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Re: [T3] distributor 009

On 11 Feb 2005 at 21:35, Mysterious J wrote:

> I'm curious about a couple thing, relating to the 009 and other 
> distributors:
> 1.  Are the advance curves in VW distributors fixed?  I fondly remember 
> in my small block Chevy days recurving the stock or aftermarket 
> distributors using different sized springs.  I haven't looked to closely 
> at the distributor I picked up last week.

They are as fixed, or unfixed, as any other dists.

By changing springs, or leaving one spring out, you can change the slope of the 
advance curve. In that case, Bosch dists are as adjustable as any other dist. 
OTOH, there's no one out there selling assortments of springs, so playing 
around is more difficult.

> 2.  Why would you want to disable/unplug the vacuum advance?  Unless 
> your cam has such a radical grind that the engine does not produce much 
> vacuum, using the vacuum advance will make the car much more responsive 
> (again, looking back at my SBC days)

Under a certain set of conditions you engine will preform best with a certain 
amount of advance. If you've already given it that amount of advance by means 
of a mechanical advance then adding extra by means of a vacuum advance will be 

I sense also that there's the feeling here that all vacuum ports are alike, but 
that's far from true. Some ports give a large vacuum at idle that decreases 
with engine load. Some give a little at idle and that increases with load. Some 
give more vacuum than others under the same conditions. Every manufacturer 
engineers his vac adv and vacuum pickoff port together to work together. There 
is no reason to expect a random pair to work well together.

Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

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