Does cooler fuel enhance power and performance?

[Buffalo]

I have an in-bed, alum. diamond plate, 115 gal. aux. fuel tank. On a recent cross-country trip, pulling my trailer, I was surprised at how hot the fuel tank was. I have a shell covering the bed which cuts down on cooling airflow over the tank. This was in the summertime & when I opened the shell, to refill the tank, I noticed the heat belching out of the interior of the truckbed.



I have a couple of heavy-duty transmission oil & motor oil coolers laying around the house. I wonder if they could be installed in the to & return fuel lines?



Any thoughts about the compatibility of the diesel fuel & the metals that make up the coolers? I've heard that brass will start to be attacked by diesel fuel after temperatures of 70 deg's. or higher.



This is another great thread. Thanks to all who have contributed to some interesting, thought provoking, reading.



Joe F. (Buffalo)

 

[AMassaro]

I really hope that brass problem you're refering to is false...

 

[Buffalo]

AMassaro,



I first heard about the brass being attacked by warm diesel fuel from TDR member "Spooled-up". He's the developer of the "fuel tank vent mod", that so many of us have tried.



In his "vent mod", you plug the stock vent hose. I called him asking about running both hoses into a "brass" tee? Would it help the tank "breathe" even better?



I believe he said that he had tried it with a brass tee & then had read, somewhere, that diesel fuel, over 70 deg's. , starts to have a reaction with brass. He said that if I was to try it, use a nylon tee. Nylon is compatible with warm diesel. I believe he said that he was going to change his to nylon.



Personally, I know nothing about chemistry or metallurgy, or how the two work with, or against one another. I'm sorry if this turns out to be inaccurate information but, it's probably better to check it out & find out, for sure.



Joe F. (Buffalo)

 

[betterthanstock]

Galvanized (zinc) has a problem, and also brass/copper, but less so.

I did some searching on this, and apparently only aluminum and stainless are the preferred metals. They say copper (in brass also) has a catalytic effect which causes some solids to form in the fuel that may clog filters (I would not worry about a small fitting, since it does not have enough time to do the damage before you change filters). I wonder if that is so bad, since it oxidizes some of the bad stuff in fuel that would probably form deposits on the injectors anyway.

Zinc they say can deposit inside the injectors, so if you honed 'em too big, put in some zinc lines and that should reduce those holes. :-laf



Bosch cautions against zinc, not copper or brass, and I know there are some brass parts in some fuel lines out there in production. They say biodiesel is worse with copper and brass than regular diesel.

 

[rbattelle]

Is brass compatible with diesel?



-Ryan

 

[betterthanstock]

I edited the prior posting.

Maybe.

 

[Cattletrkr]

I got bored reading about too many guys trying to re-invent the wheel so maybe something similar has already been mentioned.



My brother works for a multi million dollar, maybe darned near bilion dollar, concrete company. That is, he drives a cement truck. They run heaters on all their trucks to heat the fuel. Not just in winter to prevent gelling, all year 'round. Supposedly they get better mileage. Enough so that the entire fleet of a few hundered trucks uses them. I don't believe everyting "big business" tells me, but when they say they save 10's of thousands of $$$ a year in fuel because of this, I listen.



My take is that hotter/warmer DIESEL should "compression ignite" easier than cold fuel. I have no science to back it up, it just makes sense.

My $. 02

 

[nickleinonen]

that diesel fuel, over 70 deg's. , starts to have a reaction with brass.

all the older emd engines i have at work have brass fittings & copper lines in the fuel system. the fuel temps can get well over 100* and they are all older than i am and don't have too many problems. . we use lots of black iron too, but every union in the iron pipes has a brass seat to seal.

 

[Amish Elegance]

I have limited physics knowledge, but hear my possibly flawed logic out... Someone stated earlier that the return fuel that decompresses after the pump is very hot. Aint that kinda backards? Compression generates heat, decompression cools, yes?



Certainly there is an ideal temperature somewhere around the "warm" range? What about atomization? Fuel that is cooled too much would atomize poorly due to the fact that density increased. The denser the fuel, the more pressure that it would require to atomize properly/efficiently/optimally. I would think ice boxes on the feed line to the pump are out.



What about too hot? It seems it is also possible to thin out fuel too much by over heating it. Say density is lowered to a point that the btu's per injection event are significantly reduced. Then we've lost power as well. Other illustrations have been used as to why hotter fuel is detrimental to performance, so I'll save the ramblings.



Ideal fuel density, which in the end is what this amounts to, could vary from application to application based on factors like injection pressure and volume. It seems to me, there should be a happy range for fuel temp. Get all the cool air in you can, (more dense), and shoot the densest fuel in you can atomize.





If i offended anyone, replace the periods with question marks. I'm off to find my marbles. :-laf



Thanks for this thread. Theory threads like this keep me entertained and usually make me smarter.

