Turbo-Charged P-51?

[Strip]

Both a supercharger and a turbocharger have parasitic drag.

However......a turbocharger requires a lot less energy to do the same amount of work.

A supercharger has multiple shaft seals, high thrust loading, bearings,gears, oil seals, and rotor tip seals (depending on the design). A supercharger also requires a heavy gearbox and drive system increasing the power loss. A turbo charger usually only has a few seals and bearings. It doesnt require a seperate drive system and everything is usually engine independent except oil supply. For a given horsepower used a turbocharger will out perform a supercharger in almost all circumstances. (This is assuming you have properly designed components through out.)

Strip(er)

[gripen]

The P-51B with the V-1650-3 outperformed P-47Ds and P-38s at high altitude when it entered service late 1943. Only the late P-47 versions (M and N) offered somewhat better performance at high altitude and that time there were even better high altitude versions of the Merlin available if better performance had been really needed.

[Lumpy]

Both a supercharger and a turbocharger have parasitic drag.

However......a turbocharger requires a lot less energy to do the same amount of work.

A supercharger has multiple shaft seals, high thrust loading, bearings,gears, oil seals, and rotor tip seals (depending on the design). A supercharger also requires a heavy gearbox and drive system increasing the power loss. A turbo charger usually only has a few seals and bearings. It doesnt require a seperate drive system and everything is usually engine independent except oil supply. For a given horsepower used a turbocharger will out perform a supercharger in almost all circumstances. (This is assuming you have properly designed components through out.)

Strip(er)

That's because the turbo uses exhaust pressure and heat to drive the compressor. The exhaust pressure is normally wasted on non-turbo car engines, and is usually not powerful enough to have an effect on the car's performance anyway. In big WWII aircraft engines however the exhaust thrust was very important, often being a significant part of the total engine power.

[Bodhi]

My "notion" is not impractical, it is the way it is done. My turbocharged Buick Regal is pretty much the standard for turbocharger systems, and the engine supplies the oil for the turbocharger. In most applications, all of them that I have ever seen or worked on, in about 30 years or so, the engine supplies the oil to the turbocharger (and the turbocharger returns heated oil, after use for cooling and lubrication, back to the crank case of the engine). That includes aircraft, passenger cars, race cars, and trucks, light, medium, and heavy duty. As well as heavy equipment and tractors. A turbocharger requires a great deal of oil, for both lubrication AND cooling. NO, it is NOT practical to have a separate lubrication system for the turbocharger. Got any idea how much HP it takes to drive an oil pump to create 70 pounds of pressure, and move several gallons of oil per minute? I do, and if you forced a turbocharger to try and drive such a pump you'd shear the shaft off of it immediately.

Virgil, just an FYI for you.

The turbos on the P-38, P-47, and B-17 all get their oil from a system seperate from the engine's oil supply.  The B-24 uses the same oil supply as the engine.

On the P-38, it is located and filled in the nacelles just to the aft of the turbos, and is a three gallon tank.
On the P-47, it is located and filled just aft of the right side of the cockpit, and is roughly a three gallon system.
On the B-17, it is located just aft of the engine nacelles in the wing, and is filled from the top of the main wing, also a three gallon tank.

[Lumpy]

Captain Virgil Hilts, I retract my previous comment regarding oil systems and your experience.

[morfiend]

   

  Bohdi,

 just outta curiousity,what drives the pump for this sepperate oil system??
 It makes sense to have the charger oil sepperate from engine oil as this would
take a large burden off the engine cooling system.

[Bodhi]

On the type B-33 in the P-38, the tank is connected to a gear type combination scavenging and pressure pump mounted on the supercharger. 

This is from the P-38L erection and maintenance manual revised 15 January 1945.

[Lumpy]

Wasn't there a test done with Merlins in the P-38?

[MiloMorai]

Wasn't there a test done with Merlins in the P-38?

No, it was only a study exercise. Result was switching to Merlins provided no advantage to the a/c.