A helpful guide to understanding GT4 Forum and general abbreviations used throughout this website:

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  Stands for? In English...
AC Air Conditioning Keeps the cabin area cool. The aircon pump has a clutch which is activated by the ECU. The clutch is used to engage/disengage as and when the aircon is required
AFR Air Fuel Ratio This is the ratio of Air to Fuel. This indicates the efficiency of the combustion process. Lean is dangerous, rich is crap fuel economy and will affect power output, but is safer i.e. less chance of detonation. Max power AFR = ~12.5:1.

14.7:1 is called stoichiometric, and is the AFR used when at light load, part throttle and cruising. This is measured by the lambda sensor that is fitted to all the GT4s

AFR can be referred to as lambda, where an AFR of 14.7:1 = a lambda of 1

A wideband lambda sensor will measure a far greater range of AFRs than the stock lambda sensor

AFM Air Flow Meter Measures the amount of air flowing into the engine and alters the fuelling and ignition timing accordingly. Acts as a large intake restriction!

Fitted to all 165s and 185s, not fitted to the 205, this is fitted with a MAP sensor instead

The AFM houses the air intake temperature sensor. The inlet air temperature sensor is mounted in the plenum chamber on the 205

The CS / RC is fitted with a larger AFM than the 165s and 185s

ARB Anti Roll Bar A metal bar that runs across the width of the car to help prevent body roll when cornering. This is held in place by rubber bushes and attaches to the suspension components at each side of the car

There is a front and rear ARB on all GT4s

ARP Automotive Racing Products A company that makes aftermarket nuts, bolts and studs

Fit ARP fasteners instead of stock kit as the ARP gear is superior - especially the head studs in comparison to stock head bolts

Common items to replace are - head bolts, conrod bolts and flywheel bolts. I personally think that the flywheel bolts are a waste of money...
ATA Air To Air The type of intercooler only found on a 185, in my opinion: poor efficiency due to it's location i.e. it sits above the engine soaking up heat...Much better to put an ATA IC at the front of the car - FMIC

The 185 CS/RC is fitted with a WTA IC
ATF Automatic Transmission Fluid The oil you put in an automatic gearbox

Sometimes used by GT4 Owners to lower the friction losses in the gearbox, BUT gear protection from the oil is lower, click here to find out more

This is not recommended if you want your gearbox to last...
Bar Barometric pressure Pressure measurement. 1 Bar = 14.5psi. For a conversion calculator click here to download (83k)
BB Ball Bearing Normally associated with an aftermarket turbo and their type of shaft support bearing

This arrangement allows the turbo to spin up quicker, and these types of turbo seem to be more efficient in their operation compared to the stock turbo

All stock GT4 turbos have a journal bearing, and therefore 99.9% of hybrid turbos also have a journal bearing
BG Boost Gauge A gauge that tells you the pressure inside the intake manifold

Max pressure for a stock 205 is 1.2 bar - providing it has been well serviced
BGB Big Green Book Toyota repair manual - coloured either green or blue!
BHG Blown Head Gasket A term used to describe that the gasket between the cylinder head and the engine block is leaking. Normally you'll have water in your oil, oil in your water and the car will run like crap

Occasionally this will manifest itself only when the turbo is producing pressure

Some symptoms include over pressurisation of the coolant system, maybe blowing an old radiator or unexplained coolant loss

A chemical test of the cooling water will show if it has been contaminated with exhaust gases or a compression or leak down test

bhp Brake Horse Power The output power of your engine. Derived from torque. bhp is calculated from this formula:

bhp = (torque x rpm)



Note that a dyno plot showing torque and bhp should ALWAYS cross at 5252 rpm. If it doesn't then I would suspect the power figured quoted to be inaccurate

BMC Brake Master Cylinder Occasionally guys add a bracing piece in front of the BMC to prevent movement, with the aspiration of increasing brake performance or "feel"
BOV Blow Off Valve Thing that goes 'tish' when you change gear, same as DV. This helps to prolong turbo life and improve driveability. Click here for an article
BVH Big Valve Head A reference to a cylinder head that has had the valves replaced with larger ones. The 205 head will accommodate +1mm exhaust and inlet valves, but it is touch and go whether the stock valves seats are large enough...

