VTEC

Variable Valve Timing & Lift Electronic Control

What is VTEC?

 

The engine was born over 100 years ago. Until VTEC, engine performance was a delicate balancing act.

 

 

Improvement in one area was always achieved at the expense of another.

Until VTEC, when ease of use was increased, the outright performance would be diminished. Or, when performance was increased, everyday drivability was reduced.

Solving a century-old dilemma!

Combining drivability in everyday situations with outright performance is what VTEC is all about.


VTEC: an entirely new approach to engine design

 

A 4-stroke engine goes through induction, compression, combustion and exhaust strokes to generate power. Before the advent of VTEC, the valves controlling the intake and exhaust strokes were operated according to fixed rules.       

If the intake valves were opened a relatively small amount to increase drivability at low engine speeds (as used in normal driving conditions), the engine could not intake enough air at higher engine speeds, sacrificing outright performance. On the other hand, if the intake valves were opened wide to increase breathing at higher engine speeds, performance at low engine speeds would be compromised. This is a dilemma that had plagued engines for over a century.

The new approach is to regulate valve operation to optimise performance at all engine speeds- opening the valves a small amount at low engine speeds, and opening the valves wider as engine speed increases. That's the breakthrough we call VTEC.

 


Optimising engine breathing: how VTEC works

 An elegant, simple mechanism switching between high and low valve lift- using two cam profiles and two rocker arms per cylinder.

The switch is made using hydraulic pressure to push/release the sliding pin, locking/unlocking the middle rocker arm and the other rocker arm.

At low engine speeds, the pin is retracted, disengaging the middle rocker arm. The valves are operated by the two outside, low-profile cams for a low valve lift.

At higher engine speeds, increased hydraulic pressure pushes the pin, engaging the middle rocker arm. The valves are operated by the middle, high profile cam for high valve lift.      

VTEC: a deceptively simple mechanism that uses hydraulic pressure to switch between different cam profiles.
100 years after the engine was born, VTEC technology finally reconciles drivability in everyday use and outright performance, creating the first uncompromising engine.