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

It makes noise and vibrates

Noise emissions were a source of concern during the development of MCE‑5 VCRi technology. With its gear system, the MCE‑5 VCRi adds a new source of noise emissions. However, MCE‑5 VCRi eliminates piston slap, which is a significant source of noise, and has a rigid crankshaft and crankcase that guarantee silent operation.

Various vibroacoustic measurements and
recordings made it possible to understand and control
MCE‑5 VCRi noise emissions

The noise emissions from the gears become imperceptible below a running clearance of 70 microns. A clearance of 30 to 50 microns was selected to ensure no perceptible noise emissions from the gears. This clearance is fairly simple to obtain in mass production given the processes used. This low clearance is also possible because the MCE‑5 VCRi gearwheel and racks always remain in alignment since there is no shaft misalignment or bending. MCE‑5 VCRi gear teeth are mounted on racks that are free to orient themselves according to the gearwheel, which results in the ideal orientation.

With regard to vibrations, the MCE‑5 VCRi behaves more like a gasoline engine than a Diesel (see the “it’s heavy” section).

The vibro-acoustic behavior of the MCE‑5 VCRi is one of its strong points.

On the MCE‑5 VCRi, the relationship between gear teeth operational backlash and noise emissions is
well controlled for both prototypes and future mass-produced engines