Converting 66cc 2 stroke to diesel.

M

Motor_Burner

New Member
I have been reading a ton about what it would take to convert a 2 stroke to diesel. Now, much of what i have found is this:
1. Massive increase in compression to around 1:25
2. Throw away the spark plug
3. Need a fuel injector placed into the spark plug hole.
4. From the compression increase, you would need a huge amount of force to start the thing, so maybe a starter the size of the motor? LOL

These are just a few basics.

Now, I read on a lawnmower forum, this guy ran diesel in his rider by accident, it didnt run to begin with. He put starting fluid in the carb, it fired right up and mowed his yard. To shut it off he had to block the intake. It was an old mower, so when he noticed the smell halfway through, he just kept going.

Here is a few questions:
1. Where should a glow plug be placed? Its for heating the air before it gets compressed making it easier to start. Some have said it needs to go where the spark plug is, others say it should be in the intake.

2. Is it possible to, say, mix gas and diesel maybe 50/50, put a toggle switch on the spark plug wire, and only have the spark plug on untill the motor gets hot? Or hook up 2 tanks, one for gas, 1 diesel and then start it with gas then switch to diesel and cut power to the spark plug?

Or could you simply increase the compression to maybe 1:12 or something and mix gas and diesel so it detonates at a lower compression? And have a glow plug only? Then if so, could the NT carb still be used?

I have been pondering this a ton. I have a spare motor and parts, could possibly try something.
 
Ok, that's uncalled for.

Diesel engines are widely mysterious to most because they aren't as mainstream as gasoline engines. I understand why he's got some concept errors, but since I actually understand how things work, I can explain. Politely.

You're correct on that a glow plugs is only for heating the air. It's not for combustion. A glow plug would go in the intake, or in a tiny chamber attached to the head.

The compression would need to be very high. The unfortunate part is that the aluminum casting wouldn't hold up to the extreme pressure. You'd need to have a new cylinder jug made of steel.

The switching over idea was cool, and probably worth a look at by some engineers (Mazda does crazy things) but I don't think that could work. The compression is too high for gas, and too low for diesel.

Mixing the fuels just won't work. They work on 2 completely different principles.

In order to get the proper atomization of diesel fuel, you will need a high pressure fuel pump. One that can support hundreds of psi at a minimum. Modern diesels run fuel pressure in the thousands. You would need to be able to distribute the fuel at the right moment, and vary it based on throttle position. Diesels don't use throttle valves. They have a completely unrestricted intake. The injector controls the fuel flow, and the fuel controls the speed.

There have been "small" diesels made, but they're hardly what I would consider small. They're roughly the size of a predator 670.
 
It would be better to start from scratch then to convert one of this. Diesel eats oil and gas 2 strokes use the fuel to carry the oil to all the parts that need oil. So you would have to make a oil system too.
 
Im Glad i set a record!!! Lol. But yes, i have read on and most people agree about the compression, some 4 stroke people suggested a couple years ago on a forum that an old Koehler with roller crank bearings might be worth changing over, but the injector would be another problem. Im sorry about the grammar in the first post, was posting while tired... Im glad I've got this beast of mine running at all. Will post pictures somewhere on the forum.
 
There is a company called Sonex that converts Rotax 2 strokes to diesel for use in drones.
Here is a pict of their conversion>
hfe.JPG

http://sonexresearch.com/technologies/3743046
Here is to hoping that you can find more info about it and share.
 
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As far as the amount of compression needed to ignite the diesel fuel it’s far lower than the pressure that is produced when the gasoline air mixture burns so really the engine is perfectly capable of that.
my approach would be to run a very oil rich lean diesel/oil mixture through the carb to lube the bottom end with the carb full open and inject the needed amount of diesel to make it run. The glow plug gets the fuel air mixture up to a high enough temperature to ignite on its own but the heating of the air is mostly due to the compression of it.
 
You know
Even though this sounds like pure madness....
Just to say it is possible. You would need a new block, piston, crank case oil system, fuel injectors and a glow plug. Honestly if you had lots of time and money and cnc milling machine lol

It could be done!

But at this point why would you? Small 2hp diesel would cost like $200 bills and in theory could be mounted like a 79cc predator built bike.

To be honest why the **** has this not been done yet lol!
 
I think it only needs a custom head and an injection method for the fuel. A total loss oil drip into the air intake to lube the bottom end would probably be good.
 
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