What Cetane Diesel do you use? - Page 2 - PeachParts Mercedes-Benz Forum

#16 01-19-2006, 12:30 PM

Quote:

Originally Posted by Old300D

I was under the impression cetane was merely ignition delay, the higher the number that faster it kicks off. If the fuel delays on ignition you won't have as much time in the power stroke to make torque, hence a drop in power.

I believe you are correct. The "energy" in the fuel is defined by the heating value of the fuel (BTU/lb.), not the cetane rating.

TX76513 · #17 01-19-2006, 03:06 PM

Quote:

Originally Posted by Old300D

I've not heard that. I was under the impression cetane was merely ignition delay, the higher the number that faster it kicks off. If the fuel delays on ignition you won't have as much time in the power stroke to make torque, hence a drop in power.

I run homebrew biodiesel, cetane whatever it is. 50?

The instrument that test the cetane uses some sort of formula with ignition delay, higher the kick off, higher the cetane =more energy/power.

Rich300TDMBZ · #18 01-19-2006, 04:13 PM

The ASTM Standard Specification for Diesel Fuel Oils (D-975) states:

"The cetane number requirements depend on engine design, size, nature of speed and load variations, and on starting and atmospheric conditions. Increase in cetane number over values actually required does not materially improve engine performance. Accordingly, the cetane number specified should be as low as possible to insure maximum fuel availability."

For gasoline engines, the manufacturer specifies whether the engine requires regular or super unlead. I cannot find such requirements for diesel cars. From the discussion so far, there appears to be diesel fuel with a cetane range from 40 - 50. Do anybody has any info that diesel engines run better on higher cetane diesel fuel (data please, not I feel it runs better!)? Does the new Mercedes diesels require higher cetane numbers for maximun operation? Thanks.

raMBow · #19 01-19-2006, 04:50 PM

I'm with "OldNavy" (Nice to find you here after all the years on the Fred's/TDI Club) and the MFA biodiesel as described, here in Missouri. MFA's are everywhere here in the central part of the state, so bring on the B20. Otherwise, I get the Amoco BP, with the minimum 50 cetane (15 gallons) and then get some B20 and top it off. Very pleased with either, as long as some BioDiesel used. Since the first time I did the B2, I have never gone back to dino and love the B20.

DslBnz · #20 01-19-2006, 05:27 PM

I don't know officially, but I remember reading that the 617 diesel required a cetane rating of at least 55 to run optimally.

Diesel Giant · #21 01-19-2006, 05:39 PM

Actually I dont know the pump number. It is never posted on the pump around here.

Tangent · #22 01-19-2006, 05:39 PM

I have yet to see a cetane lable on the pumps in central florida

Diesel Giant · #23 01-19-2006, 05:43 PM

Yea I dont think most pumps have it listed.

Rich300TDMBZ · #24 01-19-2006, 05:58 PM

Since the new diesel fuel coming to the pumps are suppose to reduce NOx and paticulate matter emissions, does it mean that they contain higher cetane numbers than the present diesel fuel? Anybody has numbers on the comparison?

bhanson · #25 01-19-2006, 05:59 PM

Almost all the diesel here is 40 cetane. I know of two stations that carry 45. One is much cheaper than the other, so it gets my business. Add a little Power Service each time too.

Ben

Rich300TDMBZ · #26 01-19-2006, 07:12 PM

Quote:

Originally Posted by bhanson

Almost all the diesel here is 40 cetane. I know of two stations that carry 45. One is much cheaper than the other, so it gets my business. Add a little Power Service each time too.

Ben

I spoke to someone at work who knows about diesel fuel. He said that the #1 diesel (winterized) has a Cetane number of 44 or 45. The #2 diesel has a Cetane number of 40. Number 1 diesel fuel is commonly labelled at the pump as "premium" diesel. Apparently, this this is the same across the US. This does not apply to biodiesel or mixture with dino.

MB-Owner-in-ind · #27 01-19-2006, 10:38 PM

I have read that the cetane value deals with how quickly the fuel will light. The quicker it lights generally the less power it contains because the power is in the longer hard to light chains not in the shorter easier to light chains.

DslBnz · #28 01-19-2006, 11:12 PM

According to the API gravity, it will tell you the increase/decrease in power output. Right now diesel is winterized. Thus heavier. Thus less power.

According to a few charts I've seen, approximately 12% less. That would limit the 617's to 108 hp, 603's to 130 hp, the 606's to 153 hp, and the E320 CDI to a measly 177 hp if all things were equal.

Oh, and a 240D would only have 59 hp. But that's not much of a drop, right?

braverichard · #29 01-19-2006, 11:20 PM

Quote:

Originally Posted by DslBnz

According to the API gravity, it will tell you the increase/decrease in power output. Right now diesel is winterized. Thus heavier. Thus less power.

I really question this whole deal of "winterized" diesel having less power and resulting in reduced fuel consumption. In comparing MPG figures for my car during the summer and winter months, I actually get much better MPG (1-2MPG more) in the winter and the winter figures seem to be more consistent than the summer ones. This is all over the same sort of driving. Perhaps because the A/C isn't used? Well, even in the Spring when I don't use the A/C, I never do better than my winter figures. With regards to power, I've never felt a reduction in power either. Beats me!

DslBnz · #30 01-19-2006, 11:44 PM

Quote:

Originally Posted by braverichard

I really question this whole deal of "winterized" diesel having less power and resulting in reduced fuel consumption. In comparing MPG figures for my car during the summer and winter months, I actually get much better MPG (1-2MPG more) in the winter and the winter figures seem to be more consistent than the summer ones. This is all over the same sort of driving. Perhaps because the A/C isn't used? Well, even in the Spring when I don't use the A/C, I never do better than my winter figures. With regards to power, I've never felt a reduction in power either. Beats me!

Well, the API gravity is a proven constant. It also has a dramatic effect on diesel engine performance.

I've felt a good hit in both power and fuel economy in the northeast. Every winter its the same deal. My mileage drops from 28 - 30 mpg to 24 - 26 mpg. Power is down, but its only noticeable when accelerating at WOT.

The AC can hurt mpg, but I'd imagine not outside the margins of the numbers you mention for improvement.