Fuel rail heat soak problem

[boofhead]

No worries. Sounds like the car will be in good hands.

[lukep6470]

OK so I just got back on to the heat soak problem last weekend. Using the phenolic spacer did nothing to lower the fuel rail temperature. I realised it is all to do with the hot air from the radiator as the cross brace is just as hot as the fuel rails after a long drive.

I have now wrapped the fuel rails in fibreglass exhaust wrap (Hands were so itchy afterwards) and that has made a big difference but looks like crap. It now hot starts like an OEM modern car.

I'm now thinking of that stick on fibreglass insulation that some guys are using in the transmission tunnel as that would look a lot better than an amateur hour bandage on the fuel rail.

[hybrid]

What about some aluminium tape or something along those lines?
I have no issues with hot starts, and I'm surprised that hot fuel would cause such issues. Clearly is though, if the wrap fixed the problem.

Edit: just re-read the whole thing. Forgot you were returnless, and forgot I had already suggested the tape


The fact that you have to prime twice says you don't have enough cranking pulsewidth when the car is hot.
You could try the "Ignore MAT correction during ASE" so it won't lean off for air temp after it catches.
But if it's not catching at all, then I would look at using a table for cranking and adding a bit more fuel when it's hot.

[lukep6470]

I think a lot of it is to do with my home made returnless system. Also with the 8 stack the fuel rails hang 1/2 way over the tappet covers so they get a lot of exhaust heat as well. I think another contributor is that I used the Holley billet fuel rail which has a lot of metal in it so there is a lot of material for the fuel to cool back down.

It copes with just the exhaust heat but once the radiator gets up to temperature for the the thermo fan to cut in it's all over.

I'm wondering if getting the fuel rails jet hot coated would help. It's an expensive outlay for a test though.

[hybrid]

Ceramic coating could work, but maybe so would some crinkle finish paint or something along those lines.

What about drilling a bunch of holes in the bracket part as well to take some of the meat out?

[lukep6470]

I've been thinking about that as well and will need some time on a friends milling machine to make a neat job of it.

I could also mill a lot of the meat out of the fuel rail itself.

[gbx78]

If its a standard setup why would one car experience this and not another? Im curious about this issue. Is it because of engine heat or outside temp?

[Shaunp]

Id just run a rising rate regulator and spill return so the fuel is always cool, you could also run a Jag fuel cooler on it if you have AC

[trav68]

That makes sense when you are driving steady state you have an relatively ambient temp fluid (fuel) cooling the internals of the fuel rail and and ambient temp gas (air) cooling the externals of the rail.

Once stopped the ambient temp in the bay will increase rapidly and heat transfer into the rails will take place. The thermal tape acts as an insulator delaying the temp increase as the engine bay cools simultaneously.

From an engineering standpoint I doubt decreasing/milling the rails ( i.e decreasing their thermal mass) will help but could perhaps even exacerbate the issue.

The extra thermal mass may be beneficial as the insulation test proves you are merely trying to delay their increase in temp.

If the system had a return and during hot restart cool/ambient fuel was cycling through then having smaller rails (i.e milled as much as practical) with smaller thermal mass could result in them cooling more rapidly as you would get heat transfer into the cooler fluid. However, this won't apply to your setup as fresh ambient fuel will not be cycling through

Have you thought of using the sleave style insulation? You could neatly cut the appropriate places for mounting to the throttle bodies and the injectors and this would atleast be neater than header tape.

http://www.summitracing.com/int/parts/tay-2582

Just throwing it out there but could you also be getting a heat soak issue with your intake air temp sensor?

Ceramic coating the rails is probably going to cost a similar amount to setting up a low pressure return to tank?

[boofhead]

Do it correctly and install a proper return fuel system.
Let cool fuel get pumped from the tank into the rails and back rather than trap the fuel in the hot rails. All solved.

[S[_]SPECT]

no experience with injection, but it seems return line is a common solution to fuel heat issues...

With a return system you could run the pump 10-15 sec before cranking and take a lot of heat out of the rails quickly.

[ozbilt]

Do it correctly and install a proper return fuel system.
Let cool fuel get pumped from the tank into the rails and back rather than trap the fuel in the hot rails. All solved.

What I have thought all along. There is no advantage in keeping hot fuel up the front & a return line is very easy to install ......

[hybrid]

From an engineering standpoint I doubt decreasing/milling the rails ( i.e decreasing their thermal mass) will help but could perhaps even exacerbate the issue.

That is why I suggested drilling holes. It's not decreasing their mass that is important. What you're doing is decreasing the surface area that is available to take on heat.

[hybrid]

And yes, I agree that a return line is the best option and will avoid having to spend all the time trying to work around the issue. It's a bit of a pain, but so are heat soak issues!

[lukep6470]

If its a standard setup why would one car experience this and not another? Im curious about this issue. Is it because of engine heat or outside temp?

There is nothing standard about this setup. The induction is custom, and the fuel system is a combination of aftermarket, C5 corvette, 69 Mustang, and snowmobile!!

It all works really well except for a couple of small niggles. I can start the car when it's hot it's just not a seamless standard EFI start.