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Old 09-09-2015, 10:22 PM
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Davezilla Davezilla is offline
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Join Date: Mar 2014
Location: San Antonio Texas
Posts: 2,710
Default Re: Anyone thought about a diesel bike?

Very well said...

About all I could add would be on the 2 stroke diesels, you could look more into how small model glow fuel engines work and try to up scale it, but glow fuel engines also tend to have a size limit where they can't perform as well, this is mainly because these use glow heads, not glow plugs, there's a wire coil heating element in the combustion chamber and it needs some electrical current to heat up the glow head then the engine can be started, and once the engine is running, the glow is maintained by the super heating of the air in the combustion stroke from the previous compression stroke.... this is why they are size limited as it takes some really high rpm to maintain this glow, we're talking in the 25000 to 35000 rpm range so this means a really short stroke to keep piston speed in check, so these engines are rarely larger than 1/2 cubic inch. Glow fuel is basically methanol and castor oil blended together so it's not exactly cheap which also makes a 49 or 66cc glow engine even more impractical...
This would be the closest thing to a true diesel 2 stroke as the engines are typically piston port or they use a hollow crank with the opening at just the right moment similar to a rotary valve, they burn their fuel by compression heat except this heat also keeps a wire red hot inside the combustion chamber and the other exception is that the fuel is metered in thru a needle valve making throttling a different story as well.

If I was to build a diesel bicycle, I would look for a 4 to 6 hp 4 stroke diesel engine and take it from there as a 4hp diesel will have an output similar to a 6 or 7hp 4 stroke gas engine, the reason for this is because of the diesel's superior torque and that they make most their power at a much lower rpm, but with the right gearing to take advantage of this torque, you could still make a very fast bike that could both out accelerate and out run a gasoline powered bike of similar horsepower.
This doesn't come without its disadvantages tho... diesel engines are heavy, bulky, and messy, not to mention more expensive in most cases. They typically have a narrow rpm range and a narrow powerband. A small diesel engine can usually rev to about 4500 rpm and make peak power at 2500 to 3500 rpm depending on displacement...
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