+1mm is currently the largest available valve off the shelf for the 3SGTE engine - ask Ferrea for availability

BVSV Bi-metallic Vacuum Switching Valve Connects carbon canister to intake manifold when the engine has warmed up to vent fuel vapour from the fuel tank
BTDC Before Top Dead Centre Normally measured in degrees. The "distance" the piston is before it reaches Top Dead Centre TDC. Often referred to when setting the ignition timing
CAI Cold Air Intake A fresh air feed to the air filter area. Helps to reduce intake air temperatures and increase output power
Cat Catalytic Converter Unit that converts nasty exhaust gases to harmless gases; vapours and water
CCA Camber Control Arm Used when referring to the 205 Superstrut suspension setup. This arm runs from the front sub assembly to a plate that is bolted onto the bottom of a front hub. Click here for some pictures
CEL Check Engine Light The orange dash warning light. For an article on how to read 165 error codes click here and for 205 error codes click here
CF Carbon Fibre Lightweight material. CF bonnets are available for the 185 and 205. The weight saving on the 205 in minimal since it already comes with an aluminium bonnet...
COR Circuit Opening Relay Fitted to all the GT4s. The fuel pump operation is controlled by the ECU with this relay
CR Compression ratio The ratio of the volume of the engine cylinder when compressed vs uncompressed i.e. volume at top of the stroke vs volume at the bottom of the stroke

165 - 8.5:1
185 - 8.8:1
205 - 8.5:1

The main difference in CR on the 185 is due to a different style piston fitted, click here for some pictures

CS Carlos Sainz A limited edition of the ST185 Celica named after a rally driver

The 185 RC is pretty much the same as the CS, but the Japanese equivalent
CSI Cold Start Injector An additional injector that is activated on starting the car. Controlled via an injector time switch and the ECU, located in the water elbow. Click here for fuel rail and CSI pictures. Not fitted to the 205
DOHC Double Over Head Camshaft 2 camshafts, one to drive the intake valves, the other to drive the exhaust valves. All GT4s are DOHC
DP Down Pipe A bit of pipe that replaces the cat. A 3" pipe is considered to be the best - the Aussie down pipe is probably the best available ~£220

Fitting a larger bore exhaust system can cause over boosting problems, particularly when using a hybrid turbo

DSBC Dual Solenoid Boost Controller Normally quoted regarding the Blitz electronic boost controller. A superb electronic gizmo that allows you to accurately alter the boost pressure electronically from within the car. I recommend the Blitz unit
DV Dump Valve Thing that goes 'tish' when you change gear, same as BOV
Dwell   The amount of time the coil is charged for. Normally measured in milliseconds

Running a high coil charge time may improve spark performance but may cause the coil to overheat

The igniter controls the charging of the coil. It seems that a good time to set for dwell is ~3ms

Programmable ECUs can set this time which normally appears to be in the range of 1 - 5ms

EBC Electronic Boost Controller Device that allows you to twist a knob or push buttons to quickly and accurately set higher than stock boost levels, same as SBC
ECU Engine or Electronic Control Unit Runs a stored program, looks at what the sensors in the engine are saying to it and does "stuff" with that information e.g. fires injectors, put on dash warning lights, limits boost, activates VSVs
EDFC Electronic Damping Force Controller A unit that is made by Tein. This unit attaches to the top of a Tein shock absorber and allows you to adjust the damping level for the shock within the car. You can adjust front and rear independently
EGR Exhaust Gas Recirculation Recirculates some of the exhaust gases back into the intake manifold. This reduces in cylinder temperatures helping to prevent detonation. This also reduces emissions but increases intake temperatures and dumps carbon/crap into the inlet manifold

EGR fitted to UK models, but not fitted to JDM models

EGR helps to prevent detonation as in cylinder temps are reduced

EGR is only active when at a steady rpm

EGT Exhaust Gas Temperature Exhaust temperatures indicate the running condition of an engine. Too hot and you'll start to melt something; normally a piston

EGT sensor best located in either No.2 or No.3 exhaust manifold runner as these run the hottest in a stock 3SGTE engine

EMS Engine Management System The brain that controls the sensors, injectors etc. (same as an ECU)
EPC Electronic Parts Catalogue Software that Mr T uses to find parts. Comes on CDs and has some nice pretty illustrations as well
EWP Electric Water Pump Usually fitted instead of the mechanical engine water pump. Useful to allow coolant to circulate once the engine has been stopped and also to provide a constant coolant flow
FCD Fuel Cut Defencer Gets around the ECU cutting the fuel when the TPS senses approx 12psi, (the exact level varies car to car and model of GT4)

Click here for an article on what is an FCD
FMIC Front Mount Inter Cooler Air To Air IC mounted at the front of the car. No GT4 comes with one of these as standard :(
FPR Fuel Pressure Regulator Used to set the fuel rail pressure. Also allows the rail pressure to increase as boost pressure increases. An adjustable FPR can alter the pressure high enough to negate the requirement for larger injectors. All GT4s are fitted with a linear rising rate FPR located on the fuel rail
FW Fly Wheel Disk of metal that the starter motor turns to start the engine and the clutch bites into when you change gear. A lighter flywheel helps the engine to accelerate faster

A stock flywheel should never be lightened...

