| Questions | 5 |
| Topics | Brakes, Exhaust Stroke, Fuel Injector, Muffler, Wheel Hub |
Brakes utlize friction to slow vehicle tires. Drum brakes employ a cast iron drum that roates with the vehicle axle. When hydraulic pressure is applied to the brake assemblies at the wheels, internal pistons expand and push brake shoes outward into contact with the brake drum slowing the rotation of the axle. More powerful disc brakes operate by pinching a rotating disc betweeen two brake pads and allow for a larger surface area to contact the disc, provide more force, and are more easily cooled.
During the exhaust stroke, just before the piston reaches bottom dead center the exhaust valve opens. The resulting gases from combustion are then pushed out through the exhaust valve as the piston travels up the cylinder to top dead center, completing stroke four of the four-stroke piston cycle.
The fuel injector sprays fuel into the air stream that's being fed into the cylinder head via the intake valve. The timing and amount of fuel are regulated by the powertrain control module (PCM) which is the main computer that controls engine and transmission functions.
The muffler follows the catalytic converter and absorbs sound to help quiet load exhaust. It is followed by the exhaust pipe which is the final exit point for exhaust gas from the vehicle.
The wheel hub is the mounting point for the wheel and tire assembly. The wheel hub can rotate while being held stable by the steering knuckle which applies the motion of the control arms to the wheels.