This is a glossary of commonly-used terms with an emphasis towards the "S12" (Nissan 200 SX / Silvia / Gazelle), as well as some performance and maintenance-related terminology applicable to these cars.
- ANTI-ROLL BAR
A steel rod or tube that connects the right and left suspension members together to resist roll or swaying of the vehicle. An anti-roll bar improves the handling of a vehicle by increasing stability during cornering or evasive maneuvers. Most vehicles have front anti-roll bars. Anti-roll bars at both the front and rear wheels can reduce roll further. See also: SWAY BAR or STABILIZER BAR.
- BOV - Blow-Off Valve
A vaccum-actuated air valve. A blow-off valve or shift valve is a device that allows boost pressure to be relieved from the intercooler hoses when shifting and the throttle blade is closed. This has two benefits:
1. Turbo stays spooled up, there is no compressor slow down due to "stacking".
2. Turbo lives longer due to boost not "stacking" up on the compressor blade.
With a high boost engine stacking can put severe stress on the turbocharger, and significantly hampers spool and thus the performance of the turbo. A blow off valve is NOT used to regulate boost. Turbocharged S12's do NOT come factory-equipped with a BOV. See also: STACKING.
- CLOSED LOOP
Control system that is constantly changing, based on inputs from sensors. See also: OPEN LOOP.
- COMPRESSOR HOUSING
Outer case around the compressor wheel section of turbocharger. See also: TURBOCHARGER.
- COMPRESSOR WHEEL
Fan-like wheel inside of a turbocharger that forces air, under pressure, into the engine's intake manifold. See also: COMPRESSOR HOUSING.
- DETONATION
Also known as "preignition". Explosive, uneven burning of fuel causing engine knock.
In a turbocharged vehicle, this is critical, because the extra added air must be precisely balanced with the proper amount of fuel to cool it, or the friction generated by compressing the air will create too much heat, igniting the fuel prematurely, and resulting in potentially severe damage to the piston, valves, cyllinder wall, head gasket, and an assortment of other components. Sufficient fuel will cool the air inlet charge and prevent detonation. Intercooling also reduced the air inlet charge to help combat this danger. See also: PRE-IGNITION, KNOCK and INTERCOOLER.
- DIFFERENTIAL
A differential allows the right and left wheels to rotate at different RPM. This is necessary because as a car goes around a curve, the outside wheel rotates faster than the inside wheel to "keep up". The differential allows the outside wheel to spin faster to compensate for the greater distance it travels. See also: LSD.
- DOHC - Dual Over-Head Camshaft
Acronym for dual/double overhead cam. The engine has two camshafts that are above the head. These engines do not have push rods, etc., that are typical of non OHC engines (e.g. typical chevy 350). Some Euro/Japanese S12 cars are equipped with a 2.0 L DOHC engine (FJ20ET, not offered in USA), also the famous SR20DET is DOHC (the "D" in DET stands for "DOHC"). See also: SOHC.
- DOWNPIPE
Exhaust piping extending from the exhaust manifold's collector (or the turbocharger's exhaust outlet) to the catalytic converter.
- ECU - Engine Control Unit
The computer that monitors and controls the various engine parameters.
- EGT - Exhaust Gas Temperature
Usually refers to a gauge that displays the temperature perceived by a sensor that is either mounted on the outside of an exhaust manifold/header/etc. or via a probe that internally protrudes into the exhaust path. As fuel leans out, the exhaust temps increase. Likewise, as fuel richens, the exhaust temps increase. For turbocharged cars it is usually best to find normal/acceptable operating temps first before tuning for higher than factory boost.
- EGR - Exhaust Gas Recirculator
An emission-control system that directs some exhaust gases back into the intake manifold to reduce cyllinder temps and the formation of nitrous-oxide (NOx) pollutants. EGRs typically operate off manifold vacuum, and therefore only operate in the off-idle state up to WOT.
- GAZELLE
Another name for S12 chassis vehicles. Sometimes referring to coupe version, with "Silvia" used for hatchbacks. See also: SILVIA and S12.
- INLET AIR TEMPERATURE SENSOR
The device that checks temperature of air entering the engine. Usually located in the Mass Air Sensor.
- INTERCOOLER
Essentially a radiator used to cool the compressed intake air for the engine. The cooled air is denser and can provide more power and also reduces pinging/detonation. Intercoolers are used for both turbocharged and supercharged engines. Most intercoolers are air-to-air type, which means that ambient air is used to cool the compressed intake air. Less common air-to-water intercoolers use engine coolant to shed heat from the intake air. Turbocharged S12's do NOT come factory-equipped with an intercooler.
- KNOCK
Engine noise caused by detonation. See also: DETONATION.
- KNOCK SENSOR
A high-frequency microphone that is factory-tuned to listen for knock in an engine. Usually this signal is monitored by the ECU, usually for the purposes of advancing or retarding timing. See also: KNOCK.
