diesel race saw

[Sharpie]

When I was a kid at the glencoe fair, i talked to a guy there racing, and he told me that his saw would run on diesel. He said that he would get it hot on gas and then could ????ch it over to diesel. Is there any truth to this ?

 

[drmiller100]

for sure.

send me a 100 dollar bill to my address and I'll tell you that secret and also the secret to getting any women you meet to fall in love with you instantly.

Send it today, and I'll include my xray eyeglasses that allow you to see their undies.

 

[gene1605]

diesel

A gasoline engine will run trouble free on diesel if they are fully warmed and the compression is 5 1/2 to 1

Grampa

 

[Sharpie]

thanks for the feed back grandpa

 

[Gumnuts]

i just choked on my coffee

Send it today, and I'll include my xray eyeglasses that allow you to see their undies.

Did you geta those glasses outa Donald or Micky comic books
Always wanted a pair of those

 

[gene1605]

specking to soon

Miller you and Gum are forgiven, because of your young age, for speaking out without knowing what your speaking about. One more time and its off to bed with no supper.

Grampa

 

[timberwolf]

Diesel 4 stroke engines run closer to 20:1 compression, I doubt a two stroke would get much out of diesle fuel a 5 or 6:1, even on gas at that low a compression they would be pretty crappy.

Other problems too...

How would you switch the fuel over, it would need two fuel systems and without a glow plug starting it on diesel would be out, also how would we get the 3000 to 10,000 psi of injector pressure to burn the deisel? and what would time the injection?

Also the RPM is much lower, so your not going to get even close to the same RPM as a gas engine.

 

[spacemule]

Diesel 4 stroke engines run closer to 20:1 compression, I doubt a two stroke would get much out of diesle fuel a 5 or 6:1, even on gas at that low a compression they would be pretty crappy.

Other problems too...

How would you switch the fuel over, it would need two fuel systems and without a glow plug starting it on diesel would be out, also how would we get the 3000 to 10,000 psi of injector pressure to burn the deisel? and what would time the injection?

Also the RPM is much lower, so your not going to get even close to the same RPM as a gas engine.

All of that is not necessary for diesel operation. Take a look at model airplane engine diesel conversions--all they do is change the head out. The compression is adjustable with a knob on the top of the head.

 

[RaisedByWolves]

I go to tractor shows and its common to hear of engines that were able to run on gas or Kerosene/Diesel fuel. You had to start and warm them with gasoline and then switch them over to Kero. The real trick was that before you shut them off you had to switch them back and run them on Gas so they would start up again next time.


.

 

[Sharpie]

The saw i saw was just a high compression two stroke gas engine that was carborated. It was started with just enough gas in the tank to get the engine hot, then shut off and filled with a diesel two stroke oil mix and restarted imediatley.

 

[timberwolf]

Yes quite true diesel can be run without injection systems, but the trouble, esp on something like a chainsaw having a variable load is that the ignition timing is going to swing all over the place depending on compression, heat and RPM. If a high compression saw like that started to get hot, ignition would advance running in an auto ignition mode and things would get ugly. Also fuel vaporization is a problem, a heated intake might help too to get the fuel and air mixed.

Easy to try mixing some deisel into the gas and see what happens, but might be some risk as diesel is a much lower octane fuel than gas.

Also the autoignition temperatures are much lower on the oil fuels so it is easy to put them into detonation, that I would think explains well why modern diesles run high compression, but delay injection of the fuel until very close to TDC avoiding this problem.

Gasoline 536F
Kerosine 410F

 

[Sharpie]

I'll try doing a gas diesel mix, but I will use my dads saw, he will never know. I'll let you know what happens. I'll start out with 10% diesel and work my way up.

 

[gene1605]

diesel high r p m

Something to think about the older saws the timeing was fixed, did not advance and at very high r p m the compresson was low, A tuned pipe pn a race saw is another story.
The 1940ies and early 50es compression ratos of cars was about 6 .5 to 1 and would idle porely but run on diesel well, I snitched enough of my dads diesel to know and spent a good portion of my youth sitting on the seat of my dad,s hand cranked stove oil burning tractors.

