Friday, October 2, 2015

Why do you need to warm diesel engines

In the Pacific Northwest, a lot of people use their trucks as everyday commute vehicles, which makes sense, since the climate is wet, and the terrain hilly, and in wet and cold conditions people feel safer in their four wheel drive vehicles. Some of these trucks are the heavy duty ones, with big diesel engines, and lately I have noticed at work a couple idling sans driver for at least 5 minutes. It got me curious about why would you need to idle a diesel engine especially since modern gasoline engines do not require idling before driving off and putting load on the engine. A web search helped piece the answer to this puzzle.

Diesels operate differently than gasoline engines. Instead of relying on spark plugs to light up the air and fuel mixture inside of the engine cylinders, diesels rely on high compression ratios that cause the air and fuel mixture inside of the cylinders to ignite.  Because of the high compression ratios, diesel engines are typically bulkier and more sturdy than their gasoline counterparts. Moreover diesels typically operate with a higher thermal efficiency than gasoline engines, which means less heat is dissipated to heat the engine block, and the lubricating fluids.

Both factors mean that the engines need a bit more time before they operate at their sweet spot. This translates to longer idling time before the engine can sustain load. The modern diesel engines have technological advances that help minimize the idling time, such as engine block heaters, and higher idling RPMs. The EPA website contains some useful information about modern diesel engines

As an aside, it turns out if you own a diesel truck, you have to be good at managing your time, since you cannot just turn on the engine in cold weather and get on with your life when you're running late; you have to wait for a little bit till the engine is ready.

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