diesel race saw

[Goicoechea]

Would a regular production 2 stroke chainsaw have enough cylinder pressure (product of compression ratio) to generate the heat necessary to reach the self ignition point of diesel?

If it would run would the diesel have enough lubricity to forgo the need for mix oil?

I hope Im not making myself look real stupid infront of others....

 

[timberwolf]

Doug, I have never made any suggestion that it could easily be done, or would be of any potential value. Whats the problem, I sure wish you would drop your petty vindetta.

Back your claims up man!

 

[timberwolf]

If your talking compression ignition (True deisel with injection) no, most saws would not have enough compression. Even bumped up saws dont get close to a real corrected 20:1. Were talking compression up at or over 300 psi.

On the other hand if running deisel on spark ignition without injection as Crofter explained, compression would need to be very low likely 100 psi or less to keep the deisel from detonating, and burnt in that way fuel vaporization and flame speed would be poor with little in the way of power or rpm. Also I would think it would be very sensitive to loading, put too much load on the saw and bog and heat it up and the fuel will easily detonate.

I think there was a system used to run deisel with a carberator on a smaller glow plug style engine using a contra piston in the head to adjust the compression as required to allow it to both start and then run under load. Some advantages over methanol glow engines for model planes with improved fuel ecconomy and increased torque allowing reduced fuel weight and also in running a larger more efficent prop at lower RPM.

 

[drmiller100]

Doug, I have never made any suggestion that it could easily be done, or would be of any potential value. Whats the problem, I sure wish you would drop your petty vindetta.

Back your claims up man!

working on the claims part.

as for the carbureted diesel, i'd love to learn about the theory of how diesel vaporizes in a carb like you say.

 

[timberwolf]

Here is some info on deisel glow plug engines. Looks like they do pretty well with fairly constant loads like propellers run where throttle response is not an issue. They need to use quite a bit of ether to make it work though.

http://www.carlsonengineimports.net/customers/dieselinfo.shtml

http://davisdieseldevelopment.com/gallery/cement.htm

 

[RaisedByWolves]

working on the claims part.

as for the carbureted diesel, i'd love to learn about the theory of how diesel vaporizes in a carb like you say.

They ran engines this way over 100yrs ago, do you think people imagined this?



The diesel dosent need to be vaporised at the carb, it is more than happy to vaporise when it hits the hot engine internals.


Next your going to say that a Venturi wont work with diesel.....

.

 

[McNeely]

I think the diesel probobally wouldn't vaporize in the carb, but perhaps in the lubrication stage of the 2-stroke motor. There is also significantly less time between ingnitions, less efficient exhaust removal, thus higher sustained combustion chamber temps in a two-stroke, compared to a four stroke.

 

[gene1605]

old tractors

The old stove oil burning tractors had up draft carb.s and the exhaust manifold heated the intake manifold, they didnt fowl plugs and only smoked when the throttle was opened to fast.

 

[Crofter]

The old stove oil burning tractors had up draft carb.s and the exhaust manifold heated the intake manifold, they didnt fowl plugs and only smoked when the throttle was opened to fast.

gene1605 I did a bit of work for a swede that was collecting old engines. He had a multi fuel stationary that I saw run. it had three tanks, gasoline, kerosene and water. Something sticks in my memory about a diverter to put more exhaust heat to the intake when burning oil but for sure they had to be hot and switched on the fly from gas to oil.

Here is a clip on the fuel process.
"in 1904 Hart and Parr invented adouble carburetor that metered kerosene through oneside and water through the other side. An enginerunning on plain kerosene had a very seriouscombustion knock problem. Hart and Parr found theycould ameliorate this problem by adding water to thecombustion air. In practice the engine was started ongasoline. When thoroughly warmed up, the operatorchanged a valve that switched the fuel from gasolineto kerosene. Then, when the engine began to knock,the operator opened a water valve that provided waterinjection to the engine. This controlled the knock.Since the engine speed was controlled by the hit ormiss method, water was consumed only when theengine was under load. It was said that waterconsumption was about equal to fuel consumption"

 

[Stihl Crazy]

My father in law in his woodcutting and heavy drinking days worked 1/2 a day running diesel in a 1960's vintage chainsaw. Between the effects of the alcohol and diesel fumes he was sick by noon. On his way out he told the boss the saw was not running very well, see if he could fix it before the next day. The boss found the problem, in his "altered" state he took the diesel jug instead of the gas jug off of the truck.

 

[ropensaddle]

The new turbo fuel injected diesel chainsaw made by cat lol!

