What is a turbocharger and how does it work in UK cars?

A turbocharger is a device that uses exhaust gases to force more air into an engine, increasing power and efficiency. In UK cars like the Ford Focus ST or Volkswagen Golf GTI, turbocharging allows smaller engines to deliver performance similar to larger naturally-aspirated units while improving fuel economy. The system works by using exhaust flow to spin a turbine (at up to 250,000 rpm), which drives a compressor that pushes additional air into the combustion chamber. Modern turbocharged engines from brands like BMW (B48 2.0L) and Mercedes-Benz (M254) combine this with direct injection and variable valve timing for optimal UK driving conditions. Unlike superchargers (which are mechanically driven), turbochargers harness otherwise wasted exhaust energy, though they can cause slight 'turbo lag' before reaching optimal boost pressure.