MITO Heavy Auto L4 flashcards

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

Compression ignition principle

In a diesel engine, intake air is compressed to a high ratio, heating it to several hundred degrees, and fuel injected near top dead centre self-ignites without a spark plug.

Common-rail injection

A high-pressure pump charges a shared rail; the engine control unit then opens each injector independently, separating pressure generation from injection timing and allowing multiple injections per cycle.

Stoichiometric diesel ratio

Complete combustion of diesel needs roughly 14.5 parts air to one part fuel by mass. Less air produces black smoke; excess unburnt fuel can raise exhaust temperature and dilute engine oil.

Black exhaust smoke

Black smoke signals incomplete combustion from too much fuel or too little air, pointing to a restricted intake, a leaking charge-air cooler, or injectors delivering excess fuel.

White exhaust smoke

White smoke is unburnt fuel vapour, typical of cold starts, low compression, retarded injection timing, or coolant entering the cylinder through a failed head gasket.

Blue exhaust smoke

Blue smoke indicates lubricating oil burning in the cylinder, commonly from worn valve guides, worn piston rings, or a failed turbocharger seal allowing oil into the intake.

OBD-II code prefixes

The first character of a diagnostic trouble code names the system: P for powertrain, B for body, C for chassis, and U for in-vehicle network communication faults.

Voltage drop testing

Measuring voltage across a cable or ground while current flows. A reading approaching zero volts means low resistance; a measurable drop reveals corrosion or a poor connection.

Torque-to-yield bolts

Cylinder head bolts tightened past their elastic limit stretch permanently and clamp the gasket by spring tension. They must be replaced at every teardown and never reused.

Hygroscopic brake fluid

Glycol-based brake fluid absorbs moisture from the air, which lowers its boiling point and risks vapour lock under heavy braking, so fluid is replaced on a time schedule.

Pressurised cooling system

A spring-loaded radiator cap raises coolant boiling point by roughly three degrees Celsius per ten kilopascals, letting the engine run hotter without boiling; a weak cap causes loaded overheating.

Ohm's law and power

Voltage equals current times resistance, and electrical power equals voltage times current. These two relations let a technician calculate expected current and resistance from measured values.

Glow plug function

A glow plug heats the combustion chamber before a cold start so diesel fuel vaporises and ignites reliably; failed plugs cause hard starting, rough idle, and white smoke when cold.

Turbocharger wastegate

A wastegate bypasses exhaust gas around the turbine once target boost is reached, limiting turbine speed and intake pressure to protect the engine from over-boost.

EGR valve purpose

Exhaust gas recirculation returns a portion of exhaust to the intake, lowering combustion temperature and reducing nitrogen oxide formation; a stuck valve causes rough running or excess smoke.

Diesel particulate filter

A DPF traps soot from the exhaust and burns it off during regeneration at high temperature. Short-stop urban duty cycles prevent regeneration and lead to blockage and derate.

Braking distance scaling

Braking distance grows with the square of speed, so doubling speed roughly quadruples the distance needed to stop, while reaction distance grows only linearly with speed.

Total stopping distance

The sum of perception and reaction distance plus braking distance. It depends on driver alertness, speed, road grip, and brake condition, not on vehicle size alone.

Payload calculation

Payload equals permissible gross vehicle mass minus kerb mass, then minus the mass of driver, fuel, and fitted accessories. Axle limits may reduce allowable payload further.

Axle load limit

Each axle has its own maximum permitted mass. A vehicle can be legal on gross weight yet illegal because one axle, often the drive or trailer axle, is overloaded.

Load friction coefficient

Friction between cargo and deck resists sliding. Wood on steel gives roughly 0.2, so most restraint must come from lashings; rubber on dry asphalt gives far more.

Load lashing force

Required lashing force equals cargo mass times the acceleration coefficient, usually 0.5, minus the friction contribution. Lashings are sized and counted from this figure.

Load centre of gravity

A high centre of gravity shortens the lever arm resisting rollover, lowering the lateral acceleration a vehicle can take before tipping, so cornering speed must drop.

Air brake leak-down test

With the engine off and service brakes applied, system pressure must not fall faster than the specified limit; excessive leak-down means a leak that could exhaust reserve pressure.

Low pressure warning

An air brake vehicle must warn the driver audibly and visibly before reserve pressure is exhausted, giving time to stop safely if the compressor or a circuit fails.

Daily walkaround check

A documented pre-trip inspection of tyres, brakes, lights, coupling, load restraints, and fluids. Any dangerous defect prohibits dispatch until it is repaired and recorded.

Tachograph manual entry

Periods when a driver card was not inserted, such as yard work or a break, must be entered manually so the record stays complete and legally defensible.

Driving break rule

Many jurisdictions require a break after a continuous driving block, for example 45 minutes after 4.5 hours in EU rules, with daily and weekly driving maxima on top.

Operator liability

Transport operators share legal responsibility for driver hours, vehicle condition, and load security. Scheduling that pressures drivers to breach rules can make the company liable.

Hazardous goods placarding

Vehicles carrying dangerous goods display placards matching the hazard classes aboard, carry a transport document, and follow segregation rules preventing incompatible loads.

Fifth wheel coupling check

After coupling, a pull test with the trailer brake applied confirms the kingpin is locked; a high hook or open jaw is caught this way before it separates on the road.

Tyre tread and pressure

Legal minimum tread depth and correct cold inflation are checked at every walkaround. Under-inflation raises tyre temperature and risks a blowout under full load.

Rollover threshold

The lateral acceleration at which a vehicle tips, set by track width and centre of gravity height. Loading high or on one side lowers it and demands slower cornering.

Jake brake use

An engine compression brake slows the vehicle on descents without heating the service brakes, preventing fade; it is often restricted in built-up areas for noise reasons.