Does cooler fuel enhance power and performance?

[CRiggan]

Im wondering if installing a fuel cooling device inline with the fuel line would increase or decrease performance of the diesel engine.



I know with gas engines that cooler fuel is a good thing.



From what I have read the cp3 uses a portion of the fuel for lube and recirculates it into the fuel filter housing. Do you think installing a fuel cooling device betweent the return line of the cp3 to the fuel filter housing would help some? Or am I way off here?



I even thought about installing one in the supply and return line.



I am under the impression that a fuel heater is needed for low temps to keep fuel from freezing up. So if it is 70 degrees or better outside , would the cooler fuel help at normal engine operating temp?



Thanks for the input.

 

[Bekim]

Cooling causes the fuel molecules to compact. Once compresssed to the exploding point the greater number of molecules in the combustion chamber=bigger boom=more power. That's how intercoolers, nitrous, or propane help(although propane burns too)

Cheers
Mike

 

[chrleb1]

I don't think cooling the fuel will give any performance gains. When cooling fuel on a gas motor it helps in absorbing energy from the air going through the intake (cooling the air). You have to remember that a lot of work is being done to compress the fuel to 6000 - 23000 psi. Most of the fuel going to the injection pump is actually sent back to the tank under normal driving. You would be better off trying to figure out how to cool the air more.

 

[rbattelle]

I would opine that a decrease in fuel temperature will increase the tendency for detonation by increasing the delay angle (aka delay period, aka ignition lag). We know (Taylor, The Internal Combustion Engine in Theory and Practice, Vol. 2, pp. 105) that decreasing inlet and jacket temperature tends to increase delay angle and rate of pressure rise. In my opinion, then, the primary effect of decreased fuel temperature would be a drop in cylinder temperature at injection. This, in turn, increases delay angle. The operator would notice a rougher running engine, similar to the way an engine runs when cold.



The question, then, is what effect this would have on power. Certainly the increased rate of pressure rise would introduce more stress on the engine components, but I'm not sure what immediate effect it would have on power. Best power timing results in maximum cylinder pressure between 15 and 20 degrees ATC. By changing the delay, we've moved that peak pressure later (farther ATC), which would imply a loss in power. But at the same time, it appears that MEP would be a bit higher in the case of the longer delay, which implies slightly more power available (or at least more torque). Perhaps the increase in MEP would be roughly balanced by the less-than-ideal maximum pressure timing, thereby resulting in no real power change.



Either way, it's unlikely the change would be noticed by the operator. What would be noticed, however, is the rougher running. Of course, I've said nothing about the effects of fuel temperature on the CP-3. I don't have any sense of the effect of fuel temperature on the delivery rate or pressure of the CP-3, nor to I have a good sense of how temperature effects fuel density (I know lower temperature will give higher density fuel, but I don't know how much... I suspect it's a very small effect).



In my opinion, then, looking only at the engine and not the CP-3, decreasing fuel temperature would not be useful.



This is all just opinion. I'm interested to see what others think.



-Ryan

 

[BHolm]

Both of my Isuzu-max trucks came with factory fuel coolers on the frame rail. Kind of a frightening concept considering I lived in central MN at the time and sub zero winter temps are a way of life. Never really caused a problem as near as I could tell.

 

[CRiggan]

Since the duramax uses a fuel cooler on the return line to the tank on thier 05 truck, seems like they are trying to cool the fuel going back into the tank after being heated by the cp3 and high fuel rail pressure.



Woulnt this help out the cummins ?

 

[nickleinonen]

i can see good and bad about a fuel cooler installed in the return. when i mod my fuel system, i am 75% sure i am going to put a cooler in the return system.

scotty posted over on the dtr about his troubles with the lift pump cooking/going bad from what appeared to be excessive fuel temprature...



if i do put one in, i will put a 3 way valve inline so i can bypass the cooler in colder months [and if in the event something happens to the cooler like road debris damage]

 

[JFaulkner]

I was told that on class 8 trucks, they are spraying the return fuel on the side of the tank to help cool it. This was brought up when the salesman asked if I wanted a fuel heater, and I asked if it was needed and he told me no because of the hot return, but he figured he'd ask.

