LW VS VVS PLANES at 4.10

[Blackdog_kt]

Just a little reminder guys...when talking about overheat in IL2, be also sure to take into account the excessively unrealistic boost/manifold pressure/ata values we are permitted to run in this sim.

In my personal opinion, it's useless discussing how much the overheat modeling in the sim penalizes the player when

a) we can reset it with no damage at all to the engine and
b) we judge overheat effects as excessive but we measure them at boost values that would cook the real engine within seconds

For example, just because the manifold pressure needle goes up to 70 mmHg, doesn't mean it's meant to be ran that way. This is a power reserve generated by superchargers/turbochargers for flying in higher altitudes where the ambient air pressure drops a lot, not normal power to be used on lower altitudes with total impunity.

It's easy to understand that the higher the pressure of the air entering the engine the more dense the air is, which means we have more air for the same volume and thus more power for each "burn" cycle.

Now let's go back to our example. If the engine is rated for a maximum of 50 mmHg of MP on all altitudes then that is already over-boosted on sea level. That means it's more than the pressure of the ambient air that's getting sucked into the engine, which usually varies around 30 mmHg. That's why an engine that's turned off will display about 30 mmHg on the MP gauge, since the gauge reads the ambient air pressure.

But what about the rest of the manifold pressure up until the 70 mmHg mark(and thus available power) that we use in IL2 on sea level with total impunity? Well, in reality that's not meant to be used to go over the 50 mmHG mark that our example hypothetical engine is rated for. In fact, just because an engine is rated for a max power of 50 mmHG doesn't mean it can run it indefinitely, that's where the rated "max continuous power" setting comes in and it's also a bit lower. Let's assume that for our example engine this is rated at 45 mmHG.

A plausible power chart would then look like this:

Take off power: 55 mmHg for no more than one minute

Absolute max power: 50mmHg never to be exceeded (except in take-off), for a time of X minutes or until oil temperature reaches Y degrees or cylinder head temperature reaches Z degrees.

Max continuous power (also called METO power=Max Except for Take Off): 45mmHg, you can run this all day long.

Then we would have a couple of lower settings for:
Climb at 42.5 mmHg
cruise climb (aka slow climb) at 38 mmHg
cruise at 35-38mmHg and finally
slow cruise at 32 mmHg.

It's obvious that the engine's ability to generate reserve manifold pressure up to the 70 mmHg mark comes in handy not to go over the engine limits, but to keep close to them as the ambient air pressure drops. It's not meant to provide a speed boost at sea level or other low altitudes, but to compensate for power loss from ambient air pressure drops at higher ones.

So, what happens if you do exceed it? Hard to say. Engine knock, rapid cylinder head temp rise (aka overheat) or it might even break something if you firewall the throttle to 70mmHg while sitting on the runway.

The way i see it, IL2 is a 10 year old engine that couldn't precisely simulate all this at the time it was created, but the developers also didn't want to let the player run totally unchecked on higher difficulty settings, hence the overheat mechanics in the game.

However, it's pretty clear that it's not much use comparing overheat behaviour in-game without comparing in-game and real-life engine operating data.