[T3] 72 FI simplified

[Jim Adney]

On 22 May 2012 at 21:45, Dave Hall wrote:

> I'll have a closer look - not sure how different the '71 twin carb dual vac
> situation might be.  It's timed at TDC with hoses, just to be different from
> the '72 FI.  Sometimes it's better to accept the truth than try to
> understand it!

Understanding is EVERYTHING!

But your dual carb setup does sound different. On the '72 FI 
adv/retard setup, removing the advance hose causes no change at idle, 
but pulling off the retard hose causes a big jump in timing and idle 
speed. VW just wants us to time it with the retard hose off so that 
our timing "start point" is known. That way, the retard moves the 
timing one direction from that start point and the advance moves it 
in the opposite direction. Since only one of those is ever in 
operation at a give moment, that minimizes uncertainty in the timing.


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