Odisha CHSE VOC-ITV Four Wheeler Service Technician flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Micrometer least count

A standard outside micrometer reads to 0.01 mm; the thimble has 50 divisions and one full turn advances the spindle by 0.50 mm.

Torque wrench calibration

Torque wrenches should be checked at least annually and after any drop or overload, at 20, 60 and 100 percent of their scale range.

Fire extinguisher classes

Class A covers solids, B flammable liquids, C flammable gases and D metals; use carbon dioxide or dry powder on fuel and electrical fires, never water.

Four-stroke engine cycle

Intake, compression, power and exhaust strokes complete one cycle in two crankshaft revolutions; the camshaft turns once per cycle.

Engine displacement formula

Displacement equals pi divided by four, multiplied by bore squared, multiplied by stroke, multiplied by the number of cylinders.

Compression ratio formula

Compression ratio equals swept volume plus clearance volume, divided by clearance volume; petrol engines commonly run from about 9:1 to 12:1.

Stoichiometric air-fuel ratio

Petrol burns completely at about 14.7 parts air to one part fuel by mass; diesel stoichiometric ratio is about 14.5 to one.

Lambda value

Lambda is actual air-fuel ratio divided by stoichiometric ratio; lambda 1.00 is chemically correct, above 1.00 is lean and below 1.00 is rich.

Three-way catalytic converter

It oxidises carbon monoxide and hydrocarbons and reduces nitrogen oxides, but works efficiently only when closed-loop lambda control holds the mixture near 1.00.

DPF regeneration temperature

A diesel particulate filter burns trapped soot at roughly 550 to 650 degrees Celsius during active regeneration, which is triggered by rising backpressure or distance.

Coolant 50:50 mix

A 50:50 mix of ethylene glycol and water gives freeze protection near minus 37 degrees Celsius and raises the boiling point; plain water causes corrosion.

Thermostat opening temperature

Most engine thermostats begin to open at 82 to 90 degrees Celsius and are fully open near 95 to 100 degrees Celsius.

Oil pressure warning threshold

Hot idle oil pressure is usually 1.5 to 4.5 bar; a warning lamp or gauge reading below about 0.5 bar means the engine should be stopped.

Clutch pedal free play

Normal clutch pedal free play is about 10 to 20 mm; too little causes release bearing drag, while too much causes incomplete disengagement and gear clash.

Final drive ratio

Final drive ratio equals ring gear tooth count divided by pinion tooth count; a numerically higher ratio gives more torque but lower top speed.

Propeller shaft phasing

Universal joint yokes must be aligned in the same plane, and working angles should be equal and opposite, generally below 3 degrees, to prevent vibration.

Tyre size 205/55 R16

205 is section width in millimetres, 55 is aspect ratio in percent, R means radial construction, and 16 is rim diameter in inches.

Positive caster effect

Positive caster tilts the steering axis rearward at the top, giving straight-line stability and self-centring steering, but it increases steering effort.

Minimum tyre tread depth

The legal minimum tread depth for passenger car tyres is 1.6 mm across the central three-quarters of the tread; wet grip falls before this limit.

DOT 4 brake fluid

DOT 4 glycol brake fluid has a minimum dry boiling point of 230 degrees Celsius; it absorbs moisture and should be replaced about every two years.

Brake bleeding sequence

Bleed the wheel farthest from the master cylinder first, normally right rear, left rear, right front, then left front, keeping the reservoir full.

ABS wheel speed sensor

The ABS controller monitors each wheel speed sensor; a dirty or damaged sensor can disable ABS and illuminate the warning lamp.

Ohm's law

Voltage equals current multiplied by resistance; power in watts equals voltage multiplied by current in a direct-current circuit.

Battery specific gravity

A fully charged lead-acid cell reads about 1.265 specific gravity; 1.120 indicates heavy discharge, and each cell produces about 2.1 volts.

CAN bus terminating resistors

A high-speed CAN bus usually has two 120-ohm terminating resistors in parallel, giving about 60 ohms measured across CAN-H and CAN-L.

Positive fuel trim

Positive fuel trim means the ECU is adding fuel because the mixture is lean; a large long-term positive value suggests a vacuum leak or low fuel pressure.

Compression test variation

Cranking compression should be within about 10 percent across cylinders; a low reading on two adjacent cylinders suggests a head gasket leak.

P0300 diagnostic code

P0300 means random or multiple-cylinder misfire; possible causes include worn spark plugs, vacuum leaks, low fuel pressure or faulty ignition coils.

Parasitic battery draw

Normal key-off parasitic draw is usually below 50 milliamps; a higher draw flattens the battery overnight and is located by fuse-by-fuse current measurement.

Engine oil service interval

Many modern petrol engines use oil change intervals of 5,000 to 10,000 km; severe duty such as short trips requires the shorter interval.

Waste oil disposal

Used engine oil is hazardous waste; store it in labelled closed containers and give it to an authorised recycler, never pour it into drains.

Five S workshop method

Sort, set in order, shine, standardise and sustain; 5S keeps tools traceable, reduces lost time and improves workshop safety.