On Mon, 23 Oct 1995, Eric L. Van Iderstine wrote:
> On Mon, 23 Oct 1995, John M. Trindle wrote:
>
> > If this message doesn't make sense give it 4 hours sleep and a cup of
>coffee.
> >
> Oh no, a .com that doesn't get much more sleep than I do......Please tell
> me that I'm going to get more sleep after I graduate......PLEASE
>
Uh, small businessmen don't sleep. And I am well under 6' so...
We just finished a convention in Atlantic City and I was working the
booth in the exhibitor hall.
> The viscosity question is a good one......
> Here's what I know (think I know, my fluid power book is at my apartment).
> SAE 20w50 means that the oil acts like a 50 weight at 0 deg C, and a 20
> weight at 100 deg C....So the viscosity decreases (easier to flow at high
> temps) with temp....
>
This is backwards... viscosity matches a 20 weight oil when BOTH are at 0
degrees, a 50 weight oil when BOTH are at 100 degrees. Or something.
> cool with all of that intake air running through them) SO, they might
> reach 110 deg F (43 deg C).....while the engine is at operating temp.
>
OK.
> If the change of the viscosity of the oil is linear, then at 43 deg C,
> the 20w50 oil acts like a 37 weight.....IF I'm right (more like, if I'm
> not wrong), then the oil IS TOO viscous (hard to flow) at the assumed 110
> def F. So YES, it would take the carb pistons longer to go down, causing
> your engine to take longer for the revs to go down.
>
It's not linear, but I'll buy your conclusion. However, it also seems to
me you want a multi-vis to make the carbs consistant at all operating
temperatures. But maybe the under-hood temp is pretty consistant once
the engine warms up.
Anyway, it seems the way to go so far is either the little bottles ($$)
or some sort of straight 20 weight or multi-vis which is similar to a
straight 20 at normal operating temps. Since I've never seen a
straight-weight oil other than 30 I was curious what the folks used...
John M. Trindle | jtrindle@tsquare.com | Tidewater Sports Car Club
'73 MGB DSP | '69 Spitfire E Stock | '88 RX-7 C Stock
Home Page: http://www.widomaker.com/~trindle
"Quantized Revision of Murphy's Law:
Everything goes wrong all at once."
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