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Re: IM vacuum reading at idle - what are the variables?

DeWitt Harrison wrote:
> In the process of investigating the control of A/C air distribution
> in my type 44 it was found that at 800 rpm, my IM pressure was
> about -5 in-hg while that of a similar car was about -10 in-hg at the
> same rpm. (All but one of the air control flaps are moved by
> vacuum motors and one of mine was balking.)

Both sport a vacuum leak. Yours a lot more than the other car.
On the '89 200TQ that I owned until recently (MC-1, 850 rpm idle,
airplate and TB adjusted dead nuts to spec, a slightly enriched DC at
35-40%, TAP Stage I, head done, valves lapped, stock cam, the leakdown
test better than 5%) the healthy condition would be manifested by -14"
Hg. A 3.5mm vacuum hose jumped off its nipple would result in -5" Hg.

My A4TQ with the tiny 1.8L shows -19" Hg at idle.

Igor Kessel
Two turbo quattros.