Quote:
Originally Posted by Big Dave
Big Dave asks:
What turns the wheels? Answer: Heat.
I recently looked into jacking up the compression on my Impala to take advantage of the honest 120 octane of natural gas. By going up to 13.5:1 compression (you can be pretty fearless with 120 octane) and maximizing spark advance an 11% efficiency improvement. In a mature technology like spark-ignition engines 11% is HUGE.
Assuming that 100 octane E85 would work OK at 13.5:1 compression, an 11% improvement in efficiency cannot overcome a 34% loss in heat content and a 27% deficit in $/MMBTU.
It's not some deep dark conspiracy. It's just thermodynamic fundamentals. Heat turns the wheels. Period. End of story. It ain't octane. It ain't spark advance or some other electronic gimmick.
The notion of getting better MPG than heat content would indicate is just unicorn manure. The great cosmic search for "something for nothing."
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I think you would agree that the particulars of HOW a fuel is burned and the energy used changes the thermal efficiency.