HPC High Performance Coating A specially applied heat coating e.g. Aussie down pipe to help stop heat transfer, and help stop it rusting
IAT Inlet Air Temperature Normally used when referring to a device measuring the temperature of the air entering the engine
IC Intercooler Used to reduce air intake temperatures, help prevent detonation, increase air intake density and "reclaim" lost output power. Comes in a variety of flavours and designs. Only the 185 is fitted with an Air To Air intercooler ATA
ISC Idle Stabilisation Control A valve that allows air into the engine when the throttle is closed i.e. when you are idling e.g. at traffic lights. Also affects the idle speed if the power steering is turned, located directly underneath the throttle body. Most noticeable when the car is started when cold as dependant upon temperature the idle is ~1500rpm and gradually reduces to 800rpm when warm

Activating the aircon requires a higher idle speed, and this is achieved with the use of a separate aircon idle up VSV

ITB Independent Throttle Bodies Rather that a single large throttle body, there may be an advantage by fitting one smaller single throttle body per inlet runner that feeds each cylinder
JASMA Japan Automobile Sports Muffler Association Normally embossed on exhaust parts. Seems to be stamped on a part when it reaches a standard, "think" this is a noise emission of <96dB read from a distance of 0.5m away from and at a 45 degree angle to the exhaust exit
JDM Japanese Domestic Market Normally associated with a car from Japan i.e. an import
KS Knock Sensor An Piezo Electric sensor that sends a voltage to the ECU proportional to the amount of knock - for knock read detonation

Click here for KS sensor pictures and here for an article on detonation
MAP Manifold Air Pressure A sensor installed only on the 205 in order to measure "air flow"

A MAP sensor replaced the AFM on both the 165 and 185. This type of sensor is a much better alternative as this offers no restriction to air flow through into the engine, whereas the AFM represents a significant "obstruction"
MAT Manifold Air Temperature A sensor is mounted in the inlet manifold to measure the temperature of incoming air, (205 only).  Sensor measures the temperature of the incoming air so that the ECU can alter ignition and fuelling to suit. Colder air = more fuel

The 165 and 185 measure the inlet air temperature through a sensor located in the AFM

MHG Metal Head Gasket A gasket that fits between the cylinder head and the engine block. Made from layers of metal, much better than the standard 165/185 gasket. Fit one of these when the stock paper gasket blows or when you want to run high boost levels >15psi - ish

Comes in various sizes e.g. 1.0mm, 1.2mm, 1.4mm, 1.6mm

Fitted as standard on the 205 only. The TTE and HKS gaskets are considered to be some of the best available
Mr T Toyota The dealer where you buy your stock parts
NA Normally Aspirated A car that isn't turbocharged or supercharged
PCD Pitch Circle Diameter The circle diameter on which holes lie i.e. if you drawn a circle connecting up the centre of a load of holes then the PCD will be the diameter of this circle. Normally referred to when fiddling about with alloy wheels
PCV Positive Crankcase Ventilation Some gases will seep past your pistons and valves while the engine is running. To stop any build up of the gases within the engine, they are allowed to escape - normally fed back into the air intake

Only the 205 was fitted with a PCV catch can as standard. There appears to be a performance advantage when feeding the PCV system back to the intake i.e. not vented to atmosphere

The purpose of the PCV catch can is to trap and stop any oil mist from re-entering the engine via the intake system

Some owners vent this to atmosphere but it is not recommended on a standard car

PFC Apex'i Power FC A direct replacement programmable ECU for the 205. There was a rare 185 ECU produced. Several variants seem to be in existence e.g. AP Engineering - the one to fit for the 205

A very easy ECU to fit, simply unplug old and plug this ECU in!

psi Pounds per Square Inch Pressure measurement. 14.5psi = 1 Bar. For a conversion calculator click here to download (83k)
PU PolyUrethane The material that replacement suspension bushes are normally made from. Harder than rubber bushes, thereby improving handling

