Fuel rail heat soak problem

[lukep6470]

So I am using the chunky Holley alloy fuel rails and since running the car without the bonnet on it I've discovered the majority of the heat soak into them is coming from the manifold, through the throttlebodies into the fuel rail via the brackets. They are getting to 60+ degrees via this path. The fuel line between the rails feels a LOT cooler than the rails themselves.

Does anyone know of a thin heat insulator I could use in this application to help cool the rails down?

[Shaunp]

put a fuel cooler on it the car has AC.

[lukep6470]

I did some quick googling and couldn't see one that integrated into the AC. This is more to solve a heat soak hot start issue more than anything else. It's exacerbated by the fuel system being returnless.

The fuel lines up to the rails are basically ambient temperature.

I've been looking at phenolic spacers. The pre cut IDA weber ones are too expensive but you can by the stuff in sheets. I was thinking of trying 5mm ones to start with under the throttlebodies.

Has anyone used these?

[unilec5544]

I did some quick googling and couldn't see one that integrated into the AC. This is more to solve a heat soak hot start issue more than anything else. It's exacerbated by the fuel system being returnless.

The fuel lines up to the rails are basically ambient temperature.

I've been looking at phenolic spacers. The pre cut IDA weber ones are too expensive but you can by the stuff in sheets. I was thinking of trying 5mm ones to start with under the throttlebodies.

Has anyone used these?

Try sending these people an email along with your pic, they may be able to help.

http://www.thermalvelocity.com.au/default.asp?

[Shaunp]

You can find a Jag wrecker and get a cooler from an XJ6 then the fuel is at the temp of the AC line from the compressor, Jags had them from about 74 basically they are cast alloy and the fuel line is cast in next to the AC line. I have some stuff they wrap the gas pipe lines out west in, it is like foil one side and some other insulation on the other about 1/8" thick.

[Shaunp]

Here you go the alloy bit between the carbs near the cam cover. It gets the fuel ice cold.

http://images.conceptcarz.com/imgxra/Ja ... US_e01.jpg

[hybrid]

That won't fix heat soak though Shaun, because it happens when the engine is turned off.

Can you not tune the issue out Luke? What do you think is the issue? Not enough fuel gets to the cylinders, or too much?
I'd put a return line in it personally.

[boofhead]

I am with Hybrid. The only real solution that I can only think is using a return line to cycle cooler fuel into the system.

All others would be ugly as you need to isolate the rails and then cover then (similar to what is often done with foam tubing over air conditioning hard pipe). It may work though would not look right.

[lukep6470]

The main problem this is causing is tough hot starts. I have to prime the system a couple of times or else it won't catch.

The main heat source seems to be the manifold, up through the throttlebodies, into the fuel rail. I think it is worth investigating thermally isolating the throttlebodies and fuel rail.

The entire throttlebody assembly gets stinking hot even though the air around it is pretty cool. I've ordered an infra red thermometer to get scientific about it.

From what I've read in the past 1 degree C increase in charge temperature approximately equals 1HP lost so even if I abandon the returnless fuel system cooling the intake down is still worth while.

[Shaunp]

I see I missed the bit that it doesn't have a spill return from a regulator, that's the real issue the hot fuel is trapped in the rails rather then a fresh dose every time you cycle the pump on start up.

[hybrid]

You could try just some aluminium tape to start with, but generally that will only help with projected heat.. Your issue is going to be that the manifold, TB's and fuel rails are physically connected and I think you will struggle to stop the heat transferring via that physical connection.

[boofhead]

Maybe a little slice of MDF between the TB and Rail alloy where you bolt up the rail. Not sure if this would affect the length for the injectors or not as I am not that aware of the finer details of your set up.

I have a red-dot thermometer I order a few years ago. It appears to work quite well (better than many I have seen). I would be interested to test it against your one that you ordered.

I also need to sometimes double prime my lines before I start (or crank longer). I am assuming the issue is line pressure as it bleeds off once the engine is rested. I have not played with this aspect as yet as it might also be to short of a prime amount or even a cranking pulse width adjustment needed (as I am working on more important tuning areas at the moment).

So are you enjoying your 347?

[lukep6470]

Due to the storm damage the 347 hasn't left the driveway I can only turn left ATM so it might make for a long test drive.

I've ordered some 1mm phenolic shee to put between the fuel rails and the throttlebodies. The other culprit may be the bracket I've used between the throttlebody and the fuel rail is it is pretty chunky. I might look into perforating it to decrease the amount of metal the heat can soak into.

It goes in to the panelbeater on Monday.

[boofhead]

Good news - nice and straight. I assume your going to set the rev limit to be rather low say they cannot do any joy rides.

I agree the isolation of the rail to the TB is great and your idea of reducing the area to absorb the heat should help as well.

If you would like me to pop around on Sunday I could bring the temp gun as a trial test. I am tuning now so looking for excuses to drive and tune her (not that it takes to much of an excuse).

[lukep6470]

Where its going they've got a lot bigger toys to play with than mine. Think Italian.

We'll have a look at the heat soak issue after I've broken it in. Dart says 600 miles. As it is it has more than an hour so far just idling and I'd like to get some road miles on it before doing more tinkering.