Comments by "John Burns" (@johnburns4017) on "Why Five Stroke Engines Are More Efficient But Still a Failure" video.

@toyotaprius79 And what relevance is that?
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@brianmack6285 Small size and weight in a hybrid engine is quite important for packaging in a car. The engine will by nature be a part time engine that will be rarely used, so fuel consumption when running on the ICE engine is not important at all. This is where rotaries score highly and even more added value in the smoothness.
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@brianmack6285 There is a Nissan car available that has a piston engine turning a generator only that powers an electric traction motor. It is simple and reasonably economical. High efficient electric motors improve matters.
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@advorak8529 In cars sometimes known as an electric transmission, as it replaced the gearbox. But performing like a CVT gearbox with no stepped gears - sort of.
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The long combustion stoke of a Wankel engine helps here, but only when burning hydrogen. When burning hydrogen Wankles are around 23% more efficient as hydrogen burns far quicker ensuing all the mixture in the chamber is burnt. Current fuels are not suited for Wankels.
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Turbo is taking energy out the back of the engine then putting it back into the front (including a turbojet). This could be in the form of pushing more air into an engine, or sending the waste energy back into the output shaft giving more power. The centre compound cylinder falls into this. When you add extra centre compound cylinder, there is extra weight, size and friction losses. Exhaust turbos sending more air into the cylinders, are about the best at sending energy out the back and putting it back into the front. I do believe an aero engine had an exhaust turbo that was mechanically attached to the crank, not sending more air into the cylinders. I believe it was more efficient but only when operated under certain revs and conditions.
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