Thermostats - 60s-70s classics run 82° not 88°. Why?
Discussion
Can't help noticing very broadly a vast heap of classics run 82° Thermostats. Whereas cars from the 80s/90s onwards run 88°. Modern cars seem to run hotter.
I get the idea 82° in a petrol engine is seen as old hat. I have the vague idea 88° is thermally more efficient and modern oils like 100° ish. Why did cars back-when run cooler? Was it that oils in that era liked cooler? I fitted a mahoosive electric fan yonks back, even with the stock fan, my classic has cooling capacity to spare and a winter warm-up would be quicker if I bunged in an 88° stat.
Clearly things can't be as simple as a stat swap. Does anyone understand this a tad more than me? I was going to suck it and see. If 88° works over the coming summer then great.
Where is the flaw in the plan?
I get the idea 82° in a petrol engine is seen as old hat. I have the vague idea 88° is thermally more efficient and modern oils like 100° ish. Why did cars back-when run cooler? Was it that oils in that era liked cooler? I fitted a mahoosive electric fan yonks back, even with the stock fan, my classic has cooling capacity to spare and a winter warm-up would be quicker if I bunged in an 88° stat.
Clearly things can't be as simple as a stat swap. Does anyone understand this a tad more than me? I was going to suck it and see. If 88° works over the coming summer then great.
Where is the flaw in the plan?
BMWs vary the target engine coolant temp based on engine mode - sport mode is cooler than eco mode. lower temp gives more power (possibly about tolerance/friction between various bits of the engine at diff temps?) whereas eco mode gives better combustion,
In older cars without direct injection, I guess the temperature of the head around the intake ports will factor into the fuel vaporisation through the intake and into the combustion chamber and so affect the efficiency of combustion also. hotter = more fuel evaporates = better mixing, I guess.
I am really very much not an expert so I am just guessing here.
In older cars without direct injection, I guess the temperature of the head around the intake ports will factor into the fuel vaporisation through the intake and into the combustion chamber and so affect the efficiency of combustion also. hotter = more fuel evaporates = better mixing, I guess.
I am really very much not an expert so I am just guessing here.
Mine list an 88, but I switched one of them to an 82 because I wanted it to run cooler and give myself a bit more "margin" when in queues on the way into events, or traffic or whatever. I can't say whether it was successful or not as I also fitted a higher capacity radiator, and haven't really been in much of a queue since. I always think that the cooling system on my older cars is less reliable than the one on my "modern" daily driver, for some reason.
That said, I've just replaced the stat in my "modern" with one that doesn't have a jiggle pin, and it seems to be warming up quicker than it ever did. I can't say that it's not something else (faulty temperature sender, perhaps) as it's also retaining heat for longer when parked up.
OldDuffer said:
... and a winter warm-up would be quicker if I bunged in an 88° stat.
It wouldn't warm up any quicker to 82 degrees with an 88 degree stat than it does now. It would just get a bit warmer before the stat opens.That said, I've just replaced the stat in my "modern" with one that doesn't have a jiggle pin, and it seems to be warming up quicker than it ever did. I can't say that it's not something else (faulty temperature sender, perhaps) as it's also retaining heat for longer when parked up.
Edited by droopsnoot on Wednesday 28th May 09:23
droopsnoot said:
It wouldn't warm up any quicker to 82 degrees with an 88 degree stat than it does now. It would just get a bit warmer before the stat opens.
That said, I've just replaced the stat in my "modern" with one that doesn't have a jiggle pin, and it seems to be warming up quicker than it ever did. I can't say that it's not something else (faulty temperature sender, perhaps) as it's also retaining heat for longer when parked up.
It might warm up a bit quicker, because the 'stat opening is not a digital response, it starts to open as it warms up and needs to be a bit warmer to be fully open.That said, I've just replaced the stat in my "modern" with one that doesn't have a jiggle pin, and it seems to be warming up quicker than it ever did. I can't say that it's not something else (faulty temperature sender, perhaps) as it's also retaining heat for longer when parked up.
Edited by droopsnoot on Wednesday 28th May 09:23
As well as the 'stat temp, be aware of the coolant properties and the pressure cap setting, as these affect the boiling point.
Also other factors lie the expansion vessel affect the system's ability to cope with coolant heating.
Old engines often ran weak AF or pure water, a modern engine may not like that.
The actual cylinder head temperature may be quite different!
Perhaps more so with an iron head?
