Ventiltiderna

Ventiltiderna is a term used in Swedish engineering to describe the timing of valve actuation in piston engines and other systems that control fluid flow. It encompasses the opening and closing events of the intake and exhaust valves, the duration of valve opening (valve duration), the maximum valve lift, and the sequence of events relative to the crankshaft position. These timing characteristics are typically expressed in crankshaft degrees and are central to how effectively an engine breathes and how its combustion is phased.

In internal combustion engines, ventiltiderna influence air intake, fuel delivery, exhaust scavenging, and combustion efficiency. The valve opening duration and overlap affect low-speed torque, high-end power, and emissions. The valve lift profile determines how much air and fuel can flow at different engine speeds. The exact timings are chosen for a given engine design to balance performance, fuel economy, and regulatory requirements. A typical four-stroke engine features intake valves opening before top dead center and exhaust valves closing after bottom dead center, with variations tailored to the desired engine characteristics.

Control methods range from fixed timing, provided by conventional camshafts, to advanced variable valve timing (VVT) systems that adjust timing in real time through cam phasers, hydraulic or electric actuators, and, in some concepts, camless designs that use independent actuators for lift and duration. These technologies enable broader torque curves, improved efficiency, and lower emissions across operating conditions.

Ventiltiderna is thus a core concept in engine design and tuning, while the general idea of valve timing also applies to other engineering systems that rely on controlled valve actuation.