I was told the opposite - by a seemingly experienced dashpot pro - that you
want thicker oil in the damper in winter resulting in a longer phase of
enriched mixture for the cold weather and thinner oil for summer resulting in
shorter enriched mixture phase in the hot weather
Carl,
My understanding of multiple viscosity oils is that they are meant to provide a
wider range of viscosities to address the extremes of cold weather (act like
5wt. oil for starting) and hot weather (act like 50wt. when the engine
encounters conditions that cause it to run hotter than normal). In most
situations a multiple viscosity oil is striving to act as an oil that is normal
"operating" oil viscosity, e.g. 20wt. or 30wt., and provide a fairly constant
operating environment for the engine.
Seems like you are striving for the same thing in your damper, that is, you want
an oil that is going to act like a 20wt. oil (the manual recommendation) and
give you a constant acceleration response from the damper. It isn't that you
want a richer acceleration response in the winter and a leaner acceleration
response in the summer. Its that you want a constant acceleration response
under all conditions.
...checking my own carbs -
they never get that hot making me think 'multivis' doesn't ever go into effect
anyway
If you assume that your engine is going to be operating at a constant optimum
temperature (hopefully) then the variable is the ambient air temperature, which
is the temperature of the air being draw through the carburetors (and hence
affecting the temperature of the damper oil). If your ambient air temperatures
are fairly constant then using a damper oil that is one viscosity probably makes
sense. However, if your ambient air temperatures vary widely, as they do where
I live, then a damper oil that can come closer to providing a viscosity "like"
20 wt. oil when the air flow through the carburetors is colder or hotter seems
to make sense. A multiple viscosity oil such as 5w50, in hot or cold air
temperatures, is trying to provide the normal "operating" viscosity of a 20wt.
oil in conditions that a 20 wt. oil might not be able to.
What you are trying to get is constant viscosity and thus a constant
acceleration response from the damper, not make it operate as an temperature
dependent fuel/mixture adjuster. You do want your fuel mixture a little richer
in winter and a little leaner in summer but you want that over the full range of
operation not just on acceleration. For that you simple adjust your
fuel/mixture needles as the seasons dictate.
And that's my $.03 worth. As always it boils down to what works for you.
Bud 71 TR6 CC57365
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