 

[CRiggan]

So if a normal operating diesel engine running at 190 degrees f to 200 degrees f. We should not worry about cooling the fuel ? I wonder who I could contact to explain to me the proper temp for diesel fuel to work its best?



But even if the temp of the fuel was at the correct temp to work its best I would need to factor in temps inside the combustion chamber.



Now I am a little confuesed. I should have not posted this thread. LOL

 

[nickleinonen]

if you can maintain an even 100*f fuel temp, that seems to be a good compromise between too cold and too hot.

 

[jelag]

I've got to step back in.....



When manufactures measure torque and HP they use controlled standards so that one test is the same as the next test... . so air temp, fuel temp, engine temp... etc etc is controlled for repeatable results..... that way when they make a change they know if the change was an improvment or not..... Now can we see those changes in our on the road, trucks... don't think so.....



Remember at up to 20,000 plus lbs in the fuel rail... . temperature of the fuel, and its ability to push through small holes in an injector is not going to be lot different from 30 degree fuel to 140 degree fuel in the fraction of a second that the injector is open... In fact I don't think that there might be test equipment to test the difference... now if we stroke each injector 1000 or 10,000 times we might find a difference... . but not measuring 5 or 10 strokes... .



Also remember that the marine verision of these engines don't use this 20,000 plus injection system yet..... so one long large spirt of fuel through a low pressure system might be a lot different than at 20,000 plus..... above 10,000 lbs there is not a lot of difference in compressability of any liquid... .



In my mind, the whole engineering arena changes with the high pressures and multi-fire per power stroke we are dealing with today... ...



Years ago... when I was taking my fuels classes in college the 100 mpg carburator was talked about... . the one taken off the shelf by the oil companies... . and our instructor kindly asked us about what it took to get an 5000 lb vehicle up to 60 mph in say 15 seconds... . we learned that friction from air, and rolling resisitance were the 2 largest factors in controlling mpg..... by reducing friction, or frontal area, and or rolling resistance, the same 5000 lb vehicle would save fuel in an acceleration up to 60 mph in 15 seconds... .



There are specific engineering formulas for all of this..... most are over my head... it amazes me about what it takes to get a 747 off the ground, and up to 600 mph and keep it there till it climbs to 35000 ft and less air resistance.....



Do I personally believe that temperature of fuel will make a difference in fuel economy, or proformance... . NOT in what we drive.....



My nickels worth.....



Jim

 

[midlife crisis]

"Remember at up to 20,000 plus lbs in the fuel rail... . temperature of the fuel, and its ability to push through small holes in an injector is not going to be lot different from 30 degree fuel to 140 degree fuel in the fraction of a second that the injector is open... In fact I don't think that there might be test equipment to test the difference... "



I am not so sure thats accurate. Again I would refer to ISO & SAE standards that Marine engine Mfgr's adhere to for power & emission standards. There is a difference, and it is meaured.



"Also remember that the marine verision of these engines don't use this 20,000 plus injection system yet..... so one long large spirt of fuel through a low pressure system might be a lot different than at 20,000 plus..... above 10,000 lbs there is not a lot of difference in compressability of any liquid... "



The Cummins 5. 9l QSB 425 is HPCR (as are others) and runs 21,765 psi in the rail.

Other's use HPCR as well as EUI, which inj opening pressures are even higher.

Besides the power/emission factor, there is a consumption issue as well, and the cooler (denser) fuel will yield higher mpg. Yes, hard to see in our vehicles, but in a vessel with a tank 100-1000 times bigger, run constantly, there is a big savings.

The other item not mentioned is a micro-organism issue in warmer fuel. The cooler in the return yields a big benefit here. . again in a marine environment

The comment of brass fittings- alright from my world, as well as ABYC standards. While there are regs relating to thread depth, fire & heat survival time, sizing to flow, location . . etc etc, (the list goes on) the use of brass is permitted in marine.

 

[betterthanstock]

Consider a few facts:

--The Sprinter van uses a fuel cooler.

-- Our stainless lines do act as a small cooler.

-- Watch out for the thermostatically controlled 300w fuel heater in the filter housing, you want to not overcool it in cold weather, which adds the complication of a thermostatically controlled cooler.

--I think the only reason for a cooler is to prevent fuel breakdown from overheating. There is less mass (BTU) of fuel in the same injected volume of hotter fuel, and hotter fuel will ignite faster and uses up less BTU to heat itself, so they kind of offset each other.

-- I would worry more about the temp. of the incoming air than the fuel, as it influences performance more.

-- Marine engines have the advantage of air-to-water intercooler, heat exchanger (radiator), and if you care, fuel heater/cooler. But if you live in the South, and use biodiesel, get a cooler. That bio is less tolerant of heat.

--A full tank provides more cooling than an empty tank.

--Metal fuel tanks provide better cooling than plastic, but they also cause more water condensation (in cold weather) from the air that comes in as the fuel is burned.