2nd Gen Non-Engine/Transmission Fuel temps

[DHRA]

Has anyone found the optimum temperature for diesel fuel in the combustion chamber? Where is the best place to measure it? I know some folks are cooling their fuel, but is there a "best" temperature for the fuel? What other factors will affect the testing?



These are some of the questions that are going to attempt to be answered with LOTS of testing. "We" hope to have some information to assist in the tests.

 

[DHRA]

Tough one huh?

 

[HVAC]

I Don't Know

I would think the best temp would be the point at which the fuel starts to gel, plus a safe margin over that to prevent the gelling effect.



I can tell you that in moderate ambient temps my fuel temps would increase about 35* as a result of carrying heat away from the pump. This takes thirty minutes of operation or so. I believe the max temp I spotted was just under 140*. This was taken at the fuel filter.



Stirring the topic, stirring the topic

 

[Rob Thomas]

Eric,



I don't know either, but now you have me thinkin' about it. I didn't give it much thought before, 'cause I haven't had any issuse's, but I remember the gasser days when vapor-lock was a problem with some of my engines.



Question, do you, or anybody else for that matter, notice any differance in performance when the air temp is, say 40*? I would think that the fuel temp would be considerably less than 140*, when the air is that cold.



I would be interested and willing to fabricate a fuel cooler, complete with pre and post cooler temp gauges, and do some testing of my own. I think the return line would be the best place to mount it, what do you think?



Later, Rob

 

[illflem]

You are more concerned about cold fuel than hot because of gelling. Engines that I've been around that have fuel temp gauges are used to know when to turn on the tank heaters or verify that the auto heaters are working. I recall one Cat gauge that was laid out with blue(too cold), yellow(watch out) and green zones, the green zone went from 30°to 200°F. Essential when you're pulling fuel out of a 10,000 gallon above ground tank of straight #2 and it's -20° outside. I've seen heaters that run off a heat exchanger in the tank with engine coolant and also exhaust gas circulating. Never seen a fuel cooler for a diesel but have always worked with oil cooled/lubed pumps. Even our little engines will heat the fuel pretty good, I've measured the temp on the bottom of my full tank go from 20° to 125° in about 45 minutes of highway, it was 20° outside.

 

[Devildog]

I know our trucks like the cooler air, I not sure about the cooler fuel...

 

[WestTN]

Temperature has a relatively large effect on the viscosity of the fuel. The cooler it is, the slower it will flow through the injectors... .

 

[DHRA]

There is a definite difference at lower temps Rob, is it a combination of the ambient air AND the fuel? These are the answers we need. Nowell, I have been told that engine temp is more important than fuel temps, I disagree, everything has an optimal point, let's find out what that is!

So many people are afraid about talking about this stuff because of being the first person on the market with the answer. Screw the greed, we are a brotherhood, let's share and go kick some GAS ass!



I'm getting pumped up! Woooohoooo. Oo.

 

[HEMI®Dart]

I un-plugged my fuel heater in 40 degree temps and I'd swear the truck ran better.



I thought I read somewhere cool diesel has more "energy" than Hot diesel fuel. You need to get the fuel HOT to notice a difference.

 

[illflem]

I read on diesel net.com (sorry if you think TDR is pricey check this one out, free for me though) where some researchers have found that diesel heated to 720°F gave the least emissions. They tried higher and lower temps. They are now developing a fuel preheater that mounts on the exhaust manifold. Won't help much with a fuel cooled 24 valve though. Generally the cleaner running the better the hp produced.

 

[HiPerf360]

I would think that a warmer fuel would atomize better giving it a better combustion... . just a thought

 

[JConley]

Since the BTU's of diesel fuel doesnt increase or decrease with temp, I dont see where it makes a difference. The only way it makes a difference is due to an effect the fuel has on the air charge. Since you get more oxygen molocules with cooler air, (prior to the intake valve closing) cooling the air is going to be where you get a noticeable difference.



Hot fuel. . Since it is oil, it would flow faster, into the combustion chamber. It would also atomize faster since you dont need to extract as much heat out of the air charge to vaporize the fuel.



Cold fuel. . Slower to enter the cylinder, and require more heat out of the air to vaporize the fuel. This could possibly resulting in incomplete combustion of all fuel delivered. ( white smoke on a cold day ring a bell??)



I think the best route would be to have the coldest air possible entering the cylinder, and the hottest fuel.



Just thinking out loud... .

 

[illflem]

Originally posted by JConley





I think the best route would be to have the coldest air possible entering the cylinder, and the hottest fuel.



Just thinking out loud... .

I agree except that the air should be 50°-90°. Cold air is what gives you smoke in the morning and below 50 a drop in hp.

 

[JConley]

Here is another point to ponder. . When you cool the air after the turbo, you have high pressure cool air (relatively speaking) When the intake valve opens, you get a very big pressure drop. This is going to instantly cool the air as it enters the cylinder. On aircraft, this is how the AC works. Pressurise the air, cool it, pressurise it again, run it through a second stage aftercooler, then drop the pressure very fast and you have instant cold air that you have to regulate to keep things from freezing. It would be interesting to see what manifold temp and boost levels would be needed to get the correct air temp in the cumbustion chamber prior to the valve closing.

 

[CMNS PWR]

Eric, take a gander at this bro:

http://www.chevron.com/prodserv/fuels/bulletin/diesel/L2_4_6_rf.htm

dang chemistry... . if it were physics, I could help hehe.

Let me do some more digging, and I'll get back with it.

 

[CMNS PWR]

the physics viewpoint

Well, I am back with more info:

http://naca.larc.nasa.gov/reports/1938/naca-report-617/

take a close look at pages 4 and 5.

Any of you who have had thermodynamics on an advanced level, should have no trouble following this data.