Torquejen

Torquejen is a term that has emerged in discussions related to internal combustion engines, particularly those with forced induction. It refers to a specific type of engine response where a significant and noticeable surge in torque occurs over a relatively narrow engine speed range. This phenomenon is often a direct result of the engine's turbocharger or supercharger reaching its optimal operating efficiency and delivering maximum boost pressure.

When a turbocharger spools up, it gradually increases the amount of air forced into the engine cylinders. As boost pressure builds, the engine can burn more fuel, leading to a rapid increase in torque output. Torquejen describes the point at which this build-up becomes particularly pronounced, often described as a "kick" or a strong push back into the seat. This effect is distinct from a linear torque curve, where power delivery is more evenly distributed across the rev range.

The presence and intensity of torquejen can be influenced by various factors, including the size and type of the turbocharger, engine displacement, fuel mapping, and exhaust system design. While some drivers may find torquejen an exhilarating characteristic, it can also present challenges in terms of traction control, especially in rear-wheel-drive vehicles. Engineers often aim to manage or smooth out the torquejen effect to provide a more predictable and usable power delivery. The term is not a formal engineering designation but rather a descriptive term used by enthusiasts and automotive journalists.