Hey all,
A recent post on an electronic ignition points replacement gives me a
chance to share some knowledge with you :-) . Unfortunately, I lost it
the first time, so this is try #2.
The Ignitor that Richard White posted about reminded me of electronic
ignitions.
Basically there are two types: There is the type Richard found that
simply replaces the points with an optical or magnetic sensing device.
The only benefit to this type of device is that you don't have to
maintain the points anymore. There's no other real advantage to having
it.
The second type of electronic ignition is called CDI. It stands for
Capacitive Discharge Ignition. Basically a capacitive unit is installed
under the hood (bonnet) and is connected to the points. Instead of
using the points as a current-carrying switching device, the CDI unit
merely uses the points as a switching device to decide when to send a
voltage signal to the coil for amplification. The advantage to the CDI
comes with the spark. The CDI allows for a hotter, more powerful spark
by supplying the coil with about 400v instead of the standard 12v you
would normally get to the coil. This allows the coil to produce a
higher-voltage spark, especially at higher rpm where the coil has less
time to build up the 12v than it does at idle. This gives more power,
better mileage, etc. The points last super-long since they carry no
current, so there is no possibility of arcing across the points. And
the point gap becomes immaterial. Even a minute opening is acceptable,
because all they're doing is acting as a switch for the CDI. I hope
this makes sense, I am trying to explain it as best as I am able. The
only time you need to replace the points is when the rubbing block
finally wears down.
This is a popular modification for those VW Bus folks. In fact, this
mod is championed by the list guru, Bob Hoover. I haven't gotten around
to doing it myself as the unit is expensive (~$100) but from what I've
heard it's worth it. An advantage to this unit is that if it fails for
some reason, the system can be reconfigured to stock simply by switching
a plug on the unit. Nice!
Bob Hoover has written more eloquently about this mod in his "sermons"
which are available for viewing at
http://www.type2.com/sermons/index.html. This is highly recommended
reading for any old car enthusiast. Much of Bob's work is VW-specific,
but there are some general car-care articles and Bob's "forever vehicle"
philosophy is right in line with the philosophy of this group of MG
owners.
On the sermons page, there is a section devoted to the CDI unit, with
four articles. Again, recommended reading. There is also contact info
there for Universal Corp, the maker of the recommended CDI unit.
I hope this info helps someone.
--
Sean Bartnik
Fredericksburg, Virginia
'81 Volkswagen Vanagon Westfalia
'74 Volkswagen Karmann Ghia convertible
http://www.type2.com/bartnik/myvan.htm
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