Electronic Ignition For ALL
"By Jim Lunson, tech committee
Last time I covered the points system and how this
switching makes the coil work. One of the biggest improvements in
the distributor function since almost the invention of the engine is the
use of electronic ignition modules to replace the old points setup.
These systems came into the picture in the mid 1970's, long before the
sophisticated computer systems we see today. They were basically an
assembly of resistors, diodes, and compacators put together to accomplish
the same function as the points had done for so many years. What
they did was provide the same "on/off" function without any moving parts.
This electronic "points" ignition was necessitated by
the ever tightening EPA emission requirements imposed on the car
manufacturers during the 1970's. These new systems provided two
advantages: first they would automatically adjust the time the points were
open and closed to make the coil produce the absolute highest voltage
possible, and secondly the timing would never vary out of adjustment.
This meant the spark plugs would always function at their optimum
potential, insuring the least emissions; and by maintaining this without
changing; the car's emissions would never rise due to wear and tear on
this element. As soon as these systems came out, there was a
noticeable increase in performance and aftermarket manufacturers began
offering replacement kits to upgrade cars with the old style points.
This is where the MG systems came into play.
British Leyland came out with their electronic system in
1975 in California and 1977 everywhere else. Their system consisted of a
ballast resistor to obtain a steady 6 volt power supply and a small metal
box built onto the side of the distributor to house the electronic
components and relay the switching back to the coil (distributor #45DE).
The system worked very well, but as usual with British auto manufacturing,
was not properly tested. It seems that since the distributor was
very close to the engine block and the engines ran on the hot side, heat
soon destroyed the components in the little box and the system failed.
In 1980, MGs relocated the box to mount it between the coil and the fender
which solved the problem (distributor #45DM). With the rapid failure
of the 1975 to 1979 models, an aftermarket system was a necessity and soon
on the market. Today, a conversion kit is available for every MG
made. These systems are all similar, but with special brackets to
make an exact fit inside the distributor where the points used to fit.
These systems work on one of two methods, either a
rotating magnet attached to the distributor shaft with a sensor beside it
to signal the switching as it moves past, or a flat disc on the
distributor shaft with slots in it and a photo cell to shine a light
through the slot as the disc rotates. Both systems work very well.
These systems contain a component to mount inside the distributor and a
small box mounted somewhere remotely in the engine compartment to contain
the electronic switching equipment, plus various wires between the two
elements, as well as back to the coil.
advantages of these systems are as noted above: absolute highest voltage
possible to the spark plugs providing maximum spark for easier starting,
increased power, longer spark plug life, better spark plug wire
performance and better coil lifespan. All this, as well as no moving
parts to either wear out or need constant adjustment. Instant
noticeable improvement will be felt in performance and reliability at
every turn, even over a brand new points system perfectly adjusted.
MG expert John Twist estimates they provide 2-3 additional horsepower
There are however, some downsides to these systems.
First, when they fail, there is no warning or erosion of performance like
a points system; they just quit when the electronics fail and the car
stops running on the spot. Secondly, when it comes to maintaining
originality in an old car such as the MG, there is now a huge flaw as a
stray black box appears, mounted somewhere in the engine compartment with
lots of additional wires coming out of it running to the coil and
distributor. It is obvious something has been added that was not
there in the original car.
Reliability: A good point system
will last a couple of years provided it is kept in top adjustment.
No one knows the lifespan of the electronic systems as they continue to
last and last. My 1979 MGB was fitted with a Piranha brand
(forerunner to the "Luminition" and "Crane" systems) sometime in the early
1980s when the original system failed. This was an early version
appearing when the problems noted above started to occur. I replaced
it in 2005 after several people told me that although it was a good system
and still working as good as new, after over 20 years, I was probably
living on borrowed time. Failures have been rare as these systems
contain no moving parts and are sturdily built to last and last.
The problem is that each system is designed to fit a
specific distributor where the old points were mounted and there is no
"one size fits all". Being an all electronic assembly, there is no
repair possible, only replace it. So if it does fail, a replacement
for an MG distributor is hard to find except through the parts mail order
companies. The only protection against failure is to carry a back up
system for your specific distributor. This runs up the cost as they
are not cheap ($100+ vs. $10 for a points set). Or just hope they
last and last like mine has and not worry about it.
The other option is to carry a set of the old points
along and be prepared to make the conversion back if there is ever a
problem. This takes some doing as all the wiring has to be changed
back, but will insure a backup in case of a failure. Personally, I
carry an old distributor with the points already installed as an emergency
kit. I think it is easier to swap distributors than redo the points
system inside. This is in spite of the fact that the old system in
my car lasted over 20 years without being touched.
In the last several years, "Pertronix" brand has come out with a system
that fits entirely within the distributor (they now even make a whole
distributor with the system mounted inside). From the outside, there
is no difference in the original look of the car with the exception of one
additional wire going into the distributor. For all practical
purposes, this solves the appearance problem yet provides all the
benefits. My only concern with this system is that it goes back to
the problem with the original MG system: perhaps too close to the engine
block and the potential for damage from heat. I have had this system
on my car since 2005 without trouble, so I am pretty sure it is more
durable than the original MG system, although it is only 5 years old at
this point. My previous system had the black box mounted on the
So the conversion is available for virtually every MG,
the cost is higher than points and there is an additional wire to the
distributor, but the performance improvement is good, all wear is
eliminated, and the reliability seems to be good at this point. The
conversion is available for every MG. The decision is yours.