Motorvarv

Motorvarv, or engine speed, is the rotational speed of an engine’s crankshaft, expressed in revolutions per minute (rpm). It is a central parameter for assessing an engine’s performance, as higher motorvarv generally enable higher power output, while lower varv favor torque at low speeds and better fuel efficiency.

Measurement and display are typically handled by a tachometer in vehicles, which reads signals from a crankshaft position sensor. Modern engines use electronic control units (ECUs) to monitor motorvarv and adjust fuel delivery, ignition timing, and throttle position accordingly. In many systems, throttle control is electronic (drive-by-wire), and idle motorvarv is regulated by an idle air control or similar mechanism to maintain stable engine idle.

Typical ranges vary by engine type. Petrol and diesel car engines often idle around 600–1000 rpm, with diesel engines tending toward the lower end. Maximum engine speed, or redline, depends on design and can range from roughly 5,000 to 8,000 rpm for many passenger engines, higher for performance models, and far lower for heavy-duty or diesel engines. Running at high motorvarv increases wear and heat, whereas running at very low rpm can cause lugging or rough operation.

Overall, motorvarv influences driving dynamics, including acceleration, gear shifting, fuel economy, and emissions. Engine designers and drivers manage motorvarv through gearing, throttle control, turbocharging or supercharging, and timing strategies, aiming to optimize efficiency and performance for a given operating condition.