^ I haven't had it to a point where it's actually boiled, but I have worrying things going on with the temperature gauge. This isn't really a good way to look at the temperature in any case, on my car it's not marked with actual temperatures, I just have the idea that it should sit somewhere in the middle and start to panic when it rises above there. As you see, the gauge is pretty relaxed about things, with quite a wide "normal" band:
The above is the Firenza which always seems to run on the cool side - the car I worry about is the Sportshatch, which is always warmer. With the 88 degree stat it would get up to the dead centre of the gauge - a good thing on my modern but that's controlled by the dash electronics to sit dead centre. Now with the 82 degree stat, it sits a little below centre and I am a little more relaxed.
I also don't have a coolant reservoir - if things get hot enough to open the radiator cap, the water just goes down the side of the rad and out.
I recall a story where some journalists drove a Magnum from Lisbon to Istanbul and then back to London, whenever theirs got a little warm in a queue they'd just idle at around 3000rpm to get the viscous fan running faster and all was well, but theirs was a new car and not a 50-odd year old viscous coupling. I added a small electric booster fan to help out, but there's not a lot of room.
The above is the Firenza which always seems to run on the cool side - the car I worry about is the Sportshatch, which is always warmer. With the 88 degree stat it would get up to the dead centre of the gauge - a good thing on my modern but that's controlled by the dash electronics to sit dead centre. Now with the 82 degree stat, it sits a little below centre and I am a little more relaxed.
I also don't have a coolant reservoir - if things get hot enough to open the radiator cap, the water just goes down the side of the rad and out.
I recall a story where some journalists drove a Magnum from Lisbon to Istanbul and then back to London, whenever theirs got a little warm in a queue they'd just idle at around 3000rpm to get the viscous fan running faster and all was well, but theirs was a new car and not a 50-odd year old viscous coupling. I added a small electric booster fan to help out, but there's not a lot of room.
Not sure about other cars but Jensen Interceptors had the water ports to the head partially blocked with smaller gasket holes to increase the cylinder head temperature for better emission’s.
Interestingly the temperature gauges were modified over the years due to customers complaining they were getting too hot, first they moved the N in the centre of the gauge nearer to the hot mark then later also made the red hot section of the gauge smaller. I am not aware anything was done to make them run cooler just change the drivers perception of the engine temperature.
Modern gauges do not move about as much as I believe it they will stay dead on centre over a wide temperature range, and we have become accustomed to this driving newer cars so start to worry when we see them go up a bit in our classics.
In 30,000 miles driving my Interceptor including many traffic jams on hot days I have only overheated once when the electric fan fuse “blew” yet still keep a beady eye on the gauge in slow moving traffic.
Interestingly the temperature gauges were modified over the years due to customers complaining they were getting too hot, first they moved the N in the centre of the gauge nearer to the hot mark then later also made the red hot section of the gauge smaller. I am not aware anything was done to make them run cooler just change the drivers perception of the engine temperature.
Modern gauges do not move about as much as I believe it they will stay dead on centre over a wide temperature range, and we have become accustomed to this driving newer cars so start to worry when we see them go up a bit in our classics.
In 30,000 miles driving my Interceptor including many traffic jams on hot days I have only overheated once when the electric fan fuse “blew” yet still keep a beady eye on the gauge in slow moving traffic.
dpp said:
Modern gauges do not move about as much as I believe it they will stay dead on centre over a wide temperature range, and we have become accustomed to this driving newer cars so start to worry when we see them go up a bit in our classics.
Yes, on my TT it shows dead centre (I think that's 90 degrees) for anything between 82 and 98, and if it does anything different I worry. On the older cars, if they get up to the centre, I worry. It's another thing I should spend a bit of time going through on mine, but haven't yet done. Interesting note about restricting water flow to the heads to alter emissions, that's a level of knowledge on how things work that I don't have.
droopsnoot said:
dpp said:
Modern gauges do not move about as much as I believe it they will stay dead on centre over a wide temperature range, and we have become accustomed to this driving newer cars so start to worry when we see them go up a bit in our classics.
Yes, on my TT it shows dead centre (I think that's 90 degrees) for anything between 82 and 98, and if it does anything different I worry. On the older cars, if they get up to the centre, I worry. It's another thing I should spend a bit of time going through on mine, but haven't yet done. Interesting note about restricting water flow to the heads to alter emissions, that's a level of knowledge on how things work that I don't have.
The main reason for higher water temperatures in modern cars is emissions though.
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