FiveSeventyZee Posted October 12, 2009 Share Posted October 12, 2009 ok so I know that gas coolers are an often disputed as to their affect on an engines power but from what I've found I get this: cooler gas means denser gas. denser gas allows you to get more fuel in the charge. more fuel in the charge means more to burn and more power. the argument I've seen often is that it doesn't work for EFI engines because the fuel o's constantly flowing through the return lines back to the gas tank and doesn't have time to sit and heat up like it can in carb bowls. also putting ice in your car isn't very practical for anything more than a quick drag race. I've seen automatic transmission fluid coolers for sale (specifically one on jegs) that has a little note at the bottom saying "these work great as fuel coolers too!" these seem to be a better/more practical for road use cars or cars that might be raced for more than one or two quarter mile runs because they use air to cool the gas just like a radiator would. now up till here I haven't put much of my ideas in this. I was thinking last night. I have a 240z with a SBC swap. I have a radiator out of a 4 cylinder camaro. the camaro was an automatic, the ATF cooler is built in to the radiator. since I have a 5 speed I have nothing going to the fittings on the radiator. wouldn't running my gas lines through the ATF cooler that is built in to my radiator work just the same and cool my gas giving me the denser fuel and all that goodness (my SB is carbed) I do see a possible flaw in my idea though. my worry is that the ATF cooler is so close to the coolant that it might actually warm the gas because the coolant is much hotter. so my question is, has anyone tried ths? does anyone have any thoughts on this? Quote Link to comment Share on other sites More sharing options...
cockerstar Posted October 12, 2009 Share Posted October 12, 2009 The ATF cooler built into my camaro radiator is cooled by the same coolant that cools the engine. Yours may be different, but in my application it would definitely end up warming the fuel. Quote Link to comment Share on other sites More sharing options...
FiveSeventyZee Posted October 12, 2009 Author Share Posted October 12, 2009 it's built into the radiator, the radiator cools the coolant. the ATF section of the radiator is cooled by air too, not the coolant. if you were to unplug the ATF Lines and run the car it coolant won't come out of them. this is what I'm doing now. my worry isn't about the coolant mixing with the gas because it won't. I'm a little worrie about the close proximity of the coolant tote ATF cooler section edit: unless the lines just go into the tank and back out and the coolant itself cools the ATF fluid. but that wouldn't make sense to me because cars that have separate ATF coolers use air to cool them like a radiator does. Quote Link to comment Share on other sites More sharing options...
rxsleeper Posted October 12, 2009 Share Posted October 12, 2009 I will take a stab at this. DON'T run fuel through the ATF cooler portion of your radiator. The maximum cooling you could get will be the exact same as the temperature of the water running through the radiator when it is the coolest. Thermal transfer of the coolant will make the ENTIRE radiator rise/fall to the temp of the coolant. Most vehicles have a 180* or slightly higher thermostat so if ambient temp of your fuel is 75* you will always be heating your fuel to 180* Cooler, denser, power making fuel is best achieved by insulating the engine heat from the fuel lines so that the fuel is as close to amibient temp as possible. Trying to take it farther, ie cool beyond ambient, will cost you lots of time, $$$$, and fab skills. FWIW, I have a external cooler for the tranny of my truck. when not towing I see 165* or so tranny temp. When towing it rises to nearly 200*. In 90+ degree summertime while towing my radiator temp rises to 200* as well. I have to watch it closely and I do service the radiator and tranny on a regular basis. YMMV Quote Link to comment Share on other sites More sharing options...
neotech84 Posted October 12, 2009 Share Posted October 12, 2009 I like the idea of using what you have but I too agree that it would heat the gas to the coolant temp. You could use it for an external oil cooler though.... if you wanted to put it to good use. Quote Link to comment Share on other sites More sharing options...
cockerstar Posted October 12, 2009 Share Posted October 12, 2009 I will take a stab at this. DON'T run fuel through the ATF cooler portion of your radiator. The maximum cooling you could get will be the exact same as the temperature of the water running through the radiator when it is the coolest. This is exactly what I was saying. I know the coolant does't cool the ATF, but in my radiator there is coolant circulating around a chamber the ATF passes through. There aren't any radiator fins dedicated to cooling ATF on its own. Now if you were going to run a separate ATF cooler as a a fuel cooler like the one pictured below, you would be in business. Using the one integrated into your radiator is only going to heat the fuel up to the temperature of the coolant. Quote Link to comment Share on other sites More sharing options...
Iceman Posted October 13, 2009 Share Posted October 13, 2009 Gasoline is a liquid. Liquids cannot be more or less dense. As long as you can get it to the carb without starting to vaporize (i.e. protect it from the engine heat) then it will be a liquid when it gets there. Since the fuel is under pressure, it is already less likely to vaporize. The only time running through a cooler is going to help at all is going to be when you are moving. When you are moving, the fuel is flowing and is much less likely to have a chance to heat up anyway. The time when fuel is most likely to heat up is going to be when you are stopped or in slow traffic. If you add a cooler (more distance for the fuel to travel) you will probably actually increase the time exposed to heat. If you were to add a little electric fan to it, it might help. Quote Link to comment Share on other sites More sharing options...
