[T3] Blue Coil

[Jim Adney]

On 27 Jan 2011 at 17:15, James Lingenfelter wrote:

>   I have also run nothing but blue coils on all my VW's- until this  
> one- for many years and countless thousands of miles (all daily  
> drivers); never had a problem. And this particular guy doesn't sell  
> any parts, so no he wasn't trying to sell me a coil.

I suspect that the early Bosch Blue coils were made in Germany and 
were of the usual excellent Bosch quality. I actually have a couple 
of those in the basement if someone wants one, but I don't recommend 
them for street use.

I measured their electrical characteristics quite a few years ago and 
then wrote a MathCad program to plot the various parameters, like 
current, voltage and energy, that the blue and black coils delivered 
at different rpms. Using Bosch's own criteria for spark requirements, 
it became clear that the standard coil delivered plenty of spark to 
well above 10,000 rpm, which is about double our red line.

The other thing that became clear was that the Blue coils drew lots 
more current at low rpms, so they would be hard on points. Given 
those facts, I see no reason to go with the Blue coils, unless you 
just like the color or are willing to put up with the extra points 
replacements in order to impress your friends.

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