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

It’s too complex;
it’s possible to make simpler VCR engines

Increased complexity is an inevitable element of automobile evolution. In 2010, automobiles are infinitely more complex than they were in 1980; they are also more energy efficient, have better performance, and are more durable and more reliable. This process will continue: in 2020, automobiles will be more complex than they are in 2010. There must be a reason behind the complexity however – for the same result, it’s always better to choose the simplest solution. Obvious simplicity can sometimes be deceiving and can lead to a solution that is in the end more complex: after having managed all the faults of the “simple” solution, you often end up with a “complicated” final solution. The art of innovation is to find the simplest way to reach the most convincing solution.

Many VCR principles exist, but their simplicity
is often misleading and can finally lead to
complex and inefficient overall solutions

Even solutions that seem less impacting
for engine architecture call for the
development of a new crankcase

Articulated VCR engines present other challenges: noise
emissions, vehicle integration, durability, flexibility
(cylinder selective VCR is impossible)

This formula can be perfectly applied to the variable compression ratio that requires meeting several objectives with a single technological solution. A VCR engine must be able to provide the best level of compression ratio control in terms of range, flexibility, precision and responsiveness. It must not modify piston motion. It must be able to handle very high average and maximum loads without increasing friction. It must have small overall dimensions, not produce additional noise or vibrations and remain economical… There are many qualities required to guarantee the effectiveness of a VCR technology and unfortunately, all of them are almost indispensable.

Ideas that immediately come to mind when imagining a VCR engine are: lifting the crankcase using jacks and guides or joint arms, adding connecting rods, using eccentrics or variable height hydraulic pistons. On paper, these ideas seem simple and yet they are deceiving and can lead to different dead ends since they don’t have the essential characteristics required by a VCR engine to be efficient and competitive.

For example, an engine incapable of controlling its compression ratio cylinder by cylinder will require a complex individual valve control system to control compression auto ignition (CAI-HCCI). A VCR engine with a piston motion that reduces combustion efficiency will “eat up” the benefits of other VCR strategies just to make up for the losses. A VCR system incapable of managing high loads without overly high friction losses will be almost useless: the essential part of fuel consumption reduction is obtained through hard downsizing, which involves subjecting the engine to very high loads. Moreover, the advantages of VCR are largely reduced, if not destroyed, by excessive friction losses, which must be avoided at all cost.

If we list the objectives that must absolutely be met by a VCR engine and that are directly managed by the MCE‑5 VCRi technology, its apparent complexity turns into extreme simplicity.

The strength of MCE‑5 VCRi is its appropriateness to the functional
expectations of VCR, regardless of the strategies implemented