Fuel Line Best Practices

[Gadsden]

I have been spending a lot of time thinking about how i want to run my fuel lines. I am interested in what others have done and think.

I have a Blueprint Engine with the Holly Sniper FI. The Sniper has an internal fuel pressure regulator, so no external regulator is needed. The fuel input is on the back driver side of the unit. The fuel return is on the back passenger side of the unit.

My initial thought was to run the lines down each side of the trans tunnel and come up the firewall, the feed on the DS side and return on the PS side, then go with a flex line to the Sniper unit. My concern is that i don't want to re-do lines in the future if i change my FI system or something else.

I have seen others run the lines together/side by side into the engine bay, and end up together on the firewall, then go flex lines to the input/return.

How have other Coupe and Roadster builders run their lines that have used a Sniper FI or similar? Right now, I am leaning towards running the lines together down one side of the trans tunnel to a single location on either the DS or PS side of the firewall. I am speculating that this will provide the most upgrade flexibility down the road, without re-running the lines.

Does this make sense? Am i over thinking it?
Thanks

[Robodent]

Talk to mark at breeze Automotive. He set me up with all the right stuff for my build
A N. Fittings and Teflon braided fuel lines , clamps etc. he’s got it all . Rob

[Logan]

I understand your question. The answer is probably simpler than you think. Run the lines together through the tunnel up to the firewall. From there, use braided stainless lines (PTFE-lined is top dog for this) to your existing sniper setup. They should already have some slack in them (you never stretch the braided section taut between the firewall and the engine). In your case, you should simply add a few inches of extra slack and that’ll solve your problem. They can both be the same length, nobody will ever notice they’re a few inches longer than normal. You can neatly secure them to nearby panels or wiring harness with zip-ties or clamps.

I don’t know what type of termination/ends they will have to connect to your Sniper, but if you do switch engines or fueling methods in the future, most regulators can be adapted to almost anything. -6AN or -8AN are common.

[Gadsden]

Thanks for the input. Maybe i could have been more clear. From a connections standpoint, I am good. I have that sorted out, AN fittings, Stainless PTFE, hard tube, and connectors from Breeze, etc. My question was really around taking completely different routing paths for the feed and return line and having each terminate on opposite sides of the engine bay.

Thanks!

[AC Bill]

On my roadster, I ran the lines side by side down the outside of the 4" tube frame, tucked up as close to the floor as possible. I have not had any issues.

My personal reasons for not using the tranny tunnel as a fuel line route were:

.-Electrical harness's was in this area, including my battery positive cable. Although I do have a driveshaft hoop, if a u-joint ever let go, there could still be risk of a fuel line rupture, and electrical sparking combined. A bad combination..
- The tunnel is a more difficult location to service, or replace, the fuel lines, if ever required.
- If a transmission, or clutch replacement is required, or even if you just need to access, say VSS sender, a switch, or the wire harness, the tunnel is already a fairly tight area as it is for doing any work, fuel lines would be just one more thing to have to work around. They could potentially suffer damage as well, if a say a tranny pinched them, on it's way out.

[NAZ]

Running fuel lines down the trans tunnel and near the driveshaft is a bad idea! There's a reason sanctioning bodies won't allow this. I've had two driveshaft explosions now and can tell you the damage is very impressive. Imagine a fuel line severed and sparks flying from steel impacting steel. And while I'm at it, let me pitch to all y'all the need for an adequate driveshaft loop. That spinning hunk of metal is turning right near your legs and if it let go, it has the potential of causing serious injury.

[Logan]

AC Bill - Not sure if you’re aware yet but just in case I’ll mention it here... the new FFR Gen 3 Coupe has a square-tube flat-floor chassis design that doesn’t have the useful room adjacent to the 4” round tubes of Gen 2 and prior Coupes (and all Roadsters to date). There simply is no other option to run the fuel lines without going through the passenger cabin (often illegal in either DOT laws or racing rulebooks). The transmission tunnel is basically the only option.

That said, I agree with NAZ, a driveshaft safety loop should be used. I’m also considering running a heavy-wall steel tube in the upper corner of the tunnel as a pass-through for the fuel lines for added protection. Even a piece 12-18” long would be great. If it is big enough, you could pass ALL fluid-carrying brake/fuel lines through it, too.

[edwardb]

Right. Based on the chassis design, no choice but to run fuel, brakes, and electrical inside the Gen 3 Coupe transmission tunnel. Alternatives would make some portion, e.g. a crossover, lower than the frame which would be a no-no. Same for installing inside the cockpit. For my Gen 3 Coupe build, ran the two 3/8 rigid SS lines (supply and return) at the top left corner of the tunnel along with the brake line, and the rear electrical harness leg down the top right corner of the tunnel. Pictures in my build thread. Also installed a drive shaft loop. I don't see any reason why the two fuel lines can't run together.