Sparks280zt Posted October 13, 2009 Share Posted October 13, 2009 Fuel coolers are regulary added to big rigs to ad power. The CAT computers actually increase fuel input when the fuel warms up to keep power and not lose it. Now, that is diesel fuel, not gas. Quote Link to comment Share on other sites More sharing options...
FiveSeventyZee Posted October 13, 2009 Author Share Posted October 13, 2009 the statement that it'll only be the same temp as the coolant also gas a flaw though. the coolant flowing to the input is at a certain temperature probably up in the 180-225 range it travels through the radiator and cools to a certain temperature. if you were to install a thermometer and get a reading for a baseline you can use that to compare. if you were to use say a second radiator between the engine output and the radiators input (an unrealistc idea for in a car but I'm making a point) that would lower the input pressure to around where the output pressure (baseline) was. then that already cooler coolant would flow through the original radiator and cool further. my point here is this: cooler input = cooler output. assume that's true (which I believe is so) then think of it in terms of gasoline. the temp would be around what 75F? much lower than 180, thus resulting in a lower output. I stand by that statement 100% and it would take a very good scientific explanation to get me to drop that. what I'm saying is, since the input is less than that of the coolant, the output will be lower than that of the coolant. what I am unsure of is whether or not that will be cooler than the gas input (75F-ish) get what I'm thinking? edit: cockerstar, what you're saying is that the lines I am thinking of just go into a tube in the reservoir and back out? I kind of thought it would flow through the cores. The thing is I haven't hacked up any radiators lately so I don't really know whats going on in there. Whether or not the ATF flows through the cores thus being cooled by air is 95% of what would make or break this idea. Quote Link to comment Share on other sites More sharing options...
Nigel Posted October 15, 2009 Share Posted October 15, 2009 the statement that it'll only be the same temp as the coolant also gas a flaw though. ???? coolant flowing to the input is at a certain temperature probably up in the 180-225 range it travels through the radiator and cools to a certain temperature. if you were to install a thermometer and get a reading for a baseline you can use that to compare. if you were to use say a second radiator between the engine output and the radiators input (an unrealistc idea for in a car but I'm making a point) that would lower the input pressure to around where the output pressure (baseline) was. then that already cooler coolant would flow through the original radiator and cool further. my point here is this: cooler input = cooler output. assume that's true (which I believe is so) then think of it in terms of gasoline. the temp would be around what 75F? much lower than 180, thus resulting in a lower output. I stand by that statement 100% and it would take a very good scientific explanation to get me to drop that. what I'm saying is, since the input is less than that of the coolant, the output will be lower than that of the coolant. what I am unsure of is whether or not that will be cooler than the gas input (75F-ish) get what I'm thinking? I'm no physicist, but I'm not sure that you're taking the second law of thermodynamics into account. Heat always transfers from a higher temperature medium to a lower temperature medium, not the other way around. This is why a radiator works in the first place. The higher temperature coolant in the radiator transfers it's thermal energy to the lower temperature air that passes through the radiator. This is also why a transmission cooler will sometimes be packaged inside a radiator like in your Camaro radiator (it will likely just be a tube with fins that runs through the lower radiator end tank that the rad coolant circulates around). While the radiator may be hot (180F), the transmission fluid can get hotter (say 220F), and therefore, that higher thermal energy in the transmission fluid will be transfered to the "cooler" radiator and then to the even cooler air (75F). So, if you pass a fluid through the transmission "cooler" built into the radiator that is cooler than the radiator, that fluid will get hotter without a doubt. In this case, the fluid we're talking about is fuel, and it's getting circulated by the fuel pump over and over again. The entire volume of fuel in the tank is completely circulated in a matter of minutes (9 min for a full 15 gal tank using a 100 gph pump. Only 3 min with 5 gals remaining!). However, just because the fuel is being circulated and is not sitting still, doesn't mean that it doesn't pick up heat. the argument I've seen often is that it doesn't work for EFI engines because the fuel o's constantly flowing through the return lines back to the gas tank and doesn't have time to sit and heat up like it can in carb bowls. In fact, heat transfer INCREASES with flow speed (up to a point). Consequently, in addition to the heat generated by the pump compressing the fuel, and the heat picked up in the fuel lines in the hot engine bay, it would now also be heated directly by the 180F radiator, so you'll just be heating that volume of fuel in the fuel tank rapidly, over and over again, and the fuel temperature will skyrocket! From my personal experience, I've found that fuel temperatures can get to be quite high simply due to the pump compression and radiant heat picked up through the fuel lines (especially the fuel rail). With a 1/4 tank left, I've put my hand on the bottom of my fuel tank after being stuck in stop and go traffic, and it's almost been too hot to touch! I've seen the impact of this on the air/fuel ratio leaning out considerably, going from 13:1 at idle to start and climbing to 17:1 after being stuck in traffic for an hour. This is with all else being equal. To remedy this, I've added a fuel cooler and insulated all of my fuel lines, not to increase performance, but to stabilize performance. I'm also considering adding a variable speed fuel pump controller, which varies the pump speed based on rpm. This would allow the pump to run slower at slower engine speeds and therefore circulate less fuel and minimize heat transfer. Wow, I didn't expect to write so much. That's all for now. Time for dinner... Nigel '73 240ZT Quote Link to comment Share on other sites More sharing options...
