Hardlines vs Stainless Steel Braided Line in trans tunnel

[kd0wda]

Is there any reason NOT to run full stainless Steel Braided PTFE Racing Hose through the trans tunnel instead of hard-lines in the tunnel? I was going to run 3/8" stainless hard-lines transitioning to the braided stuff on each end, but am now wondering if it wouldn't be easier to just run full lengths of the braided lines. It would be fewer fittings and less work because I wouldn't be bending the hard-lines. Initially I was thinking the hard-lines would be tougher or more resilient to debris that might come up under the chassis, but the braided stuff seems equally strong. Is there any sort of motor vehicle code that would require the hard-lines??? Hoping someone with more knowledge than me can explain one vs the other. Thanks!

[PaulProe]

Hoses can be compliant (expandable). When you generate high pressures for the brakes, any amount of expansion detracts from the pressures applied to the calipers. It can be to the point your brakes are in-effective.

Braided Teflon hose is better about this than a reinforced rubber hose, but again, any amount of expansion is not your friend. The more hose length you have, the more this can occur. Good engineering design has the hoses at each wheel as short as possible to help reduce this.

Hard lines do not expand with the increase in pressure. They also are self-supporting much more-so than a braided hose. Do yourself a favor - use hardline like the manuals call for.

Also rethink your size. You commented 3/8". Should be 3/16" You don't need to move a lot of fluid, just transfer the pressure. Fuel line is different - there you want to move a lot of fluid so the larger sizes.

FYI

Paul

[P100DHG]

I think he’s talking about fuel lines

[kd0wda]

I think he’s talking about fuel lines

Sorry, yeah, I should have mentioned this is just for fuel.

[NAZ]

I urge you to rethink running fuel or brake lines through the trans tunnel or close to the driveshaft or rear end, it's a safety hazard. You can peruse driveshaft explosions on YouTube and see that they happen violently and can cause significant damage. More likely on a drag car but they do happen on street cars too, just not as many videos of a street car driveshaft explosion and the ones you find are usually on a dyno. I've experienced two now (both street only vehicles) and seen a lot more on the track.

As for SS braided vs tube fuel lines, either work well. Braided is much more expensive but can add a safety factor as they are harder to cut. Both my race cars have SS braided fuel lines running to and from the fuel cell to the engine as it is less likely they will be cut in a crash.

[kd0wda]

I must be using the wrong nomenclature regarding the transmission “tunnel”. I’m referring to the space where the manual says to run all the hard lines (brake and fuel) down the center of the chassis, front to back that is then covered with sheet metal to form the center of the cockpit. Basically thinking I could use the braided lines for fuel here instead of the hard lines.

[edwardb]

First, short of significant modifications (and I'm not sure what that would be...) there really is no choice but to run the fuel lines, brake lines, e-brake cables, and rear wiring harness leg through the tunnel that connects the engine compartment with the rear section of the Gen 3 Coupe. The space frame chassis is basically a flat pan other than in that area. Running any of those line outside this area (e.g. on the bottom of the frame) would make them the lowest point on the chassis. An even worse option IMO. Running any of them on the other side of the chassis would put them in the cockpit which also would be a worse option. I put mine in the very top corner of the tunnel on each side. They are a decent distance from the roughly 6-10 inch long driveshaft (depending on drivetrain combination) plus the area slopes up and away from the driveshaft about halfway down it's length. I followed this slope with mine to maximize the distance. Maybe isn't the best location from a pure race or sanctioning standpoint, I don't know. But I suspect the cars that are being tracked, including those doing it exclusively, have them in the same location. Mine is a 100% street driver. So I'm fine with it.

I used 3/8" SS hard line in mine for both supply and return. Because it's smaller in diameter than flex able to get that much farther away. Plus I just prefer it. The kit comes with slightly smaller diameter steel lines which, depending on your engine setup, may be adequate. I don't know that either is any more or less durable than flex. But by definition you would need to tie down the flex more than hard line to make sure it stays in place.

[mtwarog]

Hi,

I ran braided hose all the way from the fuel tank in my coupe.
Can see some pictures here and in the following posts in my build thread:
https://thefactoryfiveforum.com/showthread.php?25341-Matt-s-Gen2-65-Coupe-Build-Thread&p=288810&viewfull=1#post288810

Thanks.
-Matt

[P100DHG]

I think the theory of hardliners is that stainless won’t deteriorate over time (or at least in our lifetimes). I was told by the guy who made my hoses that Ethanol in the gas now at ever increasing rates. Lower grade hoses will deteriorate but that Teflon lines are resistant to that. I think your probably good with either the higher end braided or the stainless hard lines.

My source for this info is VF Sales in North Hollywood CA. They make hoses for all the high end hot rods in The Valley. They have been around forever.