@gruntguru
OK, watched that video again, perhaps more awake this time. You're certainly right on some points but let me clarify why I said that it's the wrong inference to make.
1. As a "rule of thumb" if fuel A burns faster than fuel B, MBT will be less for fuel A.
Agreed. But if fuel A is...
Some interesting and useful thoughts around using E85 - thanks for those. But only Brian has related this to my search for a "rule of thumb".
In looking for a CR rule of thumb, I was hoping to get some kind of relationship (theoretical, empirical, vague even) between an original CR for a petrol...
To clarify: Otherwise mechanically identical.... So it is mechanically identical except for the CR.
i.e. If we have a petrol engine with a particular CR and we wish to convert it to E85, making no other changes than CR (and non-mechanical to ignition and carburation), then, on what basis...
Is there a good rule of thumb for compression ratio where we know the original manufacturer's CR for a given petrol engine and wish to know the desired CR for an otherwise mechanically identical engine running on E85?
Any thoughts and theoretical basis on this would be appreciated.
