'Beamer's,
This is somewhat long, and may not be of interest to non
technical or non historically interested individuals, but it
does have an ending 'point', IMHO, suitable for today's
decisions. Stop here, if you want. This is for the street
driver who wants more reliability and performance, less
maintenance, and low buck solutions.
With all the discussion about points on the list, both SU
fuel pump points and hot ignitions, I thought I'd relate a
question I recently had, and the answer I provided. Since
this can equally apply to Alpines, I've included that list
in the distribution.
A friend asked about upgrading his ignition system. He was
considering his regular single point distributor, dual point
distributors, high performance distributors, electronic
substitutions for points, hot coils, and high energy
ignition systems, like capacitive discharge and the like.
There were just too many pitches, and not enough facts. I
thought I'd share my answer to those with a similar
uncertainty, for what it's worth.
Reluctantly {9->, I gave him some information on the
experiences I've had, and my recommendations.
BASICS
1) Points are closed to charge the primary side of a dual
winding coil, setting up a magnetic field.
2) The secondary windings, which have many more turns, hence
act as a transformer and greatly multiply the voltage when
the magnetic field changes.
3) When the points are opened, the magnetic field collapses,
and the secondaries release the higher voltage, usually
1,000 times the primary voltage.
4) This creates the spark when it jumps the plug gap to
ground.
5) The current being switched in the primary is very high,
and points arc when the circuit is broken. A capacitor is
placed between the points and ground to bleed off some of
this energy to reduce the arcing of the points.
6) As the points arc, the alloy material of the contacts
erode, changing the gap, the "dwell", and the timing. After
a while they just don't make contact at all, and the engine
stops.
OK that's the "primary" information. (pun)
HISTORY
The first "improvement" was the introduction of dual point
ignition systems. Each point took half the load, and wore
half as fast, so you replaced two at twice the mileage.
That's OK, they were cheap, and the labor for two isn't much
different than for one. Keeping them in "sync" was a small
problem.
Electronic ignition systems were developed when
semi-conductors could almost handle that current about
1960's. The first ones used a transistor to replace the
points as a contact switch. They didn't work very well, or
at least for very long. Semiconductor technology wasn't up
to it yet. I believe these were the first silicone power
switching transistors.
Couple of years later the first Capacitive Discharge systems
were released. The points charged a very large capacitor,
which held the energy until the points opened, and then
discharged itself into the coil at a very rapid rate. This
very high rate of field change enhanced the coils output
significantly (factor of 2 to 5), and simultaneously reduced
the current being switched by the points to practically
nothing.
This is where Delta Electronics Mk I (Denver) and I meet.
My new '66 911S couldn't go for 1,000 miles on a very
expensive set of Bosch plugs before they were fouling out. I
added this magic box from Denver, and some inexpensive, but
very good NGK plugs from Japan (just introduced to US) that
had a copper electrode center that could automatically
adjusted a broad 'heat range'. Wonderful. Could now go
5,000 to 7,000 miles on a set of plugs. Unfortunately the
first Delta's didn't go much further than 2 sets of plugs.
But Delta stood behind their product and the Mk II's came to
me free. Even had a switch on the box, in case it failed,
to return the circuit to points operation. It didn't fail.
Sold it 10 years later, still working.
THE FROG IN THE MARTINI:
Here's the kicker. Now that the point spark erosion was
eliminated, point adjustment and replacement were a thing of
the past, right? Wrong! The ignition designers were very
clever. In order to keep the gap as constant as possible,
they designed the material of the rubbing block (the plastic
part of the points that rode the distributor cam) to wear as
fast as the points wore (leverage arm accounted for). The
points were no longer wearing, but the rubbing block was,
requiring gap adjustment, anyway. At less frequent
intervals, though.
CURRENT TECHNOLOGY
Now, here is the relevant information to today's choices.
Capacitive discharge ignition systems are even better now
than they ever were, and more reliable. Some even have
automatic rev limiters that 'roll-off' your revs when you
reach the limit you choose by module, or knob, Won't help
on a missed downshift, though. Now you can just use points,
except the blocks wear.
But single point, dual point, electronic point distributor
which one?
Since the current across the points was now insignificant,
splitting it two to sets of points was more trouble in
synchronization, and no benefit. Forget them, unless you
just want the mechanical advance only feature. I would
forgo mechanical only as well, unless your just racing at
WOT. The single diaphragm pre smog models gave really great
mileage saving at light loads and high advance, without
penalty if you step on it.
Bottom line. If your going to mess with the ignition, one
of the easiest ways is to replace the current points system
in your own distributor, with the newer optical or magnetic
effect points now available such as Unilite, or my favorite,
Pertronics. This gives you a much sharper opening, and
field collapse, can take a hotter coil, and never needs
adjusting. Spark voltage 50% more with stock coil, and can
be doubled with a "hot" coil This is the simplest and
cheapest way out , about 15 to 17,000 volts depending on
coil (about $65 - $85). If you want a "hotter" coil you must
use "Points Type" hot coil to limit current to the
electronic points. Probably need the resistor that comes
with them, instead of the stock one. Can tell with an ohm
meter and the directions that come with the points. Be
safe, if you don't measure the resistance, use the new
resistor. They still have limits, although much higher now,
and no 'point float'.
Want 50,000 volts or more? The Mallory M6-AL high energy,
rev limited system, coupled to these new triggers will fry
your hair and make the underside of your hood glow blue at
night. This is the big buck solution. Well worth it for
racing applications. Say $165. BTW: Your going to need
those high priced silicone wires now. Give up another $65.
Dual point distributors? Pull both points and put in the
Pertronix. Same for single point systems, like the stock
Tiger or Alpine. But you'd be stuck with the single advance
mechanism. Not a real advantage on the street.
Recurve your distributor to start ramping up just after
idle, and be full-in mechanically at about 1800 to 2300
rpm. Don't exceed top advance, mechanical plus static
(idle). For Fords, about 34 degrees (arguable). The vacuum
advancers can go way beyond that, because they only do it on
light loads. This change alone, for the cost of $5 worth of
springs, is the single, most cost-effective change you can
make, even if you do nothing else. If you can find someone
with an old distributor machine, it may cost you $65,
including a re-built distributor.
Well, that's the long and short of it. My experience and
considered advice. I am certain to hear other views, but I
am equally certain they will have unique uses for their
vehicles than daily driving. Hope it helps allocate your
bucks.
--
Steve Laifman < One first kiss, >
B9472289 < one first love, and >
< one first win, is all >
< you get in this life. >
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