Thermostat Housing

[2cams70]

I've read on Internet that it's about power but I wasn't there when they designed it, so who knows. The heater is certainly there to let the ecu have some control over opening the thermostat more.

Don't believe everything you read on the internet. The engineering logic says it opens because of thermal management reasons and because of the metallurgical limitations of the materials the engine is made of. If you plunge a red hot poker into cold water the red hot poker cools very rapidly and the energy is dissipated into the water. If you could on the other hand make the water the same temperature as the red hot poker the energy would stay in the poker and not be dissipated into the water. Same deal inside an engine. You want to keep the heat in the combustion chamber and not transfer it to the outside.

If it's running under light loads and therefore the heat being produced by the engine isn't as great the metallurgical limitations don't come into play as much and so the coolant can be run at a higher temperature in order to maximise the amount of useful energy extracted from any given quantity of fuel.

These engines aren't known for cracking heads or blocks or for blowing head gaskets so basically they do seem to have the thermals properly managed even with 110c+ nominal coolant temperatures

t's quite a clever system when you think further about it.

[rgh0]

110C versus 90C is a question of clearances and emissions with a little influence on power. The designers make theoir choices. Lotus was a lot cruder compared to today and they chose a lower thermostat to compensate for the higher heat load being imposed on the Spitfire radiator.

I think you can over think these things. If it works do it

cheers
Rohan

[2cams70]

110C versus 90C is a question of clearances and emissions with a little influence on power.

Not true Rohan. It's about efficiency and extracting the most energy out of a given quantity of fuel. Times have changed since the 1960's but the physics hasn't. Overcooling your engine is not a good thing.

[mbell]

Don't believe everything you read on the internet.

Agree. Never gave it much thought really, likely it allows ECU some control, so maybe preventatively open the thermostat proactively when driven harder, rather than waiting for increase in heat from combustion to cause it. So keeps temps more consistent.

The m62tu engine basics are good and it's nice engine to use but it has some significant short coming, being the plastics used in the cooling system and timing chain guides. (Mine made it to 155k miles before falling, that wasa 27 hour job and lot of parts!)

[rgh0]

110C versus 90C is a question of clearances and emissions with a little influence on power.

Not true Rohan. It's about efficiency and extracting the most energy out of a given quantity of fuel. Times have changed since the 1960's but the physics hasn't. Overcooling your engine is not a good thing.

I dont think you understand Otto cycle themodynamics. Go and read up on it and then we can have a discussion. The difference in 110C versus 90C in coolant temperature is insignficant.

[2cams70]

dont think you understand Otto cycle themodynamics. Go and read up on it and then we can have a discussion. The difference in 110C versus 90C in coolant temperature is insignficant.

Why then did Ford increase the thermostat rating of the LTC engine when they dropped it into an Escort with it's better cooling system? They could have just stuck with the 78c one that Lotus used? They obviously thought 85c was better for the Escort application than the 78c one.

The m62tu engine basics are good and it's nice engine to use but it has some significant short coming, being the plastics used in the cooling system and timing chain guides. (Mine made it to 155k miles before falling, that wasa 27 hour job and lot of parts!)

Plastic timing chain guides are a common issue with many modern cars these days. I'm surprised you haven't mentioned the transmission at all. Be prepared. Guaranteed to crack an A drum at some point in it's life. Nice car but Jeez..... and expensive. Expensive for BMW parts that is - not expensive to buy.

[mbell]

I'm surprised you haven't mentioned the transmission at all. Be prepared.

It's a six speed manual, getrag 420, so pretty robust and issue free.

[2cams70]

I'm surprised you haven't mentioned the transmission at all. Be prepared.

It's a six speed manual, getrag 420, so pretty robust and issue free.

Nice - rare combination you have there.

[Sadbrewer]

110C versus 90C is a question of clearances and emissions with a little influence on power.

Not true Rohan. It's about efficiency and extracting the most energy out of a given quantity of fuel. Times have changed since the 1960's but the physics hasn't. Overcooling your engine is not a good thing.

With all due respect 2c70, you're overthinking this, or at least giving the theoreticals too much credence as opposed to the practical aspects of 50/60 yrs ago..
The wax stats were cheap and cheerful... and open and close all over the place, the temperature probes and dash gauge were not lab instruments, they only provide a roughish guide to the driver. From the manufacturers point of view they only had to provide enough heat to the interior in winter and enough cooling capacity for the engine in summer...that on a cooling system with multiple years of rust particles running around and blocking the radiator.
On a race car it may be a factor, but the priorities for a road car are different.

[2cams70]

110C versus 90C is a question of clearances and emissions with a little influence on power.

Not true Rohan. It's about efficiency and extracting the most energy out of a given quantity of fuel. Times have changed since the 1960's but the physics hasn't. Overcooling your engine is not a good thing.