 

[evldsl]

Im wondering if installing a fuel cooling device inline with the fuel line would increase or decrease performance of the diesel engine.



I know with gas engines that cooler fuel is a good thing.



From what I have read the cp3 uses a portion of the fuel for lube and recirculates it into the fuel filter housing. Do you think installing a fuel cooling device betweent the return line of the cp3 to the fuel filter housing would help some? Or am I way off here?



I even thought about installing one in the supply and return line.



I am under the impression that a fuel heater is needed for low temps to keep fuel from freezing up. So if it is 70 degrees or better outside , would the cooler fuel help at normal engine operating temp?



Thanks for the input.

WATER INJECTION!

 

[jelag]

Ryan has many good points and a couple of you don't understand some of the basic theroy..... I have to think back to my old fuels class... . but here goes...



Gasoline was cooled to prevent it from turning from a liquid to a gas in the fuel lines when carburetors were used... . early systems would cycle some of the fuel back to the tank, and this was also done with fuel injection allowing a small portion of fuel to return..... remember if you shut down a gasoline engine some of the fuel would go off as vapor and make the engine hard starting... . dropping the pressure at engine shut down and returning excess fuel to the tank helped this... .



On diesel engines, fuel temperature is important only to prevent clouding in the winter and that's why some engines have fuel heaters... . I don't beleive that the salesman in the dealer knows a thing about fuel return..... on all the new trucks we supply parts for the fuel return is nothing more than a port in the top of the tank to allow fuel return... If you ever had a diesel cloud the fuel and stop running you know why fuel heaters are so nice... .



Also, fuel flow through moving parts for lubrication is more import, so the volumn of fuel is kept high... to take away the heat and lube the moving parts in the injection system... .....



As mentioned above the lower the temperature of the air means more dense air and more power...



A diesel engine has excess air moving through the engine so some people will inject propane to add to the excess air... this extra fuel with the air provides better combustion and more power release with little or no added heat... ..... that's why propane functions as a way to increase HP.....

 

[rbattelle]

I'd like to make a small clarification. In my previous post I tried to only address the effect on engine power with a drop in fuel temperature. However, if we considered only the health of the CP-3, or we considered a condition like Scotty had (where his fuel was so hot it was melting things), then certainly a fuel cooler makes sense.



Now, if you're going to mount a cooler, the return line is a good choice, since you probably don't want to be sending cold fuel into the engine (for reasons I discussed earlier). A return line cooler will keep the tank temperature closer to ambient, which is good.



As jelag points out (and Nick), having a fuel cooler in MN or Canada in the dead of winter might not be such a great idea. Hey Nick, it would be cheaper to just make yourself an insulating blanket to cover the fuel cooler in the winter rather than plumbing in a 3-way bypass valve.



-Ryan

 

[CRiggan]

So I guess my final question is this...



Install a fuel cooler such as a tube and fin (radiator) design or aluminum unit with fins . Install this unit in the return line from the cp3. Run the line in front of the a/c condenser and install the fuel cooler. Run the line from the fuel cooler back to the tank. The winters down here arent too bad so maybe place a covering over it at that time and during the other seasons let it cool.



I think my first project will be installing a temp probe in the return line and monitor the temp and then if I need additional cooling I can do as above.



It seems a modded cp3 could use this config but I will know further after I install the gauge.

 

[Benson]

The coolers on the Duramax trucks are just mounted at the front of the tank underneath the truck.

 

[CRiggan]

Thanks for the info Benson,



Since this is a project for me I am going to install a temp probe in the return line and go from there.

 

[midlife crisis]

I'll throw this out there. Many Engine manufacturers, incl Cummins, use fuel coolers on Marine Engines.

You could infer 2 reasons, emissions & power. These coolers are almost always on the feed lines, but some can run feed & return. Typical coolers exchange with seawater, but keel cooled vessels exchange with the fw solution in that circuit. (The fuel is usually the "first in line" in the cooling circuit for max benefit.

The ISO 8665 standard for HP is a max fuel temp,(40C) at the inlet on the inj pump. I have seen some mfg's take some liberties here... but thats a whole different story.

