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Engine Specific Info and Questions => IDI Engine => Topic started by: vwmike on April 26, 2005, 11:10:55 pm
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A post from another thread got me thinking about fuel coolers. A few months ago i ran a can of diesel hi-test through my truck and after it had been running for a while the contents of the can were steaming it was so hot.
The same way charge air becomes heated due to pressure generated by the turbo, fuel would also be heated by the injection pump. Obviously the pressure is much higher so the temperature rise should be higher. On the good side, it has that whole tank of fuel in the back to mix with and cool down....but the lower you are on fuel, the hotter the fuel would become.
My question is: For our purposes, how beneficial would it be to keep temperatures in check?
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Incompressible liquids do NOT heat up when pressurized the same way as compressible fluids (air) do. Fuel becoming heated upon exit from an IP may happen, but it has nothing to do with the the thermodynamic reasons that a turbo heats the air. I suspect that it's mostly just from plain old conduction heat transfer.
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Most of the heat generated within the pump is the result of windage. Stirring any viscous fluid will generate a fair bit of heat.
I would like to have some kind of thermostatic regulation of fuel temperature just for consistancy in performance. My car smokes a fair bit when its cold but as it warms up the fuel loses density and the power (and smoke) falls off a bit. It would be nice to have a consistant fuel temperature of 90ºF or so. I was considering a pelteir cooler of the type used in "Koolatron" type coolers. It would have the advantage of being able to heat the fuel in the winter as well. Might be a bit technical but I have the necessary parts in stock, now I just need the time...
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I found relocating the fuel filter in the passenger fender was effective in helping to keep the fuel cool and maintaining consistent performance.
I had the worst fuel temperature problems when I was running a short exhaust system terminating after the shift boot with a turn-down before the fuel tank. During an 800 mile road trip the turn down fell off, and the hot exhaust blew directly at the fuel tank! Performance was noticeably down as a result.
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Incompressible liquids do NOT heat up when pressurized the same way as compressible fluids (air) do. Fuel becoming heated upon exit from an IP may happen, but it has nothing to do with the the thermodynamic reasons that a turbo heats the air. I suspect that it's mostly just from plain old conduction heat transfer.
Ah, for some reason that fact esxaped me in my moment of brainstorming. I wonder if it's still worth trying sometime.
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Things don't always work the way we hope. But, the nice thing about this forum is that we're all trying to come up with some neat stuff and help each other out. I think it's great.
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I guess a better question would be how fuel temperature affects performance. I've never really seen any reference to this, but does anyone have any data to shed some light on this?
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I read somewhere that the IP was already temp compensated. I dono if it's true since I have no data...
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I read somewhere that the IP was already temp compensated. I dono if it's true since I have no data...
for my SVO conversion (in progress) I have rerouted the fuel return line with a t-fitting so that the returned fuel goes directly back into the injection pump rather than back to the tank. This was necessary to keep vegetable oil out of the fuel tank. I wonder if this will affect performance? I always thought the hotter the fuel, the better the viscosity, the better the atomization that the injector is able to produce. Maybe I am wrong?
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I think this is an area where diesel requirements are different than gasoline requirements. In a diesel, you want the fuel to burn immediately when it squirts out the injector. On a gas engine, you want the fuel to not burn until the spark plug fires, and the cooler the fuel, the less likely it will explode from compression heat.
Other than a slight density advantage, I don't see cold fuel as being an advantage on a diesel engine. You might get a little more in, but it will take longer to atomize and burn, too. If you're trying to run highr RPM's for higher horsepower, that's going to hurt more than it helps.
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I have some peltier 350W coolers if anyone is interested in trying a fuel cooling device. All you need is a big enough heatsink on the hot side, and the cold side will get extremely cold :D
I also thought of using the power generating peltier's to generate the power from the turbo exhaust to power the peltier cooler (not as hard on the battery/alternator)
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I guess a better question would be how fuel temperature affects performance. I've never really seen any reference to this, but does anyone have any data to shed some light on this?
The coefficient of volumetric expansion for diesel is 0.00046 per degree F, so if the temp of the fuel rises 100F between the tank and the injector pump, each stroke of the pump injects about 4.6% less fuel than if the fuel were 100F cooler. That will definitely affect performance, since the power of a diesel is pretty much directly proportional to how much fuel is being injected.
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I guess a better question would be how fuel temperature affects performance. I've never really seen any reference to this, but does anyone have any data to shed some light on this?
