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!

The restriction comes from the smaller ID, not the hardline construction. The smoother surface of the hardline offers much smaller flow restriction than a rubber hose.

For the same ID a metal hard line offers the least restriction.

good info Mycailo! did you ever put that AMS fuel line that runs to the fuel rail? if so did you see any improvement?

Thanks for proving my point with math. -6 feed line with stock return line is plenty for 99.99999 percent of Evo's in the world.

It's not better than the hoses you mentioned, it's just readily available from Jegs/Summit.

In my case, I just hook up my -6 line directly to the outlet on the filter of the Buschur Double Pumper. I'm going to a different filter next season to get away from the barb/clamp setup that Buschur supplies, but same concept, just with AN fittings connections.

I tried installing it, but it doesn't mate with the factory flare fitting where the hardline terminates. At this point, I think I'm going to run -6 AN from the pump to the rail.

Yep, I was curious to see the factor of improvement going from stock to -6 to -8.

You're not bothered at all by the lack of clamp?

Pusloc/socketless/etc style fittings are designed to be ran with no clamp and hold pressures up to 250+ psi. Used them for years with no issue. Aeroquip Socketless is a far, far safer setup than the barb/clamp setup that a lot of people use. Once you assemble one, you'll see why it'll never come off unless it's cut. In fact, it'd be physically impossible to pull off without damaging the hose. If hooked to a truck, it'd rip the hose first. You get the point.

you have to look at the whole fuel system as not just send/return; if the return is opened up; it helps the sending

No, the SIZE of the factory hardline comparatively restricts the flow.

Factory hardline = 1/4" diameter = .025" diameter = .049" area
-6AN replacement = 3/8" = .0375 diameter = 0.11 area (more than 2x stock fuel line)
-8AN replacement = 1/2" = .196" area (nearly 4x stock fuel line)

Going from a stock to a -6 more than doubles the area. Going from a -6 to a -8 nearly doubles the area again.

is the factory return more than capable for a 6an feed setup - pushing up to 800whp?

stock lines are 8mm which is closer to 5/16".

I just checked - OD is 8 mm (0.315"). I've been talking about ID.

I think it´s better to simply run a new hose from the fuel pump assembly to the fuel rail. A -6AN hose fits perfectly to the outlet nipple of the assembly and you can connect it to the fuel rail with any sort of 45º AN fitting.

Installing a hose also made a lot easier to install a fuel pressure sensor for a Defi Gauge.

Using the stock hard line looks a lot clear, tho.

I've posted the answer about a dozen times now, but here it is again...

YES


I'm making 790 WHP on E85 with Buschur DP (modded 255's) -6 feed, stock return line, stock fuel pressure regulator. Zero issues.

:rolleyes:

fuel rail
 

What's your thought on fuel rails?

Both the AMS and Buschur are great. Just use the STM adapter to connect -6 to it. I did not know it was available, so I tapped mine for a 3/8"NPT to -6 union. Works fine but I would of used the STM piece if I knew it was available.

old thread but i'm glad i found it.i just decided to pull my hard line and run hose all the way.i wasn't sure if it would be OK,so i went with ate aeroquip startlite race hose which is a little stouter than the push-lock but has a push-lock inner tune/kevlar outer.i feel better after reading the thread.

the hard line ID is just so small and i even found a spot where it went down to .200" just before the rail.