Jump to content
SAU Community

Recommended Posts

Hi All,

Been reading up on fuel line size in the forums here and it seems that 5/16ths size line which is about 8mm ID, (ie, standard skyline size) seems to be sufficient for 500 - 550hp plus. (This will be my target)

Just want to ask if anyone sees any issues with the following..

My feed to the fuel rail from a Walbro 460lph will be 5/16ths rubber hose from the pump to the hard line under the car and rubber hose again to the rail.

Rail to reg is also 5/16th and reg back to tank is 5/16th split into 2x 1/4" hard lines. (original carby setup)

All other overflow and feed lines are also 5/16th.

Only issue that I'm concerned with is that I believe the Walbro 460s have a 3/8th outlet and I didn't want to downsize from 3/8th to 5/16th after the filter... Will this be an issue??

Thanks for the feedback in advance..

G

The 460's outlet can squeeze into the 5/16 hose with a little persuasion. My evo runs 6mm return with the same pump, you will have no issues.

Make sure you check the fuel pressure if keeping the stock reg to make sure it doesn't skyrocket. I have only ever fitted one using the Nismo reg, and I know the stock s15 one can't flow enough.

Hey Scotty, no worries and thank you for your help throughout the recent months during my research on this. As you can understand, I don't want to get to my dyno slot and have overlooked something.

Using a sard reg so should be good.

As long as 5/16th lines can see over 500hp.. ill be happy.

As long as 5/16th lines can see over 500hp.. ill be happy.

I have made well over 400kw on factory lines, the only issue was the fuel filter in a few cases. Changing that to a 40 micron stainless mesh filter fixed any flow issues. Worst case just bypass the stock filter on the dyno.

I use GJ drivelines for the earls. Motorsport Connection is another a good supplier for Speedflow etc. Even Scotty's Customs usually keep one or two in stock for customers. :P

  • Like 1

I've just measured the inside diameter of the hardline running along my car and it's 6mm

Of course, 5/16th fuel line has an 8mm diameter and I am setup to run 5/16th from a walbro 460. I figured the hardline would be 8mm ID as well but now I am concerned I will have a flow issue.

Scotty, you've mentioned to me that 5/16th line will be fine but are the standard hardlines on a skyline 6mm ID as well?

This is interesting. Im planing on max 800hp thats to the crank. Will number 6 feed work for this goal and number 8 for the return. I have removed the hard line from my r32 gtr. Im planning on running the braided stuff.

I would be swapping the lines around, you want the larger one on the feed usually.

Power isn't the measurement, it depends only on your pump capacity. If you had a 2000hp pump you will need larger lines and reg.

Thats interesting. I always thought return line has to be bigger. Looking at the hydraulic machines at my work. All the return line are bigger. If the fpr can't return the fuel fast enough because the lines become the resistance and if that becomes the issue why have a fpr if it cant regulate the fuel pressure.

Can anyone else contest to this fact Hmmm.

Most regs only have a 2mm hole to return fuel, how could a 6mm line be a restriction if that's the case? Yes, the return is low pressure, but it won't be that much of a restriction. As long as the return can flow more than the reg needs to bypass (while the injectors are off) you are fine. Even better with the fuelab style reg which automatically slows the pump down.

More important than the return line size is to remove (or drill out) the vac generator from the fuel tank, as most cars have a restriction in there these days.

The guys at race car engineering recommend -6 fuel line to rail, -8 return to surge and even -10 surge overflow to tank.

All in the name of reducing pressure where you don't want it. Especially when using twin pumps that can handle some big flow.

If upgrading the lines then by all means, but sometimes you need to work with what's there from the factory.

My 6an return is fine running twin 255 Walbro's. If you can run 35psi at idle then your return is large enough, any larger is wasting cash.

Large single pumps require massive lines on the feed side though, to stop cavitation.

Im planing using 3 044 pumps. To supply my small 800cc injectors. I want to invest in a good fuel pump set up for future use. So ill spend some time looking at line sizes and the way it should set up. One trip at a high end car show should by itself lead to seeing other drag racing setups. I do feel that I should run a line that can flow my needs and more, but for some reason in my head I still feel my return should always be bigger than my feed line. But ill contact some drag racing shops and see whats going on when it comes to fuel setup.

Buying my cell and surge tank and using all the lines and fittings ill need I can see me running into 3k plus. I need to sit down and plan this out.

Does any one have the size and thread pitch for the feed and supply. Side of a bosch 044 pump. Thanks.

All good, but a drag setup won't suit if you plan to drive the car on the road. Those of us with fuel heating issues will warn you will require a large adjustable speed pump to keep fuel temps under control.

3 Bosch pumps will look the part, but you can max 1000's with a single Walbro on factory lines.

  • 2 weeks later...

Hmm. I would disagree to a point. I feel a wolbro pump doent have enough volume, now dont get me wrong here but why would you see all these big 044 pump setup im most peoplea trunks if it isnt needed and the hp goals are around 1000hp.

I ant think no single wolbro pump can do that. I do believe that variable pump would be better but never really have had any experience with them. And for the heat issue a cooler can easily be installed.

