Engine Temperature
Discussion
I have read with interest, the various threads with reference to engine temperatures and to the subject of keeping temperatures down.
I cannot recall, however, anyone mentioning what the optimum operating temperature should be.
My 450 generally runs at about 70, but is this the correct temperature (assuming the temp guage is correct!!)?
Foggy
I cannot recall, however, anyone mentioning what the optimum operating temperature should be.
My 450 generally runs at about 70, but is this the correct temperature (assuming the temp guage is correct!!)?
Foggy
ATG said:
The OP is asking what is the optimum temperature, not what range of temperatures is safe, I assume. It's a good question. I have no idea what the answer is. Hope that helps 
Edited by ATG on Monday 12th February 17:08
Fair comment. But I don't think that an engine will have a temperature that is that specific, more a range of temperatures. As long as it is 'up to temperature' and not overheating it should make a difference to the performance.
saddpj said:
but is this the correct temperature (assuming the temp gauge is correct!!)?
Bad assumption (& I corrected spl for free)! Gauges / senders may vary a bit ~ if its not overheating you will get to know the normal ranges for your car & then notice when there is a problem...
Dave
There isn't such a thing as an optimal engine temperature: as WazzaL suggests it will be a range of temperatures dependent upon other circumstances. This range could be wider than 30°C. For example, driving at speed in winter may see the gauge reading as low as 60°C whereas in standing traffic in summer it could reach 95°C or higher.
And because of variations between individual temperature senders and gauges, a 'normal' reading maybe 70°C on one car but 80°C on another. So, if you believe your car to be running properly and the coolant system to be in good condition, take a mental note of what the gauge reads in various circumstances. If it starts to show readings different from these, start to investigate.
Whilst it's purely subjective, my car will, on any particular journey, show readings between 70°C and 90°C. But at its extreme (in different weather and speed conditions) I have seen 'normal' readings of 60°C and approaching 100°C.
And because of variations between individual temperature senders and gauges, a 'normal' reading maybe 70°C on one car but 80°C on another. So, if you believe your car to be running properly and the coolant system to be in good condition, take a mental note of what the gauge reads in various circumstances. If it starts to show readings different from these, start to investigate.
Whilst it's purely subjective, my car will, on any particular journey, show readings between 70°C and 90°C. But at its extreme (in different weather and speed conditions) I have seen 'normal' readings of 60°C and approaching 100°C.
It may not be of great practical importnace, but I'm sure you can talk perfectly sensibly about a single optimal temperature for an engine for a given set of conditions (those conditions being things like external air temperature, grade of oil). It may not be very important to keep the engine at exactly that temperture, and keeping it within a fairly broad range may be perfectly OK. Nonetheless, there will be a single temperature which best balances lubrication, thermodynamic efficiency, internal mechanical losses, etc.
I'd be very surprised if there was no difference in the engine's thermodynamic efficiency if the block's temperature varied from 70 to 90 degrees C. It may not be much of a difference, but I'd be surprised if it wasn't measureable.
I'd be very surprised if there was no difference in the engine's thermodynamic efficiency if the block's temperature varied from 70 to 90 degrees C. It may not be much of a difference, but I'd be surprised if it wasn't measureable.
ATG said:
I'd be very surprised if there was no difference in the engine's thermodynamic efficiency if the block's temperature varied from 70 to 90 degrees C. It may not be much of a difference, but I'd be surprised if it wasn't measurable.
I heard about the results of a detailed test into this which concluded that the difference in economy and power output was negligible just from the temperature itself, but there are other effects that I imagine would be more significant. If the heads run hotter then the water jacket in the head will be more prone to fail locally and develop hot spots that can lead to failure. The engine management system may run the engine too rich if it detects that the engine is not up to temperature, and (not in this car) derate the engine if it detects overheating.
I've only had mine for a month but done over 1,000 miles 
- Within a few minutes of starting the gauge indicates 90°C and stays there - no matter what the outside temperature is or how it's being driven. Admittedly the o/s temp has only been between about -2° & 12°C thus far but the reading is unvarying - which seems about right to me - my Audi 
is the same.
- Within a few minutes of starting the gauge indicates 90°C and stays there - no matter what the outside temperature is or how it's being driven. Admittedly the o/s temp has only been between about -2° & 12°C thus far but the reading is unvarying - which seems about right to me - my Audi is the same.
ray_von said:
Ian at what temp do your fans kick in or do they not?
Me?
I'm guessing they come on somewhere around 90-91°C I think. They appear to do a good job maintaining a constant temperature so that once 'running temperature' is attained they only switch on when needed. I've noticed that they are often on after 'spirited' driving when I park up, though the gauge has not (so far) exceeded 90°C.
Lord Grover said:
Within a few minutes of starting the gauge indicates 90°C and stays there - no matter what the outside temperature is or how it's being driven.
My temp gauge used to go up and down according to a load of random factors until I used the "spare" temp sender (and the matching mod-wise kit). Now it has the behaviour described above. The old sender location is apparently at the end of a pipe and so doesn't get good water flow past it (I think that's right).
Thank you all very much for your input.
