Compression Ratio control

Compression Ratio control must not lead to unexpected limitations for VCR strategies implementation in the future. To make sure such a situation will never exist, the best choice is to combine the following features:

1) A wide range and continuous Compression Ratio (CR) control (example: from 7:1 to 20:1), to serve:
Lowest CR needs: cold starting procedures, turbo lag reduction, extreme supercharging;

Highest CR needs: adaptive Atkinson cycle at low loads.
2)
A high reactivity Compression Ratio control to ensure the best operation conditions under engine transient load and speed:
A rapid actuation from high to low CR: about 100ms and lower to go from 20:1 to 7:1 to respond to an immediate driver power need;

An actuation time of about 500ms and lower to increase CR from 7:1 to 20:1 (a rapid CR increase permits reaching the highest average efficiency).
3) A cylinder per cylinder Compression Ratio adjustment:
To set the same volumetric ratio to each cylinder when assembling the engine by compensating for moving parts machining variations. This reduces the need for costly high precision machining;

To serve ultra sensitive strategies in the future such as Compression Ignition, taking into account thermal and aerodynamic features of each cylinder.
4) A high precision control:
To serve ultra sensitive strategies;

To reduce the need for Compression Ratio safety margin (better final efficiency).

Conclusion

In the future, Compression Ratio (CR) control limitations can lead to impossible implementations of various VCR strategies. To avoid such a situation, an independant, rapid, continous, precise, low-energy consuming and wide range CR control is required for each cylinder.

(see: The MCE-5 technology response to VCR engines’ Compression Ratio control requirements)
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