This isn't really a necessary question but I'm trying to learn more about cars so I don't sound like an un-educated ricer. Questions are turbo-related.

Firstly, when the exhaust spins the turbine, how does this power the compressor?

Wastegates re-route excess pressure around the turbo, correct? Is the wastegate a tube on the turbo (part of the big circle) or a seperate piece? When people specify that they have "external wastegates," what is the difference between external and internal?

Am I correct in thinking that external wastegates release the air into the atmosphere and internal just re-route it back into the cycle, bypassing the turbine?

Also, how exactly does a blow-off valve work? What is the difference between a BOV and a wastegate?

I never claimed to know that much about cars so bear with me here. Just trying to educate myself so when I (hopefully) get my MR2 Turbo this summer I'll know what I'm talking about.

 

The turbine and compessor are connected with a shaft..
Wastegate usually have a pipe goin after them to the down pipe and is welded back in.. if you care about smell and the ozone... and the wastegate is usually on the header before the exhuast housing...
a BOV just sits somewhere between the compressor and the cylinders and when you shift, it opens to release the compressed air so that you dont get back pressure and bend your turbo blades's... a wastegates on the exhuast side.. no where close but same basic opperation.. just different sides of the cylinders...
and a by pass is a blow off but instead of just venting to the atmosphere it routes it back to after the mass air or vane air or whatever kind of meter you have but before the compressor.. so you dont run rich after a shift..

 

read maximum boost by corky bell.