HeatRaveR Posted May 20, 2005 Share Posted May 20, 2005 This may seem like an unusual question, but does anyone know about how hot the gas gets by the time it gets to the fuel rail (particularly for an L-engine)? The reason I ask is because I saw a fuel cooler from Flex a Lite that mounts inline with the fuel lines for cooling the gas. But I was thinking, just how hot could the gas be if it was just in the tank, pumped, and filtered? Shouldn't the temp not be much higher than ambient? Or does radiant heat soak from the exhaust under the car, fuel pump heat, etc. increase the temp of the fuel? Quote Link to comment Share on other sites More sharing options...
260DET Posted May 20, 2005 Share Posted May 20, 2005 Nice question and I don't know the answer. But because the inlet sits above the exhaust on the L series its higher than it needs to be. Solution - dump the boat anchor L and put in a crossflow engine Quote Link to comment Share on other sites More sharing options...
quicker240 Posted May 20, 2005 Share Posted May 20, 2005 I too would be interested in an answer to this.I had substantial problems with fuel temp in that my external electric inline fuel pump would overheat and leave me stranded on long road trips or stop and go traffic.My fuel would get very hot(I can fit my hand into my fuel cell).On one occasion,on the side of the interstate 100 miles from home,we had the idea of putting bags of ice on the top of the fuel cell and over the fuel lines.Not only did this cure the problem,the car IMMEDIATELY ran much better AND got significantly better mileage(22 mpg).I put an intank walbro 255 fuel pump in place of the inline Edelbrock supplied 255 pump and it ,being cooled by the fuel,solved the shutoff problems.However it cant run the engine AND nitrous both like the edelbrock pump did.Fuel pressure drops like a stone as soon as I hit the fun button.Now I either have to upgrade the intank pump or run a 2nd complete dedicated nitrous fuel line.Working on the fuel cell is a huge PITA! I've been putting it off for a while now,but something has got to give soon.I have new MT ET drag slicks and skinny fronts screaming to be broken in. Quote Link to comment Share on other sites More sharing options...
Here comes trouble Posted May 20, 2005 Share Posted May 20, 2005 Vapor lock is the old school term you fellows are describing and has been a perpetual problem plauging the internal combustion since conception.. Actually wooden clothes pins connected onto Ford Model T fuel lines would radiate heat out of the fuel line. Summer temperatures and any source of under hood heat, exhaust and even the road blacktop near the fuel line can cause this problem. I had a Dodge truck that was suceptible to vapor lock that i fitted an auxillary electric fuel pump to. When vapor lock occurred, I switched on the electric pump momentarily which cured the problem (and most likely cooled the fuel) Insulating fuel lines or fitting radiator type fuel line sections should work. When gas gets warm it wants to evaporate and that is why there was always an insulator between the Datsun carburator and the manifold to keep the fuel temperature down while the carburator vaporized the fuel correctly..Cold air intake is another term....The air filter on an EFI Z is right out front in the breeze to suck in the coolest air... Check your air intake and fuel lines and insulation between vaporization and the manifold. Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted May 21, 2005 Share Posted May 21, 2005 This may seem like an unusual question, but does anyone know about how hot the gas gets by the time it gets to the fuel rail (particularly for an L-engine)? The reason I ask is because I saw a fuel cooler from Flex a Lite that mounts inline with the fuel lines for cooling the gas. But I was thinking, just how hot could the gas be if it was just in the tank, pumped, and filtered? Shouldn't the temp not be much higher than ambient? Or does radiant heat soak from the exhaust under the car, fuel pump heat, etc. increase the temp of the fuel? As far as i am aware the temp increase of the fuel is created by the fuel being pressurised by the pump. Therefore this problem is much worse with the high fuel pressure efi systems (just like air heating up when compressed by a turbocharger). In the past on a race car, i have had a water/ice tank (for intercooler sprayer) that i ran fuel through a large coil of copper piping that was submerged in the water/ice tank to cool the fuel prior to entering the rail. I think now a days you can buy Co2 fuel rail cooling systems (is this what you are refering too?) Another important note here if you are running a surge tank on your efi setup, is not to run the fuel return back into the small surge tank as this is not giving the fuel a chance to cool down (better off returning to the larger fuel tank) Hope this is of some help. Quote Link to comment Share on other sites More sharing options...
HeatRaveR Posted May 21, 2005 Author Share Posted May 21, 2005 Thanks guys, I think I got the answer to my question. Btw, I have a 280ZX Turbo, so it's no secret how hot that can get. The fuel cooler I mentioned looks like a 2-pass tube-and-fin section of piping (like a tiny oil cooler). I figured I could simply splice the cooler between the fuel filter and fuel rail and mount it on the right side of the radiator. Quote Link to comment Share on other sites More sharing options...
zpeedracer25 Posted May 24, 2005 Share Posted May 24, 2005 Just thougth I'd add my 2 cents worth. I didn't see anyone mention the fact that your fuel gets heated while in the rail directly above a huge heat source and the excess (heated) fuel gets dumped back in the tank thus increasing the temp of your gas even in the tank. I'm not sure how hot it gets on the inlet to the rail...too many factors like ambient temp, time driven, and driving style/conditions. A fuel cooler is a good idea. Good luck with it! Quote Link to comment Share on other sites More sharing options...
Phyxius Posted May 24, 2005 Share Posted May 24, 2005 I don't think you'd want your fuel to be too cool. If it gets too cool, it may not completely vaporize when injected. Vaporization takes heat from the intake charge. It takes more heat to vaporize a cool fuel as compared to a hot fuel. Since vaporization cools the intake charge, you'd want the fuel to be just cool enough that it takes the most possible heat from the intake charge to vaporize it. So I guess what I'm saying is that the more effort you put into cooling your intake charge before the injection, the less you want to cool your fuel. On the other hand, if you don't have an intercooler or water injection on a turbo motor, you may want the fuel as cool as can be. I'm not sure this is making any sense....or if you could even possibly get the fuel too cool by conventional methods. Quote Link to comment Share on other sites More sharing options...