- LSD - Limited-Slip Differential
A special differential that limits the amount of slip (spinning) that will occur on a wheel that has no traction before the other wheel (with traction) begins to move.
- MAF/MAS - Mass-Air-flow Sensor
The device used to measure volume of air being consumed by the engine.
Generally speaking, Mass Airflow measurement is more precise than the speed-density system (Manifold Absolute Pressure, or "MAP") which has been largely replaced in newer automotive designs. Its (MAF) calibration is not affected when mods that change the engines volumetric efficiency are performed.
CA20E-equipped cars (2.0L SOHC non-turbo) have a trap door style that measures the position of a flap that is increasingly forced more open as air flow increases. CA18ET-equipped cars (1.8L SOHC turbo) and VG30E (3.0L V6 SOHC non-turbo) utilize a hot-wire system, where the speed of the air cools a wire in the airpath (depending on air speed), thus changing the resistance in the wire in a measurable amount.
- O2 SENSOR
See: OXYGEN SENSOR.
- OCTANE
A numeric rating of gasoline’s resistance to detonation(premature ignition). The higher the octane number, the less chance of detonation. High octane (above 91) is usually worthwhile only if the manufacturer specifically recommends it. Octane is actually a hydrocarbon(C8H18).
- OPEN LOOP
Control system using preset values in the computer to operate engine. See also: CLOSED LOOP.
- OXYGEN SENSOR
Also called an "O2" sensor. Device that monitors oxygen content in engine exhaust to correct air-fuel ratio. These can be one, two, or three-wire sensors. They are usually mounted in the exhaust manifold or the downpipe. Many turbocharged vehicles mount the O2 sensor in an "O2 housing" that sits between the turbocharger's exhaust outlet and the downpipe. On the S12, CA18ET-equipped cars have the O2 sensor on the O2 housing. For CA20E-equipped cars, it is in the exhaust manifold.
- OVERBOOST
A condition where the positive pressure from the turbocharger exceeds the factory-tuned limitations of the engine and supporting fuel system. Some vehicles have countermeasures to prevent this. See also: POP UP VALVE.
- POP UP VALVE
A safety device on the intake manifold of a CA18ET (turbo) S12 that releases boost when PSI exceeds factory-tuned limits. A spring-loaded door opens when you go above the factory boost. This prevents an "overboost" condition and protects the engine from damage. If you want to go over the factory boost level you must permenantly seal this valve. See also: OVERBOOST.
- PRE-IGNITION
Ignition of fuel before it is fully compressed in the cylinder. See also: DETONATION.
- READING SPARK PLUGS
Determining cause of a problem by examining condition of the spark plug.
- RPM - Revolutions Per Minute
Used to state how fast an object is rotating (e.g. the crankshaft of an internal-combustion engine). The tachometer displays the RPM of the engine of a car.
- RWD - Rear-Wheel Drive
The engine and transmission of a vehicle transfer the power to the ground via the rear wheels.
- S12
The Nissan Motor Corp. chassis designation given to the 200SX, between 1983-1988. For ease of discussion, these cars are simply referred to as "S12". See also: SILVIA and GAZELLE.
- SILVIA
Name given to "S12" chassis-based vehicles in some countries. Called the "200SX" in the United States. See also: GAZELLE and S12.
- SOHC - Single Over-Head Camshaft
An engine with a single camshaft that is mounted over the head. Certain S12 cars are equipped with a 1.8 L SOHC Turbo (CA18ET) or a 2.0 L SOHC non-turbo (CA20E) engine . See also: DOHC.
- STABILIZER BAR
See: ANTI-ROLL BAR
- STACKING
Stacking is when the pressure in the intercooler hose's is greater than the turbo output. This is the noise you hear when you shift with an open element air cleaner, and it's very bad for the turbocharger. It also results in loss of turbocharger spool, meaning the turbo will need to spool back up after each shift. a blow-off valve can eliminate this. See also: BOV.
- SWAY BAR
See: ANTI-ROLL BAR
- TSB - Technical Service Bulletin
Sometimes referred to as "silent recalls". These are service notices that the automaker sends to the dealers to notify them that certain conditions have been experienced by a significant number of owners. They suggest actions that can be taken to try to solve the problem. These are NOT safety recalls; the dealers are not required to perform the service suggested by the TSB for free (or even at all). If you know of a TSB by number, call dealers in your area to be sure they know what you are talking about, before you just drop off your car for a known (at least to this list) service problem.
- TURBOCHARGER
A device that compresses air before the engine receives it. The denser air allows the engine to produce more power. It uses a turbine to drive a compressor. The turbine, driven by hot gases in the exhaust manifold, spins the compressor. The compressor increases the intake air density, and combined with additional fuel, produces more power.
- WOT - Wide-Open Throttle
The throttle plate is open 100%. This is a condition when your right foot (with the accelerator pedal beneath it) is firmly planted on the floorboard of the vehicle.For a more comprehensive glossary of automotive terms, visit oddballautoparts.com's "Glossary of Automotive Terms"
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