Also for the warmup case, tolerances inside the engine are designed assuming a hot engine. At lower temperatures, the metal hasn’t expanded yet causing also more stress on various parts such as the piston (seals).
And for the turbo I forget to mention that if you leave a turbo engine idle for a few minutes that this allows both the temperature and speed of the turbo to reduce. Many trucks have a sticker in the dashboard saying “do idle engine x minutes before shutdown to avoid turbo damage”. (But also do not idle for extended periods which I’m not 100% what’s the reason. I guess it’s due to diesel engines in some cases getting too cold while idling.)
When a combustion engine is idling, it’s usually not burning anywhere close to 100% of the fuel that it draws, which means higher quantities of unburnt fuel are reaching downstream parts of the engine system (like the exhaust system) that are only designed to be moderately resistant to fuel.
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Also for the warmup case, tolerances inside the engine are designed assuming a hot engine. At lower temperatures, the metal hasn’t expanded yet causing also more stress on various parts such as the piston (seals).
And for the turbo I forget to mention that if you leave a turbo engine idle for a few minutes that this allows both the temperature and speed of the turbo to reduce. Many trucks have a sticker in the dashboard saying “do idle engine x minutes before shutdown to avoid turbo damage”. (But also do not idle for extended periods which I’m not 100% what’s the reason. I guess it’s due to diesel engines in some cases getting too cold while idling.)
When a combustion engine is idling, it’s usually not burning anywhere close to 100% of the fuel that it draws, which means higher quantities of unburnt fuel are reaching downstream parts of the engine system (like the exhaust system) that are only designed to be moderately resistant to fuel.