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RE: [T3] Which Distributor?


On 6 Jun 2001, at 9:22, Miller, Gary (G.) wrote:

> With dual vacuum dizzy:

> Advance hose disconnected: idle advance 5¡, 2000 rpm = 18¡, 3000
> rpm = 24¡, 4000 rpm = 30¡ 

> Advance hose connected: idle advance 5¡, 2000 rpm = 25¡, 3000 rpm
> = 40¡. 

>From these numbers, as well as your vacuum measurements, I 
think it is likely that the vacuum port you are connecting the dist to 
is not correct for this dist. These distributors DO NOT connect to 
straight manifold vacuum. They need to connect to a drilling that is 
carefully positioned in a particular place relative to the throttle valve. 
With the proper positioning you will have ~30 deg mech adv at 
speed, plus 10 deg additional, IF the engine is under light load 
(cruising.)

Since you have a vacuum gauge, connect a long hose to it so you 
can watch it while you drive (you can leave the vac adv 
disconnected for this test.) If you can verify that the vacuum pretty 
much disappears at idle as well as at half throttle or more under 
any driving conditions, but maxes out while just cruising at a 
steady 50-60 mph, then you should be fine.

The point is that the 30 deg limit really only applies to an engine 
under full load, which is what a RACE engine sees all the time, 
unless you're braking. Under partial throttle the engine can safely 
accomodate more advance and get better fuel economy in the 
process. Thus the vac advance portion of the late dists is a fuel 
economy device.

> Crank angles were calculated from measurements from existing, known notches on the pulley)

This is reasonable. The |    | | |  notches are at 0, 7.5, 10, & 12.5 
deg.

-
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA

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