AGENDA

• Anatomy of Automobile• Engine• Driveline system• Brake system• Suspension system• Steering system

Modern Two-Stroke Spark Ignition Engine

Stroke 1: Fuel-air mixture is introduced into the cylinder and is then compressed, combustion initiated at the end of the stroke

Stroke 2: Combustion products expand doing work and then exhausted

* Power delivered to the crankshaft on every revolution

Two Stroke Spark Ignition Engine

Intake (“Scavenging”)

Compression Ignition

ExhaustExpansion

Fuel-air-oilmixture

Fuel-air-oilmixture

Crankshaft

Reedvalve

ExhaustPort*

TransferPort*

*No valves and thus no camshaft

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Advantages of the two stroke engine:

• Power to weight ratio is higher than the four stroke engine since there is one power stroke per crank shaft revolution. • No valves or camshaft, just ports

Most often used for low cost, small engine applications such as lawn mowers, marine outboard engines, motorcycles….

Disadvantages of the two-stroke engine:

• Incomplete scavenging – limits power• Fuel-air short circuiting – low fuel efficiency, high HC emission• Burns oil mixed in with the fuel – high HC emission

Functions of a Suspension SystemFunctions of a Suspension System

• Provide vertical compliance so the wheels can follow the uneven road, isolating the chassis from roughness in the road.

• Maintain the wheels in the proper steer and camber attitudes to the road surface.

Functions of a Suspension SystemFunctions of a Suspension System

• React to the control forces produced by the tires – longitudinal (acceleration and braking) forces, lateral (cornering) forces, and braking and driving torques.

• Resist roll of the chassis.• Keep the tires in contact with the road with

minimal load variations.

STOPPING DISTANCE

NORMAL STOPPING

STOPPING IN RAIN – 50%

STOPPING IN SNOW – TWICE NORMAL

STOPPING ON ICE – THREE TIMES NORMAL DISTANCE

CLASSIFICATION OF BRAKE SYSTEM

1. Hydraulic brakes

2. Power assisted brakes

- Vacuum assisted

- Compressed air assisted

3. Air brakes

COMPONENTS OF HYDRAULIC BRAKE SYSTEM

• Tandem master cylinder• Wheel brakes• Brake booster • Vacuum pump• Pressure control valves • Brake fluid reservoir

TANDEM MASTER CYLINDER

• Converts driver’s foot effort into hydraulic pressure and transmits the pressure to wheel cylinders.

TANDEM MASTER CYLINDER

• Tandem master cylinder has 2 compartments for safety.

• Each compartment is connected separately and independently either front or rear wheel brakes.

• Failure of one circuit (leakage) will lead to brake failure in that particular axle.

• The vehicle can be brought to stop with working brakes in the other axle, with higher pedal effort.

POWER ASSISTANCE

• Power booster reduces pedal force required to stop vehicle.

• Engine vacuum is used to actuate a large diaphragm.

PRESSURE CONTROL VALVES• When a vehicle is braked at high speeds, weight

transfer happens. The vehicle weight shifts to the front axle. There will be relatively less weight on the rear axle.

• As the brake fluid pressure is same for the front & rear wheels, the locked rear wheels will lead to vehicle instability and skidding / Tail swing.

• Pressure control valves reduce the brake fluid pressure to the rear circuit under these conditions.Pressure control valves are classified as:– DCRV (Deceleration Conscious Regulating Valve)/G valve

Eg: Bolero– LCRV (Load Conscious Regulating Valve)/LSPV

Eg: Scorpio