Re: Changing the Bomb

[steveb@falcon.kla.com (Steven Buchholz)]

> 
> >and the
> >fact that a turbo engine under boost doesn't supply vacuum.
> 
> Would have to disagree there...  In fact a turbo car under full boost can 
> provide more vacume than a N/A engine...... You just have to know where 
> to look for the suck.  (I'll give you a hint....  There are some REALLY 
> Fast spinning blades REAL Close....)
> 
You may be right Eric, but auto manufacturers seem to like to use the mani-
fold as their source of vacuum ... perhaps it is related to the fact that 
turbos can break and hoses can leak, but if the engine stops drawing air 
from the intake manifold there probably ain't much else going on ...
It also seems to me that you only get a vacuum in front of the turbo 
under boost.  You never get that wonderful vacuum source of the 2+ liter
air pump sucking the back of the throttle valve ...  ;)

It seems that the other power brake/turbo applications I've seen employ 
an electric vacuum pump to supply the brake servo.

One comment about some of the original content of this thread ... there
is a third configuration.  The 1983 QTC has a single pump with a propor-
tioning system that drives the steering and brakes on the PA bracket 
(rather than two separate hydraulic pumps in the pump unit (a la '88 5kT).  
This system specifies ATF, but I recall reading that it is acceptable to 
add Pentosin w/o problems.  I wouldn't be surprised to hear that the other 
Audi turbos of that vintage (i.e. 1st generation 5kT) use the same system.
Other than replacing the bomb I have not had a problem with the pump or 
the brake servo or the rack on my '83 ... wish I could say that about the 
'88!

Steve Buchholz
s_buchho@kla.com
San Jose, CA (USA)