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

It "boosts" everything that exists

The MCE‑5 VCRi does not compete with any other strategies
or technologies but on the contrary, it boosts their effectiveness

We often hear about secret technologies that are being developed by carmakers that could change the world – they don’t exist. All carmakers are basically working on the same topics at roughly the same time. If this were not true, given how long this myth has existed, we would have seen a miracle solution by now.

The first electric vehicles date back
to the middle of the 19th century

Gasoline direct injection appeared
on Junkers engines in 1937

Duesenberg 1931:4 valves per cylinder
and double overhead camshafts

1954: first gasoline direct injection
applied to a car engine (Mercedes SL)

BMW Valvetronic:
the more "variable" it is, the more "efficient" it is…

The situation is completely different: all carmakers are trying to improve the energy efficiency of their vehicles, often without reaching their objectives. In the framework of the Kyoto protocol, that was put up for ratification on 16 March 1998, and put into application in February 2005, the EAMA (European Automobile Manufacturers Association) committed to reducing the average emissions of vehicles sold in Europe to 140 g of CO2/km. This objective was not met, not because the will was lacking, but because it is a difficult one, proof that no carmaker has the ideal technology hidden away.

Most strategies developed today are old ones: the first automotive vehicle to exceed 100 kph was an electric one in 1899 with the “La Jamais Contente” built by the Belgian engineer Camille Jenatzy; the first hybrids date back to 1906; direct gasoline injection has been used in airplane engines (Junkers Daimler Benz) since the 1930’s and was first used on a car in 1954 in the Mercedes 300SL; and the turbo compressor was invented in 1910. In 1931, the Duesenberg Company was already proposing engines with 4 valves per cylinder and a double overhead camshaft. There is nothing radically new, not even the variable compression ratio whose interest had already been identified in the 1920’s without a technological solution applicable to mass production ever being found.

We talk about downsizing as though it were something new, while we have been applying it for over 100 years. Downsizing actually consists in obtaining the same torque and power from a smaller capacity engine, and we reduced engine capacity at same power by a 25 factor between 1900 and 2010, which means that most of the downsizing work was done prior to 2000.

The main strategies that can be applied to improve engine efficiency and performance and to control emissions have been identified for quite some time now.

The real progress made for automobiles comes from the increasingly astute application of old strategies with, in particular, ever more sophisticated electronics, IT and mecatronics. Carburetors as used on cars 15 years ago and a modern electronic injection system have the same function: to mix air with fuel in the most homogeneous way possible. The plus points added by electronic fuel injection systems are more accuracy in fuel dosing and more “intelligence” via an air/fuel ratio defined according to a variety of parameters and laws that can be adapted to any situation. The essential advances made for engines are more precision, more intelligence and also more variability. In parallel, the sciences of materials, calculation, sizing and manufacturing processes have enabled considerable progress for IC engines.

When a new technology such as multi-port fuel injection is developed, all its fields of application are not immediately known. For example, injection was initially planned for a more precise fuel dosage and this precision was then used to implement 3-way catalytic converters for after-treatment purposes. Fuel cut-off during deceleration also became possible, as did pre-injection before starting the engine, which replaced the choke or starter.

Another important point is “variability”. We have been able to decide on the amount of fuel injected at what moment, as well as the ignition timing for quite some time now. The aim now is to make valves more intelligent: after camshaft phase shifters that can adjust valve timing so that the valves open and close at the most appropriate moment, we are now seeing the appearance of different devices to control valve lift (Valvetronic®, Variocam plus®, Avus®, VVTLi®, Multiair®). Valve control systems are being designed that would be able to freely “vary” valve lift (camless).

It is therefore surprising that the compression ratio has not yet been made variable since it can have the most impact on what it will be possible to do with a reciprocating IC engine. The compression ratio directly conditions engine efficiency. The compression ratio determines the engine’s sensitivity to knock and its ability to be surpercharged and, therefore, to be downsized. It determines the engine’s fuel compatibility and is the main determining factor for the compression auto-ignition of the air-fuel mixture (HCCI, CAI). The compression ratio has so much influence that by becoming variable, it virtually makes it possible to have several engines in one. By becoming variable, the compression ratio corrects a serious shortfall of IC engines: conventional engines have a compression ratio that is too low at low loads and too high during high supercharging. The truth is that a fixed compression ratio engine is like a stopped clock that tells the correct time twice a day. When variable, the compression ratio is always at its optimum value.

The variable compression ratio does not compete with any other strategy and, as a matter of fact, it boosts their potential with a leverage effect that leads to a sizeable amplification of their effectiveness. This is the case for downsizing, downspeeding, expansion ratio optimization, combustion of lean homogeneous or stratified mixtures, compression ignition and variable valve actuation dethrottling strategies (VVA). When combined with VCR, the efficiency of GDI, supercharging and VVA is reinforced.

In this context, MCE‑5 VCRi technology will be a new part of the technological mix applied to gasoline engines to make the most important parameter variable: the compression ratio. This will push back the limits of gasoline engines by boosting the efficiency of all existing strategies and technologies.

The principle of downsizing is not new: it has been applied to IC engines since the origins of the automobile

VCR can be combined with any technology to maximize the effectiveness
of all strategies applied to engines

The MCE‑5 VCRi technology will be a new part of the technological mix applied to gasoline engines