MCE-5 VCRi engine offers high output in small package

  • 17-Mar-2009 11:39 EDT
MCE-5 CR_min_max.jpg

VCRi can vary the compression ratio from 6.0:1 to 15.0:1 by raising and lowering the drive piston in the cylinder bore.

­MCE-5 Development, based in France, displayed a Peugeot 407 in the Green Pavilion at the Geneva Show powered by an engine equipped with its variable-compression-ratio four-stroke engine technology, which the company calls VCRi (Variable Compression Ratio, intelligent).

Figures provided by the company suggest that, from the 1484-cm³ gasoline engine, equipped with two-stage turbocharging, variable valv­e timing, and a compression ratio that can be varied between 6.0:1 and 15.0:1, maximum power output is 217 hp (162 kW) between 4000 and 5000 rpm and maximum torque is 420 N·m (310 lb·ft) at 1500 rpm. The compression ratio can be varied independently for each cylinder.

In European testing, the company quotes combined-cycle fuel consumption of 6.7 L/100 km and has a target of less than 6.0 L/100 km for 2010, when the system will be applied to a direct-injection gasoline engine.

The technology was invented by Vianney Rabhi, currently head of strategy and development at the company. “It is based on a gear transmission system,” Rabhi explained to AEI. “Normally, you have a piston, a rod, and a crankshaft. Here we have a piston, two racks, a wheel, a rod, and a crankshaft, so you have three new parts in the engine.” Rabhi also claims that the system reduces internal friction.

The engine will support HCCI strategies. “HCCI and all lean-burn strategies are served,” said Rabhi. “The brake specific fuel consumption (BSFC) map has to be considered as an intermediate one because we work on the combustion chamber at the moment. We have improvements to make in the combustion chamber geometry.”

The variable-valve-timing system reduces the valve overlap in high-compression mode because less overlap is needed, said Rabhi. It also removes the potential for contact between valves and the piston crown. But as Rabhi pointed out, the ideal situation would be to provide variable valve lift, but such a system is not yet available for the VCRi system.

Compression is varied by altering the height of a secondary piston, which moves vertically in a chamber parallel to the drive piston. The height is altered hydraulically. The secondary piston is attached to a rack, which engages the teeth of a gear wheel whose pivot point is the “small end,” attached to the top bearing of the connecting rod. Gear teeth on the opposite side of the wheel engage on a second rack attached to the bottom of the drive piston. This rack has a finer rack on its opposite face, which engages a small gear wheel; the rack moves up and down against the small gear wheel transmitting the piston’s motion to the crankshaft via the large gear wheel and connecting rod. As the secondary piston moves down, the large gear wheel pivots around the small end, causing the drive piston to rise in the bore, raising the compression ratio. As the secondary piston moves up, the drive piston is lowered in the bore, and the compression ratio is reduced.

MCE-5 Development has more than 60 technical partners and expects investment in research and development to exceed €44 million in 2009.

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