How does cam timing work for a car?
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Cams are rods that are ground in a manner where they have a lobe on them. As the rod spins the lobe pushes on a rod that opens and closes a valve. There’s 2 things you can adjust on the lobe profile.
1. How tall the lobe (lift) is which changes how much the valve is open at it’s fully open position.
2. Duration, which is how long the valve stays open.
These 2 features are permanently part of the cam profile and can’t be changed (as the cam wears down the amount of lift gets shorter). Newer engines can adjust lift by using 2 cam profiles. 1 cam profile is used for low RPM and low load while a second lobe profile is used at high RPMs high load.
Timing is adjusting when the valve opens and closes in relation to where the piston is through a process called phasing. They normally use a system that controls oil pressure that advances the cam gear a few degrees forward or retards it a few degrees back to adjust when the valves open and close. [Here is an example of Toyota’s system called VVTI](https://www.youtube.com/watch?v=YjIKUrre4FQ) other manufacturers have similar systems like Honda’s VTEC or BMW’s VANOS. I’m pretty sure every car manufacturer has a version these days.
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