On Mon, 26 May 1997 09:28:10 +0800 "Jerry Causey" <reecau@whidbey.com>
writes:
>Bill Schooler asked:
>
>> We've seen this thread on a recurring basis. And I've seen people
>say
>> the same thing you did. What I want to know is just what you mean
>by
>> "good results"? And what would be "bad results"? And the corollary
>
>> question, to all: why would anyone want to use something other than
>what
>> the factory recommended? (Engine oil)
>>
>>
>In my case, although my GT isn't really a daily driver, because I take
>a
>bus-ferry-bus combo to work, it is a year 'round week-end driver. In
>the
>winter, even with our relatively mild daytime temperatures (mostly
>35-45F
>range), I have experienced really bad throttle response until the
>engine bay
>warms up (about 8 to 10 miles of driving). I think this is due to
>over-damping
>at low temperatures, due to high fluid viscosity. A quick blipping of
>the
>throttle, such as when down shifting, doesn't have any effect on the
>engine
>speed. I've tried many fluids in my dashpots in an attempt to overcome
>this
>non-responsiveness, including, ATF, 5w-30 motor oil, Mystery Oil, and
>Penrite SU Oil (or whatever it is that Moss sells). None have made any
>real
>difference. My next attempt will be a 0W-30 synthetic motor oil, if I
>can find
>one. I've read about them, but none of the my FLAPS carries anything
>lower than
>5W-30.
>
>Regards,
>Jerry Causey - 1967 MGB GT
>Whidbey Island, Washington, embraced by the Puget Sound
>(fairly close to Seattle, and the rest of the USA)
>
Jerry,
It sounds like you have a case of lack of "accelerator pump" (I know,
the SU doesn't have one) What you need is not a lighter oil but a heavier
oil in the dampers.
The effect of the heavier oil is to slow the RATE of piston movement,
causing the airflow across the jet to speed up. As we know the pressure
of a gas (air) is inversely proportional to it's speed, thus the
pressure at the jet face is lower causing a larger proportion of gasoline
to be pulled into the airstream, resulting in a temporarily richer
mixture. When the piston reaches it's balance height, the mixture has
returned to normal. SU, in their manuals refer to this as the
"accelerator pump effect".
Try running a straight 50 wt oil and see if the problem resolves itself.
Rick
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