interesting concept ... article doesn’t give enough information for a really valid assessment. The second power stroke seems to be dependent upon a lot of inefficiency in the first power stroke. Is this correct? Is there enough unburned fuel and oxygen in the cylinder after the first power stroke to even make a second power stroke?
“ The second power stroke seems to be dependent upon a lot of inefficiency in the first power stroke. Is this correct?”
Yes. At the end of normal power stroke the piston drops deeper and pulls in a bit of fresh air. The normal exhaust stroke after that becomes a second compression stroke, albeit compressing a little less than a normal compression stroke. What it’s basically doing.. per my understanding.. is spreading out the *Total* combustion time across two strokes instead of one giving the fuel a little more time and a little bit more air to burn. On paper it might mean a a little more efficiency and maybe their tests show there is measurable improvement. I don’t know.
Ever listen to an engine with the exhaust manifold off or with a bad muffler? That loud sound is caused by high pressure air suddenly being released to the atmosphere while it still contains a lot of energy.
Optimally, the exhaust gas should be at the same pressure as atmospheric pressure, which would mean every last bit of expansion was wrung out of the burning volume of gas.
The fact that it makes a loud popping sound when the exhaust port opens tells us that we are wasting energy. We are releasing the gas with perhaps a pressure of around 100 PSI.
So yeah, getting further expansion out of an engine would increase efficiency. There have been several schemes to accomplish this going all the way back to the late 1800s. The "Atkins cycle" comes to mind. I think the "Miller Cycle" is another.
“ Is there enough unburned fuel and oxygen in the cylinder after the first power stroke to even make a second power stroke”
There is quite a lot, but I don’t know the %.
That’s what the catalytic converter does and is why the output temperature of the converter is much higher than the intake.