Engine

Identifying the drive wheels:

The way the engine mounts itself usually tells us which wheels are drive wheels. These wheels drive the car. If the engine mounts longitudinally, the car usually has rear wheel drive. Engine power flows through the transmission and drive shaft to the rear wheels. However, some rear wheel drive vehicles may also drive front wheels. These vehicles usually have a transfer box. It can send or transfer some of the engine power to the from wheels. This is called four wheel drive or all wheel drive.

If the engine mounts traversly at the front of the vehicle , the vehicle has front wheel drive. Engine power flows through the trans axle to the front wheels.

The engine:

The automotive engine is an internal combustion engine. Burning a mixture of air and fuel inside cylinders in engine produces power. Each cylinder is a tin can in which a round piston slides up and down, this movement is carried through gears and shafts to rotate the wheels and move the car. To continue running an engine must have four supporting systems. These are the fuel, ignition, cooling and lubricating systems.

Some fuel systems use carburettor that mixes air and fuel into a combustible mixture. Instead of a carburettor most engines have electronic fuel injection. An electronic control module or computer controls fuel injectors; whenever engine needs fuel a signal from ECM opens the injector, fuel then sprays into the engine cylinders.

The ignition system provides sparks for the power stroke. Today all ignition systems are electronically operated. Many use an ignition distributer to distribute the sparks to proper engine cylinders.

The lubricating system keeps all moving parts inside the engine coated with layers of oil. It reduces wear and allows the parts to move freely. The oil pan at the bottom of the engine holds oil. The engine drives an oil pump that picks up oil from the oil pan and sends the oil throughout the engine for circulation.

The cooling system removes just enough heat so the engine runs at proper temperature. A water pump circulates liquid called coolant between the engine and radiator. Outside cooler air flows through the radiator that picks up and carries away the excess heat. A thermostat helps to keep the coolant at proper temperature. A fan helps to keep air moving through the radiator.

The power train:

The drive train or power train carries power from engine to drive wheels. Major power train parts may include clutch, transmission or transaxle, transfer case, driveshaft and differential. Transmissions and transaxles may be either automatic or manual. The transmission or transaxle provides several forward gear ratios between the engines and drive wheels. Gear ratio is the difference in rotating speed between the engine and the wheels. Reverse allows the vehicle to move backward. Neutral disengages all gears for starting and running the engine without moving the vehicle.

When the engine is running slowly it cannot produce enough power to get the vehicle moving. The transmission gear ratios provide the necessary increase in torque.

In automatic transaxles or transmission, it shifts automatically to match the driving conditions. For example, when the car is going up a steep hill the transaxle will downshift. This allows the engine to turn faster and produce more power. Automatic transmissions and transaxles are controlled primarily by devices that react to vehicle speed and engine load. An eletronic unit controls when and how transmission shifts.