engineoff

Engineoff is a term used in automotive engineering to describe the deliberate deactivation of an internal combustion engine when vehicle conditions permit, with the aim of reducing fuel consumption and emissions. In modern vehicles, engine-off routines are commonly integrated into start-stop systems that shut off the engine at idle and restart it when needed.

The core concept involves a state machine that switches between engine-on and engine-off states based on inputs such as vehicle speed, brake status, climate control needs, battery state of charge, and transmission position. Safe operation requires interlocks to ensure essential systems (power steering, braking assistance, electronics) remain powered, and to prevent engine shutdown during critical conditions.

Implementation typically relies on sensors and actuators, a control unit (ECU or integrated powertrain control module), and software logic that manages transitions, restart strategies, and feedback. Standards and calibration practices address fuel economy benefits, driver-perceived responsiveness, start-up wear, and cold-start behavior.

History and adoption: Start-stop technology began appearing in mainstream vehicles in the late 1990s and has become widespread in many markets. Variants include micro-hybrids and mild-hybrids that extend engine-off logic with electric motor support. In fleet and telematics contexts, engine-off policies may be enforced remotely to optimize energy use.

Critiques focus on durability under frequent restarting, apparent drivability concerns, and user acceptance. Ongoing research explores improved restart speed, reduced wear, and integration with hybrid powertrains. See also idle stop, stop-start system, and engine management.