|Rendering of the Ilmor 5-stroke concept engine. Click to enlarge.|
Ilmor Engineering will present a new cutaway version of the Ilmor 5-stroke concept engine at the upcoming Engine EXPO 2009, 16-18 June, in Stuttgart, Germany.
Ilmor is a UK-based independent engine design, development, testing and manufacturing company, founded in 1984 by Mario Illien, Paul Morgan and Roger Penske. It traditionally has focused on racing engines, although its business is becoming increasingly diversified, with recent projects in production automotive industries (including diesel), among others. It is also a member of the UK Low Carbon Vehicle Partnership.
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
- Exhaust from the low-pressure cylinder.
The overall expansion ratio will be the product of the volume ratio of the first expansion and the volume ratio of the second expansion.
The work chamber of each combustion cylinder in the Schmitz engine communicates with the work chamber of the low-pressure cylinder via a decanting valve and manifold. The volume compression ratio of the combustion cylinders is relatively low, and can be highly supercharged.