FAQ Library


Terms in glossary: 34

Unit of pressure. 1 bar = 1 atmosphere, or approximately 14.5 Pounds per Square Inch (PSI).

Blow Off Valve (BOV)
Mounts between the turbo and the throttle body, allows excess boost pressure to be released when the throttle plate closes when you let off to shift or slow down.. makes that nice sound, and prevents compressor damage from a sudden wave of high pressure smacking into the turbo trying to force it backwards.

Bypass Valve (BPV)
Same thing as a BOV, only the air isn't vented to the engine bay, it's vented to PAST the throttle body. Not only does it not make a noise, but it's needed for cars using a MAF sensor, so that all "air in the system can be explained" Cars that use MAF and BOV's stutter/stall when the BOV goes off.

Catalytic Converter (Cat)
Scrubs excess emissions causing chemicals from you're exhaust and excess fuel via more voodoo you don't need to know.

Distributorless Ignition System (DIS)
A ignition system without a distributor, a fully computerized ignition system. Digital if you will. all j-bodies after like 90ish are DIS.

Downpipe (DP)
Bolts to the turbo, then to the exhaust. It's the "intermediate" usually it's cast iron.

Electronic Boost Controller (EBC)
Just like a MBC, but computer controlled. All stock turbo cars after the mid eighties have these.

Electronic Control Module (ECM)
THE BRAIN! This baby does it all! It monitors the engine and transmission and makes everything work together. For example, it will check the vehicle speed, RPM, throttle position and tell the transmission when to do a 2-3 upshift or downshift when necessary. It also logs trouble codes if there's a problem.

Exhaust Gas Recirculation System (EGR)
Takes a small amount of exhaust gas from combustion, at high throttle, and feeds it back into the intake, to "cool" the combustion temp off so that NoX (nitrosomething of Oxygen aka Greenhouse Gas) cant' form. J-bodies after 2000 don't have these (thank god). It also reduces detonation when the engine is stock (there are better ways to fight it).

Exhaust Manifold (E/M)
Bolts to the head, directs exhaust air out. duh.

Fuel Management Unit (FMU)
A piggy back FPR or sorts that raises fuel pressure based on boost. It's a handicap for turbo cars with improper fuel systems for running happy amounts of boost.

Fuel Pressure Regulator (FPR)
Regulates the pressure of fuel to a constant level to maintain fuel rail pressure for the injectors. It's the little can on your fuel rail.

With an adjustable FPR you can change the pressure setting. Also, some factory boosted cars have a vacuum line running to their FPR that raises fuel pressure based on Boost pressure. Also called a "rising rate" FPR.

Intake Air Temperature (IAT)
Measures the temperature of the intake air, is used in fueling calcs by the ECM.

Intercooler (I/C)
A "radiator for air" that absorbs intake air heat to cool down the hot air charge from the turbo. There are several types of I/C's but this isn't the pace to discuss them.

Metric unit of pressure. 100 Kpa is equivalent to 1 BAR.

Limited Slip Differential (LSD)
Locks both tires when accelerating in a straight line, so that not just one tire is gripping the road. Better ones even lock in turns at lower speeds. These give you better traction.

Manifold Air Pressure Sensor (MAP)
Also called Manifold Absolute Pressure. Measures the pressure OR vacuum of the intake air. These are used as the primary means of measuring air in "Speed density" style fuel injected cars, like j-bodies.

Manual Boost Controller (MBC)
A simple twist valve normally, that changes the amount of boost pressure required before pressure is sent to the wastegate, thus opening it. this is used to actually SET maximum boost.

Mass Airflow Sensor (MAF)
The "modern alternative" for MAP's, this actually measures the amount of ACTUAL air entering an engine via weird technical voodoo you don't want me to explain. You don't have this, forget you heard of it.

Multiport Fuel Injection (MPFI)
In this system each cylinder has number of injectors (usually one) to supply/spray fuel in the cylinders as compared to one injector located centrally to supply/spray fuel in case of single point injection system.

Normal Band O2 (O2 or NBO2)
What j-bodies normally have. these measure a/f on 0-1 volt scale, and it's very UNLINEAR, that is to say it gets very unaccurate when measuring anything other then perfect A/F.

Port and Polish (P&P)
To smooth the ports in a cylinder head, to enlarge them slightly, to make the air enter the combustion chamber smoother, and to put a mirror polish on the exhaust ports and a rougher one on the intake ports. Why? That's another lesson.

Port Fuel Injection (PFI)
Generic name for MPFI. All j-bodies after 90ish have some form of MPFI.

Powertrain Control Module (PCM)
See ECM.

Sequential Fuel Injection (SFI)
Another type of MPFI.

Tachometer (Tach)
Measures engine RPM.

Throttle Body (TB)
The throttle body is the throat through which the air passes when you step on the gas pedal. The throttle plate is a steel "flap" that lets air in. The gas pedal is connected to the throttle plate, and it opens and closes based on how far the gas pedal is pressed.

Throttle Body Injection (TBI)
A type of electronic fuel injection system that uses a single injector or pair of injectors mounted in a centrally located throttle body. The throttle unit resembles a carburetor except that there is no fuel bowl, float or metering jets. Fuel is sprayed directly into the throttle bore(s) by the injector(s).

Torque Converter (T/C)
The automatic tranny equivilent of a clutch (damn I'm oversimplifying).

Turbo Manifold (T/M)
Bolts to the head, directs exhaust air into the turbo. duh.

Vacuum (Vac)
What you're engine is under, when it isn't boosted.

Vehicle Speed Sensor (VSS)
The Vehicle Speed Sensor (VSS) is a sensor in the transaxle which sends a signal to the PCM, which the PCM converts to Kilometers Per Hour (km/h) and Miles Per Hour (MPH).

Wastegate (WG)
Limits maximum boost by allowing some exhaust gas to bypass the turbo, can either be external to the turbo (looks like a BOV) or internal (is a flapper door). Externals generally allow for higher boost levels without "creep" where maximum boost slowly get's higher.

Wide Band Oxygen Sensor (WB or WBO2)
0-5 volts range, linear scale, for measure A/F ratios very accurately, Dynos and serious tuners and smart people use these ;-) can be found stock on some uber-low emmisions cars (read honda's toyotas, etc). Costs about 100 bucks per sensor.