82 or 88 degrees.....?

[sprint95m]

Should I change the thermostat from a 82 to a 88 degree type?



I am using Evans Coolant, the version for performance cars (because of the alloy cylinder head) on the 1850.
The takeoff for the heater is directly from the back of the cylinder head. Since I converted to EC the heater has
not been as efficient, only being as good as a standard heater (supplied via the inlet manifold).
This is because I believe the back of the cylinder head is no longer the hot spot within the cooling system
due to the properties of EC preventing such localised occurrences.
Going from ye olde fashioned antifreeze to EC saw no difference indicated in running temperature on the dashboard gauge.



Any thoughts please?

Thanks,


Ian.

[Jon Tilson]

Given that you spend most of your time in a colder environment than the rest of us I would have thought the heater was pretty important.
Its also easy to try an 88 degree stat with little coolant loss so go for it.

I can drop the temp gauge quite a bit on all my slants with the heater on max and full fan in traffic if I need to.

So are you also running a TR7 heater outlet? Also be sure you have a stat with a foot to block the bypass- you know this of course but others may not.

Jonners

[MIG Wielder]

Hi Ian, I reckon the answer is a yes. The reason being ( from my experience of EWC ) is that my 1850 runs much hotter when compared with standard anti-freeze mix. For example in an outside temperature of 78 deg F the engine runs at 93 deg C at 70 odd mph. And the heater runs hot quite nicely. But putting the heater on makes very little difference to dragging the water temperature down. That is more influenced by slowing down for the traffic jams and the traffic queues.
Hey; no problem; EWC doesn't boil.
But last Winter was a slight problem. O.K. it was a mild Winter down South but the heater was not working well. Demisting was only just adequate. And this is what I reckon is one of the problems with EWC.
The temperature gauge is well down to about 80 deg.
The problem is 3-fold.
Assuming the basic compound is Propylene Glycol ( they are not saying) but there is enough on the www to determine this.
The specific heat of EWC is 0.59 cal/ gm / deg C.
The Thermal conductivity of the EWC is 0.206 W.m.K compared with 0.58 W.m.K for water.
And the viscosity is much higher at 25Deg C at 48.6 centipoise
Then for a given temperature and given water pump pressure... the flow rate through the heater matrix will be less ( more viscous ) and the heat given out into the matrix will be less for a given inlet temp; ( specific heat ) and as the thermal conductivity is less the water outlet temperature will be higher , i.e. Less heat extracted.

So yes; starting with a higher engine temperature at 88 deg C will help.
Its what I will be trying come the Autumn. Plus a blanking plate in front of 1/2 the rad to get nearer to the 93 deg C running temperature in Summer.
Having read the physics of propylene glycol I was immediatly a bit worried about the increase in viscosity at low temperatures with the 1850 skew-gear driven water pump. So I've been keeping the revs; down until the water temperature starts to rise. Not good for getting the oil up to the top end in Winter which is why I also use a 10W-40 oil in winter.
What do you reckon ?
Tony.

[sprint95m]

I have fitted an 88 degree thermostat.
However the car has only seen a little use this winter so I cannot draw any conclusions, instead
I can give what are first impressions:

Heater works better. Engine temp reaches half way on the gauge (compared to 1/4 - 1/3 before).
Warm up time seems the same.

It has not been tested with a frosted windscreen yet.



Ian.

[Toledo Man]

I might fit an 88 deg one next time I change mine. The coolant gets up to temperature on mine but the heaters feel lukewarm.

[Magenta Auto Sprint]

Old school said that 88 c was for winter due to colder ambient temperatures and 82c for summer due to warmer ambient temperatures.

I still do this but I notice the difference in the way the engine runs if I leave my 88 in when the warmer weather arrives and this then tells me to change it.

malc

[sprint95m]

Interesting Malcolm,
I will leave the 88 degree thermostat in and see how it goes during the summer.
That is how it was when the 1850 was sold new.

This model of 88 thermostat is a really common choice among a wide variety of makes for all year use including Saab.





Ian.

[Edin Dundee]

That IS interesting, I've never been happy with how an 1850 warms up, and it's not like it would make a difference when your engine is very hot.