[Lx]

mamelukesabre is correct. You are wrong. They are taking the exhaust gasses to drive a turbine which coverts the exhaust energy to mechanical. It doesn't connect to another compressor to compress the intake air like a turbocharger. The output of the compound turbo is converted mechanically and is effectively added to the mechanical output of the engine.

[Niteflyr]

They are taking the exhaust gasses to drive a turbine which coverts the exhaust energy to mechanical.

You are correct sir...