HeatRaveR Posted May 25, 2005 Author Share Posted May 25, 2005 Just thougth I'd add my 2 cents worth. I didn't see anyone mention the fact that your fuel gets heated while in the rail directly above a huge heat source and the excess (heated) fuel gets dumped back in the tank thus increasing the temp of your gas even in the tank. I'm Ooh! Good point! Haha, some good brainstorming goin' on up in here! I do not have an intercooler, so the intake charge isn't being cooled by anything (though I haven't raised boost pressure yet either). Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted May 25, 2005 Share Posted May 25, 2005 Just thougth I'd add my 2 cents worth. I didn't see anyone mention the fact that your fuel gets heated while in the rail directly above a huge heat source and the excess (heated) fuel gets dumped back in the tank thus increasing the temp of your gas even in the tank. I'm not sure how hot it gets on the inlet to the rail...too many factors like ambient temp, time driven, and driving style/conditions. A fuel cooler is a good idea. Good luck with it! Already mentioned about excess fuel being returned to tank, better this than to the surge tank (if you are running one) Quote: S15 200SX OWNER "Another important note here if you are running a surge tank on your efi setup, is not to run the fuel return back into the small surge tank as this is not giving the fuel a chance to cool down (better off returning to the larger fuel tank)" Quote Link to comment Share on other sites More sharing options...
fl327 Posted May 25, 2005 Share Posted May 25, 2005 fuel pressure is what cools fuel. in an efi system its pumping so fast i dont think it really gets a chance to heat up to a point of any significance. Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted May 25, 2005 Share Posted May 25, 2005 fuel pressure is what cools fuel. in an efi system its pumping so fast i dont think it really gets a chance to heat up to a point of any significance. Its the high pressure that is one of the main factors of it heating up. When you presurise some thing it is compressed which causes heat, just like the compressed air from a turbo, it is hot, hence why we use intercoolers. EFI is even worse that a low pressure carb system! Quote Link to comment Share on other sites More sharing options...
fl327 Posted May 25, 2005 Share Posted May 25, 2005 Its the high pressure that is one of the main factors of it heating up. When you presurise some thing it is compressed which causes heat' date=' just like the compressed air from a turbo, it is hot, hence why we use intercoolers. EFI is even worse that a low pressure carb system![/quote'] prove it... Quote Link to comment Share on other sites More sharing options...
zpeedracer25 Posted May 25, 2005 Share Posted May 25, 2005 fuel pressure is what cools fuel. in an efi system its pumping so fast i dont think it really gets a chance to heat up to a point of any significance. I'd have to agree. My point was that the heat is exchanged from the heat of the engine through the rail. Since when can you compress fuel?? How come pressurized coolant in your engine stays cooler then non-pressurized...hmmmm? The only heat that the pump adds is the heat it transfers from itself(i.e. pump gets hot doing work of pumping fuel). Take out your Raytek and measure the fuel line temperature at the fuel filter and the fuel line temp out of the rail and I'm sure you'll see a big difference. Quote Link to comment Share on other sites More sharing options...
zpeedracer25 Posted May 25, 2005 Share Posted May 25, 2005 Its the high pressure that is one of the main factors of it heating up. When you presurise some thing it is compressed which causes heat' date=' just like the compressed air from a turbo, it is hot, hence why we use intercoolers. EFI is even worse that a low pressure carb system![/quote'] Couldn't resist this one! If high pressure adds so much heat, how come the new Audi's that I work on are running 1700 PSI of fuel pressure directly injected into the combustion chamber on the new 2.0L Turbo?!?!?!?!?!?!?!?!?!?!? Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted May 25, 2005 Share Posted May 25, 2005 When a fluid is pumped the fluid temperature will rise due to the work of the pump. Also most FI pumps are also cooled by the gas. On a hot day there is probably more heat added to the gas from the time it leaves the fuel tank until it reaches the engine compartment. The reason Datsun insulates the fuel lines in the engine compartment is to stop vapor locking by minimizing the heat transfer between the hot engine compartment and the fuel line. The higher the fuel pressure the higher the temperature required to vapor lock the system. Penske back in the 60s on the Trans Am series Camaros would pack there gas cans in dry ice to get more fuel into the tank. I did a quick look at the cooling effect of gasoline, for dry air there is a 42°F drop in air temp due to the latent heat of evaporation at 14 to 1 air fuel ratio. When humidity is brought in it is closer to the high 20s. Quote Link to comment Share on other sites More sharing options...
Sparks280zt Posted May 25, 2005 Share Posted May 25, 2005 Its the high pressure that is one of the main factors of it heating up. When you presurise some thing it is compressed which causes heat' date=' just like the compressed air from a turbo, it is hot, hence why we use intercoolers. EFI is even worse that a low pressure carb system![/quote'] Your statement is correct regarding gas, but not a liquid. One of the gas laws (Charle's Law or Boyle's Law??) says that a compressed gas increases in temperature. (gas as in the state of matter not gasoline) Quote Link to comment Share on other sites More sharing options...
S15 200sx owner Posted May 26, 2005 Share Posted May 26, 2005 Your statement is correct regarding gas, but not a liquid. One of the gas laws (Charle's Law or Boyle's Law??) says that a compressed gas increases in temperature. (gas as in the state of matter not gasoline) Thanks for correcting me, i accept defeat All i know is that the fuel does get bloody hot, and that there are power gains to be had by cooling it, as we have done this on a race car to good effect. Quote Link to comment Share on other sites More sharing options...
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