Supercharger / spotting AI
 

Hi everyone. Not so an active member here, however an old IL-2 fan. (played with longer pauses for the last couple of years)

I hope it's okay if I post a couple of questions here. (4.12.2)

1) Firstly, what's the deal with the supercharger? When flying the F4U I can see a noticable amount of manifold pressure gained if I toggle to speed 2 immediately at ground level. If more MP = more engine power, are there any side effects in switching to speed 2 right from the start and not at recommended 2000m?

2) How do I report enemy planes to my (AI) squad if I see them first? It says in the manual that you have to center the view on them, but nothing usually happens if I do so. Usually on night flights I sometimes see the enemy first and want to report it to my AI guys in my flight.

3) And possibly related to 2) What does the W:Bandits command in the radio menu do? How does it work and when do you use it?

Thanks in advance.

I also noticed this and usually switch stages right below 1000m in the F4U. I think if changing stages raises the MP without lowering the RPM, then you should change stages.

You can report enemy planes to friendly planes by pressing F4 (This is the default button I believe). If a friendly plane is in range he will confirm that he spotted the aircraft.

It would be interesting to research how real pilots used the supercharger stages on various WWII aircraft.

I am an expert on internal combustion engines and I know that in the real world a supercharger increases cylinder pressure. Aircraft use them to make up for the lower air density at higher altitudes.

In a real combustion piston engine running too much boost the fuel detonates instead of burning smoothly and it quickly destroys the engine. Guys that drag race automobiles or run a mechanical supercharger on a street car can buy different sized pulleys to vary it's speed and boost, and exhaust driven turbochargers use a waste-gate to bleed off pressure and keep it below a certain setting.

The automobile only has to run at one altitude usually so it does not have to vary it's boost as much as an aircraft would. Mixture also has to be manipulated along with boost, either automatically or manually, so if you have too much air forced into an engine and the mixture control does not compensate for it then the engine will lean out, overheat and again detonation and pre-ignition will set in and destroy it quickly.

The IL2 aircraft have some mixture, boost and prop pitch settings that can be manipulated for better performance, but they are much more forgiving and uncomplicated than most real-life engine management jobs be they automatic or manual.

I used to have a 60s Mercedes with Bosch mechanical fuel injection, basically what was developed and used for the WWII german fighters, it is a little mechanical marvel.....as were all the WWII aircraft parts.

Full boost at low altitude
 

[QUOTE=The Stalker;515390]Hi everyone. Not so an active member here, however an old IL-2 fan. (played with longer pauses for the last couple of years)

1) Firstly, what's the deal with the supercharger? When flying the F4U I can see a noticable amount of manifold pressure gained if I toggle to speed 2 immediately at ground level. If more MP = more engine power, are there any side effects in switching to speed 2 right from the start and not at recommended 2000m?

Jumoswanz says: "The IL2 aircraft have some mixture, boost and prop pitch settings that can be manipulated for better performance, but they are much more forgiving and uncomplicated than most real-life engine management jobs be they automatic or manual."

'Boosted' aircraft engines have a "minimum full throttle altitude." This is the altitude below which running full boost will probably damage or destroy the engine. My feeling is that running full boost at sea level in in the F4U would soon destroy your pistons. As Jumoswanz implies IL2 modelling in this area is very basic and far from real world engine management.

So what about the actual game? More power but no consequences?

I understand also that running something like power 100% on 60% prop pitch would also ruin the engine, but is not modelled and not the case in the game... Generally running much greater power than PP would damage real life engines also. Is that true?

This might help.

http://www.youtube.com/watch?v=5J0BYq3yevs



Ok for the "aviation engine experts" amongst us please don't watch this film.

For everyone else who is willing to learn something about Super/turbo chargers in WW2 1940 have fun :)

http://www.youtube.com/watch?v=KFwwgbj9Bi8

Thanks for the vids. They were most informative. Speaking as one of the 'aviation experts' whom you were so contemptuous of, I take your point and will offer no advice in the future. Of course I did learn about these things when I was training for my pilot licence. I also knew men who flew some of these aircraft in WWII so might know a few things you will not read about in the history books, but I know you would find these stories upsetting.

Nice vids, very interesting. Shows us just how much some of the things are still very simplified in the sim.

Does anyone know about the Bandits radio command though, what's that for?

