MCE-5 VCRi: Pushing back the fuel consumption reduction limits

Crankcase

The MCE‑5 VCRi crankcase comprises two rows of cylinders: one row is dedicated to combustion while the other is for compression ratio actuation. The MCE‑5 VCRi crankcase resembles that of a “U” engine whose 8 chambers are covered with the same cylinder head fastened by 15 screws. Only the combustion cylinders are cooled. On current MCE‑5 VCRi prototypes, the combustion cylinders are made directly in the crankcase of cast iron, according to processes that are strictly identical to those used for conventional engines (double helix honing). The VCR actuator bores integrate hydraulic jack-type liners, i.e. made of a material with a surface roughness that guarantees the correct operation of the VCR actuator piston’s composite seal.

The MCE‑5 VCRi crankcase resembles that of a “U”
engine whose 8 chambers are covered
with the same cylinder head

The MCE‑5 VCRi crankcase has a rigid bearing
line that cooperates with a rigid crankshaft

The MCE‑5 VCRi crankcase cylinder head oil drain and blow-by chimneys are located on either side of the combustion chambers, as is the case for conventional engines. The combustion cylinders are offset with respect to the bearing line at the same distance as the VCR actuator cylinders (50 mm offset). This offset does not cause any distortion of the cylinders after the bolting of the crankshaft bearings or the bolting of the cylinder head.

The MCE‑5 VCRi crankcase has additional side machining to accommodate the synchronized roller plates and hydraulic pushers. The synchronized roller plates are housed in windows on the combustion cylinder side, while the hydraulic pushers are housed in lined bores on the VCR actuator side.

High-pressure conduits (40 to 60 bar) are located in the MCE‑5 VCRi crankcase to circulate the oil between the upper and lower chambers of the VCR actuators and also between the pressure accumulator in the oil sump and the hydraulic pushers + VCR actuators.

Current MCE‑5 VCRi prototypes have a cast iron crankcase, said to be “under development”. This crankcase has received many modifications and its weight is not yet optimized (61 kg). The next generation crankcase has been in design since 2009. Its geometry and material (aluminum) have been optimized. The mass of the MCE‑5 VCRi 1.5L engine crankcase has been reduced to 31.3kg (-52kg compared with the current one), making it a very light crankcase in view of the engine’s performance (250 hp and 480 Nm in twin-turbo GDI).

The MCE‑5 VCRi crankcase is currently equipped with a bed plate. This configuration must be validated or invalidated for mass production (advantages/drawbacks compared with a “deep skirted” configuration).

The length and width of the 1.5L MCE‑5 VCRi crankcase are comparable to those of a conventional engine with the same cubic capacity. Its height is its only penalizing point: it is similar to that of an average sized Diesel engine (2L). This height must be considered in view of MCE‑5 VCRi’s torque, power and energy efficiency performances.

The MCE‑5 VCRi aluminum crankcase will be ready for 2011. Fully equipped, this crankcase weighs
52 kg less than the current cast iron version

The main characteristics of the MCE‑5 VCRi crankcase