Fuel Talk - PeachParts Mercedes-Benz Forum

Monomer · #1 04-20-2008, 09:32 PM

Since it's not yet been covered.

What would the highest BTU fuel be for out benzes, and whats the cutoff limit before we start breaking stuff?

I usually fill up with 45 cetane petrol, with half a bottle of MM oil added per fill up. (now switching from MM to 2-stroke oil)

#2 04-20-2008, 10:19 PM

Quote:

Originally Posted by Monomer

What would the highest BTU fuel be for out benzes, and whats the cutoff limit before we start breaking stuff?

Straight #2 diesel.

From wikipedia:
Generally, diesel engines run well with a cetane number from 40 to 55. Fuels with higher cetane number which have shorter ignition delays provide more time for the fuel combustion process to be completed. Hence, higher speed diesels operate more effectively with higher cetane number fuels. There is no performance or emission advantage when the CN is raised past approximately 55; after this point, the fuel's performance hits a plateau.

GREASY_BEAST · #3 04-20-2008, 11:47 PM

I would venture a guess that a fuel like bunker fuel, or maybe some other less-refined petroleum fuel would be a higher BTU fuel than diesel... likely won't have cetane rating worth a crap though.. and will pump out the particulates... and will require a centrifuge to process, as well as enlarged 2 micron fuel filters to protect your engine... oh wait, have all of the above.. so where do you get bunker fuel?

GREASY_BEAST · #4 04-21-2008, 12:04 AM

a follow-up:

Quote:

The heat*producing capacity of fuel products is measured in British thermal units (Btus). A Btu is the amount of heat required to raise
the temperature of one pound of water by one degree Fahrenheit. One gallon of no. 2 heating oil contains approximately 138,000 Btu.
One gallon of no. 6 residual fuel oil contains approximately 148,000 Btu. The Btu content of no. 4 fuel oil depends on the percentages of
the distillate and residual components of the blend, but is commonly 143,000 Btu per gallon. Thus, all other factors being equal, a build*
ing will require less no. 6 oil than no. 4 oil or no. 2 oil to heat the same amount of space because it has the highest Btu content per gallon.
The higher the Btu content of the fuel, the less of it you need attain the same results.

I won't vouch for the credibility of this source, but here's the URL:

http://www.castleoil.com/content/media/pdf/MannRpt200610.pdf

They are claiming a 7.2% higher BTU content of #6 than #2, and a 3.6% higher BTU content of #4 than #2... I'd go with the #4 because it should be run-able in a SVO system, but I'd worry about heating the #6... they need fairly high temperatures to run it effectively... over 200°F if I remember correctly.

Monomer · #5 04-21-2008, 05:02 PM

also; what temperature would the fuel perform at it's best. We have fuel heaters on our cars, but what range would give the best atomization?

FI; I expect a short, breif answer that shoots down all my questions with one blow.

...don't disappoint!

#6 04-21-2008, 05:32 PM

Bunker oil would take a lot of work to use, its nasty stuff.

I'm pretty sure 180*f is as hot as the fuel should be allowed to get. The cooler it is the more dense it is.

Here is an attachment to get those gears tuning.

Lower cetane has more energy but higher cetane burns better.

Monomer · #7 04-21-2008, 08:29 PM

Quote:

Originally Posted by ForcedInduction

Bunker oil would take a lot of work to use, its nasty stuff.

I'm pretty sure 180*f is as hot as the fuel should be allowed to get. The cooler it is the more dense it is.

Here is an attachment to get those gears tuning.

Lower cetane has more energy but higher cetane burns better.

Yes, the more dense it is; but - by heating it, couldn't we use a worse burning oil with higher BTU (since it'll get close to burning temps)

will the higher BTU offset the lower fuel density?

GREASY_BEAST · #8 04-23-2008, 12:28 AM

what needs to be found is the rate of expansion of #4 fuel oil with respect to temperature, or a table, graph, or function with density vs. temperature, then you figure #4 has something like 4% more energy per volume than diesel... does it expand 4% more when heated to xx temp?

babymog · #9 04-23-2008, 08:56 PM

Most of the volume in the cylinder is air, and air will expand more with more heat. Maybe I'm coming into the middle of the movie, ...