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Why change from "points" to electronic ignition????
This is easy. I hate setting/ resetting contact breaker (points) gaps.
Points have a number of downsides, these primarily being that the points act as
a mechanical and electrical switch which over a period of time (in my case every
3000 miles) need re-setting as the electrical spark erodes the contact surface.
Also, the plastic heel strip wears in contact with the distributor cam making
the gap close up. When the points begin to wear, the efficiency of the system is
thrown out and the engine begins to misfire, usually at the lower end of the rev'
range. The only solution is to remove, clean and reset or change the points which
on a VW air cooled engine is not very easy to complete. The second problem associated
with points is "bounce", which usually occurs at high engine speeds were the points
cannot physically remain in contact with the distributor cam and "bounce", meaning
that the points gap is not constant. This is not usually a problem on VW engines
due to the slow speed.
Benefits of Electronic ignition.
Electronic or transistorised ignition removes the need for the points to act as
an electrical switch. The transistor within the circuit acts as a high speed switch.
This means that apart from mechanical wear, there is no reduction in efficiency due
to erosion of the contact surfaces.
Different electronic ignition kits use different methods to mechanically switch
the system. Many systems use a light emitting diode, with a segmented divider
positioned on the distributor. As the divider passes over the diode, the circuit is
switched. On the system I have used (because it was the cheapest!!!!) the points remain,
but instead of transmitting a voltage, the points only act as a mechanical switch. This
means that mechanical wear will still take place but at a much reduced rate. Typically,
the points will need to be changed every 50,000 miles instead of every 3000.
Electronic ignition Kit.
Vellerman make the system I purchased, from Maplin Electronics Ltd. (product code K2543)
and cost £12.99. The kit consists of a circuit board, components and a heat sink.
The kit is very easy to build up with the only tools needed being a soldering iron
and a pair of wire snips plus wire to connect to the existing vehicle wiring.
The instructions are very easy to follow, with each component identified by number.
The only difficulty with the kit is that the Zenor diodes within the kit can only be
fitted one way. A black band on the diodes indicates the direction but this was not
made clear in the instructions. The only changes I made to the system was to mount
the large condenser on the opposite side of the board to allow easier fitment into
the protective box I had chosen. Total time to build the circuits was under 30 minutes.
The instructions suggest that the system be enclosed within a box or with resin to
protect the electronics from heat and humidity. This is where the difficulties began.
The electronic circuit board needs to be enclosed but the heat sink has to be open
to moving air to cool the board down.
I eventually found a box suitable from RS Components
(Product No. 291-6863) which cost £1.56 and brackets (Product No. 262-6317) at £0.31.
The fitting of the circuit was a little fiddly as a hole has to be cut into the box, to
allow the transistor to be mounted in contact with the heat sink. In the end, the time
spent messing around was worth while as the finished article looks very professional.
The system only needs 4 wires to connect as shown in Fig. 1.
Results / Findings.
At the moment, the distance I have travelled using the system is low. The instructions
with the kit point to easier starting, improved m.p.g. and cleaner running.
I have never had a problem with starting and as the majority of my driving has been
around town were I typically get under 20 MPG, it is difficult to find measurable
improvements. The main benefit to me is that the system will remain consistent for a
much longer period giving peace of mind.
Typically, I change the points and condenser every 3000 miles at a cost of around £4
(I always buy service items in advance from shows!!!). If the points now need changing
at even half the manufactures recommendations (50,000 miles) then over 25,000 miles,
points and condensers would cost me £33.33 where the electronic ignition kit has cost
me a total of £14.86 with the savings increasing the more I travel.