Cooling Fuel

[tkach]

As I was cleaning my garage today I found a spare transmission cooler. Seeing that I have an integrated trans cooler in my radiator I really don’t have any use for it. So while I am redoing my fuel system I figured I would use it to cool my fuel. It has 3/8 in/out this leads my to believe that it wouldn’t slow my fuel flow down. Pressure shouldn’t be an issue as I am running a carbureted system at 8 psi. By cooling the fuel I should be able to eliminate vapor lock although that hasn’t been a problem, I might pickup a small horsepower increase. Id like to route it to protect it from any impact. Has anybody had any experience with this? any input?

[Challenger]

I was planning on doin something like this but with a oil cooler maybe. Interesting to see what others thoughts are.

[Tony D]

A 1 gallon thermos wrapped with 16 feet of copper tubing and filled with ice to the top will attain 120 degrees in 2 hours driving across the desert, but the car will not vapor lock in stop n go traffic on the Vegas Strip. You will have to refill the container every two hours.

 

Fuel coolers will be rather innefectual using ambient heat. Wrapping your pickup line on the cool side of the AC plumbing is a better bet. Matter of fact some new vehicles do this to stabilize the fuel temp.

 

The only reason the thermos heated up was because the fuel return wasted the cooled fuel sending it back to the tank. Ever feel your tank when it's having problems? You will be amazed how hot it is! Once it goes into the engine bay and heads back to the tank...it just starts building on itself.

 

Perhaps some Peltier devices on the bottom of the fuel tank or along the way? JeffP, you watching this thread?

[Challenger]

Arent there returnless fuel systems. You could keep all the cool gas if it didnt go back to the tank, right?

[280Zone]

I run a cool can similar to what Tony describes but it is for the 1/4 mile car. If what Tony says is true about tank heating up the trans cooler might be of some help.

[Tony D]

Not really, you have to get the gas below ambient, all a 'cooler' will do in that case is warm it back up to ambient after being cooled by the cool can.

 

Now, stick that cooler IN the cool can and you might have something. I made that setup for a Japanese Clubmember who had terminal vaporlock on his 240Z. It was 'stop every hour' time, took forever to get anywhere driving through Barstow, Needles, etc.

 

Installed that little cooler, and he was good to go, no more surging nothing! Of course, he had to refill the thermos with ice every time he filled up, but most service stations sell ice for $1 a bag or thereabouts, so for an extra dollar a tankful he had NO problems. Even cruising the strip in Vegas at 110F in June Heat. Problem solved till he returned to Japan! LOL

 

We run a Cool Can on our Bonneville Car, and if humidity is high you can see condensation on our fuel cel. We only carry two gallons onboard so the cool can will chill all the fuel to 32 F rather quickly. They sell very efficient units in Summitt. They just won't run for Two Hours at a time. For that you need more ice capacity.

 

The returnless systems are just now coming on to line, using PWM control of the fuel pump and a fuel pressure sensor to regulate fuel pressure, instaed of a bypas fuel pressure regulator. This gives advantages in that the ECU can boost fuel pressure to trim for extremes in fuel demand, without the use of larger injectors, etc. Thing is, you need some residence time for the ice to cool that fuel, and with a returnless fuel system that may actually work better.

 

If anything, putting that cooler on the return line to cool it down would be the thing to do, but it's like farting in the wind. Very little effect at all. You need to get it COLD, not merely 'less hot'!

[Cruez]

I thought I read somewhere that the hotter the fuel is, the better it is to vaporize and burn more efficiently, like the system Smokey Yunick had on a Fiero.

 

The air charge is the main concern with keeping cool..

On that same note though...vapor lock would pose a problem in most cases.. I guess there is a fine line there..

[Challenger]

A cooler fuel is more dense (more fuel), but I think the largest reason to have it cooler is so it wont detonate as soon. It takes longer to rise to the temperature that it will ignite. Therefore you can run more boost/compression. Right?

[Tony D]

Cool Fuel has a desnity of BTU's that is higher. For a given injected volume, the cooler the fuel, the more horsepower it will produce.

Gasoline at 100F will have a 'power density' due to expansion almost 10% less than Gasoline injected at 60F.

 

This is why there is a call for temperature compensated fuel pumps for gasoline now. Fill up at 58 degrees, and you get 'less' gas mileage per volume consumed compared to when you fill up at 100 degrees.

 

The BTUs you get in a gallon of gas at 58F is radically different than what you get at 100F. Ever wonder why the Z31 EFI systems used a fuel temperature sensor? Why most now do?

 

The detonation issue from cool fuel is because you won't run 'lean' because there is 'more' fuel when it's cold as opposed to when it's hot.

 

Hot fuel and running a vapor flash pan vaporization scheme for induction is an OLD trick from the 50's and the mileage marathons. There is a lot more to it than simply heating the fuel. I can show fuel mileages in almost every case when you heat the fuel...but it is purely due to non-temperature compensated fuel metering. You run leaner, plain and simple. As long as the car is not put into lean surge you will never experience it in any way other than increased fuel mileage.

 

When Detroit Diesel did Dyno Testing and reports for acceptance testing, one of the critical temperatures measured was "FUEL TEMPERATURE"...and all HP derived was compensated for that number, amongst others. Old time truckers new if you got a Detroit to run on hot #2D (above 130F into the unit injectors from the lift pump) you would see a great increase in fuel mileage. They were simple mechanical injectors, and you got a set volume per injection event. Hot Diesel injected less BTU's per cycle, but volume wise it was the only way they measured their fuel consumption. Many guys would run a 'heater loop' for the fuel along the radiator hose when deadheading with the tractor, or an empty trailer. But bypassed to another fuel line that provided cooler fuel when they were pulling a grade on the next segment, or were heavily loaded. On OTR trucks, 3% is huge, and deadheading saving 3% or more of fuel is huge when your independent.

 

Did I digress too much?