My brain has been working overtime on this themal barrier thing. Anyways I know carb people have used many methods to keep the fuel cool for the extra horsepower. So would not the same thing work for a fuel injection system.

On a LT1/TPI system you have a fuel manifold with a pressure regulator that feeds the injectors. Looks to me that the fuel manifold will heat up with the motor and also heat up the fuel.

So would it not be beneficial to isolate the fuel manifold to keep the heat out or at least lower it. Here are my thoughts. Spray the outside of the manifold and fuel lines with a thermal barrier. Install phenolic isolators where the manifold bolts to the manifold. Maybe bore out the mounting holes one size larger so that the themal barrier reaches inside the mounting holes to isolate the manifold from the mounting bolts.

Goofy idea or something to it.

 

We use to do it with a "cool can"ya put ice in the can and run the fuel through it. It isn't popular these days because of the line hook ups for the injection.
The pump causes a lot of heat in the fuel also. I like a bigger pump with a controller to turn it down under normal use and go wide open under WOT.

 

Put an inline air-to-fuel cooler in the recirculation loop. That's done when you run a really big fuel system, and the recirculation at low engine loads pours heat back into the tank.

 

[QUOTE=89TramsAmGTA
So would it not be beneficial to isolate the fuel manifold to keep the heat out or at least lower it. Here are my thoughts. Spray the outside of the manifold and fuel lines with a thermal barrier. Install phenolic isolators where the manifold bolts to the manifold. Maybe bore out the mounting holes one size larger so that the themal barrier reaches inside the mounting holes to isolate the manifold from the mounting bolts.

Goofy idea or something to it. [/QUOTE]

As I mentioned in my other post in the Thermal Coating thread, the recommendation of the tech people at Swain Technology, is for the top of the manifold to be coated with a heat emitting coating (like their BBE material), but that would most likely cause extra heat to be radiated to the fuel rails. Looks like they should at least be coated with a thermal barrier coating, and phenolic isolators would help even more.

The only thing, if you're concerned about appearance, the TBC is about the color of Gray Poupon mustard.

 

Thanks for the replys. Cehan the looks is the main reason I don't want to use the heat emitting coating on top of the manifold. Just wondering how much of a benefit if any there would be by keeping the fuel cooler by say 10 to 20 degrees F or more. May not be worth the effort.

 

I don't believe it's worth the effort.

When you've got fuel running through the injectors at ~50 PSI, give or take, physics says that higher pressure = higher temperature. It seems to work in my opinion.

How is cooling fuel beneficial to this since vapor lock is a thing of the past? I remember that carbs icing up isn't a great thing for fuel atomization, either...

 

It makes it more dense and ya can pack more in a given space.
It wont ice up any carbs............
A cool can or cooler don't cool it to the point of 32* dude.

 

cool fuel and cool air = dense = bigger bang, yea I've been debating where to hook up a "cool can" on my carb setup, mainly it's really hot under my hood from thin headers anyway. the benefit really is determined by how hot the fuel is, like if your fuel in your carb is actually percolating (boiling) stopping that will produce significant (massive) gains. but the gains that i've seen are spotty, some report immense gain, others report no difference.

now that that's said here's some food for thought, back in the old days when they had the gas pumps that had the big glass container up top... they used to measure how much gas you used by how much gas left the glass container, which typically held 5 gallons. Now on a hot 90* day, you keep your fuel cold, say 60* (i dont know how cold they kept it, but... this is my guess, they may have put it in the freezer and got it to 30*). and you poor 3-4 gallons of your 60* or less fuel in the empty glass container. The hot sun heats the gas up and it expands and fills the complete 5 gallons, now someone puts that 5 gallons in their car, you made free money because they paid for 5 but you only gave them 3-4 gallons.

This is the reason that gas is held in tanks far below ground at a standard temperature (about 60* i cant remember precisely)

but it would help you to some degree, you'd need to cool it after the pump, and where you cool it you'll want thin aluminum fuel line (don't even try it at the auto parts store, you gotta get it from a performance shop, summitracing.com has it) and once you cool the fuel, I'm feelin' that idea on the manifold, but i always fear boring mount holes larger, adds some play where there shouldnt be any... i'd just use phenolic isolaters, and a thermal barrier on the part of the bolt that touches the manifold, i dont know how much space you have to work with, but just my .02 you may also be able to use a gasket material that's cut to fit around the bolts to help out.

fuel rails would also be a good thing to put a barrier on, as they're so close to the engineand for that matter, any part of the fuel line close to exhaust and/or motor.

hopefully this helps

 

and higher pressure = higher temperature because of chemistry, the molecules collide more often and more energy is released, but like 1racerdude said, you don't get it to 32* and you'll only ice up if you have water mixed with your gas and below 32*(but if you have water in there you need gas line antifreeze to fix that issue) gas freezes far below zero (like here in Wisconsin we run our cars in 20*F below 0 and we dont freeze fuel)

and i've never had vapor lock but it's prevented by pressure, 50 psi fuel aint gonna boil, keeping it denser by keeping the molecules from spreading out as much, means you blow up more gas and produce more bang

 

No2 will freeze a carb in a heartbeat.(and when it does it is lean and hurts parts) They had lot's of trouble with that way back when.

