Quote:
Originally Posted by wwest40
Turbocharging...
In order to take advantage of turbo boost the engine's "native" cylinder compression ratio must be "derated". Boost, once it arrives, will then raise effective compression ratio back up into the 13:1 range. So the 13:1 "native", off-boost, compression ratio of an Atkinson cycle engine would likely be reduced to something in the range of 10:1 or less.
Obviously that would result in the lowering of the performance of an Atkinson cycle engine to an ever lower level. That, in turn, results in even less exhaust flow/energy for spinning a turbo up quickly and thus the onset of turbo boost would become even more intolerable than with an Otto engine.
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I think you need to study more. Or study to begin with.
Who ever said you couldn't use a turbo on a 13:1 engine?
Then again, you're working with theoretical values to begin with... who ever said the Atkinson engine had to be 13:1? Or the Otto 10:1? Who said the Atkinson's
static (correct terminology) compression ratio had to be 30% more than the Otto?
First of all, Compression ratio is determined by comparing the volume at BDC to the volume at TDC, assuming 100% VE on the intake stroke. It has nothing to do with expansion of gasses or combustion in itself.
Therefore - If the Atkinson's only difference is that the combustion stroke is longer, then the static compression is measured using the intake stroke. This would mean that an Atkinson engine and an Otto engine could (and
must) be compared using the same compression ratio. I think you've lost this bit of data. Since the static compression ratio of both engines is the same, and the Atkinson engine is capable of drawing more power from the power stroke than the Otto engine is, Then the Atkinson engine is more efficient. That's all there is to it.
Couple that with the broadened efficiency of turbocharging, on a linear scale, and the turbocharger only makes the gap between the Otto and the Atkinson that much more obvious.
Please, read a book about these things. Arguing the matter is pointless if you don't have valid data or knowledge.