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I'm not a gear head, which may be apparent with my question.

Why don't both cams stay active? Why have the 2nd kick in at 6200?
 

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The second lobe offers better breathing to produce power above 5000ish RPMs. The first lobe runs out of wind at higher RPMs, but offers less emissions and better fuel economy. Most people spend more time on the first lobe, and thus, get better fuel economy.
 

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You are confused about what is meant by '2nd cam' when referring to the VVT on the intake came.

There are indeed 2 cams in the engine, and they are always active. One for exhaust and one for intake.

The intake however has two possible cam profiles on it, and at 6200 the cam switches from using one profile to the other, changing the performance to better suit the engine for the higher RPM.


When people talk about the 2nd cam kicking in they mean the 2nd profile of the intake cam, not an entire other camshaft.



I'm sure someone can post a picture to explain further.
 

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Well theres two overhead cams, one for intake valves and one for exhaust valves.

The 6200 crossover doesn't change cams per say, it changes the profile of the cam. So it's still the same cam, it just changes how it operates.

Here's a great site that explain a version of this.

HowStuffWorks "Variable Valve Timing"
 

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Best not to think of it as a second cam, Its a second stage of the intake cam, as the guys are pointing out. If you go look at the Dyno plots of our engine you will see where it kicks in, extrapolate the two curves (Before and after 2nd stage) and you will clearly see why it doesn't stay active. The first stage doesn't allow the engine to breath at high revs. The second stage has too much lift and duration to make power lower in the rev range. So the 2 stage cam is actually a brilliant concept, you get low end drivability and then the high end performance like with racing cams in other cars.
 
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