No overheat @ 9k

[III/JG2Gustav05]

I fly a Yak to 9k and close the oil and water radiators, then you can see both water and oil temperature go up to 110C, but not over temperature message shows up I keep it running like this do engine damage. Is that normal?

[SAG]

Maybe its because its in normal mode? i dont really know

[Finkeren]

This is just a wild guess, but could it be, that at 9000m the air pressure is so low, and therefore the mixture so lean, that the combustion produces a lot less heat which combined with the very low outside temperature (we're talking minus 40 degrees centigrade or below) is enough to just barely keep the engine from overheating even with radiators closed?

Edited May 28, 2015 by Finkeren

[[BTEAM]_Shifty_]

Yes, it could be comparable to flying at low altitude at 30% throttle. Which happens a lot when escorting IL-2s. And I have to actually close all radiators to not freeze my engine

[216th_Jordan]

Yes, it could be comparable to flying at low altitude at 30% throttle. Which happens a lot when escorting IL-2s. And I have to actually close all radiators to not freeze my engine

 

Better keep your speed up and do some circles around the il-2s to be able to act when you're ambushed, but that's offtopic

 

yes, at an altitude that high you engine has a lot less power then when you are near ground (take a look at the manifold pressure gauge..) and it's also a lot colder up there, so that's pretty normal.

[III/JG2Gustav05]

check my screenshot, the problem is that the meter already indicates the temper is 110C, that 's the point.

[von_Greiff]

check my screenshot, the problem is that the meter already indicates the temper is 110C, that 's the point.

 

....and this is maybe another reasonable failure of the instrument, it's so cold outside that the temperatures aren't mesurable, like a weighing scale when you are to "light" or to "heavy", like an error

 

yours

v. Greiff

[Willy__]

 

 

....and this is maybe another reasonable failure of the instrument, it's so cold outside that the temperatures aren't mesurable, like a weighing scale when you are to "light" or to "heavy", like an error

 

Thats valid for real life, but I really doubt that the game engine simulates that... 

[Finkeren]

check my screenshot, the problem is that the meter already indicates the temper is 110C, that 's the point.

Yes, but there's a difference between the coolant temperature and the cylinder head temperature, which is what actually damages the engine (and which is quite a bit higher than 110C when the engine is running normally) The coolant may well be much too hot because the radiators are closed, so the coolant can't lose the heat, but the cylinder heads still be at safe temperature levels, simply because the mixture is so lean and so little combustion is going on, that the engine can't overheat at all, even if it can get the coolant above 110C.

 

There is a way to test this: Go up to 9000m in the La-5, lean mixture appropriately and close both sets of cowl flaps. The Ash-82 engine is air cooled, so the temperature gauge shows the cylinder head temperatures directly. Then see, if you can damage the engine at those lean mixture settings or if the engine temps stay below damage threshold.

[von_Greiff]

Thats valid for real life, but I really doubt that the game engine simulates that... 

 

..therefore I said "maybe"

[LukeFF]

 

 

Yes, but there's a difference between the coolant temperature and the cylinder head temperature, which is what actually damages the engine (and which is quite a bit higher than 110C when the engine is running normally) The coolant may well be much too hot because the radiators are closed, so the coolant can't lose the heat, but the cylinder heads still be at safe temperature levels, simply because the mixture is so lean and so little combustion is going on, that the engine can't overheat at all, even if it can get the coolant above 110C.

 

He's flying a Yak-1, so no cylinder heads.

 

Besides that, the safe coolant temperature limit in the Yak-1 (and all other Klimov-powered planes) is 110 degrees, so I don't see an issue here.  

[Finkeren]

He's flying a Yak-1, so no cylinder heads.

All internal combustion piston engines have cylinder heads, and that's generally where overheating occurs (though at very high RPM it can also occur in the crankshaft)

 

The difference is, that the Yak-1 (like most planes with liquid cooled engines) measures the engine temperature indirectly by measuring the temperature of the coolant.

 

On the La-5 and other planes with air cooled engines, the engine temperature is measured directly at the cylinder heads (at least that's what I've read)

 

However, there is really no difference. In both cases overheating damage occurs in the engine itself and at much higher temperatures than 110C.

[donkeycods]

A leaner mixture actually leads to the engine producing more heat. A rich mixture cools the engine as the excess fuel helps cool it.

[JtD]

It's true what you say donkeycods. Lean mixture = high temperature. At high altitude, however, without proper fuel metering adjustment, there'd be less air for the same fuel in the cylinder and therefore an extremely rich mixture, which can actually lead to engine cut outs. Usually this gets corrected either automatically or manually, and mixture stays the same. There's just less mixture burned in each stroke at high altitude. As a trend, water cooled engines of the era don't really run a lot hotter or colder at high altitude than they do at sea level.

 

But, as Gustav said, these physics aren't the point. It's odd to have the gauge at the limit, but neither warning nor damage.

[III/JG2Gustav05]

I can keep it running with the temperature is a little bit higher than 110C (just as the screenshot shows)without damaging the engine till running out of fuel. even no overheat message shown up.