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

It’s compatible
with any type of combustion chamber

During the 20th century, the most important advances were made in the upper part of engines. Carburetors were replaced by multiport fuel injection and now gasoline direct injection. We went from 2 to 4 valves per cylinder and they are now more “intelligent” with cam phasers and/or variable valve lifters. The cylinder head cooperates with supercharging and aftertreatment systems. Pressure sensors are now starting to be integrated into Diesel engine combustion chambers.

The MCE‑5 VCRi exists in MPFI and GDI versions.
Prototypes have pressure sensors directly installed
in the combustion chamber with the fuel injector

Some VCR engines that were experimented in the past had additional pistons that were more or less introduced into the combustion chamber. Others were equipped with two face-toface pistons in the same cylinder. These principles are incompatible with the equipment of a modern cylinder head.

For these reasons, MCE‑5 VCRi does not impose any constraints on the definition of the combustion chamber. It’s possible to keep all of the current equipment, including a GDI injector located on the side, as have the GDI MCE‑5 VCRi prototype engines running on the test bench.

In future, VCR engines will also have a sensor to measure pressure in the cylinder. This information will be useful to know the effective compression ratio with a high level of precision and also to control compression ignition. MCE‑5 VCRi offers a decisive advantage for locating this sensor: it’s possible to house it directly in the upper chamber of its VCR actuator.

It’s only possible to place a cylinder pressure sensor directly in the VCR actuator if the engine has an actuator per cylinder, which is the case of MCE‑5 VCRi.

The prototype MCE‑5 VCRi engines currently running on the test bench already have a pressure sensor in the upper chamber of the VCR actuator in addition to a pressure sensor housed in the combustion chamber. The transfer function that can deduce the pressure in the cylinder from the one measured in the upper chamber of the actuator provides very high precision. It is therefore possible to measure the pressure in the combustion chamber from a single sensor located in the upper chamber of the actuator. This configuration makes it possible to clear and simplify the combustion chamber. Indeed, adding a pressure sensor to the combustion chamber of a GDI engine with 4 valves per cylinder and a spark plug would make the casting of the cylinder head more complex and would make it more difficult to cool. Hence, the importance of placing the sensor in the upper chamber of the VCR actuator is clear. What’s more, being located in the hydraulic actuator, this sensor will operate in a colder and less aggressive environment and it may therefore be possible to make it simpler, less expensive and more reliable.

In conclusion, MCE‑5 VCRi is not only compatible with any type of combustion chamber, it also facilitates pressure measurement in the said chamber. This distinctive feature is essential to maximize the energy performance of variable compression ratio engines.

Though constraining for engine integration, a side-positioned direct injector is also
compatible with the MCE‑5 VCRi: this is the current configuration