60Driver

Anyone ever thought to cool something in the engine with fuel? Say maybe run the fuel and the coolant next to each other in a small radiator? I know they do that in some turbine engines (i.e. the GE 700 and 701C I know for a fact have a liquid to liquid cooler that cools oil and heats/atomizes fuel before it enters the combustion section)

I know it's probably not realistic to do this in a 951; but I'm just wondering what people think about the idea.

They way I was taught, such a system is twofold. Not only does it cool whatever fluid you need cooled, but it also heats up your fuel and atomizes it which, apparently, makes the combustion process more efficient.

Whitt944

Liability for manufacturers would be through the roof!! It would probably be cost restrictive for the average guy.

tommo951

I was always of the impression that the fuel had to be cooler to make HP as the fuel becomes vapour as it gets hotter
Diesel may be different, but thats not my bag!

anders44

yes, cold fuel = hp, hence the old old dragtrick to cool the fuel, it's forbidden in most race classes.

tommo951

Hey Anders on my 7.1 V12 Jag we cool the fuel through the air con plant! Works well!!!

nick_968

Diesel needs to be cool as well for optimum performance.

bleucamaro

Generally speaking its a bad idea for gasoline engines. With a carburetor, vapor lock is a common problem but that is with a low pressure suction type fuel pump. With high pressure in tank (or near tank) fuel pumps used with EFI cars, its not as bad a problem, but on Hot Rod's Power Tour a couple years ago, several high performance (twin turbo V8s & supercharged V8s) running high flow pumps and return style fuel systems (like 944's) began experiencing vapor lock because the fuel was being warmed on each trip to the engine compartment. Decreasing fuel pressure makes people do things like this:



links from: http://www.pro-touring.com/forum/sho...er+tour+cooler

Bri Bro

On turbine engines using aviation kerosene it does work. There were experimental engines developed that heated gas to vapor before combustion with good results on fuel mileage. It is a tad bit dangerous with gas vs kerosene.

I think this would fit in a 951 hatch with a little work.

60Driver

I guess the idea is a little crazy. What's the biggest difference? I'm thinking that it has something to do with the different stages of a piston-driven engine vs. the continuous burn of a turbine.

On the turbine, the fuel goes through the oil cooler/fuel heater just before it hits the pump which sends the fuel to the nozzles. So the gas isn't vaporized for very long. And it's a continuous stream of fuel.

I guess there are probably also issues of vaporized fuel seeping through the valves and into the pistons during the wrong stage? Or could it be more dangerous due to premature ignition of the heated fuel?

You could probably fit a turbine under the hood. It's not going to have the same output as a big GE turbine. Plus you'd better have a lot of money to spend on fuel!

Droops83

FWIW 996s/997s/Boxsters use the air conditioning system to help cool the fuel. I know that is not exactly the same as what the original poster was saying, but of course the A/C has to be running (and working properly) for the cooling effect to work. My 951 had some hot start/vapor lock issues at the track a few weeks ago, as I know others have had, and this could be why Porsche has installed this from the factory in newer cars. But, you generally don't run your A/C at the track anyway, and I'm not sure what kind of HP gains we're talking here . . . .

Acetylene

Cool fuel = hp +2

Chris White

aero turbines tend to work in a lot cooler environment than automotive engines....

bleucamaro

Turbines and piston engines are completely different beasts. Now, I'm nowhere near an expert on turbines, but my understanding is that the more heat in the burn chamber is a good thing (similar to having more heat in the hotside of a turbo is a good thing). With a gas piston engine, the gas is two things, first its a fuel, and second its a coolant. When gasoline vaporises (transforms from atomized liquid to vapor) in the combustion chamber it pulls alot of heat out of the piston, head, and cylender surfaces (read more by googling : Heat of Vaporisation). This is the reason why you richen the mixture when increasing boost, to cool the cylinders, cool the intake charge, and therefore prevent predetonation.

S2cab

That's a pretty ghetto set-up, but I've seen people cool a CPU down by the same method.

bleucamaro

When you're hundreds of miles away from home or anything resembling a shop, where there is however a home depot and quickie mart, its a pretty ingenuitve cure to keep a car on the road.