Speaking

Situation 3 Introducing the Operating Principles of an Automobile Engine

Sample Dialogue 1

(Lily and Peter meet each other again.They are talking about the four-stroke process of the engine.)

Lily:Hi,Peter.I'm wondering how the modern engine makes the wheels turn.

Peter:Let's take the internal combustion gasoline engine for example.It runs on a mixture of gasoline and air.The ideal mixture is 14.7 parts of air to one part of gasoline by weight.Since gas weights much more than air,we are talking about a whole lot of air and a tiny bit of gas.One part of gas that is completely vaporized into 14.7 parts of air can produce tremendous power when ignited inside an engine.

Lily:Wow,it's awesome.

Peter:You bet!The four strokes are Intake,Compression,Power and Exhaust.As the piston starts down on the intake stroke,the intake valve opens and the fuel-air mixture is drawn into the cylinder.When the piston reaches the bottom of the intake stroke,the intake valve closes,trapping the air-fuel mixture in the cylinder.

Lily:Oh,I see.

Peter:Then the piston moves up and compresses the trapped air fuel mixture that was brought in by the intake stroke.When the piston reaches the top of the cylinder,the air-fuel mixture is squeezed to about one tenth of its original volume.

Lily:If so,the engine must be strong enough to hold the high pressure.

Peter:Yeah!When the spark plug fires,it ignites the compressed air-fuel mixture.The combustion process pushes the piston down the cylinder with great force,turning the crankshaft to provide the power to propel the vehicle.This is the power stroke.

Lily:Then with the piston at the bottom of the cylinder,the exhaust valve opens to allow the burned exhaust gas to be expelled to the exhaust system.

Peter:How wonderful you are!

Lily:Thanks to your clear explanation,I can better understand Figure 1-7 on the textbook which illustrates the working of the engine.

Peter:Good for you!

Lily:Thanks!If there is something wrong with the engine,what should we do?

Peter:A good question.Since they are working in changeable conditions,it will often go wrong.If it occurs,check the engine driving belts,oil level,or coolant level,and replace spark plugs.So the engine should be maintained and checked regularly.

Lily:You're really an expert in the engine.

Peter:It's nothing.

Task 5

Pair work.Take Sample Dialogue 1 as an example.Start a conversation with your partner according to the situation:

Suppose you are a technician of an auto manufacturing company.Your partner doesn't understand the working of the engine.So you explain it to him/her.

Situation 4 Introducing the Car Body

Sample Dialogue 2

Windy:Wow,look at your new car!She is so beautiful with a lovely convertible body.

Steven:Yeah.It's the unique design of the car body that attracts me much.

Windy:I'm interested in the car body.Can you introduce it in detail?

Steven:Certainly.An automobile body is a sheet metal shell with the built-in windows,doors,a hood,a bumper,seats,instrument cluster and a trunk deck.

Windy:Is the car body always composed of metal?

Steven:Of course not.Usually the car body is made of steel or aluminum,but it can also be made from fiberglass,plastic or composite material.

Windy:What functions does it have?

Steven:The car body shoulders many important functions.In the first place,the body forms the passenger compartment,withholding the force of an accident and protecting the drivers and passengers from the bad weather,the noise and exhaust gas and offering comfort.

Windy:Yes,it can create very pleasant driving environment.

Steven:Indeed.In the second place,it offers storage space and houses the automobile's systems.Look,this car has very large storage space,so we can easily load and unload all the stuff we need for the travelling.

Windy:Yeah.

Steven:To guarantee the passenger safety,the front and hood are designed to crumple in a crash,thereby absorbing much of the impact.A firewall between the engine and the interior of the car protects the passengers in case of an engine fire.

Windy:The car has a very stylish appearance and streamlined body.

Steven:Definitely.Such a shape reduces aerodynamic drag as the car moves,and allows the driver to increase fuel efficiency.

Windy:Great!I've learned a lot.Thanks a lot!

Steven:You're welcome.

Task 6

Pair work.Take Sample Dialogue 2 as an example.Start a conversation with your partner according to the situation:

You're introducing the car body of your newly bought Honda SUV to your friend Tom.

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