The 5-stroke concept engine is a self-funded proof of concept. It uses a novel design to achieve a diesel-like expansion ratio on spark ignition—the high effective expansion ratio provides improved fuel consumption.The 3-cylinder, 700cc engine delivers power output comparable to a 1.8-liter four-stroke engine, with minimum fuel consumption of 226g/kWh, with less that 240 g/kWh for more than 30% of BMEP. The engine generates better fuel consumption than the latest downsized, turbocharged GDI engines, and is optimal for use in an range-extended electric vehicle application, according to the company.
The 3-cylinder engine uses different-sized cylinder bores…
There have been several “five-stroke” engine designs proposed and patented. One, invented by Gerhard Schmitz, proposes the use of at least one larger low-pressure cylinder functioning in a two-stroke mode located between two smaller high-pressure combustion cylinders, functioning in a four-stroke mode.
The design decouples the compression ratio and the expansion ratio by adding a second expansion cycle for the exhaust gases by means of the third cylinder. The five-stroke cycle of the Schmitz engine thus includes:
Intake into the smaller high-pressure combustion cylinders;
Compression in the combustion cylinders;
Combustion and expansion in the combustion cylinders;
Exhaust from the combustion cylinders and intake/expansion into the larger low-pressure cylinder; and
Hard to believe its that great. Its 2009 already if it was that powerful and that efficient i’m sure we would have seen a major manufacturer hitch their wagon to it already.
Sounds like the latest fad in internal combustion to me. It can take its place in line with the Wankel, Atkin’s cycle, miller cycle, etc.
Hmm… double-expansion in engine cylinders has been tried before - in compound steam locomotives. They found that it tended to complicate things, as 1) how do you balance the piston forces when energy levels differ (the secondary pistons were larger) over the entire operating range, 2) simple expansion over four cylinders (vs. 2 and 2) tended to generate more power, because of exhaust resistance in filling the secondary cylinders, and 3) simple expansion was in essence, mechanically simpler.