Quote:
Originally Posted by Old Tele man
Uh, an exhaust turbo-charger with controllable waste gate is likewise a 'variable compression ratio' combustion engine...and far less dynamically complicated.
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The expansion ratio is much higher at low load this way. A normal turbocharged engine cannot have both high power and high mechanical compression ratio.
When the engine is at low load and not developing boost, the low compression ratio really really hurts efficiency because the combustion temperature is low and the expansion ratio is low.
It seems really really complicated but if it doesn't cost them much to build then I suppose there isn't a problem. I personally feel like a better solution is to rev an engine higher when you need power and rely on the transmission to do the downshifting to make that happen, instead of trying to maximize specific torque at considerable expense. Electric motors are the future and electric motors have great instantaneous response so you don't need that low end grunt.