Flexicoker Posted October 15, 2009 Share Posted October 15, 2009 Fuel's density will change with temperature, but you're fuel system is already capable of delivering more fuel than you will need for a given situation. Cooling your fuel is not going to make any more power. But keeping the temp constant will keep you from losing power if the temperature starts to increase. I like the idea of insulating all the lines, I too have noticed very different AFR's after sitting in traffic with air temp, and coolant temp not changing much. I wonder if you could just use a fuel temp sensor to compensate? I saw an interesting presentation the other day about fuel heating to improve efficiency. The jist of it was heat the fuel to near boiling after its pressurized, then when the fuel is injected, the rapid pressure drop causes really efficient vaporization of the fuel. Quote Link to comment Share on other sites More sharing options...
FiveSeventyZee Posted October 15, 2009 Author Share Posted October 15, 2009 Thank you Nigel. That was the type of informative scientific reasoning I was after. And no, I did not account for the 2nd law of thermodynamics. Now that I think about it, I learned that last year in chemistry... Oh well. And the ATF cooler is only cooled by the coolant? not the air? Thats what I'm getting from what you're saying. Quote Link to comment Share on other sites More sharing options...
cockerstar Posted October 20, 2009 Share Posted October 20, 2009 Thank you Nigel. That was the type of informative scientific reasoning I was after. And no, I did not account for the 2nd law of thermodynamics. Now that I think about it, I learned that last year in chemistry... Oh well. Thanks for drawing the entire picture Nigel And the ATF cooler is only cooled by the coolant? not the air? Thats what I'm getting from what you're saying. That's what I was saying all along Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted October 20, 2009 Share Posted October 20, 2009 Fuel starts at ambient temp in the tank. Why put it through a "radiator" that (at best) is at ambient air temp? Am I missing something here? Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 20, 2009 Share Posted October 20, 2009 We had a 240Z that was vapor locking in daily driving only after highway runs. We put a makeshift fuel cooler into the car that was constructed out of a one-gallon igloo cooler and copper coils, we could put a whole 7# bag of ice in there, and it would prevent (ABSOLUTELY) any vapor locking of the vechile under any conditions. One thing we noticed was that after 2 hours of highway driving the ice was totally gone and the water was up to near ambient temperature in the engine bay (around 140 on a 90-100 degree day). We realized that as the tank got lower, the ability of the fuel in the tank to act as a heat sink and dissipate absorbed heat picked up from the engine bay was less and less. People with EFI cars have noticed their AFR's go crazy sometimes when they operate high specific output cars with less than 1/2 or 1/4 of a tank. The fuel heating affects the heat content of the fuel (BTU's)---this is the impetus for requiring fuel dispensers to be temperature compensated. Fueling stations make money selling 'hot fuel' later in the day than they do in the morning and overnight when the fuel can be as cool as 58F. Even small changes in gasoline can make for a large (up to 10+%) difference in volume. When everyone says their injectors are 550cc, do they mean at 60F, or a 160F. The heating value of the 550ccs delivered at 60F will be far different than 550CC's at 160F. We generally use volume delivery systems, which are uncompensated for temperature (air temp on EFI helps). When you do that, your power levels are inconsistent. Drag racers chill the fuel not only for maximum density, but for maximum consistency---taking fuel temperature out of the equation leaves only air density, and they measure that and jet accordingly. No cool can and your air density measurement is a guess in the dark! Depending on the temperature of the fuel delivered, it's heating content can vary GREATLY! Combined with air density that will not be changing at the same relative rate... and you have an issue. Small power steering coolers were always on my mind as fuel coolers. The factory rally cars in European Winter Campaigns had differential coolers in the fuel tanks! Helped keep the fuel warmer to prevent icing of the tripple carbs in winter rallys. In short, if the cooler is on the return, the goal is to lower the temperature on the return and keep it from rising above ambient (the assumption that fuel in the tank is at ambient temperature is seriously flawed, get a temp gun and take a reading sometime, the only time It's at ambient is before you start the car in the AM. After that, it is consistently, and in some cases considerably above ambient temperature!) If the cooler is on the fuel feed side, it has to incorporate some sort of artifical cooling (running the line along the A/C Cold Line, inside the insulation for instance, or ice bath coolers) to lower fuel temperatures for highest density and consistent fuel delivery temperatures. Note the Z31 computer uses a fuel temperature sensor, and has a compensation table to go with it... Even Nissan acknowledge there was an effect on emissions and power that is related to the temperature of the fuel. Quote Link to comment Share on other sites More sharing options...
brokebolt Posted October 22, 2009 Share Posted October 22, 2009 Link to a search briefly covering tank heating, return lines and cold cans. http://forums.hybridz.org/showthread.php?t=79631#5 Quote Link to comment Share on other sites More sharing options...
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