Why do autos have a vacuum chamber for the double throttle? What makes them different than manuals?

 

Not sure - but if you notice there is also an additional check valve on the inlet for the double throttle mechanism for the auto.

I had asked about the purpose of the check valve a while back - but I suppose if you are to keep a vacuum chamber charged, it makes perfect sense to have a check valve.

Not to hijack the thread - but I'm curious too.

 

My theory (and that's all it is) is that the automatic tranny uses the throttle in such a way that it needs double throttle actuation when the intake is not in vacuum.

Dave

 

^^ Maybe

BUT

The automatic's double throttle solenoid is still piped to the turbo inlet duct whereas the manual is vented to the atmosphere with a filter only. Wouldn't the automatic double throttle still be in vacuum all the time anyway?

SO here is my theory:

The automatic utilizes the double throttle vacuum tank while the engine is cranking and the TID isn't seeing vacuum?

I dunno.