Date:         Mon, 14 Oct 1996 08:15:15 -0800 (PST)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         The Chameleon <ktgatlin@csupomona.edu>
Subject:      Re: Vacuum gauge install

> 
> From the tee, I hooked up a long hose to a vacuum gauge and fed it through
> the wheelwell and in through the door for the time being.  Didn't want to
> install the hose under the chassis and up through the floor till I was sure
> it was going to work as planned.
> 
> I started it up and drove around a while.  I have two vacuum gauges at the
> moment, one is a 2-1/16 no-name gauge that reads 0-30 psi in less than a 90
> degree sweep.  The other is a 4" Sears vacuum gauge that reads in
> increments of 1 psi over about 270 degrees.  MUCH more accurate.  The Sears
> gauge showed a max vacuum of about 20 psi (engine warm, trailing throttle)
> with a low of about 2 psi (full throttle - does this mean my throttle plate
> isn't opening all the way?).  Normal idle is around 14 psi.  The smaller
> gauge didn't give much useful information because of it's small sweep.
> 


You will likely never see your vacuum drop all the way to zero at steady 
state cruising, wide open throttle. About 1.5 inHg is the lowest your 
likely to ever to see it go. In pounds per sq in I do not know what that 
equates to.  



> On the freeway, I was happy to see that very slight changes in throttle
> position produced a noticable change in vacuum.  Cruising at 55 mph, I saw
> around 10 psi on average. 62 mph saw closer to 5 psi, and was getting close
> to floored.  This is going to make a really good MPG indicator.  I'm very
> pleased with this and am going to complete the installation by ordering a
> 30 psi vacuum gauge from Summit (new style with fibre optic lit needle,
> $27.95, ) and mounting it in the dash by running the vacuum hose up under
> the floor at the front of the bus.  Despite the great distance in the hose
> (the hose from the tee to the gauge alone was over 20 ft) gauge response
> was pretty much instantaneous.
> 
> One big problem with the whole setup - the needle of the vacuum gauge
> vibrates wildly at part throttle.  Enough that it was hard to read and even

This is hard to determine the cause - you are probably right about the 
vibration. But I would double check. A VW engine is a very PULSY engine. 
It is likely to affect the guage. I have not checked my engine I have 
checked other engines with vacuum guages and the needle DOeS NOT vibrate 
wildly. It would be nice that someone could concur that this is indeed 
the case with VWs

> made some noise.  I don't think it's a problem with the engine or gauge - I
> think it's just the result of the engine only producing vacuum during the
> intake stroke(s).  I managed to  reduce the vibration by pinching the hose
> - I was able to pinch it enough so that the gauge still responded quickly
> but didn't vibrate.  My plan is to insert a spare fuel jet into the vacuum
> line to restrict the air flow down to a very small amount.  I figure with
> all of the different sizes of jets available I should be able to find one
> that will be just about right.
> 
My 2 cents - hope the info helps

Chameleon
_______________________________________________________________________________
GATLIN DESIGN                                   IZCC #1928
25422 Trabuco Rd #105                           1971 240Z
Lake Forest, CA 92630                           Graduate, Bob Bondurant 4day
714-445-1952

"People who know...drive 240 Z's"  
                      Kyle Gatlin