The coefficient of volumetric expansion for diesel is 0.00046 per degree F, so if the temp of the fuel rises 100F between the tank and the injector pump, each stroke of the pump injects about 4.6% less fuel than if the fuel were 100F cooler. That will definitely affect performance, since the power of a diesel is pretty much directly proportional to how much fuel is being injected.
Alright, that is the answer I was looking for :D
The only thing I was really able to come up with before was heat and it's relative effect on viscosity. I didn't really think about expansion rates. Thanks!!
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someone needs to try one of these and see if there is a increase in power. http://store.summitracing.com/default.asp?Ntt=fuel+cooler&Ntk=KeywordSearch&DDS=1&searchinresults=false&N=0&target=egnsearch.asp
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I was just going to hook an automatic transmission cooler into the return line (those are cheap and/or free). I would think putting it on the feed would probably make the pump have to work too hard to draw in the fuel.
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I was just going to hook an automatic transmission cooler into the return line (those are cheap and/or free). I would think putting it on the feed would probably make the pump have to work too hard to draw in the fuel.
if you put it on the return line you'll pop all the little return hoses off of the injectors because of too much back pressure.
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I was just going to hook an automatic transmission cooler into the return line (those are cheap and/or free). I would think putting it on the feed would probably make the pump have to work too hard to draw in the fuel.
if you put it on the return line you'll pop all the little return hoses off of the injectors because of too much back pressure.
hmm.... I wouldn't think there would be much backpressure from the cooler, but maybe... :?:
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Isn't the Summit/Moroso stuff for drag racing where you put ice in the can? But the question remains, is cooling beneficial to power...
In the gas engine sense, the cold fuel helps cool the air charge which makes it denser and you can suck in more air/fuel mixture. Thus more power.
If it only makes the fuel denser so you can get more fuel in then now you have an improper AF mixture. You could do the same thing with a simple carburetor jet change.
There's a limit though. You could start icing up your carburetor. This is a concern on alcohol motors due to the much higher latent heat of vaporization. The fuel evaporating gets the carburetor so cold that ice starts forming in various places it shouldn’t
This same mechanism won't work in a diesel because no fuel evaporates and no charge air cooling will happen. Perhaps you could use LP fumigation, alcohol injection, water injection, or intercooling to cool the air going into the intake. Or just crank up the fuel and smoke it like you didn’t care. I suspect that these methods will have more effect on power output.
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Isn't the Summit/Moroso stuff for drag racing where you put ice in the can? But the question remains, is cooling beneficial to power...
In the gas engine sense, the cold fuel helps cool the air charge which makes it denser and you can suck in more air/fuel mixture. Thus more power.
If it only makes the fuel denser so you can get more fuel in then now you have an improper AF mixture. You could do the same thing with a simple carburetor jet change.
There's a limit though. You could start icing up your carburetor. This is a concern on alcohol motors due to the much higher latent heat of vaporization. The fuel evaporating gets the carburetor so cold that ice starts forming in various places it shouldn’t
This same mechanism won't work in a diesel because no fuel evaporates and no charge air cooling will happen. Perhaps you could use LP fumigation, alcohol injection, water injection, or intercooling to cool the air going into the intake. Or just crank up the fuel and smoke it like you didn’t care. I suspect that these methods will have more effect on power output.
I don't think you meant that it was, but lot of what happens on the alcohol cars and whatnot isn't all that relavent to this discussion. Regardless, it is good information. If in fuel, colder temperatures drive the molecules closer together then the result of cooling the fuel would be more "potent" fuel being injected into the combustion chamber. As for messing with the mixture, that really doesn't seem to be a concern because how much power you make with a diesel is all about how much fuel you can inject and still maintain safe operating temperatures (EGT's). Therefore, since we have a fixed oriface and mechanical pumping limits, a more dense fuel charge would increase power output potential. Of course this is making the assumption that you've maxed out your fueling potential. In the same aspect, I wonder if it would help or hurt mileage. The cold can really is for one time use though. I think a normal liquid/air cooler would work just fine. :D
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This same mechanism won't work in a diesel because no fuel evaporates and no charge air cooling will happen.
Absolutely correct. Fuel temperature control on a diesel would be about consistancy, not power. I just want the same power whether the engine was just started or if it has been idling in traffic for 2 hours. If I only wanted more fuel I could just crank the quantity adjuster in some more. I'm not quite at the limit yet, very close though...
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Well, after 2 hours of sitting in traffic, you would also have to worry about heat soak in your cooler.
I just don't think the benefits would be much for a fuel cooler on a diesel engine. And you could usually get the same increase in fueling by adjusting the pump. But it's your car, and if you want to try it, go for it. It's not going to hurt anything, and there's no real risk to yourself or anyone else.