Does it make a difference? Oh Yeah.

You would think the size of fuel tanks down in a cool bilge might not be affected, but you would be wrong.

Engine room temps can easily reach 125F, and hp losses due to high fuel temp can be very high.

We have seen this on the dyno, and real world boats that were propped right on the edge up north- then would not be able to make correct rpm when down south Florida or Caribean. Higher ambient & fuel temp were to blame.

Cat, Cummins, Yanmar, Volvo, DD, all use fuel coolers on some of their (Marine)products. There my . 02--

 

[CRiggan]

I got the following off the DANA automotive website:



Recent reductions in emissions from High Speed diesel engines have created a new need to cool the diesel fuel. The extremely high injection pressure provide many benefits, but one side effect is a large increase in the fuel temperature when the fuel is depressurized and sent back to the tank via the return line. This can create extremely hot return fuel that exceeds the limitations of the fuel tank (often plastic) and the fuel injection equipment.





Maybe the above is why Chevrolet uses a cooler on the return line. I guess if Cummins or Dodge thought we needed it they would have installed it at the factory. Im not sure but there is so much gray area with these new diesels and what should have been installed at the factory. Now that the stock fuel filter does not filter enough to keep our injectors in good running condition, I now have started wondering what the return fuel system temps are. I know that chevy uses a cp3 pump and I think they run higher fuel rail psi than the Dodge Cummins. I am no expert and its all a project to me so I will be off to install a fuel temp on the return line. Maybe I could also put a temporary temp sensor in the supply line to see if temps increase along while driving. That way it would tell me if the small return of fuel to the tank is heating the existing fuel and by how many degrees. .

 

[RoadGoesOnForever]

Im wondering if installing a fuel cooling device inline with the fuel line would increase or decrease performance of the diesel engine.



I know with gas engines that cooler fuel is a good thing.



From what I have read the cp3 uses a portion of the fuel for lube and recirculates it into the fuel filter housing. Do you think installing a fuel cooling device betweent the return line of the cp3 to the fuel filter housing would help some? Or am I way off here?



I even thought about installing one in the supply and return line.



I am under the impression that a fuel heater is needed for low temps to keep fuel from freezing up. So if it is 70 degrees or better outside , would the cooler fuel help at normal engine operating temp?



Thanks for the input.

The short answer is yes, fuel temp has a huge effect on power. Simply put and as others have said, cool fuel is denser, so for each firing of the injector, you get more fuel in the combustion chamber. So even though your BSFC (brake specific fuel consumption) does not change significantly, your actual power output will increase.

 

[nickleinonen]

Hey Nick, it would be cheaper to just make yourself an insulating blanket to cover the fuel cooler in the winter rather than plumbing in a 3-way bypass valve.

maybe, but when i eventuallly drop my tank for a vent mod [think i am going to go home made, not spooled up's kit] my tank also will get an assortment of other fittings attached [future pickup fitting, and extra return or 2 fittings] so if i put the cooler down near the fuel tank, it won't be a overly long run from the cooler outlet to the tank. stick it in one of the return fittings, and put the 3 way valve just before the cooler inlet, then the other end of the 3 way will return straight to tank. . i'll end up with some trapped fuel in the cooler, but if i get a brass valve, i can bore a small hole through the ball to allow a little bit to bypass into the cooler to keep the fuel stuck in there from going bad

 

[AMassaro]

This makes me wonder, with my current fuel setup w/ bypass at the cp3, if I'm doing good or bad as far as fuel temps are concerned. I have 20psi at the cp3 with a bypass installed between the cp3 inlet and return. This allows alot of fuel to/thru the cp3 for cooling and lubricating. I guess time will tell...

Anyone care to state what temp is too high for diesel fuel?

 

[JLEONARD]

If you look at Cummins marine engine specs they are rated differently for different fuel temperatures.

For example the 6BTA 270 hp that I had was rated at 270 hp with fuel at 77 F... . and 260 hp with fuel at 104 F.

My engine had an inline fuel cooler (by sea water) to cool the fuel on the return to the tanks.

Hope this helps.

Jay