Today we learn how does Vtec work.
Some would call it the punch line of all Honda jokes, and often described by its critics as turbo lag without the turbo. But it is actually a very useful and interesting system, and in a nutshell, gives you two engines in one.
So how does Vtec work?
In essence V-tec is a secondary cam profile that is used over a given engine speed commonly 5000 or so Rpm. This means a V-tec camshaft has an extra lobe per cylinder, which has its own rocker arm; this rocker won’t actuate the valves until it’s connected to the other two when a slider pin, controlled by oil pressure, links them together. This causes the rocker assembly to follow the secondary profile, which has longer duration and higher lift.
This video explains the details of how it works.
How does Vtec work in practice? This other one shows us what goes on inside a Honda engine cylinder head.
But, what does V-tec do in terms of performance?
It gives you an economy oriented, reliable engine under 5000 rpm, and a performance oriented, responsive, high revving engine after Vtec is engaged. This behavioral dichotomy is what makes the Vtec engines so popular and sought after.