I still don't see how fitting a cooler 'stat makes the engine run any
cooler, if in warm weather the 'stat is wide open anyway. At this point,
with the engine fully warmed up and operating at a stable temperature,
say, 187 degrees, both the 165 and the 180 degree thermostats would be
wide open, and there would be absolutely no difference between them.
Meanwhile, a 190 degree thermostat would be cycling open and shut,
presumably. Now if the ambient temperature were lower, so that the engine
would reach equilibrium at, oh, 172 degrees, then you would notice an
effective difference with the "cooler" thermostat. BUT (and this is a big
"but"), from my experience, at this kind of ambient temperature you are
more likely to want to run the heater at full efficiency, and are not
concerned at all with overheating or low oil pressure. In other words,
it's cold out, and you would prefer the high temperature thermostat at
this time, anyway. This is why I don't believe in fitting a unreasonably
low temperature thermostat, like 165 degrees. The engine will never
stabilize at that low a temperature EXCEPT when it's already cold out
(and you don't want it to).
Obviously, if you have fitted a larger radiator, larger oil cooler, or
extra cooling fans, this may not apply to you. But then you have to
consider whether 165 degrees is the most efficient operating temperature
for the engine. IMO it is not.
Paul Hunt had this to say:
>The other thing, and the real reason why hotter and cooler thermostats are
>recommended for extremes of climate (well, extremes when compared to the UK)
>is that there is always some cooling via the engine surfaces. Small engines
>in very cold weather may never get up to temperature when cruising, which is
>why people blank off the radiator in winter. They are not really blanking
>off the radiator of course because the thermostat is closed anyway, what
>they are doing is reducing the icy blast through the engine bay and hence
>the block cooling.
>
>When an engine is run in a relatively hot climate there is relatively less
>block cooling for a given load, so more heat has to travel through the
>radiator to get cooled, and heat is retained in the engine for longer,
>raising the internal temperature of the engine above what is ideal. A
>cooler stat helps to compensate for this reduction in block cooling.
>Indeed, at one time the cooler stat was fitted as standard in order to
>increase (or rather restore) oil pressure. This works by reducing the
>internal temperature of the engine, so running with a cooler stat really
>does allow the engine to run cooler. Likewise a hotter stat in cooler
>climes helps to compensate for the *increased* block cooling and resulting
>lower internal temperatures.
>
>PaulH.
>
>----- Original Message -----
>From: Bruce Burrows <bburrows@webtv.net>
>To: <mgs@autox.team.net>
>Sent: Wednesday, April 19, 2000 4:39 PM
>Subject: Re: (Paul) Shroud Question
>
>
>>
>> --WebTV-Mail-8772-525
>>
>> Your reply (which appears below) was a good one, Paul, and much
>> appreciated. I have to say you forced my mind to work just a bit! Here
>> is my best take:
>
>...
>
>
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.
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