Originally posted by bindegal Basically a turboŽd engine is "off boost" most of the time.
Most people think that a turbo car running 1 bar boost is seeing an extra atmosphere's worth of pressure all the time
Well, it aint!
Most of the time it's off boost (vacuum in the inlet) so that's what a boost gauge should show.
When under full throttle a n/a engine would approach atmosheric pressure, but still remain under vacuum (as a general rule)
A turbo engine, under full throttle will see *more* than atmospheric pressure (the "PSIs of boost")
...remember what 'throttle' means - it strangulates the engine intake. You can't have boost pressure with the throttle closed, as the pressure would have nowhere to go (that's where the dump-valves come in!)