Reddit mentions of Vees For Victory!: The Story of the Allison V-1710 Aircraft Engine 1929-1948 (Schiffer Military History)

This paper about supercharging the Allison V-1710 might be of interest. Originally producing 1000 horsepower, a turbo compound prototype of the V-1710 developed 3000 HP at 3200 RPM on the test stand with a manifold pressure of 100 inches Hg, or 49 PSI of boost. This system differs from the VDT because the turbo unit was actually mechanically connected to the crankshaft of the engine. The hot expanding gases of the engine spun a blowdown turbine geared to the crank. Testing showed that the blowdown turbine generated 890 shaft horsepower, nearly the same power generated by the first iterations of the piston engine itself. Add the boost from the turbo compressor and water injection and the result was just shy of 2950 HP on the stand.

Source: Vees For Victory!: The Story of the Allison V-1710 Aircraft Engine 1929-1948 by Dan Whitney