VTEC
Valve Timing Electronic Control-it`s like having a high lift/duration, RPM cam for higher breathing.

On a DOHC VTEC, on the cam, there is a second set of higher lift/duration and different timing cam profile LOBES on the SAME camshaft.

So between the 2 intake lobes (2 valves per cylinder), there is a single higher lift cam lobe, the VTEC one.
There are 3 rockers, 2 outside ones for the 2 valves that follow the 2 intake cam profiles.
The middle one is the VTEC rocker, which follows the higher VTEC cam profile in the middle. The VTEC rocker is equipped with a oil-pressure activated piston inside (very small). This piston, when the oil pressure is raise, will slide and lock up the other 2 outside intake rockers with the center VTEC one. All the rockers now follow the higher lift and different timed VTEC cam profile.
Better breathing at a longer duration.
So those VTEC controllers control the VTEC pressurized oil solenoid valve. :::lost yet??:::

The Second part of VTEC
This is the part everyone either doesn`t know about or miss it.
VTEC also involves the intake manifold. There are actually 2 sets of intake plenums.
If you can get higher breathing in the heads, should you also get higher airflow in the intake to help? A VTEC intake has a short and a long runner per cylinder.
The long ones open during non-VTEC and the short ones butterfly valves open during VTEC. longer for better torque and constant airmass flow and shorter for faster air flow and other fluid dynamics stuff.



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