BTU Content

[MRFost]

OK, I've been monitoring some of the biodiesel stuff. Apparently there is at least two methods of removing the glycerins. But I haven't yet seen anything that gives me the BTU content of good biodiesel vs. #2. I mean hard numbers, not "I go as far with bio". I've searched all over, and since I'm an engineer, I like real numbers. Has any scientific testing been done to evaluate the fuel on this basis? I just want to know, as I suppose if it's half as good as #2 it's still a bargain at the price. Sure would hate to foul-up the accuracy of the overhead mileage indicator ...

 

[SHobbs]

According to DFWbiodiesel.com.

#2 has 131,000 btu/gal, cetane 45, sulfur con. 300, could point -15, viscosity 2. 7.

B100 soybean oil has 117,000 btu/gal, cetane 50, sulfur con. <1, cloud point 0, vicosity 4. 1.

B20 same formula has 128,000 btu/gal all the other numbers are pretty close.

B5 same formula has 130,000 btu/gal same for all the other numbers not much of a difference.

 

[67guzzler]

Cetane vs. BTU

#2 has 131,000 btu/gal, cetane 45, sulfur con. 300, cloud point -15, viscosity 2. 7.

B100 soybean oil has 117,000 btu/gal, cetane 50, sulfur con. <1, cloud point 0, vicosity 4. 1.

This has been a confusing thing to me.



Cetane vs. btu



#2 has less cetane but more btu. In the diesel engine, which carry the day? Would you be hurt or helped by gaining or losing 5 points of cetane or 14,000 btu? Which will have the bigger effect?

 

[SHobbs]

JGann,

The way I understand it the lower btu's result in a 10% loss in overall power by running B100 ie. less heat. As far as cetane it is to #2 what octane is to gasoline, that is why I think the engine feels stronger and more pep. You definitely loose as far as I see it by dropping btu's, but also I am really gaining due to the higher viscosity for the VP44 and cleaner running. For myself I can deal with the loss as long as my fuel dollars stay here at home and not going to the Arabs.

I don't pull or race quarters I just need to get the 5er down the road and I can make up the loss with injectors. I definitely like the way my truck runs on B100 sometimes it sounds like a 1st gen the pinging is not as noticable, definitely quieter.

 

[bighornram]

As a result of the lower energy content, biodiesel will require about 1. 1 gallons of fuel to do the same work as a gallon of diesel fuel.



http://www.ext. nodak. edu/extpubs/ageng/machine/ae1240w.htm

 

[MRFost]

Sweet. That satisfies my curiosity.

Next question -- where am I going to find room in my garage to do this -- my house/garage is cubed as it is. I don't know of any place that sells bio of any size. Hmmm. Conundrum...

 

[Huff N Puff]

Can you effect the BTU content

By how you mix your brew,e. g can you mix in more or less Methanol to effect the BTU content.

 

[JGK]

A little more on cetane. According to what I've read, the higher cetane number will improve combustion timing on CI (combustion ignition) engines. That is, it occurs slightly earlier than with lower cetane rated fuels. So bioD goes off a bit earlier in the compression cycle. The added benefit of this is that it slightly advances engine timing. Cool!



-Jay

 

[67guzzler]

JGK -- After researching this issue this is what I've learned.



Cetane and BTU's are different. The higher the cetane, the earlier (easier) the combusion during the power stroke. The BTU's represent the energy in the fuel itself not how easily combustable it is.



So, you can have lower cetane and higher BTU's (#2 diesel) or higher cetane and lower BTU's (biodiesel). They represent different properties. The lower BTU's in biodiesel are why people running biodiesel may get up to 10% less fuel economy. But the higher cetane makes for easier starting -- provided the fuel hasn't gelled.



Huff N Puff -- The BTU's represent the energy in the oil itself. I don't know what additives you can add to raise the BTU's.

 

[SHobbs]

JGann

I do know that running B100 will decrease overall HP by10%, I have not seen anything about that big a loss in mpg in fact I gained 1mpg by running B100. I thought I was crazy but I checked the mileage 3 times and it was the same. I drive real easy these days and stay below 65 and no hard starts. Hard to imagine a dually getting 22. 5mpg but I am and at times I get a little more.