 

[drmiller100]

Here is some info on deisel glow plug engines. Looks like they do pretty well with fairly constant loads like propellers run where throttle response is not an issue. They need to use quite a bit of ether to make it work though.

http://www.carlsonengineimports.net/customers/dieselinfo.shtml

http://davisdieseldevelopment.com/gallery/cement.htm

sorry, i mis understood this part:
To enhance the ease of starting and to allow fine balancing of fuels to speed and temperature, all modern diesels have variable compression. This is conventionally achieved by the use of a moveable contra piston located at the top of the cylinder. The contra piston is adjusted downward and closer to the piston to increase the compression by screwing in the compression vernier or "T" bar on top of the cylinder

later it talks about running half and half ether so the thing will light off and stay running.
so you are running a variable compression engine, and half ether?????

 

[drmiller100]

They ran engines this way over 100yrs ago, do you think people imagined this?



The diesel dosent need to be vaporised at the carb, it is more than happy to vaporise when it hits the hot engine internals.


Next your going to say that a Venturi wont work with diesel.....

.

a venturi might work with a diesel, but for sure a venturi and throttle plate are not the "normal" way of having it all work.

so the theory is that we suck liquid diesel into the intake stream, it hits the intake valve or piston and instantaneously turns to vapor????

I'm probably telling your story wrong. You go ahead.

Better yet. Send us some pics of a chainsaw running on diesel.

 

[RaisedByWolves]

Are you being a tool just for the heck of it?


.

 

[Crofter]

Are you being a tool just for the heck of it?


.

"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."

RBW, you might think he would feel a bit of a retraction was in order rather than finding some flaw in what others have written here on this thread, since the above statement of his is the only one in the whole thread that is blatantly incorrect. Certainly seems to be a man on a mission!

 

[timberwolf]

so the theory is that we suck liquid diesel into the intake stream, it hits the intake valve or piston and instantaneously turns to vapor????

Thats the exact problem, if the engine is hot enough to flash the fuel into vapor, it is most likely going to be hot enough to hit the autoignition temperature, and because deisel is very low octane it goes pretty much straigt to detonation. That is given there is enough compression to run as a true deisel. They get away with this with reasonable results only on very small model engines of only a few CCs that are inherintly detonation resistent, and in order to make it work it requires careful manipulation of the compression to provide enough heat to autoignite but not that ignition is too far advanced and detonation happens.

There are other problems as well, as diesel engines produce much higher torque at roughly half the RPM of gas, to get the same HP, torque is going high, maybe enough to be breaking parts. So to make a saw with the same HP as gas it's going to need beefing up. I would buy needing more flywheel mass in this low RPM high compression senario.

 

[Brownpot Deaton]

ooops!!

I know for a fact a husky 359 can run on diesel if need be(not sure how long) but it will smoke like a mwsquito killer. Lets just say when i checked the 'gas' for color, it had color, but some idiot didn't let the rest of us know that there was diesel in the same place we stored our gas...was easy fix, but it didn't start back up till ALL the diesel as pumped through(LOTS of cranking on the pull cord!). but it still runs perfect (diesel has enough oil in it anyway..) and i still get mad at the whole event...was quite embarrassing, but not entirely my fault...

 

[husky hustler]

Diesel has an octane number of about 15-25. The reason for this seemingly terrible number compared to the ones we're used to from gasoline is the fact that diesel is combusted in a totally different type of engine. Diesel has low volatility, low knock resistance, yet high energy per volume. Because of its low knock resistance, diesel should not be used in a gasoline engine as it will destroy it very quickly and efficiently.

Generally speaking, diesel fuel ignition quality is not measured in octanes, as these are a unit for gasoline. A similar reference value, but for diesel, is the cetane rating. The higher the cetane number, the easier the fuel ignites when injected into an engine. The cetane number is determined by an engine test using two reference fuel blends of known cetane numbers. The reference fuels are prepared by blending normal cetane (n-hexadecane), having a value of 100, with heptamethyl nonane, having a value of 15. The higher the cetane rating, the higher the fuel's propensity to knock! Choosing a very high cetane number will not make the car run better, but using a fuel with too low cetane number may prevent the engine from starting or running.

 

[gene1605]

15 25 octane

Husky I have a question, With a fully warmed gasoline engine, what compression ratio would it take for a gasoline engine to run well. The compression ratio numbers that I gave previous was for burning stove oil in a tractor engine with a 5 in bore. I received my information 50 yrs ago from the gentleman that designed the first stove oil engine for case tractor when they phased out steam tractors, I still have the letter.

Grampa

 

[Crofter]

On a spark ignition engine the mixture ratio must be matched to the compression to get dependable ignition. Lower compression richer mixture. What really governs maximum compression is the pressures that develop AFTER ignition. A large very slow moving heavy piston will see pressures rise much higher after ignition because the piston escape speed is low in relation to charge expansion rate so its initial compression RATIO must be much lower than on a smaller displacement free revving engine.
A compression ignited engine with kerosene fuel fed gradually into the fire is going to need totally different conditions than an engine with the same fuel vaporized and mixed with air and then spark ignited. Detonation limits compression in the carbureted spark ignition and ignition of the charge sets lower limit in the injected compression ignition one.