)Use Aeroquip pushloc. It's the most readily available Ethanol compatable fuel line. Most of your braided line is not, and even if you can find it compatible, it's more expensive, heavier, and a PITA to cut/terminate.

Good info. Thanks. Can u explain how u replaced the stock feed line then?

I left it in place (incase I wanted to use it in the future), and used Adel clamps to hold the new line.

fair enough...

Hard line (e.g., stainless steel tubing) is a better option.

Enlighten me

Stainless tubing is guaranteed to last forever. Good quality braided line that you suggest is fine but at some point, it will need to be replaced. I suppose it depends on the timespan that's important. 10 years of life from ethanol compatible braided line seems quite reasonable, so it should be good for most people.

Show me where I suggested braided line...

ok, you got me, Aeroquip Socketless (I assume this is what you meant by pushloc) has a rubber external sheath and not a braided external sheath.

{thumbup}

Properly routed, it'll last the life of the car. Even if it had to be replaced once or twice, it's still way easier than farting around with bending a solid line. Aluminum is not compatible with all fluids, and stainless is a pain to flare correctly.

When I bought my car it came with a blue -6AN Aeroquip hose running from pump to fuel rail. I changed it for a black one -aesthetics, you know - mostly because I was concerned about a 7 year old hose. On the end the old hose was fine, without cracks and no britle feeling. At least I´ve got a cleaner looking engine.

So I did a bit of research on ethanol compatible hose. Aeroquip socketless looks fine, but its not obvious to me that there is something about it that makes it stand above the rest. Goodridge 811 or 910 PTFE lined smooth bore hose looks good to me, and attaching the AN fittings doesn't look difficult.

I've not had time to get a look under the car - is there a fitting, e.g. at the transition from flex to hardline, where I can easily switch over to hose?

For kicks, I did a few pressure drop calculations using different ID fuel lines and flow rates (http://www.pressure-drop.com)

**Inputs**
- Fuel line length - 10 ft (approx distance from the tank to the fuel rail)
- Assume straight pipe
- Fluid - pure ethanol (0.789 gr/cm3, coefficient of viscosity = 0.001095 Ns/m2)


**Pressure Drop Results**
*Scenario 1* --- Flow rate: 4.4 l/min (Four 1100 cc/min injectors maxed out)
Factory hardline (~0.25" ID) - 4.5 psi pressure drop
- 6 AN hose (~0.38" ID) - 0.6 psi pressure drop
- 8 AN hose (~0.50" ID) - 0.2 psi pressure drop

*Scenario 2* --- Flow rate: 6.7 l/min (~800 whp on E85)
Factory hardline (~0.25" ID) - 9.3 psi pressure drop
- 6 AN hose (~0.38" ID) - 1.3 psi pressure drop
- 8 AN hose (~0.50" ID) - 0.4 psi pressure drop

Scenario 1 approximates my setup. For a Walbro 255, a ~4 psi pressure drop reduces fuel flow by about 12 L/hr or reduces max power potential for a given AFR by about 25 whp (due to the reduced flow).

wow, the hardline really restricts flow!