In today’s video we are comparing four different kinds of ignition systems for car engines. A distributor based single coil ignition system, a wasted spark ignition system, a coil on plug or direct ignition system and an aftermarket racing coil near plug system.
We’re starting with the oldest and therefore most primitive setup of the bunch, the distributor. Unlike any of the other ignition systems shown today the distributor controls ignition timing by relying on a mechanical connection to the engine. The distributor is connected to and rotated by engine internals (most often the camshaft) and the speed of the movement of the rotor inside it is synced to the speed of the rotation of the engine. Although it’s a system that performs it’s duty fine it’s obsolete by today’s standards and has bay disadvantages over all other ignition systems. The distributor is a source of friction because it adds moving parts to the engine. It’s a source of potential oil leaks because the lower part of it’s shaft is immersed in engine oil and thus needs to seal it away. On top of this it employs long spark plug wires that generate (extremely small but still present) voltage drops and voltage differences between cylinders. Spark plug wires also need to be replaced as they erode over time, along with the distributor cap that is also a service item. But all of these downsides can be tolerated, the biggest one, that is difficult to tolerate is that the distributor system has limited potential when it comes to delivering spark at high rpms. The single ignition coil which drives the distributor must fire twice during a single revolution of the crankshaft in a four cylinder engine (four times in a v8), which means that in a four cylinder engine spinning at 6000 rpm there’s only 5 milliseconds between spark events. This extremely short time frame can result in the ignition coil being forced to fire the plugs before it’s fully charged and create a weaker spark or a reduced chance of the spark even happening, which means that the distributor based single coil ignition system can be prone to misfires at higher rpms and is a strong limiting factor if you want the raise the redline of your engine.
Compared to this the coil pack based wasted spark ignition setup is a much better ignition system. It doesn’t have any moving parts or gears and no oil seals either. The system relies on a crankshaft position sensor that relays the engine position of the ECU which then tells the coil pack when to fire the spark plug. This results in much greater accuracy of the ignition timing. Another key benefit is that inside a coil pack there are multiple ignition coils, and a single ignition coil always handles only two cylinders. This means that, unlike the distributor, the wasted spark coil pack must fire only once every single rotation of the crankshaft, regardless of the number of cylinders of the engine. This means more voltage and better operation at high rpm. A coil on plug system takes things even further. It completely removes spark plug wires as a service item and gives every cylinder it’s own ignition coil. This means that a coil on plug, or direct ignition system must fire only once every two revolutions of the crankshaft, meaning even more voltage and even better operation at high rpm and greater power potential and a higher redline. Also because the cop (coil on plug) system gives each cylinder it’s individual ignition control it enables the ECU to adjust ignition timing individually for every cylinder resulting in more power, less emissions, better mileage and a smoother idle. The modern coil on plug system is truly powerful and versatile but it too runs out of talent when it comes to highly modified and racing applications. In that scenario you need to step things up to the AEM IGBT (insulated gate bipolar transistor) coil near plug smart coils. These consistently deliver 40.000 volts in all conditions and can handle any amount of rpms or boost you throw at your engine.
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