It is basically reverse process of quick warm up after ignition on.
It is especially important for turbocharged cars – once again physical laws are merciless.
Stop the car and let it idle for few second to allow cool down engine oil and lubricate all parts.
For turbocharged cars – depending on ambient temperature, distance driven and engine load – this process takes one to five minutes!
Imagine turbine is propelled by exhaust gases, which generate temperatures about 600deg C or more – if you stop engine right away, one of following things happen:
- a shaft of turbine rotates (at 100,000-250,000 revs) on thin oil film (there is no ball-like bearing) – cheap oils causes disintegration of oil film and everything will just cook together.
- turbine housing deform by gravitation
- turbine rotor/blades deform by gravitation
- in worst case scenario – deformed housing and blades can touch and turbine seizes.
It cost less to let your car idle and cool down and lubricate engine and turbo. Modern diesel cars consume 0.5 litre/hour – a turbine for Skoda Fabia 1.4TDi 59kW cost 700€.
I’ve been told stories about how turbocharged cars are rubbish because turbo is dead after 20k km. My last car had almost 300,000km on ODO meter and 70,000km on a brand new turbine – I had my turbo dismantled from car and checked. Guess what, as new 😉
It’s always down to ultimate question in the Universe…
What happen if you realise that everything is your fault?