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123ignition Family

123ignition for four cylinder Mercedes-Benz

The 123ignition system represents a remarkable advance in ignition performance for four- and six-cylinder Mercedes-Benz models from the fifties through the seventies. More than a distributor, the 123ignition is an elegant synthesis of new and time-tested technology, driven by a sophisticated microprocessor with onboard nonvolatile memory and a bank of preset digital advance curves that permanently eliminate the need for springs and weights.

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 tightening European emissions standards, the 123ignition has been widely praised by the motoring press and adopted by enthusiasts as simply the finest electronic ignition system available for classic Mercedes-Benz automobiles. Order today: 123ignition for 4 cylinder6 cylinder classic models, or modern 6 cylinder models.

Spark Balancing

Four cylinder 123ignition with cap and rotor removed, showing trigger disc.

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 and until now has been out of reach for drivers of classics.

Here’s how it works:

  • As the engine runs, the rotational velocity of the distributor shaft will differ slightly with each power stroke, as a result of the unique combustion characteristics of each cylinder.
  • The embedded microprocessor in the 123ignition measures these velocity changes by sensing the Hall Effect induced by magnets embedded in an aluminum disc mounted on the distributor shaft (visible with the cap removed).
  • The 123ignition records the actual time elapsed between each of these magnetic impulses, and this stored event history is used to calculate the optimal timing and energy level for the next spark sent to each individual cylinder.
  • This spark balancing program aims to equalize power strokes between cylinders, attenuating internal vibrations and resulting in a very smooth running engine with cleaner tailpipe emissions, improved fuel economy and enhanced full range power response. 

Gated Switching

123ignition for six cylinder Mercedes-Benz

The second dramatic advantage of the 123ignition lies in its electronic switching system. The 123ignition uses a high quality, high speed electronic switch to turn coil current on and off with minimal losses. As a result, more energy is immediately available for each spark event, leading to better combustion and less unburned fuel in the exhaust: this improves engine power output, decreases pollutant emissions, and significantly improves engine starting, warm or cold.

Other significant benefits of the 123ignition over any other system include its minimalism of design, reducing moving parts that can wear and degrade performance over time; perfect geometric firing initiations resulting from precise digital control; and no loss of energy response at high RPM operation, as a result of the synergy between digital switching and spark balancing functions.

Preparation and Installation

The 123ignition was designed for simple installation, and we further adapt each unit to make installation and operation as trouble free as possible. Prior to shipping, we install electrical connectors on the wire ends, provide mating connectors for the coil, set the internal mechanism to correspond to your engine number, coordinate the engagement lug orientation with the rotor and, when needed, modify the base of the 123ignition housing to mate flawlessly into your engine’s distributor cradle.

We recommend that prior to installation you inspect your ignition wires, spark plugs, and coil. If you have never replaced these items, this would be a good time to start fresh with all of the ignition components. We prefer and sell the ‘red’ coil from Bosch (now silver with a red tag).

It is essential to have a clean 12V supply to the unit. This will require bypassing the ballast resistor with a jumper wire. Any previous electronic or magnetic ignition system should be fully removed. There are no additional components to install with the 123ignition: no black boxes or secondary wiring harnesses are needed. The 123ignition uses a standard distributor cap and rotor, both supplied. All you have to do is drop it in, make the electrical connections, time the ignition, and start the engine.

Installation simply requires the red and black leads from the 123ignition to be attached to the coil.

After installation, normal ignition timing is set as per Mercedes specifications, facilitated by the timing LED built into the 123ignition.

It should be noted that no matter how sophisticated the management program, no ignition system alone is able to compensate fully for fuel induction variations per cylinder, especially bad carburetion. That said, while carburetion is often believed to be the cause of much poor engine performance, our experience suggests that frequently ignition timing and spark quality are the real culprits.


The 123ignition is capable of improving consistent variations. Other items contributing to bad spark timing include timing chain stretch or slack, worn distributor drive gear sets or bushings, low compression and a crankshaft with excessive end play. All of these will evidence themselves particularly during neutral throttle position. This type of impairment cannot be anticipated by the 123ignition and should be addressed independently to achieve optimal performance. We have found the 123ignition to be a useful diagnostic tool, as it eliminates any question of distributor function and allows us to focus on the other underlying causes of reduced performance.

The gains in engine performance and behavior seen after installation of the 123ignition will be particularly marked if the distributor it replaces was in deteriorated condition. While we have performed no empirical measurements, in our experience it feels like an eighty percent improvement in engine behavior can be expected over the typical worn distributor. A properly working distributor replaced with a 123 unit feels as if fifteen percent improvement has been gained.

Demonstration video

Video © Leen APK, Gouda, Netherlands

This video compares the timing accuracy of the 123ignition to mechanical and add-on electronic systems.

View or download a high quality version of this video here (QuickTime™ format).