Another opinionated screed:
What temperature does an engine run at? It all depends where you measure
it. It will be very high inside the combustion chambers during combustion,
and fluctuating wildly. From there as you move out to the water jacket the
temperature drops and fluctuates less. You can see this by the way the temp
rises above normal after switchoff, because heat is being transferred into
the water from the metal but isn't being circulated through the rad (other
than a very small amout of thermo-syphonic action) to be cooled. Unless you
have a problem with your heater there is no way you can have a water temp of
160 and yet "the heater wouldn't do diddly".
If the ambient is very cold it is quite possible for the surfaces of the
block and head and the heater and hoses to cool the water to such a degree
(ho ho) that it never gets high enough for the thermostat to open, and
*then* you may well find that the heater gives no useful output. In this
case the temp needle would be way below normal.
Does your temp needle remain quite close to normal during quite a wide range
of loads and ambients? It should do. The stat opening is continually
changing to maintain the water temperature to about the specified point. If
the load increases beyond a certain point, and/or the ambient rises above a
certain point such that the rad cannot dissipate the required amount of
heat, the stat will become fully open. Any increase in load or ambient
beyond that will cause the temp needle to go *above* normal.
The reason for winter and summer stats is to try and compensate for the
greater and lesser amount of cooling that occurs on surfaces other than the
rad in an effort to achieve a more constant temperature *inside* the engine.
As long as the engine gets hot enough for the stat to start to open, and as
long as it does not get hot enough to be constantly fully open, then that is
what changing the stat winter and summer does.
PaulH.
----- Original Message -----
From: Max Heim <mvheim@studiolimage.com>
To: MG List <mgs@autox.team.net>
Sent: Wednesday, August 01, 2001 2:10 AM
Subject: Re: what's your 62-67 MGB water temps?
> [totally opinionated screed follows <g>]
>
> Everyone seems to think that a 160 degree thermostat means your engine
will
> run at 160 degrees. Maybe, if the ambient temperature is below freezing.
At
> which point you would regret it because the heater wouldn't do diddly.
>
> Seriously, the normal operating temperature of the engine (in moderate
> conditions) is going to be somewhere in the range 170-200 degrees.
Remember,
> all the thermostat rating means is the temp at which it starts to open.
Once
> it is fully open, it's up to the car's cooling system to limit the
> temperature. In summer driving, that's going to be around 190, or more.
This
> is entirely based on the heat output of the engine and the size of the
> radiator (assuming everything in good condition).
>
> - In the winter, the engine temp stays at 160, and you don't get any heat
> from the heater;
>
> - In the summer, the temp climbs rapidly past 160, at which point the
> thermostat is wide open and has no further effect -- might as well take it
> out;
>
> - Or, say you've installed an oversize radiator and quadruple fans, and
the
> engine actually does run at 160 -- what have you accomplished? How is that
> any better for you or your engine than running at 190 with your "winter"
> thermostat? Cooler (other than in the sense of "cooler than boiling") does
> not mean better.
>
> On the other hand, if you use a 190 degree thermostat year round:
>
> - In the winter, you have a nice, toasty (well, at least noticeable) flow
> of heat;
>
> - In the summer, the thermostat actually modulates the engine temperature
> and keeps it at a stable 190, which, you may note, is the straight-down
> position on the dual gauge, indicating that it is the nominal (or
"normal")
> temperature.
>
> In your own words, "No boiling over, water loss or other overt hot
signs" --
> what would make you think that it was "too hot"?
>
> Far from being "too hot", 190 is actually a more efficient operating
> temperature from a thermodynamic standpoint. And it is far from being
close
> to boilover -- if you have any pressure in the system at all you can get
to
> 215-220 degrees or so. And unless you're stuck in stop-and-go traffic on a
> sweltering day, you'll never even get close to that.
>
> Sorry to run on like that. In short:
>
> - 190 is "normal"
> - chuck the160 thermostat
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