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Transcript
Restoration Bruce L.
Corner Adams
E lectronic
I gnitions
M
A s E asy as 1-2-3
echanical points and condenser ignitions have been used
in the automobile since first used in Cadillacs in 1910.
The heart of the breaker point system is the distributor. The distributor contains a rotating cam driven by the engine’s drive, a set of
breaker points, a condenser, a rotor and a distributor cap. External to
the distributor is the ignition coil, the spark plugs and wires linking the
distributor to the spark plugs and ignition coil.
Breaker Point Ignition Systems
As the engine turns, so does the cam inside the distributor. As the engine reaches the top of its compression cycle, a high point in the cam
causes the breaker points to open.
This breaks the primary ignition coil
circuit and abruptly stops the current through the breaker points.
Without the steady current through
the points, the magnetic field generated in the coil collapses inducing a high voltage in the coil’s secondary windings.
The ignition coil’s secondary
windings are connected to the
distributor cap. A turning rotor located on top of the breaker cam
sequentially connects the coil’s
circuit to wires leading to each
cylinder’s spark plug. The extremely high voltage from the coil’s secondary causes a spark to form
across the gap of the spark plug.
This ignites the compressed air-fuel
mixture within the engine resulting
in the engines performance.
The disadvantage of the mechanical system is the use of breaker points to interrupt the current
through the primary winding of the
coil. The points are subject to mechanical wear where they ride the
cam to open and shut, as well as oxidation and burning at the contact
surfaces from the constant sparking.
They require regular adjustment
The 123ignition Electronic Ignition, cut away to
to
compensate
for wear, and the
show the interior components. On the exterior,
opening of the contact breakers,
the system looks just like a distributor, and
which is responsible for spark timing,
installs in the same way.
60
THE STAR®
September-October 2009
is subject to mechanical variations. The quality of spark
is dependent on the quality of the breaker point contact. Poor sparking leads to lower engine efficiency and
a decrease in engine performance.
Anything mechanical is subject to wear. The mechanical breaker point ignition system is no exception. The gap point is critical for an efficient running
engine. Point gap is changed by:
• Wear on distributor cam,
• Wear on point block,
• Wear on distributor shaft and bushings,
• Wear on point contacts,
• Wear and dirt on springs and weights,
• Engine rpm causing point bounce.
Electronic ignitions solve these problems by eliminating moving parts or wear that cause a change in
timing. Magnetic or optical technology is used to trigger the igniter module.
The electronic ignition provides a constant high
voltage to the spark plugs when used with the recommended coil, allowing for a more even and quicker
burning of the air/fuel mixture in the cylinders, resulting in more efficient power from the engine. Increasing the speed does not affect the timing, as there are
no mechanical points to bounce at higher rpm. High
voltage remains constant from idle to maximum engine speed, resulting in a smoother and more efficient
running engine, including fuel economy.
In the early 1960s, with the advancement of
transistor technology, Mercedes-Benz introduced
a system that used a transistor-switching unit to
fire the ignition coil in response to the breaker
points. This system reduced current flow across the
points, increasing point life, but did not address
the wear factors on the distributor shaft and dwell.
It was eventually replaced with M-B electronic
breakerless ignition in 1976 with the introduction of
K-Jetronic (CIS) fuel injection, and was used in all
U.S. models: 107SL, 116 S-class and 114/115 models.
Previous models benefit greatly from conversion to
Pertronix electronic ignition.
Today, there are several aftermarket systems that
can be installed to upgrade our vintage (pre-1976)
Mercedes-Benz Bosch distributors.
Crane Cams Ignition System
The Crane Cams product uses a non-mechanical
technology to trigger the ignition coil. An optical pickup and a shutter wheel replace the points and condenser. Using a light emitting diode (LED), the beam
of light triggers a photocell to switch the ignition coil
to fire. There are no points to wear out, no condenser
to short out, and a worn distributor shaft has minor
impact, as the shutter wheel is wide enough to compensate. (For information on the Crane system, see article in
May-June 2008 STAR, p. 78-79. Note: Crane Cams has recently
changed owners and products may not be available.)
TECHNICAL
Pertronix Ignitor II Ignition System
Pertronix is another popular ignition upgrade system. Pertronix offers
a product called an “Ignitor II” which utilizes a magnetic pick-up in the
existing distributor to replace the breaker points. The company also offers
a high voltage (45,000 volt) and low resistance (0.6 ohms) ignition coil
called the “Flame-Thrower R11.” The advantages of the Ignitor II are:
1. All components fit within the distributor, with no external modules
as compared to the Crane Cam System.
