View Full Version : Supercharger

08-23-2005, 08:58 PM
Tried it out for the first time today, have no idea what it does, just seems to slow me down... Could someone educate me? http://forums.ubi.com/images/smilies/blink.gif

08-23-2005, 09:27 PM
The supercharger was used to maintain rated horsepower as planes climbed higher. It does this by increasing the air pressure to the cylinders when the air gets thinner. For example a F4U Corsair would use stage one up to 8500 feet (altitude game recommends for changing to stage two) then switch to stage two. Stage two would be used up to 24,500 feet (altitude game recommends for changing to stage three). Different planes have different altitudes when they change supercharger speeds. You can find this in the manual & read me files. If you have stage two selected below 8500 feet for example the performance will be lower because the supercharger is now a load and is not helping the engine. You must increase and decrease the superchager speeds as you transition through the different altitudes. Not all planes had manual superchargers. Many had automatic superchargers and some had turbosuperchargers like the P-47D. This allowed the Thunderbolt to maintain 2000 hp from the deck to 30,000 feet. Hope this explains it.

08-24-2005, 12:33 PM
hmm interesting, thanks for the reply, I'll have to play around with it.

08-24-2005, 03:53 PM
Let's back up real quick http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

A supercharger is a mechanical device that uses engine power (classically by a belt in automotive applications) to drive some type of device to pack more air into the combustion chambers than is normally possible at atmospheric pressure

Any internal combustion engine is an air pump. Get more air into and out of it, and more efficiently, and the power goes up

That said, a supercharger can have speeds or stages to compensate for altitude, but I think we should keep that as an important feature of the supercharger, and not it's end all and be all. Yes, a supercharger generates additional power by it's own virtue at altitude- but it also does it on the ground. Stages or speeds need to be used to keep that supercharger working efficiently

Take the most well known application- a big V8 powered dragster. There's a big scoop on top of the exposed engine, usually with a couple or three circular plates in front that open and close with the throttle. The thing it sits on, the part which vaguely resembles a rectangular upside down bowl with ribs is the most visible part of the supercharger (not all of them work this way, it's just the easiest to describe since most folks know what this looks like) Incidentally, classically, the air scoop is actually the housing for a single carburetor, or a pair of carburetors

Inside that ribbed chamber is a pair of impellers. Sort of like two gears that mesh together, except they are almost 10" or so long. They are driven by a big belt that comes off of a 'snout' on the rectangular ribbed chamber, that is driven by the crankshaft pulley- that's the automotive application, the aircraft one is different but the idea is the same- grab the air, force it into the engine, pack it in tight, get a more even, smoother and complete burn from the fuel you have in the chambers- the belt driven impellers make a characteristic whine, or can- my supercharged car doesn't make a whine at all

A turbo is similar, except that exhaust gasses spin a turbine that in turn powers a device that packs air in the engine. This is the cause of the classic 'turbo lag'- you need to 'spool up' that turbine. Different size turbos need various amounts of time to spool up. Big ones make more power, but you need time to spool them- and that time means rpms. A naturally aspirated (no super- or turbo- charger) car with a good power band can beat the turbo powered car in that instance, because it's power is in a more usuable rpm range. if the turbo powered car had it's rpm up at the start, that race might very well end differently. In recent years, variable vane turbines and better computer controls have reduced that turbo lag significantly. In an aircraft, where you typically aren't maiking very fast, wide throttle changes, the turbo is very effective for an internal combustion engine's power-adder