Kawasaki plan for two-stroke hybrid

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Kawasaki has plans to develop a range-extender hybrid with a supercharged two-stroke, four-cylinder engine charging a battery that powers an electric motor driving the rear wheel.

It seems like a clever idea.

They call it a range-extender hybrid because the fossil-fuel engine doesn’t directly drive the vehicle.

It’s not an original idea, though. The cheap Chevrolet Volt and expensive Fisker Karma had similar arrangements.

Holden Volt hybrid power
Chevrolet Volt

However the Volt has been discontinued and Fisker has gone broke, so it seems to suggest it was not a popular concept.

Supercharged two-stroke

Kawasaki has filed a patent in the Japanese Patent Office for a slightly different take on the range-extender hybrid with a supercharged two-stroke engine.

Two-stroke engines are very fuel efficient and powerful, but have largely been discontinued around the world because of their high emissions.

There remain only a few esoteric low-volume and expensive two-stroke motorcycles available and an Australian inventor believes there is a lot of scope left in two-strokes with his invention.

2 stroke CITS engine events fail flywheel
Aussie-designed two-stroke CITS engine

Kawasaki’s two-stroke cycle does not have the usual port-transfer system, but is similar to the highly efficient supercharged two-stroke diesels used on ships.

Instead of ports in the cylinder walls, it features poppet valves like a four-stroke, with double overhead camshafts. However, the cycle is two-stroke with forced injection and exhaust.

Kawasaki claims it burns cleaner because no unburnt duel escapes into the exhaust.

Given the fuel efficiency and the power such an arrangement could generate, you wouldn’t need a big engine to simply charge the battery.

It also suggests that range from the battery could be quite substantial.

And you wouldn’t need to sit around for hours charging the battery again.

When you run out of fuel, the battery would have enough charge left to get you to a servo where you could fill up wth fuel and get going again in minutes!

Another advantage would be for those stroker fans who love the sound of the high-pitched engines.

  1. Supercharged two strokes were very common, eg the Detroit diesels used for many years. But also the famous ‘Deltic’ two stroke used in British trains. It had 18 cylinders arranged in a triangle. A unique sound.

    “It’s not an original idea, though” Well, that’s certainly true. The 1920s Owen Magnetic was a very large luxury car that had a gasoline engine driving a generator. There is a perfectly restored one that is driven in the Fountain Head museum in Fairbanks Alaska. It looks like a conventional Packard or similar from the period.

  2. Think I found an explanation.
    1. Start at the expansion stroke, plug sparks, all valves closed, petrol ignited.
    2. Piston forced down, as it approaches BDC, exhaust valves open.
    3. Somewhere before and after BDC, exhaust valves close, inlet valves open and supercharged air is forced into the cylinder. Fuel is forced in via injectors.
    4. Inlet valves close for the compression phase.

    That’s the best I found, but I’m thinking the supercharger needs to be up and running before this can work.

    1. The exhaust valves stay open for a while so the incoming air displaces the burnt mixture. The fuel is injected after all valves are closed. No unburnt
      fuel escapes.

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