B100 and running great

 

[Huff N Puff]

JGK -- After researching this issue this is what I've learned.



Cetane and BTU's are different. The higher the cetane, the earlier (easier) the combusion during the power stroke. The BTU's represent the energy in the fuel itself not how easily combustable it is.



So, you can have lower cetane and higher BTU's (#2 diesel) or higher cetane and lower BTU's (biodiesel). They represent different properties. The lower BTU's in biodiesel are why people running biodiesel may get up to 10% less fuel economy. But the higher cetane makes for easier starting -- provided the fuel hasn't gelled.



Huff N Puff -- The BTU's represent the energy in the oil itself. I don't know what additives you can add to raise the BTU's.

Wouldn't extra methanol in the biodiesel make for earlier combustion and may achieve more complete combustion which would create more BTUs because you are burning more of it, less soot going out the tail pipe.

 

[67guzzler]

Huff N Puff -- If everything else is equal and the diesel engine is tuned the same way, there is less soot in the biodiesel exhaust primarily because there is almost no sulfer in biodiesel, not because of a more complete burn with biodiesel. It's pretty much widely accepted that as SHobbs stated above in Post #2 the BTU levels for B100 are about 10% less than that of petro diesel. The fact is that on average, petro diesel has more energy in the form of BTU's.



SHobbs -- The one thing about biodiesel unlike petrodiesel is that it can be made from so many different oil sources. Soy, rapseed, etc... as well as animal such as beef tallow. Even though the biodiesel might comply with the ATSM D6751 standard there will still be variances. Many report a slight loss in MPG and HP. Some such as you report other results. Personally I have seen a slight loss in both & I'm running beef tallow based biodiesel. It doesn't bother me one bit, however. I don't have any real need to conserve a renewable resource that puts American farmers to work anyway so if I burn 10% more, that's ok by me.....

 

[jwgary]

SHobbs, where are you buying your bioD from and how much are you paying for it? I know of a few stations on the north side of town, but I have never been to one of them since I hardly ever get up that way.



My thoughts about the cetane/BTU thing is that with higher cetane you will have better ignition and advanced fuel timing. Some of this might offset the energy content loss. If you are spewing lots of black smoke with dinoD and less with bioD you are extracting the energy out of the fuel that would have just turned to soot as it passed through the flame front but didn't really burn. With better ignition properties your engine will run smoother and quieter because you don't have the ignition delay especially when running cold. You should also have an advantage running WOT at high RPM (racing) since that is where ignition delay is the most prominent.



I love these kinds of discussions. It really makes you think about it.

 

[SHobbs]

jwgary

I am getting the bio from DFWbiodiesel.com, they are located of I35 and Long Ave. If you go north on 35 exit 33rd and Long, Cummins is located at this exit. After you exit get in rt. lane and go to the yield sign. Turn left and go under 35 toward Thermo king, this is the same way you go to Ft Worth gear and axle. At the stop sign turn rt and go past Thermo king. Get in left lane go back under 35 and DFWbiodiesel is on the left, you will see the tanks and the signs.

Last time I filled up B100 was $2. 82, B20 is $3. 03. You can get B20 at the pump by swiping a card. The B100 is not tied into the system yet, the are working on it. If you want B100 call ahead of time to see if someone will be there to fill up. Call Bobby Camp @ 817-875-5147, he is one of the owners. He and a friend of his started this and had no idea it would grow like it has, they are having growing pains and are working to improve things.

I have been running B100 for 3 months and really like the way the truck is running. Bobby runs the same stuff and really cares about getting good quality stuff.

 

[bighornram]

This information from 2004 Biodiesel handling/use guidelines on page 6 section 2. 4 "Drawbacks of Biodiesel Use".



Biodiesel contains 8% less energy per gallon than typical #2. 12. 5% less energy per pound. The difference between these two measurements is caused by the fact that biodiesel is slightly more dense than diesel fuel, so there are slightly more pounds in a gallon of fuel. All biodiesel, regardless of it's feedstock, provides about the same amount of energy.





Typical #2 Btu/lb=18,300 Btu/gal=129,050

B100 Btu/lb=16,000 Btu/gal=118,170