When I'm driving and I hit 4K RPMs, I hear the turbo spool up and the sound of rushing air. But when I'm sitting still, in neutral, and rev up to 4K RPMs... no sound at all.

What makes the turbo not spool up when you're sitting still? Is it not enough pressure due to lack of engine load or is the wastegate (or whatever it's called) computer controlled to stay open if the car is not in motion. I have no idea how that works.

 

OK so to kinda explain why engine load helps spool, at least the way i see it.

First when putting load on the engine you need to add in fuel because the burn is going to take longer then a free rev. This in turn creates more heat which means more pressure so when the exhaust valve is released a more violent expulsion of said gases blast through the turbine.

The wastegate is mechanical even if the computer said not to boost you would still get around 12psi.

 

Thanks - that makes sense.

 

i think that's pretty good....do you hvae pic?

 

vacuum and pressure

 

Not enough load (pressure) to spool the turbo in neurtral.