FWIW, I've said the same thing on both forums a bunch of times for Roadster builds. Run everything outside the tunnel for safety. Took a little thinking adjustment on my part to realize I had no choice once the Gen 3 Coupe was in the shop and saw what my options were.

[AC Bill]

AC Bill - Not sure if you’re aware yet but just in case I’ll mention it here... the new FFR Gen 3 Coupe has a square-tube flat-floor chassis design that doesn’t have the useful room adjacent to the 4” round tubes of Gen 2 and prior Coupes (and all Roadsters to date). There simply is no other option to run the fuel lines without going through the passenger cabin (often illegal in either DOT laws or racing rulebooks). The transmission tunnel is basically the only option. .

Thank you Logan, no, I was not aware of that. I don't believe I have seen an underside picture of one....Odd how FFR would let that flaw slip by, when doing the new Gen 3 design? I guess builders have no choice.
If there is room, perhaps one could weld a short section of steel pipe to the frame, for the fuel lines to pass through, adjacent to the driveshaft area?

[edwardb]

Thank you Logan, no, I was not aware of that. I don't believe I have seen an underside picture of one....Odd how FFR would let that flaw slip by, when doing the new Gen 3 design? I guess builders have no choice.
If there is room, perhaps one could weld a short section of steel pipe to the frame, for the fuel lines to pass through, adjacent to the driveshaft area?

Here's the Gen 3 Coupe chassis underside. I don't consider it a flaw. Just what it is. These are early pics of my build before any of the lines were installed. Only the rear suspension. But you get the idea. For perspective, in the first pic, you can see the motor mounts at the bottom and back wall of the radiator tunnel in front of the engine.

[AC Bill]

Here's the Gen 3 Coupe chassis underside.

Thanks for the pictures Ed.
Well that is certainly leaving builders with little choice, as to the routing. I suppose one could weld a section of rectangular tube steel under the frame at the bottom of the cockpit, and feed the fuel lines through it. That way it remains out of the cockpit, and clear of the tranny tunnel. It shouldn't be a factor as far as ground clearance goes, given the fact the previous tube frame would have hung at least that low. It should be thick enough that it could take hit from a speed bump, just in case.

[NAZ]

Let me share with you what I did on my hot rod as that may give you some ideas for the Gen-3 Coupe. First, I should mention that I removed the FFR chassis from the firewall back and fabricated a new one that is designed much like the photos of the Gen-3 Coupe, except in 1.625” round tubing (1st photo below). My chassis has the driver’s side floor mounted tight against the chassis tubing with no space to run wires, tubing, or hose (2nd photo). Similar to the Gen-3 chassis. However, on the passenger side I mounted the floor 1” above the chassis tubing so that I could use this space to run all my lines to the rear.



I had to lower the driver’s side floor 3” from the FFR floor to get my helmet below the roll cage enough to meet NHRA rules. There is no room between the floor and the chassis on this side. The passenger side doesn’t have to comply with NHRA rules as passengers are not allowed. And the 1” higher elevation on that side still provides enough head room that my 5’10” frame still clears the roll cage with several inches of safety margin (a helmet is more than 1” thick at the crown). In the third photo below it is hard to tell but the passenger side is 1" higher and that's plenty of room for running lines.



There is also a belly pan on the bottom of the chassis mounted tight against the chassis so there was no provision for running lines under the chassis. The only thing running through the driveshaft tunnel is a discharge hose from my catch can (4th photo).



Another idea that might work for the Gen-3 is to fab a sheet metal channel that runs from firewall to rear bulkhead. This “pipe chase” would be bolted to the floor and run under the passenger seat. If you have at least 1” of space under the passenger seat that would be enough to run brake lines, electrical harness, and fuel lines through. Technically, this would not be considered running these lines through the driver’s compartment and is no different than running them directly under the floor. A local HVAC or sheet metal shop can easily make this to your sketch on a napkin. Don’t forget to design flanges to bolt the u-channel to the floor.


Where there is a will there is a way. If you believe like I do that running fuel and brake lines through the drive shaft tunnel is a safety hazard then there are ways to avoid this. That’s where creative problem solving comes in.


Chassis Old and New.jpgDriver Side.jpgPass Floor.jpgBellypan.jpg

[Olli]

What routing does FFR specify in the Coupe build manual?

Olli

[edwardb]

What routing does FFR specify in the Coupe build manual?

Olli

Fuel lines: "From the filter we generally run the lines to the middle of the frame then down the transmission tunnel."

Rear brake line: "At the back of the inside footbox, run down the 1” transmission tunnel tubes to the bottom 1.50” tube then to the back of the transmission tunnel."

Wiring harness: "Run rear harness from the driver foot box inside wall, along inside the transmission tunnel straight back to the rear of the frame."

No mention of a driveshaft safety loop. But I think most of us agree, myself included, it's a good idea. Especially in this case.