Crank Position Sensors - CKP

Hello HPA and members,

I dont know if this question has rise before, but I would like to know and my questions is...

How do car manufacturer decided on trigger tooth such 36-1, 36-2-2-2, 60-2 etc and they came in various diameters too and not forgotten the CKP sensor selections such Hall Effects and Magnetic Sensors?

Thank you

Quite often the trigger pattern used is determined by the choice of ECU for that engine. Typically a vehicle with a Bosch OEM ECU will use a 60-2 crank and a variant of the Bosch 40 140 cam trigger patterns. This is even more common when the engine is DI and equipped with VVT. The type of sensor is often determined by the cost of the sensor, though it is becoming more common to see Hall effect sensors on current engines.

When EFI first started to become mainstream, there was a lot of experimentation by engine and OEM ECU manufacturers to determine the best options, and so there was a lot of variation in what was seen. Subaru with their different crank triggers and cam patterns as the EJ engines evolved from basic operation to having quad VVT is a good example of this progression.

They do it for various reasons, sometimes the complicated wheels (like 36-2-2) are used to allow quick locking of the signal so the direct fire ignition can start the engine with sequential ignition & fuel. Sometimes the higher resolution wheels (60-2), are used to give more precise engine position on low-cylinder count engines. Sometimes it's just tradition -- they have used 36-1 trigger wheels since the first fuel injected cars... Wheel diameters are usually a results of packaging. Large diameter wheels are easier to make more accurate, and some manufacturers put these on the flywheel. But often the wheel size is slightly larger than the diameter of the crankshaft pulley.

Many times Magnetic sensors are more immune to interference, particularly at high RPM. But Hall Effect can be reliable too.

Engineering usually is faced with the need to design reliable products, or lower the costs, or get it done quickly. All of those factors probably have a role in details of the components they select.

Thank you BlackRex and David Ferguson for your respond....