So when does the variable valve timing change?

[mauleed]

My understanding is that the valve timing has two settings. What RPM do they switch at?

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[Higgs Boson]

it's constantly moving and changing based on RPM and throttle position.

 

[jasonstang]

They are constantly moving given fuel type too.

 

[Anthony 05 GT]

That's right, each camshaft is independently adjusting in relation to the crankshaft to optimize torque and hp. The knock sensors play a large part in this. Oil and spring pressure are what change the timing through the phasers in the front of the heads.

 

[mauleed]

So only the timing changes? I thought I had read something about how the lift changed as well, but only in one stage. I guess that's where I was confused. I must have been reading about a different engine.

 

[whirledpeaz]

http://twoguysgarage.com/tgg-909-2011-mustang/

 

[kris5597]

Lift and duration do not ever change, that is not variable. What is variable is valve overlap, intake valve opening position, and exhaust valve closing position.

 

[Anthony 05 GT]

That's right, as the cam rotates the valves will always lift and close the same way, only they can vary in timing in relation to the crankshaft (piston timing) and each cam can vary in timing to each other. Keep in mind, there are 2 cams in each head...one for intake valves and one for exhaust valves and they adjust in relation to each other to optimize power in a given situation such as rpm, fuel quality and temperature.

 

[ScottsGT]

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