I was referring to engine experts not just aviation in general, don't be so sensitive its a forum and your opinions are more than welcomed here.

And IL2 has a simplified engine management system as its not a "study sim" or simulator but a game with generic management for most aircraft engine control systems.

:)

2000m is probably an outdated recommendation. It's about true at high speed with lots of ram pressure when flying without water injection. With water injection, or at lower speeds, you need to switch earlier.

Higher MP doesn't always mean more power, because the higher gear supercharger consumes part of the extra power. So while MP might go up for the F4U at sea level, the engine actually delivers less hp until you're at about 1000m altitude, the exact figure depending on atmospheric conditions and your engine settings.

With water injection activated, 2000m is to high to switch stages, try 600m and 2000m may even be to high without water injection.

In Il-2 you can usually switch charger stages a few 100m early or late without significant disadvantages in power output, and it doesn't matter what stage you use -you will never ever get your engine damaged even if you use stage 3 at tree top level or stage 1 at 10km.

This is modeled in the game?

Yes, it is.

Think of prop pitch like the transmission in your automobile. If you were to put a stick-shift automobile in high gear, 5th gear of a 5 speed for instance and then drive very slowly at speeds you would usually use 1st gear for, the engine would have a tough time. And if you floored the throttle while running really slow in high gear it would have a high risk of damaging the engine or drive-line parts.

The job of the pressure in an internal combustion engine has the job of pushing the piston down it's bore and spinning the crankshaft. Under normal operating conditions the design engineers expect the pressure to be able to push the piston down it's bore in a certain time and then exit through the exhaust system. If your automobile or aircraft is stuck in a transmission gear or prop pitch that keeps the engine rpm much lower than the designers had in mind then the very hot gases are in the cylinder for much longer and have more time to make the engine hot before they are pushed out and a very cool charge of fresh air and fuel are pulled into the cylinder. It is a delicate balance that engineers figure out for operators of combustion engines in advance, but they can be circumvented by "determined" individuals.

The heat produced by combustion is hot enough to destroy the materials the engine is made of, but it does not because the heat is supposed to be carried away by air or liquid coolant systems. Yes the fresh charge of intake fuel mixture is one of the engine coolants.

On a very hot day you might notice the temperature gauge in an automobile go up while you are sitting at a standstill in traffic and then go down while you are at cruising speed on the highway. Same as an aircraft engine, the cooling systems are designed to work best with air going over them. Going slow with little airflow but at high throttle and high pressure and heat in the engine can overheat the engine.

New computerized engine management systems have knock sensors in the cylinder heads that will automatically alter the mixture and ignition timing if the engine starts to experience pre-ignition or detonation. Before these management systems a lot more was up to the operator.

When the air fuel charge in the engine is ignited by the spark plug the gas in the cylinder increases in volume many times but is held in relatively the same space, you can imagine the pressure increase, it goes from roughly atmospheric, up to hundreds or thousands of pounds! Altering the point at which the ignition lights the fuel charge will alter the pressure in the combustion chamber. Early ignition will burn the fuel charge more completely but will put maximum pressure in the cylinder, if there is too much pressure before the piston reaches top dead center then a power drop and overheating will result, too little ignition advance and un-burned fuel will be pushed out the exhaust and wasted, so again it is a delicate balance with the ignition. Older engines had ignition lead altered by a combination of initial, mechanical and vacuum, currently this is almost all done with computers of course.

Lots to know and learn and it is a hobby unto itself.

Nice post Jumo.
Extremely nice.

Jtd is correct on that, I believe.

You can still though, switch back and forth between supercharger 1 and 2, to see if there's any notable increase in manifold pressure.

I'm not sure about low lever supercharger gear 2 myself, I don't seem to recall using it at low level AND having it increase manifold pressure significantly, and sustainably.?

What happens to your airspeed, rpm and manifold pressure if you go to supercharger 2, right at 600m altitude?

I think Jtf is of course correct about less horsepower available, this is true for regulard superchargers, which exist in aircraft such as F4U corsair.

From wikipedia:
P-47 on the other hand has turbosupercharger. Turbocharger is powered by a turbine that is driven by the engine's exhaust gas.

Regular supercharger is mechanically driven from the engine, often from a belt connected to the crankshaft

In real life this sort of regular supercharger operating procedure - switching back and forth between supercharger gear 1 and 2, would not be good for the safety of the engine (but this, is not modelled in game)