As the output level of performance and racing engines increases, so does the importance of precision measurements, component strength and accuracy. Horsepower advantages come through a collection of the small efficiencies of an engine build. One area of importance, especially with high compression, boost and rpm, is a precise ignition trigger signal.

Accurate ignition timing is a basic engine tuning factor that contributes to overall power production. Ignition timing determines when the spark plug will fire in relation to the piston's position in the cylinder moments before Top Dead Center on the compression stroke. Precise timing is essential in producing the most efficient combustion event through all engine speeds and loads.

The standard component used to trigger the ignition system is the time-proven distributor. Distributors incorporate a mechanical or electronic pickup that is triggered from a paddle wheel or reluctor, mounted to its spinning shaft. This system is a reliable form of triggering the ignition for street cars and mild-to-medium performance engines. When you start increasing compression, cylinder pressures and extreme rpm, however, a distributor falls far short of accuracy, resulting in timing inconsistencies and lost performance.

Swapping to a crank trigger system is the most accurate way to trigger the ignition. MSD offers a number of kits for Chevy, Ford, Mopar and other GM applications including LS engines.

Just think of all the twisting mechanical action necessary to spin the distributor. First, the camshaft which is driven through a chain or belt drive. There’s also the meshing of the cam’s gear and the distributor gear, not to mention the flex or twisting motion of the camshaft and its tendency to walk out the front of the engine block. Small as they may be, all of these mechanical variances add up to form timing variations that can cost engine power at best, or worse yet, cause engine damage.

That’s the beauty of triggering the ignition from the crankshaft – it’s the most stable rotating component of the engine. Therefore, the ignition trigger signal is coming straight from the crank and bypassing all of those mechanical variables to produce a much more accurate and stable timing signal through the rpm range of your engine.

Operation

Crank trigger technology is not exactly new. In fact, MSD introduced their Flying Magnet Crank Trigger system long before the OEMs did away with distributors and moved their ignition trigger sensor to the crankshaft. For race engines, it is by far the most accurate way to trigger the ignition on a standard single coil ignition or through an ECU with multi-coil ignitions.

The unique thing about the Flying Magnet design is that the only way the pickup can be triggered is by the magnets. Some crank trigger systems use steel studs or teeth that produce a signal when passing by a stationary magnetic pickup. These pickups can be ‘false triggered’ by track debris or even engine disturbances. False triggers will lead to inaccurate timing resulting in engine damage and loss of power.

With the MSD system, there are four rare earth magnets embedded in an aluminum wheel 90-degrees apart (three magnets at 120-degrees on even-fire 6-cylinders). These magnets are the only way to trigger the non-magnetic pickup that mounts perpendicular to the trigger wheel. With this design, there can be no false triggers and the timing signals are the most accurate from idle to redline rpm to trigger an ECU or ignition unit.

Installation

Installing a crank trigger system is pretty straight forward, as most kits are designed to fit a specific engine and balancer and include the brackets, wheel, pickup and hardware for a complete installation. One aspect you need to consider is that the trigger wheel bolts to the front of the balancer, which means any drive pulleys for accessories such as the water pump, an alternator or blower will need to be spaced out about 3/8” further out.

One of the most important things during assembly is ensuring that the trigger wheel is mounted in the correct position. There is an arrow machined into the wheel that must face out and in the direction of the engine rotation and be centered on the balancer. Most trigger wheels have different bolt patterns as well as a centering ring, to ensure an accurate and square mount. With the trigger wheel installed, mount the brackets and pickup. Most kits come with spacers so you can position the pickup on the centerline of the trigger wheel.

The location of the pickup now determines the timing and needs to be set. With the number one cylinder at TDC, or your desired total timing, slide the pickup mount until it is aligned with the nearest magnet. (Also, make sure that the distributor rotor is pointing at the number one spark plug terminal.) At this point, the goal is to be able to start the engine, then fine tune the timing with the engine running.

The next step is to adjust the air gap between the pickup and the wheel. The air gap does not affect performance however the signal created does vary with engine speed. In short, the pickup needs to be close enough to create a strong enough signal to start the engine at cranking speeds. Conversely, on big cubic-inch engines at higher rpm, there can be excessive crankshaft flexing, so you don’t want the pickup to be too close to avoid contact. The gap is recommended to be in the neighborhood of .025” – .050”.

Upgrading to a crank trigger will deliver the precise and reliable trigger signal that a high performance engine requires. With a quality timing pointer and degreed balancer, you’ll be able to adjust the timing in precise increments. Also, you’ll now be able to control the timing electronically through accessories or an ECU to compensate for high rpm, nitrous loads or boost.

MSD introduced the Flying Magnet Crank Trigger over 25 years ago yet it remains the most accurate way to trigger the ignition. It can be used for both distributor fired ignitions as well as coil per cylinder systems such as their new Pro 600 CDI Ignition.

When stepping up to a crank trigger, you’ll need to consider any accessory drive pulleys that may need to be spaced out due to the trigger wheel. Also, note the position of the pickup mount.

The non-magnetic pickup supplied with each kit is a simple design with an iron core and fine wire windings. This design is less susceptible to electronic noise and cannot be false triggered by other metal pieces of the engine – only the magnets.