Grampa
ps Miller and Gum where are you at.

 

[Sharpie]

Thanks a lot guys for you're input. Timber Wolfe the way you explained diesel timing and injection just before tdc was something I had always wonderd about. I always thought that diesel was harder to ignite thus the high compression. It all makes sense to me now, thank you for the education. So the timing is way to advanced in a high compresion spark plug engine for diesel fuel, and would cause detination, is that right?

 

[drmiller100]

Easy to try mixing some deisel into the gas and see what happens, but might be some risk as diesel is a much lower octane fuel than gas.

Also the autoignition temperatures are much lower on the oil fuels so it is easy to put them into detonation, that I would think explains well why modern diesles run high compression, but delay injection of the fuel until very close to TDC avoiding this problem.

Gasoline 536F
Kerosine 410F

i think you are incorrect on everything you wrote.

diesel has a much higher octane then gas. hench the higher compression.

I would be curious as to how you guys think the carburetor is gonna vaporize the diesel.

also, many of us have actually tried running diesel in a gas engine.

you rapidly become a pedestrian, she stinks badly, and your head will hurt from the fumes.

 

[timberwolf]

Doug, I'm thinking you were in too much of a rush to discredit me to check the facts first.

http://en.wikipedia.org/wiki/Gasoline

Read down under the "Energy Content" section, though diesel is rated in Centane it's equivilent octane is about 25. I would call that low.

Here is another link with some good info.

http://www.prime-mover.org/Engines/GArticles/octane.html

Here is a quote from the above link, "Diesel and Jet fuel (along with kerosene) have, indeed, terrible octane numbers; typically about 15-25 "octane". They tend to ignite easily from high compression. Their use in a gasoline engine will quickly destroy the engine."

Anything else Doug that you feel is incorrect?

 

[gene1605]

biodiesel

Timberwolf you seem to be well schooled in diesel, I have a questin, if diesel has a octane equivlent of 25 what is the biodiesel equivlent ?

Grampa

 

[timberwolf]

I think the first question would need to be what is biodeisel? I would think there could be more range in biodiesel than standard petro diesel. It's made from all kinds of stuff, some processes with fairly good quality controls, filtering and ph balancing sold comercially, other stuff is home brew without full tranestrification not much more than filtered waste vegetible oil blended with petro deisel and maybe some alcohol.

In general Bio should have slightly higher cetane, maybe as high as 60 compaired to petro deisel at 45. It is in general slightly less volitile, thicker and a bit more dense. Auto ignition temp is higher though. Otherwise I would think it's properties would make it even more problematic to run in a gas two stroke. Just in the last 2-3 years some diesel vehical manufactures have added heated fuel systems as well as improved pumping and filtering setups to allow running bio without problems.

One thing for sure is without going to a high pressure injection system it is going to smoke big time. And no mater what you do I cant see getting much RPM out of it.

 

[Crofter]

The issue gets really confused when you burn fuel commonly called diesel, in the spark ignition mode in a gas engine. Diesel does indeed have a much lower octane rating.. When spark ignited, the fuel is all in the cylinder at time of ignition and detonation is an issue. Grandpa tractor is right about needing a low compression ratio to run it at full load. Lots of the old multi fueled engines also carburetted in some water along with the kerosene to control detonation. Burning diesel fuel in a spark ignition engine does not make it a diesel engine. Totally different operation.

A fuel injected, compression ignition engine burning diesel ignites the fuel by the heat of compression and the fuel charge burns gradually as it is injected so detonation of the whole charge at once cannot occur thus the octane rating is irrelevant. Usually this will take about 20 to one compression ratio for decent starting.

 

[drmiller100]

Anything else Doug that you feel is incorrect?

sure.

post a pic of your chainsaw with retarded timing running on diesel.