Having It All?

HAVING IT ALL?

Open a Harley’s throttle at 1500 rpm and you get impressive thrust, the result of large displacement and short valve timing. But as the engine revs up, the shortness of valve timing causes cylinder filling to fade and the torque curve to fall. Aftermarket longer-duration cams gain torque at higher revs, but lose bottom end from mixture back-pumping-an unattractive compromise. Now along comes the “Smart Valve” from Engintec (www.engintec.com), which is a special intake valve and a floating ring (shown here in cutaway form) that’s free to move between valve and seat. Like a reed valve, it stops mixture back-pumping at low rpm when cylinder pressure pushes the ring into a position that obstructs back-flow. At higher rpm, it moves with the valve (Alfa Romeo once put reed valves upstream of intake valves in one of its engines). The device is claimed to improve driveability and especially to reduce the loss of bottom-end power associated with longer-duration cams.

Kevin Cameron