Antilag system

An anti-lag system (ALS) or misfiring system is a system used on turbocharged engines to minimize turbo lag on racing cars. It works by arranging for fuel and air to be in the exhaust duct after the engine, and before the turbocharger. This ignites in the hot ducting and the combustion process that occurs there keeps the turbocharger spinning when the engine is not delivering enough exhaust gas.

Overview

ALS was first used in the early days of turbocharged cars in Formula One racing circa mid to late 1980s, until fuel restrictions made its use unsuitable. Later it became a common feature in rally cars because of the increased turbo lag from the mandated restrictors at the intake manifold inlet. Due to the pressure drop across the restriction, the pressure ratio for a given boost level is much higher and the turbocharger must spin much faster to produce the same boost as when the engine operates without restriction. This increases turbo lag significantly compared to unrestricted turbochargers.