More Comments on Re: <VV> Two Questions
FrankCB at aol.com
FrankCB at aol.com
Thu Jun 28 16:04:46 EDT 2007
Andy,
Did you measure the spark timing change before and after you installed
the Dale vacuum advance/pressure retard unit? The stock turbo Corvair, unlike
EVERY OTHER Corvair, has FIXED timing all the way from idle to nearly 4000
rpm (or until boost is achieved). The speed of the combustion in the chamber
varies with the density of the mix, so, for best efficiency, it is necessary
to use MORE timing advance with LIGHT throttle openings which give LOW
density mixtures and LESS timing advance with HEAVY throttle openings which give
HIGHER density mixtures. When boost is achieved the density of the mix becomes
even HIGHER necessitating further reductions in timing advance which we call
RETARD since the resulting timing is LESS than the base timing at idle.
It is also possible that your carb is so far out of adjustment that the
enrichment of the mixture occurs at the relatively high intake manifold
vacuums that are present with normal highway driving with advanced timing.
In order to ascertain true mpg values, you have to measure for many
"fillups". I'd say at least for 1000 miles of driving and preferably more, since
each time you fill up, you most likely have a different amount of gas in the
"full" tank.
Frank "timing is (almost) everything" Burkhard
In a message dated 6/27/2007 8:51:20 PM Eastern Daylight Time,
slowboat at mindspring.com writes:
Have never experienced this "bog" that so many of you have described. I have
the Dale P/R unit on the 180 and it accelerates from idle just fine.
One thing, though, I never did get ANY improvement in gas mileage when I
installed the P/R pot.
Anyone have any idea why?
Thanks
Andy Clark
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