Miller-Cycle Wankel

Miller cycles are up to about 10% more efficient than Otto cycles. The Miller cycle is different from an Otto cycle because of the compression stroke. The only real difference between the two is that the intake valve is left open for part of the compression stroke in a Miller cycle (Miller cycles require a supercharger). When the intake valve is left open and intake gases are compressed into the supercharger and then re-compressed back into the cylinder, the engine gains efficiency because the supercharger compresses the charge using less energy than the piston would have.

Well, my idea is to use this concept on the Wankel engine. The Wankel would be direct-injected and would have camshaft-operated slide valves to uncover a port in the compression section. Just like in a piston Miller cycle, there would have to be a supercharger. The more efficient the supercharger is at compressing the air, the better, so the supercharger would be centrifugal with gearing as to provide maximum gains off idle to about 4000 RPM. The supercharger would be connected to both the intake and compression ports. Now with Miller cycles, the efficiency of the supercharger's compression wears off at high RPM since at that point the engine is more efficient at compressing the air than the supercharger. So in my idea I propose a supercharger and turbocharger combination like in the Volkswagen Golf 1.4L. However in a Wankel engine, this method would almost certainly work better, with a supercharger creating a lot of low-end torque and a turbocharger boosting the rotary's high rpm powerband. Oh yeah and around the same RPM that the supercharger stops creating any real boost gains, the Miller effect really stops coming into play so the camshaft that opens the compression-cycle ports would be de-activated.