RE: BOSCH blow off valve

[glen powell <gpowell@acacianet.com>]

In the interest of defining some terms, I'll take a stab at it.

blow-off or pop-off valve: 

vents excessive boost pressure to the atmosphere to limit
peak system pressure and prevent turbo damage with very
high boost pressures

bypass valve or recirculation valve: 

vents high pressure in front of the closed throttle-plate back to the inlet of the turbo
to keep the turbo spinning when the throttle is closed

I guess you could even use both, the blow-off valve to control peak pressures to
prevent blow-off of hoses and blowed-up hoses; and the bypass valve to help keep the
turbo spinning when the throttle is closed but the pressure is below the setting
of the blow-off valve (and below peak boost pressure).

-glen