<VV> Regular Gas and Fuel Economy in a 110hp Corvair
Mikeamauro at aol.com
Mikeamauro at aol.com
Thu Jan 3 22:19:53 EST 2008
Greetings and salutations:
I posted on this topic several days ago, and someone (who shall go unnamed)
promptly responded by saying I'm full of cr--; near as I could tell, the
person's position is: "simply lowering the compression ratio, via thicker
gaskets, is a sufficient fix for ping and detonation." Perhaps I, with my first
post, failed to fully explain myself and the process taken to come to my
conclusions. I feel what I've learned over the years, about making the Corvair engine
perform well on today's lower octane pump fuel, is important enough to
thoroughly share with the Corvair brethren... here goes.
Since 1970, I've owned and built Corvairs (before then I was a small block
Chevy guy, and a head mechanic on a regional stock car team). Beginning in the
80s, as high-octane pump-grade fuel became harder-and-harder to find, I
began to experiment with various methods of maintaining a high level of (Corvair)
engine efficacy (read: power and fuel economy), while at the same time
insuring the engines were capable of holding together for many thousands of miles.
My efforts first centered around simply lowering compression through thicker
head gaskets and/or base gaskets. What I found with this approach was
engines had less power (than with stock compression), and fuel economy suffered.
And, sometimes, especially at higher ambient temperatures, the engines were
still prone to knock & ping. (I drive my Corvairs every day, and the poor
performance of lowered-compression engines was simply unacceptable.) My next step
was to pay particular attention to the stock cooling system (de-flashing heads
and removing the lower shrouds in the summer); with restored stock
compression ratios: efficiency was back, but knock & ping remained prevalent in hot
weather. I then consulted with contacts in the professional race engine
business, and cross checked what I was told against the body of literature
available on the topic of modern combustion chamber construction. Now, I (still)
build my engines paying particular attention to optimizing the stock cooling
system, maintaining the stock compression (for my 110s... 9.5:1, verified by
CCing), keeping base ignition timing up near 18 BTDC (about 36-degrees overall),
but also hold the quench space to about .032. I also run premium fuel. The
results are excellent: my cars are very drivable, don't knock and ping, and get
very good fuel mileage.
I hope some find this information useful.
Regards,
Mike Mauro
Of Various Corvairs
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