The results highlighted in Geneva are on a development engine that is not equipped with GDI (gasoline direct injection) or optimized combustion chambers. A 2010 version of the MCE-5 VCRi engine will be equipped with GDI, optimized combustion chambers as well as the advanced management of engine temperature, of the cylinder head, pistons and exhaust manifold.

The power and torque on the 2010 version will respectively be ramped up to 270 hp (201 kW) and 460 Nm (339 lb-ft), while average consumption on the NEDC will drop below 6.0 L/100 km (39 mpg US), with less than 140 g of CO₂/km. With this type of engine, reaching the target of 120 g of CO2/km seems realistic by 2012-2013 for high-performance vehicles, with a strong reduction in fuel consumption for the whole vehicle range, MCE-5 suggests.

The MCE-5 engine has been 12 years in development. Earlier this year, twelve companies including major European Tier 1 automotive industry suppliers, combined to propose to carmakers a program intended to develop and manufacture the MCE-5 VCRi engine in the coming 6 to 8 years.

Main components of the MCE-5 VCR engine block. Click to enlarge.

The VCRi engine principle. The MCE-5 engine provides continuous and reactive compression ratio control with a range between 7:1 and 20:1 to each cylinder of the engine. The MCE-5 engine block integrates power transmission and compression ratio control through a combination of a rod-crank mechanism, long-life gears and exclusive actuators.

A common cylinder head is used for both the combustion chambers and upper control jack chambers—one for each combustion cylinder. The jacks are placed on the cold side of the cylinder head and under the intake pipes.

MCE-5 Compression Ratio control system with common CR control shaft. Click to enlarge.

The compression ratio control mechanism is placed under the control jacks and is based on an eccentric shaft driven by an electric servomotor. A non-reversible wheel-worm ensures transmission between the servomotor and the eccentric shaft. The time to change from minimum to maximum compression ratios is less than 100 ms.

Rocker arms are driven by the eccentric shaft to maintain the control jack rods in the required vertical position.

MCE-5 moving parts. Click to enlarge.

The MCE-5 VCR engine block has no impact on other engine parts or vehicle components. Its connection to gearbox, pipes and peripherals requires no additional device, as well as its integration into vehicles, which remains conventional.

Other attributes of the MCE-5 approach include:

• Piston kinematics remain exactly the same as that of a conventional engine with the same rod/crank ratio. This remains true whatever the compression ratio.

• The crankshaft is particularly rigid (crank is reduced by half).

• The crank-case rigidity is at least equivalent to that of conventional engines, providing a rigid and precise bearing line and an optimum geometrical environment for all moving parts.

• The roller-guided piston is no longer subjected to rod thrust (no piston radial stress) or to piston slap. Forces that generate torque on crankshaft are entirely assumed by rollers: this arrangement reduces friction losses and widely extends the cylinder lifespan. This constitutes a strong response to the durability problem of highly downsized high-loaded engines.