<VV> Economics - Regular Gas and Fuel Economy / Thermal

[Jim Burkhard]

Well, yeah, Matt for highest economy, higher engine temperatures help 
(I'm sure you are familiar with this on gas turbines as well... same 
deal.)  -- that's were people start talking about totally insulated 
"adiabatic" engines.  Those are always *diesels* though -- the bugaboo 
with too-high head temperatures on a gasoline engine will be spark 
knock. I think that is *especially* the case on an aircooled engine 
which will probably have a wider temperature profile (less even 
cooling) than a water cooled engine.  So, yeah, maybe a slightly 
hotter engine will help fuel economy, but not if it makes the car more 
knock happy and you need to retard spark timing or drop the 
compression ratio to counter it.  I can't give you any better advice 
than that.  I think lower hanging fruit can be had by tall skinny 
tires and tall gearing...

best regards

Jim Burkhard

PatioMatt at aol.com wrote:
> Jim,  what is your feeling on Engine / head temps for best efficiency?
> 
> To me,  especially for a "commuter car"  I'd want the engine  / heads to be 
> at 400F  as much as possible?  But have no current fuels  experience.....the 
> car like this was run in the 70's  ...120 mile round trips daily...
> 
> Matt