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In places where it gets below zero in winter, weather reports are always both the air temperature and wind chill is, how it feels cold with the wind blowing wind makes the temperature feeling cold, because it transports heat our body in this update of science, you will hear how the wind affects car engines in a similar way.
Cranking a cool car and I'm Bob Hirshon is science update.
The onset of winter makes this question from David Yount Duluth, Minnesota, particularly timely.
Yount I wonder why it is that a car left outside in subzero temperatures has more difficulty from a car left in an unheated garage.
Well, David, we asked Naeim Henein, director of the Center for Automotive Research at Wayne State University in Detroit He says if you drive your car around and park in the garage, it won t as cold as if you kept outside.
Henein When stopping the engine, the engine is hot, it takes a long time for internal engine components to cool it may take up to 8 or 12 hours.
That's because there's no wind to carry heat away So even if it feels cold in your garage, the engine can still be hot.
Henein adds that no matter if your car is inside or outside in the winter, it will start faster if you use thinner, low oil viscosity, and make sure that your air filters and fuel are clean.
If you got a scientific question, we will get crank we just call 1-800-WHY ISIT If we use the show you'll get a free cup of Science To update the American Association for the advancement of science, I'm Bob Hirshon.
To understand why don t start the car when it's cold, you need to understand how the cars start first Briefly, it is a kind of chemical reaction called a combustion reaction in other words, in this case a fire , a very small and controlled.
To put it very simply when you turn a car's ignition key, he spark the spark plug of the engine, which a good day ignites the fuel and air mixture yes, the air inside the engine the oxygen in the air is an essential element of this reaction without it, the combustion reaction can t take place, so that the fuel won t ignite, and the car won t start is the same reason you can put out a fire by smothering fires can burn without air t.
In winter, the air is there, but it is very cold and since all chemical reactions slow down to cold temperatures, it is more difficult to trigger this combustion reaction What is more, the car battery also cold, which means that its chemical reactions slowed, which means that he won t be able to send power to turn the highly efficient engine is a result of all this, if the temperature falls below a certain critical point, the combustion reaction may not occur at all.
Now, if you drive your car all day and park in a garage, which is less likely to occur as the Henein emphasizes on is because the engine itself takes a long time to cool off and also long as the engine components are hot, the air around them will be hot too.
But if you are parked outside, the wind rushing carries hot air away from the engine that makes the engine loses more heat, which is carried by the wind, etc. The end result is an engine cooling with cooler air inside, and a rough start.
The process by which objects transfer their heat to the moving air is called convection cooling convection cooling also explains the wind chill making windy winter days feel colder than calm a windy day, wind constantly carries heat from your body; on a calm, a thin layer heated air surrounds and help you to isolate elements.
What are the essential ingredients in the combustion reaction that starts a car.
How the wind affects the engine temperature.
If you left a car in an unheated garage for a month during a cold snap, do you expect to begin Why or why not.
The principle of convection also explains how a hot radiator heats up a cold room Can you guess why Be specific.
How Working Car engines How Stuff Works, gives you a detailed overview, illustrated in an internal combustion engine.
Cold Start Science For science updates NetLinks, cold start, science.