[T3] 72 FI simplified

[Dave Hall]

The definitive info on this from VW is contained in a rather nice
maintenance supplement I have (dated 1981 - superceding the 1978 edition).
The timing details are well set-out in a chart at
http://home.clara.net/hallvw/type3ign.htm , but of course, if your engine
now has a different distributor, or fan pulley fitted, it may not match up
as it should.  There are details oulined in the adjustment section in the
later Bentley, though it doen't mention the carbed models of course.

Boilerplate or not, I just follow the factory instructions.  You can also
inspect the hose for splits while it's off!  It certainly makes a difference
on the dual vac FI engines, where they say hoses off.  On the dual vac with
carbs, hoses are left on.  On the twin carb 1500S, you even have to remove a
plug lad or two to get idle below normal.

My head's spinning thinking about it - doesn't the 'vac advance' actually
reduce the advance when the throttle is opened, as the manifold vacuum
pressure rises?    At high rpm and small throttle openings or closed
throttle, the manifold vacuum is greater, and so is the advance - isn't that
right?    

Dave.
UK VW Type 3&4 Club
===================


-----Original Message-----
From: type3-vwtype3.org-bounces at lists.vwtype3.org
[mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of Jim Adney
Sent: 22 May 2012 06:33
To: type3 at vwtype3.org
Subject: Re: [T3] 72 FI simplified

On 21 May 2012 at 20:12, Keith Park wrote:

> That makes sense, you don't want anything messing up the static 
> centrifugal advance timing so you need to get the vacuum hoses 
> disconnected and then of course the idle speed back down via the air 
> adjustment so that the centrifugal advance is us fully OFF to set the
static timing.

You can pull the vac hoses off if you like, but on the dists with mech adv,
the vac adv does nothing at idle. You can verify this easily with a timing
light.  

I know all the books say to pull them off, but that's just boilerplate; it's
not necessary for most of our cars.

--
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************

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