Turbo related question

[x2xtreme360]

Got into a small discussion with a professor of mine about turbos. He was talking about superchargers and how they use the drive belt for operation and I mentioned how they are useful on larger engines that can take the small loss in power from the drive belt. I then said that although superchargers rob engine power via the drive belt, turbochargers also rob some power through exhaust restriction. He then told me that actually turbochargers rely on the EXPANSION of exhaust gasses, not the FLOW of exhaust gasses.

After all the reading and knowledge I've acquired on turbocharged systems, I don't think he is right on that. Anyone want to confirm?

[onebadmollafolla]

Expansion of exhaust gases creates the flow. Spooling a turbo up leaves restriction in flow and thus expansion how I see it.

[DocWalt]

He's partially correct, and so are you. Call it a draw

[x2xtreme360]

I mean, I understand that combustion causes expansion in exhaust, but he's saying that exhaust expansion causes a turbo to spool. I feel like the increasing flow of the exhaust is what causes the spool up, that and the backpressure due to restriction.

[Goallie11]

If you think of the gas as expanding from 0 at the moment it's compressed by the piston to 100% when it leaves the exhaust pipes then yes expansion does turn the turbos.