View Full Version : Supercharger in B-25

05-07-2005, 01:34 PM
Hello, I would like to know what is the altitude fine for change the supercharger 1 to 2 in the B-25 aircraft.


05-07-2005, 01:34 PM
Hello, I would like to know what is the altitude fine for change the supercharger 1 to 2 in the B-25 aircraft.


05-07-2005, 02:13 PM

05-10-2005, 12:04 AM
Some document or table with supercharger altitudes for all aircrafts of IL2-Pacific Fighters?.

Thank you very much.

05-10-2005, 12:46 AM
from the PF readme

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">B-25J:
Switch supercharger speeds at 2,700 meters (8,850 feet)
Maximum traverse speed for the electric top turret is 60 deg / sec

05-10-2005, 12:59 AM
Related - Is it possible, in the game, to blow up an engine being in high gear at low altitude? I've never been able to do it.


05-11-2005, 05:58 AM

05-11-2005, 01:53 PM
Whats the difference between a supercharger and turbocharger, i'm talking about cars. Wouldn't it be better to pro-charge car instead, you know supercharger with the turbocharger together.

Ohh almost forgot its OT.

05-15-2005, 11:54 AM
do you get confirmation when you switch stages??

05-15-2005, 02:23 PM
For adadaead

A turbo has a vain (fan) that is turned by exhaust gas. That vain is connected to a shaft that turns another vain that sucks air from the outside and compresses it into the engine. You can also multistage the turbos; one turbo's output drives another then the final turbo's output goes into the engine. I don't know the max number for that but I the most I've heard of is 5 stages, 2 being pretty common.
A supercharger is basically a compressor that is turned, either buy belt (car) or direct dive/transmission (plane). The compressesed air is then fed into the engine.
Both can use an intercooler. Compressed air is hotter then ambient air but cold air is better for power and fuel economy. For that reason it is important to cool the air before it enters the enigine.
That being said you question was more along the lines of turbosuperchargers. I have heard of things like this for large planes for extra take-off power (bombers and airliners). I think most U.S. heavy bombers had such a thing (B-17, B-24, B-29). The only time I have had this system described was in refrence to a Constallation. Just even more OT, the Constallation was Lockheed's proposal to the USAAC for a heavy bomber. The airplane that won that contract was Boeing's B-29. Of course the Constallation went on to be a sucessful airliner.
Wow, went way of course. Anyway, a turbosupercharger takes exhaust gas and uses it to turn a vain. The shaft that it is connected to is geared back to the crankshaft. In other words, it doesn't put air into the engine. It simply helps turn the engine with exhaust gas. For a Constallation it added 200hp per engine on takeoff.
Sorry, couldn't help myself.

05-17-2005, 11:29 PM
All of the USN fighters use supercharging. The F6F and F4U with the various R2800 installations used a two stage unit with three selections; neutral (just uses primary stage next to engine); Low blower with the auxiliary stage driven at a lower speed; and high blower where the gears are literally shifted to drive the supercharger form the engine shaft through gearing at it's highest speed.

The reason for the gearing is that the supercharger takes a LOT OF POWER to drive it, up to 400 hp in high blower. The maximum boost cam be obtained at lower altitudes with lower supercharger output (and power drain).

Superchargers are somewhat simpler and more compact in installation than turbochargers. Turbochargers are better at very high altitude, altitudes which were not common for combat in the Pacific.

The USN philosophy for fighters, keep it simple, keep it compact.

Large multi engine long range aircraft are another matter........

09-30-2005, 11:29 AM
Just for clarification, both types are superchargers. A turbo-supercharger simply uses a turbine (thus the "turbo" nomenclature) to drive itself, while a supercharger uses a mechanical device (gears or belts) attached to a camshaft from the engine to drive it. The name supercharger comes from the fact the the air mixture is now "supercharged" because of its higher pressure. Both types of superchargers are thus measured in PSI of boost (or metric equivalent) or atmospheres (ATA's.)

09-30-2005, 11:36 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by sammy4657:
do you get confirmation when you switch stages?? </div></BLOCKQUOTE>

It will tell you on the right hand side of the screen.

09-30-2005, 04:55 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by marine428:
Wow, went way of course. Anyway, a turbosupercharger takes exhaust gas and uses it to turn a vain. The shaft that it is connected to is geared back to the crankshaft. In other words, it doesn't put air into the engine. </div></BLOCKQUOTE>

This is not entirely correct. Both superchargers (positive displacement and centrifugal) and turbo-superchargers (always centrifugal) compress air into the engine. A turbo-compound (I think that's the term) is also geared to add power directly to the crankshaft per the above. I believe it was first used on the P&W 3350s that were installed in the B-29s. I've seen a cut-away (either in Pensacola or Galveston) and it is an amazing piece of machinery.

Because superchargers are driven directly by the engine, they produce power nearly instantly. Turbochargers require a little time (depending on the size) to spool up to a speed at which they provide boost.


09-30-2005, 06:06 PM
Supercharging systems are of 2 types - internally driven and externally driven (turbosuperchargers). Internally driven compress the fuel/air mixture after it leaves the carburetor whereas externally driven superchargers (turbochargers) compress the the air before it is mixed with the fuel from the carburetor. Some of these systems are designed to maintain near sea level pressure at the intake manifold up to a certain altitude where it begins to drop off due to the lack of ambient air pressure, and other systems are able to boost the manifold pressure above and far beyond that of sea level pressure. These latter systems allow flight at the 30-40 thousand foot level due to their ability to maintain a suitable manifold pressure even with very limited ambient air pressure.

10-01-2005, 02:50 PM
The turbo-compound 3350's weren't on the B-29. They arrived post-war (This is why it was so difficult to locate rebuildable engines for KeeBird and their subsequent loss so disappointing). Six cylinders fed a turbo that turned a shaft that was connected to the accessory section. Three turbos, 200Hp each. The B-29 had a conventional supercharger (geared) that was fed by a turbo (like on the B-17 and B-24). The turbo came in as the supercharger failed to provide full boost with a rise in altitude. This, of course, depending on the application, could raise the cylinder intake air temp to a point where detonation couldn't be avoided (a bad thing). An intercooler (between the turbo and supercharger) would then be installed (as on the B-29 or between the two supercharger stages as in the Corsair) or, rarely, an aftercooler (between the two compressors and the engine, car "intercoolers" are technically aftercoolers).

To clarify, turbos on otherwise Supercharged engines were for altitude performance, not takeoff. Allisons were originally intended to have a turbo first stage for altitude performance.

10-02-2005, 02:25 PM
Its OT, but the R-3350 were used on the mighty Skyraiders. http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif