2 stroke/4 stroke Hybrid motor-possible motorcycle someday?

(Duplicate Cross Post from Mailing List since no one replied yet)

With the 2 and 4 strokes fighting it out in the dirtbike and
snowmobile arenas, and MotoGp being dominated by 4 strokes, I have
watched the technology with some interest, and stumbled upon this
subject in one of the snowmobile mags.

It is an interesting concept: to marry the positive aspects like
weight and simplicity of a two stroke motor with the reliability and
torque of a four stroke. Apparently one company has been doing this in
their weed-wackers, based on 1980's and military technology. Who knew?
Not I! It is sort of long but the bottom half of the page has some of
the technical stuff, but not many specifics.

Hybrid from Shindaiwa

I like the rather grandoise claims made, *Like BMW cars and Nikon
cameras, Shindaiwa products are well known and preferred for their
high levels of performance and long-term durability. Second to none,
they are bought again and again by satisfied commercial users.* and
most impressively: *An exciting, colorful logo will represent our
proprietary new technology and the line of products to come.*

If someone smarter than I could explain how it works and if it is at
all applicable to larger engines, please post a reply.

 

The only thing I can make of it is its a regular 4 stroke but it runs on mixed gas with no seperate oiling system. The only real advantage I can see for using it in larger engines would be the simplicity and the weight advantage.

"combines the best features of the 2-stroke engine (compactness, power-to-weight ratio, minimum-moving parts), and the 4-stroke engine (precise metering of combustion gases)."

those are the only advantages I can see.

 

Re: 2 stroke/4 stroke Hybrid motor-possible motorcycle somed

Mark Morland from the mailing list posted the following link, which I could not find for some reason. Has pictures and an abstract/preamble which I can ALMOST understand except for the fact I am an idiot.

Patent Info

Interesting look to it

 

Re: 2 stroke/4 stroke Hybrid motor-possible motorcycle somed

This is a four cycle engine like we have on our XJs with the exception that the oiling is provided by passing a fuel/oil/air mixture through the crankcase on the way to the combustion chamber as in a 2 cycle engine.

Advantages:

1) Because there is no oil sump, the engine can be run in any position (upside down etc.) like a chainsaw or weed wacker.

2) There is no need for oil pump and passages reducing weight and probably manufacturing cost because boring oil passages through the block, crankshaft and camshaft are unnecessary.

3) The pistons moving downward into the crankcase push the fuel/air mixture to the combustion chamber just like in a two cycle. The difference here is that the engine is a four cycle so fuel only enters the combustion chamber every other revolution. The plenum between the crankcase gives a place to store the unused fuel/air charge until the next revolution when the intake valve opens and lets in a DOUBLE (almost) charge to the combustion chamber.
----------

The thing that makes 2 cycle engines such torque monsters is that you get combustion in every cylinder every revolution. This engine brings some of that advantage to a four cycle with the extra fuel charge it introduces by using the crankcase/pistons as a pump.

Since two cycle engines have no valves they can be run at much higher RPMs than four cycle engines. This is because of "valve float" in four cycle engines, a condition caused by the inertia of the valves keeping them from staying on the cam as they close. Valve float can result in the piston hitting partially open valves. The reason we can rev our XJs to the 9K range is because of the DOHC design which keeps the inertia of the valve train down. The old style car engines with rockers and lifters and pushrods had so much mass that 5K meant death. The valve configuration on this design seems to be more like our XJs, high reving but nothing like the 12K you can get from a two cycle.

I'll try and make a schematic to post.

 

So you are still burning oil, and the exhaust gases are similar to the usual two stroke, I imagine, right?

I found another website with better text and pics New Linky

 

Re: 2 stroke/4 stroke Hybrid motor-possible motorcycle somed

Still burning oil. I believe oil is a minor issue in the 2 stroke exhaust gasses, it's the unburned hydrocarbons that are the big pollution issues. This engine, emissions wise, I think would be very similar to a supercharged 4 cycle.

 

Re: 2 stroke/4 stroke Hybrid motor-possible motorcycle somed

anything's possable
http://www.minimodelengines.com/Feature5R.htm

 

Re: 2 stroke/4 stroke Hybrid motor-possible motorcycle somed

Just thinking about trying to work on that tiny engine is making my head hurt. :? Looks like somebody put a *few* hours into that project. 8)