Aluminum fuel lines - sizing and E85

[drzed]

After much searching I'm still not clear on what to install for new fuel lines for the 260Z. This car is a late 260Z and has 5/16 supply and return fuel lines stock. Originally I was just going to upgrade to 3/8" steel lines as the engine and trans are out. But as usual, since I'm going to upgrade anyway I might as well look at what I might do in the future. If (when) we finally get E85 available in my area I would like to convert the 260Z to run on it - 105 octane sounds good to me and I've been reading way to much about 1000 - 1500hp cars in Car Craft and Hot Rod using this stuff.

 

So given the increased amount of E85 I would need to run, now I'm thinking about 1/2" lines. I had a hard enough time bending 5/16" lines out of steel for the last car I did so now I'm leaning toward aluminum lines but I'm concerned about the E85 attacking the aluminum over time. Is this a problem or is this just with pure methanol?

 

Also are the 1/2" lines overkill? I've seen so many different numbers regarding line size vs. HP that I'm paranoid about under sizing the system. The 1/2" tubing will still fit (barely) in the modified stock mounts so it seems like the way to go. Then if I get tired with the L series I can step up to something larger without redoing the lines.

 

Oh ya, I almost forgot to add that although I have never had a problem with fuel flow up till now I have finally shelved the old Rayjay and am stepping up to something much larger with the capability of running a lot more boost so there will be a much higher demand on the fuel system now.

[drzed]

Hey just noticed that I'm finally over 100 posts!!! Only took 3 1/2 years - slow typer.

[Six_Shooter]

I'm sure you've read some sites about E85, I can get a few links from a guy I know that is running E85 in his turbocharged V6 Cavalier with great results.

There was quite a bit of discussion about the corrosiveness of E85 and how it might attack and possibly ruin the stock components on his car.

 

He performed a 24 hour, or maybe it was 48 hour test of placeing the suspect components (fuel pump, fuel rail, an injector, and the flexible fuel lines IIRC), into a bucket submerged in E85, prior to the change over. He saw no effects that made him worried and so he started with the E85 and tuning for it. I believe he's ran it for about 2 years now, and hasn't seen any problems with any of those stock components.

FYI, the fuel pump and hard parts of the flexible lines are stainless, and the fuel rail is aluminium.

 

Getting into the aluminium discussion, I have seen talk about the aluminium needing to be anodized, which seems to be false. The fuel rail in question on the Cavalier is/was not anodized, and has held up fine. Other discussion I have read would also support this.

I'm sure the grade of aluminium has an effect on what will and won't survive with E85. Unfortunatly I don't know the grade of the stock fuel rail, nor the aftermarket fuel line that is offered from Russel, Earls, Aeroquip, etc.

 

As far as sizing goes.

 

You can have too large of a fuel line, if you're pump and return are not up to providing sufficient flow, pressure and bypassing abilities. The regulator plays a part in this as well, but that gets into a more in depth discussion.

 

From what you have said, I would probably go 1/2" now, and save needing to do it later. You may not need all that fuel that a 1/2" line will provide, in fact you'd rarely need that much fuel, in a street car. At cruise and idle, even part throttle accel, the fuel requirments of most engines is actually quite small.

I've actually seen a large line being a problem in getting some engines to idle and cruise properly, but with a proper regulator, return line and even where it enters the fuel tank for the return can all have an effect on how well the rail is bypassed with the un-used fuel. Some cars even need to go as far as using a fuel cooler, or using a secondary bypass that bleeds off fuel before it gets anywhere near the engine compartment, to be circulated back into the tank. The reason for this is because the higher the flow rate of the fuel, or circulation of, the more it heats up. As that fuel gets nearer the engine compartment and especially in the fuel rail, quite a bit of heat is transfered to the fuel itself, and is then carried back to the fuel tank/cell. When the flow rate is smaller, the fuel will sit in the tank/cell longer allowing it to cool.

This can also been seen as vapour lock. "I just upgraded my fuel system to a huge x big system and now I can't start it when it's warm" is a pretty common problem when some parts of the system were not thought out well.

 

Also I don't know what you're final goals for power are, but you might want to consider a dual fuel system. Two pumps, two feed lines and two returns (or one really large return), and run on only one pump on a "smaller" feed line, and have the second fuel pump come on at higher RPM/boost/nitrous activation/etc. From what I've read there have been a few members here that have done this with success, at least the two pump deal, I haven't read too much about the details of the plumbing of the system.

 

I don't recall how much power the guy with the Cavalier was making, I want to say low 300ish HP, with a 3/8" feed and 5/16" return, so take that into consideration when designing your system. I feel he was maxing out his fuel delivery though.