Thank you, Dave, for spotting the deliberate mistake!!!
My 450 runs between about 70 and 90 and I am happy with that, but it is the ideal temperature that interests me. Most engines are happiest at a particular temperature ie when least wear and tear takes place.
Good luck to you all. Foggy
Thank you, Dave, for spotting the deliberate mistake!!!
My 450 runs between about 70 and 90 and I am happy with that, but it is the ideal temperature that interests me. Most engines are happiest at a particular temperature ie when least wear and tear takes place.
Good luck to you all. Foggy
From memory the standard Rover v8 stat opens at 82'c, so this is the point the main cooling system comes into play. If engines are running at 70'c it must be very cold so the block and heater must be loosing enough heat not to need the rad, or the themostat is modified or non standard (I dont know if TVR do any mod's). The increase above 82'depends on the cooling system efficency and available air flow.
That sounds like you were more interested in the oil temp issue then. The water temp is not an absolute definition of 'Engine Temperature' ~ your title/question may have been a little misleading. There is a relation between the 2 temps ~ but there is quite a delay between them... Plenty of discussions on here which you can read regarding this.
Basically I try & keep the simple ideas in mind:
Oil works best when at nice temp 80-110C; too cold = too thick; too hot = too thin + it will kill it faster
Stat keeps engine temp to limit; rad & fans (+switching) should be able to supply cooling when needed (not act as the stat!)
Latent heat in the engine bay is not good ~ it destroys components!
Cool air mixed with petrol gives a bigger bang
The 'engine temp' is a bit of a generalism... You have too look at each cause/effect in isolation ~ but consider your solutions as a whole. Each of us seems to have our own ideas these issues
Dave
Basically I try & keep the simple ideas in mind:
Oil works best when at nice temp 80-110C; too cold = too thick; too hot = too thin + it will kill it faster
Stat keeps engine temp to limit; rad & fans (+switching) should be able to supply cooling when needed (not act as the stat!)
Latent heat in the engine bay is not good ~ it destroys components!
Cool air mixed with petrol gives a bigger bang
The 'engine temp' is a bit of a generalism... You have too look at each cause/effect in isolation ~ but consider your solutions as a whole. Each of us seems to have our own ideas these issues
Dave
I spent years investigating TVRs before I bought, and overheating was a major concern. I remember passing a Grif up near the Lakes with steam shooting from the bonnet.
Now, my Chim runs colder than Steve's Bible suggests is the "optimum" temp, there's a graph in the Bible which states 80-90 is the optimal temp. The factory otter switch is set to kick in at 90. I think mine has had a larger radiator fitted and the fans kick in at 70.
I spoke to David Batty about it and he said don't worry, if it's running hot, worry, if it's not, don't.
In mid-winter it takes ages to get to 70, and on the hottest days last summer, even on a track day, I never saw 90. Maybe I soundl be grateful as David suggests, but I still wonder if the thermostat has been replaced, or if I sould get replace the otter switch with a hotter one.
Now, my Chim runs colder than Steve's Bible suggests is the "optimum" temp, there's a graph in the Bible which states 80-90 is the optimal temp. The factory otter switch is set to kick in at 90. I think mine has had a larger radiator fitted and the fans kick in at 70.
I spoke to David Batty about it and he said don't worry, if it's running hot, worry, if it's not, don't.
In mid-winter it takes ages to get to 70, and on the hottest days last summer, even on a track day, I never saw 90. Maybe I soundl be grateful as David suggests, but I still wonder if the thermostat has been replaced, or if I sould get replace the otter switch with a hotter one.
overhere said:
I still wonder if the thermostat has been replaced, or if I sould get replace the otter switch with a hotter one.
If it takes a long time to warm up, that's a problem. It may be the stat is missing or faulty. Where abouts is the otter switch on yours? One possible mistake is fitting a low temperature otter switch in conjunction with a normal stat. If the otter switch is on the swirl tank this can lead to the fans coming on far more often than they should.
Hi
I believe there is an optimum temperature in the combustion chambers that result in the best performance. I suspect that a well maintained RV8 (cooling system in good condition) in a TVR runs with the combustion chambers too cool normally - that is why the heat insulator between the plenum and the inlet manifold improves performance NOT by cooling the air intake BUT by keeping heat in the combustion area.
Just my theory - anybody care to comment?
Rob
I believe there is an optimum temperature in the combustion chambers that result in the best performance. I suspect that a well maintained RV8 (cooling system in good condition) in a TVR runs with the combustion chambers too cool normally - that is why the heat insulator between the plenum and the inlet manifold improves performance NOT by cooling the air intake BUT by keeping heat in the combustion area.
Just my theory - anybody care to comment?
Rob
my 450 runs between 60-70 (usually nearer 60, moving to 70 in slow traffic and 90 when stationary for a while). The fans come on a bit at 80 and a lot at 90 and consequently i've never seen the temp above 90 - even on London Thunder sitting in traffic all day! This seems to be pretty good but i'm not sure why it runs this cool - the splitter is in my garage and I still have a normal sized number plate... maybe if I fit the splitter and a small plate it'll run at 55! 
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