external waste gate

[Jared Grant]

what does an external waste gate do? is it the same as a bov

[Jason Gilbert]

Blow off valve:
Prevents the pressurized air in the intake tract from surging back down the tract torwards the turbo, and "slamming" into the turbine compressor blades, once the throttle body blade is closed. If this happens, damage can occur.

Wastegate:
Regulates exhaust flow from the engine, that drives the turbine exhaust wheel.("Spooling" the turbo and making boost)

An external or internal wastegate achieve the same results, with different methods. Externals allow more flow to be passed, and are usually more accurate in controlling / regulating boost.

HTH
Jason

[John Hartman]

put simply a wastegate regulates maximum boost, regardless of throttle setting.  All things else being equal.