want to verify mech boost gauge readings...

[Swann, Benjamin R. (BSWANN)]

Jim,

I'll have to verify that again especially the idle reading, but I know my
guage will hit in the high 20's vac(according to my JC whitney special and
other previous guage) when downshifting and that is around sea level.  I've
been driving around the new blue 4kQ for the past weeks now and my memory on
the TQ's vacuem and boost readings well..may have faded.

I recalled the idle readings from N/A cars in general, and that should apply
to the turbo as well, that idle should be a steady 15 PSI or more in a tight
motor.  I guess more vac in higher compression motors, less in low
compression engines, and I don't believe the turbo has any real effect on
vacuem at boost.  If your throttle plate is not shutting all the way or idle
screw leaking you will likely be experiencing lower vacuem.

I am certainly not a regular mechanic or engine builder, so my recollection
may be incorrect.

It does sound like you have a slight leak though, as your boost should be
closer to 1.4(really tight system), and the vac sound a little low.
Replacement of all the vacuem lines is a good idea because old hoses can end
up resulting in a lot of little leaks.  I had one leak that went on for some
time and was causing the Climate Control not to work properly on AC.

Anyway the points were 1) that the motor should read vacuem at idle and 2)
it is OK to tee into the back of the ECU, which is probably the easiest
place if you are running a guage inside the car.

Regards,

Ben

-----Original Message-----
From: jim rose [mailto:sf5ktq at hotmail.com]
Sent: Wednesday, June 13, 2001 5:01 PM
To: BSWANN at arinc.com
Cc: quattro at audifans.com
Subject: Re: re. want to verify mech boost gauge readings...


Ben,

>I think your mechanic is wrong on both accounts.

i suspected so. thanks for verifying. i had a feeling he was confused.

>You can tee in at the back of the ECU - that is what is being measured.

Since i already have it all installed (rather nicely, i might add :) im just

gonna leave it  as is, if its reading right, which im now certain it is 
(several off-list replies-THANKS, ALL!)

>You should be pulling vacuem at idle - around 18 at idle up to 30 when
>seriously downshifting.

WOW. you'rs really SUCKS ;) mine's actually -12/14 at idle and about   -25 
on big downshifts. i get 1.2 bar + 5/6 psi on full boost. im continuing on 
the de-vaccumleaking campaign. hopefully ill get my motor to suck n blow a 
little harder. (couldnt resist the obscene metaphor).

Thanx again!

jim

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