4.11 and Engine Overheat

[Robo.]

Originally Posted by -)-MAILMAN-

5000 feet is still too low to be shifting from supercharger 1 (neutral blower) to supercharger 2 (low blower) in the F4U-1 Corsairs. The Real Life Corsairs (F4U-1/-1A/1C/1D) used the R-2800-8 and -8w engines and maintained 44" MAP up to 8000 feet before shifting from neutral blower to low blower then maintaining 48" MAP. This matches exactly the USN Pilot training film for the Corsairs and until v4.11 the game matched this.

Hi Mailman, I said it was around 5000-5500ft at that particular map (Crimea). The MFP is obviously very much depending on the atmospheric pressure and this is actually modelled in Il-2, e.g. your results may vary on a different map.

44'' up to 8000ft.? Which source is stating this as the alt where pilots normally switched from neutral to low blower?

US manual section b ''Power plant'', page 6:

neutral - S.L - 5500ft
low - 16500ft
high - 22000ft

= exactly what 4.11 Il-2compare states and what is also replicable in game in my climb test including best climbing speed and limit temperatures.

With water injection used, neutral blower only up to 2000ft, low from 2000 up to 15000ft. (e.g. page 24 of the British AP2351A manual)

It seems to me that the blower altitudes in 4.11 are pretty much spot on for Corsairs. Coud you please post some sources (preferably links) stating otherwise?

Originally Posted by -)-MAILMAN-

Hellcats used the R-2800-10 and -10W engines and had a different carburetor than those used in the Corsairs. Once source has the Hellcat shifting from neutral blower to low blower at 5500 ft (USN training film uses this altitude) and another source has it at 7000 feet. The Hellcats in versions previous to v4.11 shifted at 5500 feet. Shifting the supercharger at 5000 feet in this version is also too low for the Hellcats.

I have not tested the F6Fs yet. Again, shifting of blowers was fairly complicated, there were certain restrictions in throttle movement in Low and High blower position especially. Also, pilot had to reduce MFP and desirably RPM when switching, actual reaction time varied from plane to plane, and from the atmospheric conditions, that in the first place. Altitudes at normal rated powers should be as follows:

neutral 2550rpm, 44'' - SL - 7000ft
low 2550rpm, 49.5'' - 7000-22000ft
high 2550rpm, 49.5'' 22000ft up

From what I know from the Hellcat FM development, the 1st blower was impossible to set correctly withinh how the game works (I know nothing about that, sorry), and DT simply focused on getting the actual performance and speeds right at any altitude. The blower alt seems to be about 600m too low which is not a biggie considering you have got correct performance now. Hope that helped.

[-)-MAILMAN-]

Here is a link to the film used for pilot training for flying the F4U-1 Corsair from wing fold, start up, takeoff, climb, and landing. the narrator gives the Manifold Air Pressure, Propeller RPM, Radiator settings and altitudes that the supercharger shifts. At the normal rated power climb neutral blower is used, 43.5" MAP at 2550 RPM and shifts from neutral blower to low blower at "approximately" 8,000 feet. Viewing the film is free. In the past you had to use Real Player to view the film, but there are now new choices, I used WMP. Over the last few years I have watched the Hellcat, Thunderbolt, P-40, P-39 and P-38. This was the first reference I had seen to 44" (43.5" to be exact) up to 8,000 feet.

The film is using the F4U-1 with the framed canopy at a time frame when the six position national insignia was being used.

http://www.zenoswarbirdvideos.com/F4U.html

[Robo.]

Originally Posted by -)-MAILMAN-

43.5" MAP at 2550 RPM and shifts from neutral blower to low blower at "approximately" 8,000 feet. (...) This was the first reference I had seen to 44" (43.5" to be exact) up to 8,000 feet.
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Very interesting movie, thanks for that. As it seems, the devs seemed to stick to the actual manual which states 5500ft. It is not unusual to see different sources stating different values, it is hard to make a decision then. In this case, the movie happens to be the only source refering to 8000ft. Both US and British manuals state 5500ft.

As long as you can fly the a/c as per book (and you certainly can as I described above), I don't see any problem.

[Bolelas]

Not a question about the game itself, but as real life aircraft behaved: In a dive, in a over-rev situation (lets say i cut throttle but forgot to pitch back), does the plane heat the same way as if i was adding more fuel? (with less pitch). I know compressed air heats, plus there is fuel going in (the idle fuel), and also friction, but should it overheat slowly?
Hope you people can understand question, because it is a little confusing.
I have not much knowledge about engine, just what i read in foruns, books etc. Also in the spitfire manual it says that in a dive they could do a little over-rev, but had to add at least one third of throttle : Was this to lubbricate pistons?