2. No need to change or adjust points.
3. Variable dwell. The Ignitor II senses current levels in the coil and
adjusts the dwell to maintain peak energy throughout the entire
rpm range. Dwell angle is increased or decreased with changing
engine rpm and operating conditions. This provides more energy at
high rpm, reducing misfires while improving engine performance.
4. No more possibility of burned up coils if you leave the ignition on
with the engine not running. Senses incorrectly wired Ignitor II or
a “key left on” condition and shuts down the system protecting
the coil and other components from damage
For more information on the Pertronix electronic ignition, see www.
pertronix.com
Albertronic 123ignition Distributor
The latest, and highly regarded. electronic ignition solution for our classic Mercedes-Benz cars is the “123ignition.” Albertronic BV manufactures this
Bosch replacement distributor in Holland. Brooklyn Motoren Werke Inc, Brooklyn, WI is the development partner and exclusive 123ignition distributor for
North America.
The 123ignition system represents a technology advance in ignition
performance for four- and six-cylinder Mercedes-Benz models from the fifties through the seventies. More than a distributor, the 123ignition incorporates a microprocessor and a bank of preset digital advance curves that
permanently eliminate the need for springs and weights to alter ignition
advance.
Optimizing the ignition timing is a good way to gain power across the
entire rpm band. The microprocessor-controlled curves result in smoother
engine torque and increase engine power. Controlling the time when the
plugs fire increase this power. A distributor with no advance mechanism
will fire the plugs at the same moment no matter the speed of the engine. A 50’s era distributor is designed to alter this timing using springs and
weights so as your rpm increase, the moment at which your spark plugs fire
is adjusted. As mentioned earlier, springs and weights are subject to wear
and dirt that build up over the years.
The 123ignition combines precise, cylinder-by-cylinder power mapping, digitally stored advance curves and an optional digital vacuum
advance sensor in a self contained design that minimizes moving parts
and is virtually maintenance free. Originally envisioned to bring classic
cars into compliance with European emissions standards, the 123ignition
has been praised by the motoring press and adopted by enthusiasts as
an excellent electronic ignition system solution for classic Mercedes-Benz
automobiles. The primary advantages of the 123ignition are:
1. Spark Balancing. The 123ignition has the ability to analyze
engine performance and tailor spark timing and energy to the
variations in each cylinder in order to achieve the best possible
engine operation. This fully microprocessor based spark balancing function is derived from Formula 1 engine management
systems. The microprocessor controls both dwell and timing.
A screw plug under the distributor reveals a 16-position advance curve
selector. There is also a built-in LED for simple static ignition timing; simply
turn the distributor until the light goes on, and your static timing is set.
2. Gated switching. The 123ignition uses a high-speed
electronic switch to turn coil current on and off
at each spark event, leading to better combustion and less unburned fuel emissions, and significantly improving engine old and warm starting.
3. The design eliminates moving parts that can
wear and degrade performance over time.
The 123ignition design is visually faithful to the
original Robert Bosch equipment.
4. Easy to install and virtually maintenance-free.
The difference between the 123ignition and the
OEM distributor, with and without the Pertronix upgrade
is illustrated in a video on the Brooklyn Motoren Werke
website. Immediately apparent is the rock steady timing, more stable advance, and better control over
dwell angle at various rpm levels with the electronic
switching of the coil current, resulting in increase gas
mileage and power from the stable advance curve.
The video does not discuss the relative performance compared to price. The Pertronix Ignitor is
priced under $100 and the 123ignition at $780. The
Pertronix electronic ignition is an upgrade to the
existing Robert Bosch distributor and the 123ignition
is intended to replace an existing distributor. A new
replacement Bosch distributor is available at the
same price as the 123ignition and still uses a standard
points-breaker system as original. Given these factors,
I would select the 123ignition because I would be
installing state-of-art technology at a similar price. The
only disadvantage is that I would lose a point or two in
concours shows because the distributor is not a Robert
Bosch Mercedes-recommended replacement part.
However, the 123ignition design comes in a Boschlike aluminum billet and nickel plated housing, and is
similar to its Bosch mechanical counterparts.
Additional information on the 123ignition and
Brooklyn Motoren Werke can be found at www.brooklyn300.com. They support all Mercedes-Benz models from 1952 onwards including the Adenauers, the
300SLs, the Pontons and the 190SL.
Bruce Adams is a member of the Triangle Section, and has owned and operated B.L. Adams, LLC, specializing in restoration of the 190SL model Mercedes-
Benz, for 31 years. www.bruceadams190sl.com
THE STAR®
September-October 2009
61