Ya went around your elbo but you are correct about the fuel.

Ya never had vaporlock and run 1/2 of a grapefruit skin on the fuel pump to stop it.
Ya ain't lived yet.

 

lol, yea i havent lived yet, but thanks man i was planning on putting No2 on my carb this summer, before i toasted my transmission, I'm keeping that freezing point in mind.

and also the grapefruit skin? i don't think i would have thought of that.

 

It was common practice for us po folk that couldn't afford a new pump right away.

Todays times they don't have as much trouble with the plate designs they have now. Just remember if it misses,sputters,etc in high gear it is rich. If it wants to run better than it should it is lean and get out of it.

 

Let's get a grip people... some of these statements are not rational.
Density relationship of an API 56 gravity gasoline would indicate that increasing the temperature from 60degF to 90degF would change the density by about 1.8%. Obviously not enough to allow "3-4 gallons" of gasoline to expand to 5 (a 25-67% volume increase). You would put 4.9 gallons of fuel into the container at 60degF. It would occupy the 5 gallon container at 90degF.

That brings things back to reality. Temperature of the fuel changes density, but its a small change.

I'm not sure how the comment "physics says that higher pressure = higher temperature" applies to this discussion at all. Heating a material causes it to expand, but pressure will change only if it is constrained by a fixed volume. Compressing a gas will cause the temperature to increase, but we're not talking about compressing a gas, or dealing with the issue of adiabatic efficiency.

Icing of a carb is not tied to the fuel being at 32degF, and icing of a carb does not relate to "and you'll only ice up if you have water mixed with your gas and below 32*". Icing occurs when the metal parts reach 32degF and the moisture in the air freezes on the metal parts. Moisture from the air - not water in the gasoline. The major contributor to the cold temperatures required to actually freeze the moisture in the air is the fact that the gasoline is vaporizing, and the latent heat of vaporization is subcooling the air. Its not because the fuel itself has ben cooled to 32degF.

Density of the fuel is important, and changing density will affect air/fuel ratio. Heat the fuel up, and it conains less energy per unit volume. And the delivery devices... injector or carb.... are volume-based delivery systems. In a carb setup, this can be a problem.

In modern, electronically controlled, closed loop fuel injection system, the control system will correct for changes in gasoline density. Less mass of fuel supplied by the injectors, leaner the mixture.... O2 sensors pick it up and increases the fuel delivery rate. Not a big issue. If you run open loop control, and need consistancy in performance, you need to standardize on a fuel, and keep it cool. The difference in specific gravity from fuel blend to fuel blend can be sustantially greater than the differences caused by temperature of the fuel.

Vaporization of fuel can be a consideration even in a 50psi fuel delivery system. The pump needs to "pull" the fuel in on the suction side of the pump, and high temperatures fuel coming from a tank at atmospheric pressure can have its pressure reduced to the point where the fuel can flash to vapor.... big bubble of vapor hits the pump = no fuel pressure on the discharge side. "In-tank" systems and pumps with low net positive suction head (NPSH) requirements minimize the tendancy toward vaporization on the suction side, but an outboard pump can present major problems, in terms of suction line diameter, elevaton of the pump relative to fuel level, and the NPSH requirements of the specific pump.

Keeping the fuel cool is important, but attempting to do that by some complicated process of reducing heat transfer to the rails is not cost effective. The recirculating fuel picks up heat from numerous sources, including the energy lost due to the efficiency of the pump in the pumping process, the use of fuel to col the pump, lines running near exhaust systems, lines running in the hot engine compartment, etc. A fuel cooler is simple and cost effective.

 

I don't see how you could maintain your grapefruit skin readiness. Some guy wants to race you - you say, " Wait just a minute while I apply a fresh grapefruit to my fuel pump." or "You only won the race cause my grapefruit was too dried out and I vaporlocked!"


Did you ever use clothes pins on the metal fuel line to get rid of vapor lock?

 

You guys are too funny and showing your age. Very informative post Injuneer. Thanks.