Mogas: what happens to EGTs?

"Jim Weir" wrote in message
...
" jls"
shared these priceless pearls of wisdom:

-
-
-Now that I have done some homework, I find your statement here to be in
-error. Please look up the alloy formula for stellite, which is the
exotic
-alloy coating on expensive 100-octane aircraft engine exhaust valves.

I know well the formula for stellite. If you are nuts enough to buy
stellite
faced valves, I know there are people willing to take your money. If you
want a
plain-jane 100 octane valve, there are those, too. I can tell you that
I've
done enough work inside Continental engines to understand the difference.
Have
you?

Yes, several Continentals, Lycomings, and even worked on a Franklin. I'm
overhauling an O-300 at the time. The 629404 exhaust valves were about $60
last time I checked. And when I bought stellite valves for an A-65 which
I'm also rebuilding, there were 2 diffrent kinds of 100-octane valves and
the stellites were cheaper.

Gene Kearns wrote:
: Having actually done this...... 1967 C172H w/ Lycoming O-360-A2A

I do this all the time. Takeoff tank has some (or all) 100LL, other tanks
100% autofuel... '69 PA-28-180 with Lycoming O-360-A4A

:-Ok... little MOGAS quiz for you.
:-
:-You run the Left tank dry and fill it up with premium unleaded car
:-gas.
:-

: Used Amoco Premium

Wilco/Hess 93 A.K.I. (R+M/2)

:-Right tank has 100LL.
:-
:-Takeoff on the RH tank and climb, level off, and set up the mixture
:-for
:-cruise flight. Either ROP or LOP. Your choice.
:-

: ROP by 75 degrees.

More or less peak EGT at 65% power

:-
:-THEN, you switch to the LEFT tank. You change nothing else.
:-
:-Later you download your JPI and plot the data.
:-
:-1 What is it going to show happened to the EGTs when you switched
:-tanks?
:-

: Increase of about 9 degrees.

Roughly the same... analog gauges so difficult to get too accurate

:-2 What is it going to show happened to the CHTS when you switched
:-tanks?
:-

: Nothing observable.

Ditto

:-3 (not in the JPI, but: ) What is the airspeed going to do? Increase?
:-Decrease? Stay the same?
:-

: No observable change.

Ditto

-Cory
--
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