This is a follow on to the discussion started in Kyle's indicator switch thread that got WAY off topic!
This will no doubt be coloured by my own rabid ravings and opinions but first a History lesson.
In the beginning cars had enormous radiators which reached way above the tops of their engines.
They had to be huge because until the 30s at least and often later, engines didn't have water pumps and cooling was entirely dependant on the thermic syphon, not very efficient!
So the water pump revolutionized cooling, followed by the viscous fan, but the whole thing was still a bit of a pigs breakfast because you were still wasting up to 6% of your engine's power driving a fan that was only needed when the car was stationary.
Enter the electric fan with thermostatic control switch (Sadly too late for Dolomite production) which stops the power wastage and gives much better temperature control than a viscous fan or anything earlier.
Now, we have modern systems with electronically controlled EVERYTHING for maximium efficiency as Rafe described in Kyle's thread, but i'm not really concerned with those as trying to get that sort of control onto a Dolomite is probably a step too far for anyone but a total electronics freak!
Because there is a second side to this debate, in that the engine works best and most efficiently when its HOT and I don't mean warm, I mean near boiling temperatures. It's why cooling systems are pressurized, to allow the engine to run at temperatures above 100 degrees centigrade WITHOUT boiling over.
And herein lies the dilemma, you need the engine hot to run efficiently but if it gets TOO hot it will boil, so there's a very narrow window when everything is bang on correct. Older cooling systems such as ours were a compromise between thermal efficiency and risk because, even in England, ambient temperatures can vary by over 40 degrees C and this makes it harder (or too easy at the other extreme) for the cooling system to do it's job.
Now add in the paranoia exhibited by most Sprint owners where one tiny twitch in that guage needle can have them running to the shops for a new rad or water pump and you have a situation where most of these cars are actually overcooled, especially once an electric, thermostatically controlled fan is deployed. Because old habits die hard! Most of us old school guys are used to a cooling system which is designed with a lot of "wriggle room" in it, to allow for unseasonal weather and other ambient conditions, because control was so poor. Add an electric fan and control is much better, but us paranoids still don't like to see that neeedle climb over the halfway mark, to us it means something is about to go bang and we don't like it!
But let's look at the situation in more detail, firstly, what does that big N in the middle signify? Well "Normal" of course, but what actually IS normal? The answer is (assuming everything is working correctly - a long chance I know!) somewhere around 87-88 degrees C. A slant engine's winter thermostat is 88 degrees so that's the theoretical optimum operating temperature, but it isn't really! What it IS, is a compromise dictated by the lack of control inherent in that design of cooling system. 88 degrees is not much more than lukewarm in engine terms, the best efficiency is almost 10 degrees higher, but running at 98 is too risky so the manufacturers lower the bar to stop too many overheating complaints when unusually warm weather hits and upsets their equations.
Now look, briefly, at the Vauxhall motor I have in my Toledo. It's not a generation ahead of the Triumph slant, it was first introduced in 1980 so was probably in design in the mid 70s. Yet it has a 92 degree thermostat (all year round) probably because it was designed from the outset to run with an electric fan. And that 92 degrees would be getting unpleasantly close to the 3/4 mark on a Triumph guage!
So what I am really saying here, is that there is overheating - and then there is our PERCEPTION of overheating, which is not the same thing at all! I have recently fitted a thermostatic switch to the electric fan on the Carledo (pure laziness, I ran with a manual switch for a couple of YEARS, just because there was no obvious place for an automatic one and I couldn't be arsed to buy a hose mount) Knowing the high stat opening temp, I had to opt for a fan switch that deploys the fan at a whopping 98 degrees and cuts out at 93 and do you know what? It's absolutely perfectly fine! And the automatic sender doesn't deploy the fan anywhere NEAR as often as old nervous Nellie here used to do it manually!
It's my contention that you could employ a similar high opening stat and thermo switch on a electric fan equipped Sprint lump and suffer no ill effects therefrom. You'd just have to get used to the "new normal"! Which might take a while!
Steve
_________________ '73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!
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