Fuel line diameter for 500+ hp?
 

Hey,

i'm just about to upgrade my fuel system, my actual setup is:

T04Z turbo (plan to upgrade to Garrett GTX or BorWarner EFR next season)
big street ported engine (oil passage mods, weightened rotors)
V-Mount, upgraded cooling system, 3" DP and exhaust system and so on...

Last point on my list was the fuel system, i already have

- NipponDenso supra pump (planning to upgrade to Bosch 044 or FueLab 41402)
- 4x 850cc injectors,

i bought 2x 1000cc and 2x 2200 EV14 bosch injectors and SARD fuel rail, i'm not sure if i should go with AN6 feed and return lines or AN8 would be better. I also read some members hit hp numbers over 500 with OEM fuel hard lines, so i guess AN8 would be too much...

What do you guys choose....?


In any case i would go with black nylon braided fuel lines, do you have any ideas for a great deal on these...?

Why are you wanting to upgrade the hardlines? They are capable of your power goal.

...i think it wouldn't be smart to upgrade the rubber lines as the flow would be limited because of the small diameter of the hard lines - but correct me if i'm wrong...?

I'm pretty sure the hard lines are about 3/8", so about equivalent to AN -6 already FWIW.

Stock lines are 8mm(5/16") and will become the limiting factor. Yes you may be able to reach your goal, but you'll be pushing it to the limit.

Really you should upgrade, and if your going to do so why pick the smaller -6 size, if you're already investing in the parts, what's the difference in going to -8?

I'm currently using -8 feed and -8 return that's equivalent to 1/2. Plenty for pump fuel or e85. 500hp is pushing it to the limit that's why I upgraded before then.

The hard lines are fine for you, and me and others. I think I've read before someone made up to 700 hp with the stock hard lines.

...well, i just thought -8 on the other hand could be too much. If its really the case that -6 is a limiting factor i will go with -8 of course. Its not a big difference in price, but i was trying to add not to much weight as neccessary - as -8 is bigger than -6, it also weighs a tad more... ;)

Keep in mind that if you run a hi volume of fluid through smaller lines, the resistence will add heat to the system. This is simple fluid dynamics! You should always size your lines to your fuel pumps flow capabilities and not for hp.

Look at the upper right hand chart. Note this is for water and 25' length of hose.

A 5/16 hard line is approximately .235 ID. Lets use 1/4" as the OEM return line.

If you use 1 GPM as the flow rate, then the 1/4" ID line is producing an estimated 15 PSI back pressure. (9.0 PSI @.8 GPM).
The pump is capable of providing this pressure to compensate for hose friction but your are at the flow limit for 1/4" hard line and loading the pump.

Same flow with a 3/8" ID hose is 1.8 PSI. The pump likes some loading so no need to operate it at no load.

Factor in your hose length, fittings and actual flow for your HP requirements.

The weight diference would be very insignificant, less than 1/2#. I would rather be safe than sorry and just go with the 1/2" line. Especially if you decide to go e85 in the future

Dash 6 is plenty. It will work.
Move on.

...well, you choose the fuel pump you need to achieve your hp goal, didn't you? As i said before, i already have a nippon denso supra pump, but as i'm not sure if that would be enough for high hp, i'm not afraid of a swap. Looking for a Bosch (dual) or FueLab pump...

...but one i have the lines under my car, i don't want to change these anymore - to change a pump is done in a few minutes, perhaps... ;)


Every post of you guys is helpful in a certain way, but if one says "-6 is fine", there is the next who states "better go with -8" ...that doesn't help me much... :D

713whp here on stock lines with no fuel pressure drop at all. I have tuned many cars over 500 with stock lines.

from my research and I am planning a parallel fuel setup and -6AN is plenty and more than enough. Many people like overkill and that's OK too but, you would not run out.

hybrid

Agreed with above, stock lines are perfect. I made over 500+ no issues on walbro 400 and 43psi base.

Now running -8 feed and factory return, still no issues with controlling fuel pressure on factory return. If both walbro 400 pumps are on, it overwhelms the line a little and raises FP up to around 50psi but thats a TON of fuel. You should be great with one high flow pump and hardlines.

likewise, my tuner indicated he's run stock lines up to 650rwhp, and it's frankly so much cleaner and fewer leak points than a full AN line system with fittings, and splitter blocks, etc.

I made 638.9whp on stock fuel lines

...sounds reasonable, i will think about it, make a few calculations, but if keeping the stock lines would be an option (at least for the return line), why not...

I'm curious on the size of the outlet on the bigger in tank fuel pumps. Anyone know? My Walbro 255 is factory 5/16

Stock lines will work fine. Anyone who tells you they don't, has never built a high HP car before.

I would think all pumps that are a drop in would be 5/16. Every one that I've seen up close and personal has been.

im wondering about that newer walbro made for e85. I believe it was like 340 or more lph

Aeromotive 340s are 5/16. Walbro 400s are 3/8 ("10mm") but they aren't really a drop in.

I installed a Walbro 400 in my FC. Installation required trimming the sock rubber "clip" but that was pretty much it. I used the supplied submersible hose that came with the kit which fit and clamped to the stock FC sending unit and pump outlet no problem.

I haven't held the Walbro 400 in my hand, but the images I found show a big bell on the bottom where the actual pump mechanism is. So it may fit just fine in a "pump on a stick" installation but it won't drop right in to a fuel module the way the 255 and such will.

I used the stock S4 sending unit.I used a large hose clamp to secure the pump to the "pole" of the sending unit and just used a razor blade to shave the sock grommet to fit. Took maybe 1/2 hour to fit. Probably not as easy as a 255, but the thing flows like crazy and is very quiet. With a quiet exhaust I can't hear the thing run at all.

...did anyone of you who kept the hardlines use E85?

I talked to a non-FD guy (but an absolute E85-Pro), who told me to swap the hard lines if i'm not sure about the material - would be cheaper than an engine failure if the material of the hardline reacts with the biofuel...

E85 requires about 30% more fuel to make the same hp as gasoline. Rotary engines require more fuel than cyl engines to make the same hp.
So if i was told 3/8", -6, is good for 700hp, I wouldn't go past 500 to 600 hp on a rotary. Now add E85 in the mix I wouldn't go past 400.
It's not a matter of if you can still make power on small line, but the reliability and i rather be safe than sorry.
I had a project Datsun 510 with sr20 and people were claiming they were using the stock 1/4" fuel lines for their efi conversion.

Good point, not to say i would hate to install new lines if the smaller one fail with E85, as the price difference isn't significant, i will go at least with -6 - it would be wrong as the upcoming setup def. has the potential to put up numbers above 600...

Found turning up a bit of nylon that slipped around the motor section of the pump, helped in mounting. The outlet barb, I found was 9mm on the minor diameter, so presumably either 5/16 or 3/8 line will work.