<VV> RE: Re: octane and alky - adjustment in a Corvair

[Jim Burkhard]

> Our Land Cruiser actually lists different horsepower based on 
> the Octane 
> (actually based on using premium or regular).  I assume it 
> adjusts timing 
> primarily by detecting knock(?) and that the adjustment 
> lowers power.  

Yes

>It could possibly adjust fuel as well.

No, it will run stoichiometric in either case.  Actually, the retarded case
will use a bit more fuel, because your timing is retarded off the MBT
optimum and you lose thermal efficiency when you do that. How much depends
on how retarded you are.  Of course you are using *cheaper* fuel at the same
time, though....

> On a Corvair, automatic detection is probably unlikely.  

Not at all ... the Safeguard ignition that Ray Sedman sell does just that.

> However, I have a  friend here in AZ that uses an MSD ignition with an 
> instrument located on  the dash to make all kinds of adjustments with all
kinds of 
> controls.  He  uses it to adjust for altitude (because it is easy to go 
> plus/minus 3-4000  feet here) and to adjust for fuel.  I believe it does
more 
> than just retard ignition, I believe it also affects the advance curve if
desired.

Maybe MSD has a newer unit, but the old "ping control" one just shifted the
whole curve (via a knob). It's pretty crude, but better than nothing. The
Safeguard is a much better system as it works automatically and does it on a
per cylinder basis.  Rarely do all cylinders have the same knock limit, so
why retard the ones that don't need it?

Jim Burkhard