Settle an argument - insulating fuel lines

[MisterCuriosity]

Hey there,

MisterCuriosity here!

I am a car enthusiast. Though admittedly I do not know all the ins and outs of lubrication and engine mechanics. That being said I am an extremely curious person.

The other day I overheard my coworkers arguing about insulating a fuel rail. One of them was arguing that their car needed it, that they had measured the heat of their fuel rail and that it was much too hot. They said adding insulation to the fuel rail would keep the fuel temperatures lower which would keep octane levels up and intake temperatures down a little. The other coworker was laughing at him and told him that if he insulates his fuel rail and brings the fuel temperature down he will effectively destroy his engine. He said that bringing fuel temperature down will help engine performance but that the colder and less gaseous fuel will wash lubricating oil off the cylinder walls and destroy the engine fairly quickly on a daily driver. They argued back and forth for a while, but this was the only piece of the conversation i heard.

seemed like an interesting debate. Thoughts?

 

[Trav]

Insulating fuel lines was sometimes necessary to prevent vapor lock mostly on carburetor engines, it can happen to FI engines depending on the type of system used but it would be rare. Insulating the line will not increase the octane or lower the intake temp to a real measurable degree.
The second co worker is just an idiot.

 

[dishdude]

Interesting first post. Both your coworkers are crazy!

 

[A_Harman]

Don't know if this argument is worth settling. Both sides are making flawed assumptions. Since the fuel rail is firmly bolted to the engine, it will heat the fuel up close to coolant temperature by conduction. Putting insulation around the outside of the fuel rails will not necessarily make the fuel cooler. Heat transfer into the rail by conduction from the engine tends to heat the fuel inside, and convection to the air surrounding the rail tends to cool the fuel. If insulation is added to the rail, it could actually make the fuel hotter by decreasing heat convection to the surrounding air. Ask your friends why they think fuel rails have ribs on them.

 

[SHOZ]

There are kits that you run the fuel line through a ice filled box. Knew one guy who use to do it on his turboed '90 Taurus SHO. I would not think with the higher fuel pressure you see now that heat would be a problem.

 

[delirious]

That was a problem with our 4.0L 1999-2004 Jeep WJs. It would get so hot because the fuel rail is right over the exhuast and intake manifold that there would be what the person described "vapor lock". There was a tsb on it.

Experienced it myself. For the jeep it happened about 5-10 minutes after shutting the jeep off and all the heat accumulates.

The only problem I see with insulation is that yes, it is good at keeping the heat out, but once it gets hot, it usually traps that heat in. I have planned on fixing mine by only having the insulation on the bottom half of the injectors that face the exhaust and intake manifold. Protects it from the mass heat wave but still allows for heat to escape. JMO

 

[The_Jeff]

The theory is sound but the logic is flawed.

While cold fuel won't change the octane of the fuel, it will help, slightly, with using it to its full advantage.

But getting the air that comes in colder is of greater benefit. There's 14 airs for every gas!

 

[SirTanon]

Insulating your air delivery components is frequently a good thing, primarily if you're looking for power.

Insulating your fuel rail is almost always useless, at best. I could be wrong, but I'd think you'd want your fuel to be on the warm/hot side. Hot fuel vaporizes better than cold fuel.

Bottom line, they're both wrong on so many levels.

 

[Donald]

In boats with big block FI GM engines they use sea water to cool the fuel before the filter I believe.

 

[Ihatetochangeoil]

Originally Posted By: Trav
Insulating fuel lines was sometimes necessary to prevent vapor lock mostly on carburetor engines, it can happen to FI engines depending on the type of system used but it would be rare. Insulating the line will not increase the octane or lower the intake temp to a real measurable degree.
The second co worker is just an idiot.


As usual, Trav is right. I'm older now, but back in "the day," I was a NASCAR fan, and the racers would add extra fuel line to the system in a coil, with the coil enclosed in a "can," and pack the can with ice...It was known as a "cool can" to avoid fuel vapor lock on a blistering hot race track, and you can probably still find some cheap knock offs at JCWhitney or eBay.

http://www.jegs.com/p/Moroso/Moroso-Insulated-Cool-Cans/747208/10002/-1 (NOT) recommended for fuel injected systems.

 

[Johnny2Bad]

Gasoline is a super efficient insulator, and with Fuel Injection, there is more fuel circulating back to the tank than being used by the engine. The gasoline being pumped at pressure through the system is also the cooling fluid to keep the fuel pump cool.

Short answer, in a carbeurated application, yes, in some cases there is a benefit, as the fuel can be stored in the float bowl or moving slowly through the system (low pressure of typically under 10 psi but can be as low as atmospheric gravity fed). In a fuel injected application, very unlikely and possibly detrimental (for example, the insulation may store moisture that encourages deterioration of a fuel system component).

 

[BrocLuno]

What he just said

 

[Trav]

Originally Posted By: Johnny2Bad
Gasoline is a super efficient insulator, and with Fuel Injection, there is more fuel circulating back to the tank than being used by the engine. The gasoline being pumped at pressure through the system is also the cooling fluid to keep the fuel pump cool.

Short answer, in a carbeurated application, yes, in some cases there is a benefit, as the fuel can be stored in the float bowl or moving slowly through the system (low pressure of typically under 10 psi but can be as low as atmospheric gravity fed). In a fuel injected application, very unlikely and possibly detrimental (for example, the insulation may store moisture that encourages deterioration of a fuel system component).


Not all FI systems are circulating systems, most today are not. A returnless system is more susceptible to vapor lock under certain condition.

http://www.underhoodservice.com/point-of-no-return-returnless-fuel-injection-systems/

http://www.aa1car.com/library/returnless_efi.htm

 

[andyd]

E 23 and E 28 BMWs shipped to the tropics have the fuel lines running through the HVAC housing. EFI fuel mgt.

 

[Jetronic]

that. coil a fuel line around the ac return, and use that to cool the fuel if you must. that way you won't cool the fuel in winter, don't need to fill a box with ice, don't have to worry about corrosion because of wet insulation material etc...

But I wouldn't care for a gas engine. I've known common rail diesels though that melted their plastic fuel tank. Tuned, ofcourse, not stock. And the fuel levels were rather low.