How does VTEC work (AKA why it is more magical than a unicorn made of fairy farts)?

How does VTEC work (AKA why it is more magical than a unicorn made of fairy farts)?

VTEC, otherwise known as Variable valve Timing and lift Electronical Control, has become a byword for Honda high-performance shenanigans since its introduction in 1989. But how does it add the magical horsepower to tiny naturally aspirated petrol engines (LIKE THIS ONE IN THE NEW EPISODE HERE)? 

The good news is there is zero witchcraft involved. Probably. VTEC is essentially a system that allows an engine to switch between two different camshaft profiles; one for highly efficient, smooth street driving, and one for manic, set-fire-to-your-underpants high-performance. In The Olden Days before naturally aspirated engines could alter their valvetrain geometry to improve performance or efficiency, we had to make a choice between having a smooth-running low-power engine or a powerful engine wtih aggressive camshaft profiles that didn't like driving low in the RPM range... or a compromise in between both.

VTEC turned all of that inside out by using the ECU to change the engine's cam profile, thereby altering the amount of valve lift and ignition timing. In a double overhead cam (DOHC) engine like a B16 or K24, each camshaft has double the number of lobes used to open the valves, as one set of lobes are for driving with your grandparents and the other is for racing tofu delivery drivers in AE86s down Mount Akina. 


The theory behind this amazing technology actually dates back to 1983, with Honda's CBR400 motorcycle. The DOHC four-stroke bike motor used REvolution-modulated Valve control (REV) to open up extra valves in the cylinder head at a pre-determined RPM point. 

Just 6 years later Honda unleashed the B16 with its DOHC VTEC into the world, with its signature boo-BAAA scream. Since then, the innovative Japanese manufacturer has sold tens of millions of engines featuring the variable valvetrain geometry technology, reportedly with no warranty claims on it.


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