[Whacker]

Originally Posted by Bolelas

Not a question about the game itself, but as real life aircraft behaved: In a dive, in a over-rev situation (lets say i cut throttle but forgot to pitch back), does the plane heat the same way as if i was adding more fuel? (with less pitch). I know compressed air heats, plus there is fuel going in (the idle fuel), and also friction, but should it overheat slowly?
Hope you people can understand question, because it is a little confusing.
I have not much knowledge about engine, just what i read in foruns, books etc. Also in the spitfire manual it says that in a dive they could do a little over-rev, but had to add at least one third of throttle : Was this to lubbricate pistons?

Over-revving any engine is very, very bad for it. It creates a lot of heat very rapidly (mostly from friction, not combustion), and it pushes parts of the engine far beyond what they were designed to work at.

Some common failures include piston rods breaking ("throwing a rod"), cam and crankshaft bearings rapidly being burnt out and seizing up, valve heads colliding with pistons, etc. Even if everything manages to hold together, it can also cause critical "soft" components like gaskets to fail, which may not cause an immediate seize-up but could cause other things to fail in a chain reaction.

It's very complicated and I don't pretend to understand the actual ways and means of doing it, but calculating a particular engine's red-line rev rating is done based on it's design. Beyond that red-line the probability of partial or total failure rapidly goes up to where it's essentially guaranteed.

Lastly, keep in mind this was almost 80 years ago. Aeronautics was a very young field and technology was pushing boundaries once held to be insurmountable. Warbird engines were pushed to their absolute limits and designed to run at just below those with minimal safety cushions. Overspeeding your prop and motor will invariably give you those really bad results, and the game seems to do a great job of simulating that as best as it can.

Hope that helps.

[K_Freddie]

So what were saying here is... a slower revving engine is a lot cooler, whether it be driven by wind or combustion.

Common sense says that combustion would be hotter

[Crumpp]

Also in the spitfire manual it says that in a dive they could do a little over-rev,

The Spitfire manual does not say to over-rev the engine in a dive. It says to keep the throttle 1/3 open in a dive to maintain 3000 rpm. Do not use the propeller rpm control to maintain rpm, adjust the throttle (manifold pressure) to maintain rpm.

That the correct way to operate a constant speed propeller while maneuvering in any aircraft. You adjust manifold pressure to maintain rpm. On many manifold pressure gauges, a green arc is provided to assist the pilot in keeping the engine within limits to maintain that required rpm while maneuvering.

http://images.search.yahoo.com/image...1pdac1f&fr=sfp

[-)-MAILMAN-]

Originally Posted by Robo.

Very interesting movie, thanks for that. As it seems, the devs seemed to stick to the actual manual which states 5500ft. It is not unusual to see different sources stating different values, it is hard to make a decision then. In this case, the movie happens to be the only source refering to 8000ft. Both US and British manuals state 5500ft.

As long as you can fly the a/c as per book (and you certainly can as I described above), I don't see any problem.

Specific Engine flight chart Airplane Models F4U-1, FG-1, F3A-1 R-2800-8



Normal Rated (MAX. CONT.) 2550 RPM / 44" MAP / 7000' Critical Altitude WITH RAM / 5,500' Critical Altitude NO RAM / N Blower

Normal Rated (MAX. CONT.) 2550 RPM / 49.5" MAP / 19000' Critical Altitude WITH RAM / 16500' Critical Altitude NO RAM / L Blower

NOrmal Rated (MAX. CONT.) 2550 RPM / 49.5" MAP / 24000' Critical Altitude WITH RAM / 22000 Critical Altitude NO RAM / H Blower

Am I wrong thinking that WITH RAM is what the pre IL2 1946 4.11 engine performance was set to while IL2 1946 4.11 is using NO RAM engine performance. This applies to 4.12m as well?
Could you please explain to me what the difference between WITH RAM and NO RAM? How are each of these conditions acheived? Is WITH RAM the condition when the carburator inlet door is open creating a ram air effect and NO RAM the condition of the carburator inlet door being shut? In the game is it true that when we open/close the radiator this operates the cowl, coolant, oil cooler and carburator air intake flaps/doors simultaneously instead of individually like the real aircraft did?
Thanks in advance for the explanation whoever explains it.

Additional question. Takeoff Power Setting is 5 minutes maximum duration, Military Power Setting is 5 minutes maximum duration, War Emergency Power Settings is 5 minutes maximum duration. In the game we get an engine overheat warning when exceeding normal operating performance at various altitudes. Does the warning in the game come at the 5 minute max duration mark or does the warning come earlier than the 5 minute mark so you had better noted the time you went to military power or war emergency power?