Nascar 9:1?

[Michael D. Porter]

Russ Highton Jr. wrote:
> 
> In regards to the "cheaper nascar engines" with 9:1 compression.  Are you
> sure?  Last I heard they were running 18:1 to compensate for a vacuum
> condition caused in the intake at high RPMs from the restrictors.  Am I
> wrong?
 
I would suppose an 18:1 CR is a bit beyond the pale, Russ. At that CR,
the heat of compression would likely cause spontaneous detonation of any
NASCAR-legal fuel. That's very close to diesel engine compression
ratios, and the cetane rating for gasoline of any type doesn't come
close to that of diesel fuel. Even methyl alcohol-burning diesels are
running about 15.5-17:1 ratios. The lower compression NASCAR engines are
probably compensating for intake restrictions by maximizing flow at
usable rpms and so concentrating on volumetric efficiency, not
stratospheric compression ratios. Higher compression ratios help, but
after the limit, they hurt.
Cheers.

-- 
My other Triumph doesn't run, either....