I know this is a lot more complex than variable valve lift, but the performance potential from variable compression ratio is amazing. Imagine idling the engine at 22:1 (great fuel economy); running under slight load and 18:1; increase load @ 30 psi and drop to 16:1; then with your twin sequential turbos at 100 psi drop to 12:1. Imagine a daily driver triple staged turbos @ 250 psi. These numbers are for example, but what the VCR allows is for more boost=power while maintaining correct cylinder pressures.
Engines today have a constant compression ratio. When an engine is turbo/supercharged, the CR must be lowered to prevent high cylinder pressures and, for gas engines, to prevent detonation. However, when the CR is lowered the engine doesn't operate as effeciently under light load or idling. Also, the CR can't be lowered too much because the engine won't start. Therefore, the engine can only safely run at a certain amount of boost. It now becomes clear why VCR would be such a breakthrough.
There are several methods integrating VCR. Some require new head designs, new block designs, or both. The system that I find has the most potential for integration into our Cummins engines is at
www.alvar-engine.se This would either require modifying a 12V head or needing to design a new head. A timing chain to drive the upper crank with phase changing capabilities would be required as well. This is not a trivial design or modification, but the power possibilities are truly out of this world!
Variable Compression??
Linear Mode
