Glossary of Engine terms (A-F up)
 

****As mentioned in the Engine Theory and Construction thread, i am putting together a glossary of terms. As with the other thread, this one will be a work in progress as well, but it won't be nearly as long as the other one will take. Some of these will be repeated in driveability. If you don't see a term here that you are confused about, it may show up in driveability as many of them pertain more to that subject than the engine. Until then, please ask about it via PM.****

A

Aftercooler- A heat exchanger that cools charge air between the Turbocharger or Supercharger and the intake manifold.

Anti-drainback valve- A valve in a horizontaly affixed oil filter which prevents the oil from draining out when the engine is switched off.

Atomization- the name of the process by which the fuel is suspended in the air in a mist of tiny droplets, like a fog.

[size=6]B

Base circle- What the cam would be without it's lobe.

Base timing- The ignition timing set before the computer starts making changes

Bimetal engine- An engine constructed of an iron block and an aluminum head.

Block-test- a test for an internal coolant leak in which a dye changes colors when exposed to exhaust gasses in the radiator

Blow-by gasses- gases that leak past the piston rings during the power stroke. These gasses contain acids as well as burned and unburned fuel.

Blow through- when a supercharger pressurizes the air cleaner above the carburetor

Blower- A belt driven airpump, also called a supercharger

Boost Pressure- The measurement of the air density a turbo/supercharger provides

Bore- The diameter of the cylinder

Bottom Dead Center (BDC) The bottom most point of the piston's travel before it begins traveling back up in the cylinder.

Brake Horsepower (BHP)- The usable horsepower at the crankshaft

Brake Thermal Efficiency- Brake Horsepower converted to BTUs, divided by fuel heat input in BTUs, with the result multiplied by 100

Butterfly valve- a valve that controls air flow

Bypass oil filter- also called a Partial Flow oil filter, filters only 10% of the oil at a time trapping very fine particles and allowing very little oil to flow through it.

Bypass valve- A valve in the oil filter that opend to allow oil past the filter element when the oil is cold and thick or the filter element is clogged due to poor maintenance.

[size=18]C

C.I. engine- A diesel compression ignition engine

cam ground piston- When a piston's skirt is oval shaped. As it warms up it becomes round.

Carbonaceous deposits- Also called cauliflower deposits, are thin hard carbon deposits caused by fuel

Carburetor- A mechanical device that mixes fuel and air in response to the amount of air coming into it.

Centrifigal Advance a device that senses engien speed and advances ignition timing accordingly

Coil Saturation When a magnetic field has finished it's buildup inside the coil.

Companion Cylinders Two cylinders that come to TDC and BDC togehter.

Compression Pressure The amount of pressure created by the piston moving up in the cylinder

Compression Ratio the difference in cylinder volume with the piston at BDC and TDC

Compression Test A test in which a pressure guage is installed in the spark plug hole and measures the cylinder pressure as the engine is cranked

Coolant also called anti-freeze. A mixture of water and Ethylene Glycol used instead of pure water in the cooling system

coolant hydrometer a tool that measures the weight of the coolant mixture against pure water to determine it's strength

Crankcase the area surrounding the crankshaft

Cross fluid contamination when oil and coolant are mixed

Cross fire induction when one sparkplug wire induces an adjacent plug wire to fire before it's time

Crossflow Head a cylinder head that has it's intake and exhaust ports on opposite sides of an inline engine

[b]Crossflow radiator[b] a radiator design where collant flows from side to side

[b]Crosshatch[b] the crisscross finish that is left when a cylinder is honed

Crusie a state of engine operation where the engine is maintaining speed

Custom Rebuild when an engine is rebuilt as a unit instead of being assembled from a variety of parts.

Cylinder bank a row of cylinders

Cylinder Glaze when the area where the rings ride in the cylinder takes a glazed appearance

Cylinder leakage test a test where regulated air is introduced to the cylinder through the spark plug hole to determine it's sealing capabilities

Cylinder power balance test a test where a spark to a cylinder is shorted out resulting in a drop in engine rpm

D

Detonation self ignition due to excess cylinder pressure

detonation sensor also called a knock sensor. peizo-electric sensor that picks up abnormal combustion through vibration frequency through the block.

dieseling also called run-on. The engine continues to run after the key is shut off through excessive cylinder pressure.

Displacement Volume the piston displaces between TDC and BDC

DOHC Dual OverHead Cam

Downflow Radiator a radiator design where coolant flows from top to bottom

Draw-Through where a super/turbocharger pressureizes air after the carburetor or air filter

Dry Start where the crank rubs on the bearings before oil reaches them

Duration amount of degrees that the crank travels while the valve is off it's seat

Dual plane manifold when each barrel supplies half the engine's cylinders

Dwell The amount in degrees of distributor rotates while the primary current is flowing to the ignition coil primary winding

E

End Gap The gap between piston ring ends when installed in the cylinder

End play back and forth clearance

End thrust side to side or front to rear force against a shaft

Engine Displacement determined by multiplying cylinder displacement by number of cylinders

Engine Kit parts sold togetehr as a group for rebuilding an engine

Engine Knocks noises that are caused by excessive clearance between parts or abnormal combustion in the cylinder

exhaust backpressure resistance to an engine's air flow caused by restrictions to the exhaust flow

F

[b]fan clutch[b] A temprature or torque sensitive device attatched to a belt driven cooling fan

firing order The order in which the sparkplugs fire in a multi cylinder engine

flat cam When a cam lobe wears out

flooding when an engine takes in too much fuel to support combustion

fouling When a spark plug is saturated with fuel or oil, or the gap is bridged by carbon

four corner scuffing Piston damage that occurs due to external cause such as mixture problems

four stroke cycle also called the Otto-cycle. Intake, Compression, Power, Exhaust

freewheeling engine An engine that will not experience piston to valve contact if the timing belt or chain breaks

full flow oil filter a filtering system designed to flow all the oil supplied by the pump to the oil filter o nit's way to the engine bearings