With all due respect 2c70, you're overthinking this, or at least giving the theoreticals too much credence as opposed to the practical aspects of 50/60 yrs ago..
The wax stats were cheap and cheerful... and open and close all over the place, the temperature probes and dash gauge were not lab instruments, they only provide a roughish guide to the driver. From the manufacturers point of view they only had to provide enough heat to the interior in winter and enough cooling capacity for the engine in summer...that on a cooling system with multiple years of rust particles running around and blocking the radiator.
On a race car it may be a factor, but the priorities for a road car are different.

Psst guys!!! - I'm currently working on a 65C thermostat for a Lotus Twin Cam. Guaranteed to keep your engine cool. Pre order now or you'll miss out. It won't be cheap though due to the extensive research and technology involved.

[rgh0]

dont think you understand Otto cycle themodynamics. Go and read up on it and then we can have a discussion. The difference in 110C versus 90C in coolant temperature is insignficant.

Why then did Ford increase the thermostat rating of the LTC engine when they dropped it into an Escort with it's better cooling system? They could have just stuck with the 78c one that Lotus used? They obviously thought 85c was better for the Escort application than the 78c one.

.

They did it becasue the Lotus 78C one would have resulted in the engine running at to low a temperature leading to issues with excess piston to bore clearances and increased water in oil contamination in these circumstances 10C or 20C coolant temperature differrence is signficant.

[2cams70]

They did it becasue the Lotus 78C one would have resulted in the engine running at to low a temperature leading to issues with excess piston to bore clearances and increased water in oil contamination in these circumstances 10C or 20C coolant temperature differrence is signficant.

Hallelujah unto God's Almighty Son
Praise the Lord, ye bright angelic choirs
In holy songs of Joy.
Man, proclaim his grace and glory,
Hallelujah unto God's Almighty Son
Praise the Lord in holy songs of joy.

We agree!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

..........and also to increase the thermal efficiency of the engine

[JonB]

I'm a bit late to the party on this one, but I've been following the thread. I hope you don't mind if I ask a basic question for the sake of better understanding the subject.

I always thought the thermostat's sole purpose was to allow the engine to warm up from cold as quickly as possible, by only opening when the coolant in the block reaches the specified temperature. Once open, cooler water enters the block from the coolant system parts external to the block (mostly the rad), but this soon heats up. I didn't think the thermostat closes once the coolant is hot and given this, how can it have any effect on the running (warm) engine? I'd have thought the radiator and pump spec would have more impact.

Given the standard (rather puny) radiator, I would assume the water temperature in a running engine is always over the (standard) thermostat rating.

Now, having followed the thread it appears my assumptions are not quite right. If one of you would care to enlighten me, I'd be grateful.

Cheers
JonB

[2cams70]

I'm a bit late to the party on this one, but I've been following the thread. I hope you don't mind if I ask a basic question for the sake of better understanding the subject.

I always thought the thermostat's sole purpose was to allow the engine to warm up from cold as quickly as possible, by only opening when the coolant in the block reaches the specified temperature. Once open, cooler water enters the block from the coolant system parts external to the block (mostly the rad), but this soon heats up. I didn't think the thermostat closes once the coolant is hot and given this, how can it have any effect on the running (warm) engine? I'd have thought the radiator and pump spec would have more impact.

Given the standard (rather puny) radiator, I would assume the water temperature in a running engine is always over the (standard) thermostat rating.

Now, having followed the thread it appears my assumptions are not quite right. If one of you would care to enlighten me, I'd be grateful.

Cheers
JonB

The cooling system should be designed to be capable of dissipating excess engine heat under the most severe operating conditions - i.e continuous full load and high ambient air temperatures. If you didn’t have a thermostat the engine temperature would be too low unless you operated continuously under those severe conditions. With a thermostat the temperature is maintained at the optimum level even under partial load conditions. The thermostat does this by constantly regulating the coolant flow according to how it senses the temperature - i.e too hot it opens more too cold it closes more.

It’s only fully open or fully closed at the extremes of the engine being too hot or too cold. Between those extremes it’s partially open and optimizing the temperature by constantly changing the amount it’s partially open.

What the “optimized” temperature should be is what all the discussion has been about.

The setting of the “optimized” temperature appears to be balanced around the system having enough “headroom” to cope under transient heavy load conditions versus the engine being too cool under partial load conditions with consequent negative effects like oil contamination, reduced efficiency and potentially greater engine wear. A lower temperature thermostat will give you more margin to cope under a transient (not continuous) heavy load. With a better cooling system you have more headroom (ie more time available when operating under high load until temperatures become critical) and so you can run a higher rated thermostat and reap other gains as well.

Be aware that the temperature you read on the guage is not the temperature your engine experiences under dynamic conditions at localized hot points. The temperature at those localized hot points is higher than what you read on a guage. This I believe is what the designers also considered when they set the thermostat temperature rather than just the average temperature of the coolant as measured by a guage.

……….. but people may disagree!!!