I have made well over 400kw on factory lines, the only issue was the fuel filter in a few cases. Changing that to a 40 micron stainless mesh filter fixed any flow issues. Worst case just bypass the stock filter on the dyno.

where are these filters available? Got a link or pic of one?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Update 3: Hi all It's been a while. Quite a lot of things happened in the meantime, among other things the car is (almost) back together and ready to be started again. Things that I fixed or changed: Full turbo removal, fitting back the OEM turbo oil hardlines. Had to do quite a bit of research and parts shopping to get every last piece that I need and make it work with the GT2860 turbos, but it does work and is not hard to do. Proves that the previous owner(s) just did not want to. While I was there I set the preload for the wastegates to 0,9bar to hopefully make it easier for the tuner to hit the 370hp I need for the legal inspections that will follow later on. Boost can always go up if necessary. Fitted a AN10 line from the catch can to the intake hose to make the catchcan and hopefully the cam covers a slight vacuum to have less restrictive oil returns from the head and not have mud build up as harshly in the lines and catch can. Removed the entire front interior just shy of the dashboard itself to clean up some of the absolutely horrendous wiring, (hopefully) fix the bumpy tacho and put in LED bulbs while I was there. Also put in bulbs where there was none before, like the airbag one. I also used that chance to remove the LED rpm gauge on the steering column, which was also wired in absolute horror show fashion. Moved the 4in1 Prosport gauge from sitting in front of the OEM oil pressure gauge to the center console vents, I used a 3D printed vent piece to hold that gauge there. The HKB steering wheel boss was likely on incorrectly as I sometimes noticed the indicator reset being uneven for left vs. right. In the meantime also installed an airbag delete resistor, as one should. Installed Cube Speed premium short shifter. Feels pretty nice, hope it'll work great too when I actually get to drive. Also put on a fancy Dragon Ball shift knob, cause why not. My buddy was kind enough to weld the rust hole in the back, it was basically rusted through in the lowermost corner of the passenger side trunk area where the wheel arch, trunk panel and rear quarter all meet. Obviously there is still a lot of crustiness in various areas but as long as it's not rusted out I'll just treat and isolate the corrosion and pretend it's not there. Also had to put down a new ground wire for the rear subframe as the original one was BARELY there. Probably a bit controversial depending on who you ask about this... but I ended up just covering the crack in the side of the engine block, the one above the oil feed, with JB Weld. I used a generous amount and roughed up the whole area with a Dremel before, so I hope this will hold the coolant where it should be for the foreseeable future. Did a cam cover gasket job as the half moons were a bit leaky, and there too one could see the people who worked on this car before me were absolute tools. The same half moons were probably used like 3 times without even cleaning the old RTV off. Dremeled out the inside of the flange where the turbine housing mates onto the exhaust manifolds so the diameter matches, as the OEM exhaust manifolds are even narrower than the turbine housings as we all know. Even if this doesn't do much, I had them out anyways, so can't harm. Ideally one would port-match both the turbo and the manifold to the gasket size but I really didn't feel up to disassembling the turbine housings. Wrapped turbo outlet dumps in heat wrap band. Will do the frontpipe again as well as now the oil leak which promted me to tear apart half the engine in the first place is hopefully fixed. Fitted an ATI super damper to get rid of the worn old harmonic balancer. Surely one of the easiest and most worth to do mods. But torquing that ARP bolt to spec was a bitch without being able to lock the flywheel. Did some minor adjustments in the ECU tables to change some things I didn't like, like the launch control that was ALWAYS active. Treated rusty spots and surface corrosion on places I could get to and on many spots under the car, not pretty or ideal but good enough for now. Removed the N1 rear spats and the carbon surrounding for the tailpipe to put them back on with new adhesive as the old one was lifting in many spots, not pretty. Took out the passenger rear lamp housing... what do you know. Amateur work screwed me again here as they were glued in hard and removing it took a lot of force, so I broke one of the housing bolts off. And when removing the adhesive from the chassis the paint came right off too. Thankfully all the damaged area won't be visible later, but whoever did the very limited bodywork on this car needs to have their limbs chopped off piece by piece.   Quite a list if I do say so myself, but a lot of time was spent just discovering new shit that is wrong with the car and finding a solution or parts to fix it. My last problem that I now have the headache of dealing with is that the exhaust studs on the turbo outlets are M10x1.25 threaded, but the previous owner already put on regular M10 nuts so the threads are... weird. I only found this out the hard way. So now I will just try if I can in any way fit the front pipe regardless, if not I'll have to redo the studs with the turbos installed. Lesson learned for the future: Redo ALL studs you put your hands on, especially if they are old and the previous owners were inept maniacs. Thanks for reading if you did, will update when the engine runs again. Hope nothing breaks or leaks and I can do a test drive.
    • No those pads are DBA too  but they have colors too. I look at the and imo the green "street" are the best.
    • I’m not sure what happened I told them about sonic tunes free OTS tune and the next the I know .. I was booted..   To funny 
    • Yea - I mean I've seen my fuel pump which is decades old and uh, while I'm not saying this with real knowledge... but I sure get the ick at using anything in the fuel system that produced the state of that pump. Many years ago I went through multiple pumps (and strainers) before I dropped the tank to clean it out with extreme violence. I'm talking the car would do maybe 50km before coming to a halt, which resulted in me cleaning out the filter with some brake cleaner and going on my way. None of my stuff ever looked like what came out of your fuel tank. I don't think I'd be happy with it unless every single component was replaced (or at least checked/cleaned/confirmed to be clean here).
    • I'm not going to recommend an EBC pad. I don't like them. Just about anything else would suit me better. I've been using Intima pads for a while now.
×
×
  • Create New...