Fuel Cooling, without a cooler?

It's hot here, I have a pump in the sump (in tank sump) and we are having hot fuel issues. It's a street car, so I really don't want to add a cooler due to risk of leaks or damage with no good place to put it.

We are using large rubber -AN fuel lines. I'm thinking of replacing the longer sections with a fuel/ethanol safe metal pipe. Or, running a small water to fuel cooler with it's own mini dedicated cooling loop but that sounds over complicated and adding stuff is the opposite of reliability. Other option, add a bunch of fins welded onto the underside of the stock tank, and remove some of the rubber tank coating.

Anyone tried any of these ideas successfully? Which of these ideas is the worst?

Some OEMs already use your first idea - they'll run an extra length of coiled hard line on the return side, and I've seen one where the coiled line wraps around the AC line after the orifice so the cold line cools the fuel. That may or may not be an option for you. 

Replacing both lines with hard lines sounds like a great place to start. Your biggest return on investment if you go to a more involved solution, if you can avoid raising return restriction too much, is to put your cooling loop in the return line, and to do whatever you can to deflect heat away from the rail on the engine. The fuel picks up a lot of heat from the engine and return flow carries it back to the tank. 

Personally, I wouldn't do a water to fuel cooler, that sounds complicated. Fuel to air coolers exist, especially in the diesel market, and even something like the simple power steering coolers that are basically just a loop of hard line with some fins tacked on behind the grille would work fine. 

Go metal. The rubber line holds in heat. Increase the sizes. Lots of people runs line too small or just at the edge of being the right size and unintentionally heat the fuel up because of sizing. Make sure your pump isn't running hot too.

So running e20, what type of hard line should I use? Raw aluminum apparently has issues, so does copper. Stainless?

What issues are you fighting? It will be a different answer if it's afr change due to heat vs vapor lock or hard starting.

The switch to metal lines sounds like a decent idea, but are you sure there's no room to squeeze in a small PS cooler? There are some models out there smaller than a paperback novel like the Hayden 1009.

How big is the fuel pump? If it's a big one, a variable speed control may help.

My tuner said he thought the fuel was getting too hot looking at the log files on the dyno. I touched the tank and it was very warm. It's running 2 walbro 450s, one as a lift pump the other one as the pressure pump. It's a Radium in tank sump. A brushless pump is a lot more money than adding some cooling.

I'll check out the Hayden 1009. But I've been told a fuel cooler on a street car is more of a liability than an asset. I'm also hoping to just keep it simple, there's already a bunch of extra stuff on the car

[frenchy]

This is why the float bowl surrounds the carb throat on a Rochester B carburetor. The cooling from the venturi helps to keep the fuel in the bowl cool. It also helps keep the carb throat from icing up.

[/frenchy]

There are many things that can be tried but none are especially easy. Some random ideas:

- Stating the obvious - keeping the tank full increases the heat absorption capacity.

- Downsize the pumps?

- Change to a gravity sump/header, thus eliminating one pump and 50% of the heat contribution.

- Switch to external pumps, which "may" reduce the amount of heat added to the fuel due to air carrying away more of it.

Just so we know, what power does the engine produce and is it forced induction? Both directly dictate fuel flow needs.

Return or returnless system? IIRC Mazda went to returnless on the NB Miata specifically to cut down on fuel heating.

I was thinking similarly about the return. Where does the return line go? All the way back to the tank? Or just to a small swirl tank or something? 

Also, do you know where the fuel is picking up the  most heat? Maybe a well placed heatshield would simply solve your problem?

FD RX7, EFR IWG 8374 turbo. Made 400whp at 0.9bar on a fully open wastegate. The E-gate had issues, so we are swapping to a conventional dual port wastegate and will go for 1.2bar, maybe 1.3 if it's happy

Not trying to re-engineer the whole fuel system.

Wrapping the lines in the engine bay is probably a good idea, also cheap and easy so that's a win.

I think I need to look at more power steering type coolers, those seem a lot more sturdy vs oil cooler types.

I think the first thing I would do is get a coil of aluminum fuel line and re-plumb at least the center sections of the supply and return.  That might be your huckleberry.  6 or 8 feet (times however many lines) of all that aluminum surface area might equal the cooling capacity of a dedicated cooler without the liability part.