Eli5. Why do tractor trailers put cardboard in front of their grill in cold weather?

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Do diesels need more heat to operate? How do they differ from gas engines?

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4 Answers

Anonymous 0 Comments

They want the engine to warm up to operating temperature and the freezing air passing over the thermostat can prevent that.

Anonymous 0 Comments

Cardboard on grills limit amount of cold air into engine compartment, keeping what’s under the hood hotter, to allow the cab to be warmer… furthermore – it protects from winter elements damaging the parts under the hood.

Edit: more info

Anonymous 0 Comments

You have some answers for your first question, so I’ll concentrate on your second.

>How do they differ from gas engines?

Both diesel and petrol engines follow the same basic cycle.

1) Fuel and air go into the cylinder

2) The fuel and air are squeezed together

3) The fuel and air ignite, expanding rapidly and pushing on the piston to generate power

4) The burnt fuel and air leave the cylinder to clear it out for the next cycle

The major difference is in step 3. Petrol engines use an electric spark to ignite the mixture. Diesel engines instead use the heat and compression at the end of step 2 to create ignition. This means diesel engines are more susceptible to cold weather than petrol engines, especially older engines.

Anonymous 0 Comments

There is the belief that too much cold air over the radiator cools the engine too much, so they block a portion of the radiator to keep it from getting too cold.

I am not convinced that it is necessary. If the thermostat is working properly the radiator is automatically reducing the amount of cooling the engine gets.

Further, the air to air (it cools the hot compressed air from the turbo to increase the density of the air going into the cylinders for better performance) is mostly blocked, reducing its effectiveness.

I used to drive truck in the northern states during winters and I never blocked the radiator and never had any problems.