Holset has a commercial system engineered for over-the-road trucks that uses turbine recovery power. Not sure if it's made production yet.
In a non-supercharged class, turbine recovery would act much like increased displacement. The power stroke of the engine becomes more than just the 180 deg of crank rotation, as it continues to supply power after BDC by using the released gases for crankshaft torque while the exhaust valve has already closed.
The reason for "staged" turbocharging with diesels is very different. While there have been single turbochargers designed to supply over 5:1 PR, none are available for purchase, they were made by Garrett for the CIA/NASA for high-altitude, long-range spycraft. Diesels can use over 5:1 PR without major issues, so what you do instead is to feed one turbo into another to get those boost levels efficiently.
But there is a drawback, regardless of what the shops who sell twins will tell you. The best compressor efficiency is 80%. Maybe. So if you need to run two turbos compounded, the best you can ever get is 64% efficiency. Most likely you'll be 70/70, or 49% efficiency. The lost efficiency becomes extra heat in the intake charge and extra backpressure (drive pressure) in the exhaust. The wet-dream, is a 6:1 PR single turbo with better than 65% efficiency, but you need connections to NASA to steal one.