These are usually fitted to the ARBs and the suspension arms
RON Research Octane Number A scale from 0 - 100 indicating the fuel's resistance to knocking

Shell Optimax is the highest rated RON in the UK - 98, BP Ultimate - 97

Race fuel usually has a higher RON than is available from the pumps...
rpm Revolutions Per Minute A measure of how fast the engine is rotating
RC Rally Champion The Jap version of the 185 CS
RR Rolling Road Place that simulates your car driving along at speed. Car driven onto a set of "rollers" which allow the wheels to turn. You can get a readout of engine output power. Later you can use it to tune up your car as it is accelerating under load...
RV Relief Valve Goes between the turbo housing and the wastegate to cheaply alter boost pressure levels and therefore performance. Click here for an article. Very similar to a Dawes Device

This device is a little agricultural and the RV does suffer from stiction when cold, due to small amounts of oil within the inlet system. This oil film coats the ball bearing and mating surface and aids to retain the ball bearing on its seat, thereby  producing boost spikes

SBC Solenoid Boost Controller A thing that enables you to twist a knob or push a button to quickly and accurately set higher than stock boost levels, same as EBC
SLD Speed Limit Defencer Normally associated with JDM models. This electronic gizmo overcomes the factory imposed maximum speed restriction of 118mph... Popular models are manufactured by HKS and GReddy
SS or SSS Superstrut Suspension The type of suspension fitted only to the ST205. Click here for a how to change the front suspension and click here for an explanation

This type of suspension is only found on Toyotas and has been used on the ST202 and Levin
TB Throttle Body Allows you to rev the car - controls the amount of air flowing into the engine. Ultimately controlled by your right foot! A sensor is attached to the side of this, (the TPS), which sends an electrical signal to the ECU to say how far the throttle is open and if it is shut or WOT. See also ITB
TCB Toyota Celica Breakers Located down in Cornwall UK, they specialise in breaking MR2s, Supras and Celicas. If you need a part why not ask them? These guys can also supply brand new genuine Toyota parts e.g. 205 suspension, radiators and diff mounts, try them!
TDC Top Dead Centre This is where the physical position of a piston is exactly at the top of the cylinder/top of it's stroke. This normally refers to No 1 piston. No 1 is closest to the cambelt
TLA Three Letter Abbreviation :-)
TMIC Top Mount Inter Cooler Normally associated with the 185 air to air IC that is fitted directly above the engine
TPS Throttle Position Sensor Informs the ECU on the position of the throttle. Note the Turbo Pressure Sensor shares the same acronym
TPS Turbo Pressure Sensor Senses the pressure in the intake manifold, makes the console boost gauge move - (may also affect fuelling and/or ignition timing on the 165/185)

On the 205 this is used to determine fuelling and ignition timing. Can be confused with the Throttle Position Sensor acronym. The TPS should not be played with on the 205 without detailed knowledge as engine damage is likely to result

TRD Toyota Racing Development TRD is the racing factory for Toyota. They help develop Toyota's cars and engines
TTE Toyota Team Europe Racing division of Toyota, now renamed Toyota Motorsport GmbH - very catchy, eh?!?
TVIS Toyota Variable Induction System A set of butterfly valves that open and close in the intake manifold, allegedly increasing low rpm pull - don't think it does anything except make things complicated and cramped in the engine bay...

The 165s and 185s are all fitted with TVIS, the 205 is not

Click here for an article
TVSV Turbo Vacuum Switching Valve Allows an extra ~2psi of boost pressure in different gears i.e.

Stock 165/185
1st - 7psi
2nd - 7psi
3rd+ - 9psi

Stock 205
1st - 11psi
2nd+ - 13psi

This is normally disabled when using an SBC.

Click here for an article

VOR Vehicle Off Road Used by the Toyota parts guys to hurry up spare parts. If you say VOR to the parts dept then they should hasten delivery of your important new shiny bit to 1 day instead of the normal 2 days...
VPC Vein Pressure Converter An electronic gizmo manufactured by HKS to replace the restrictive AFM to help produce more power. Only fitted to 165s and 205s
VSV Vacuum Switching Valve Normally a signal from the ECU activates this unit which is normally used to route air to/from somewhere. E.g. ECU sends a signal to the Fuel Pressure Regulator VSV and causes air to raise the fuel rail pressure. VSVs are fitted to all sorts of things in the engine. Commonly measuring 30 ohms resistance
WAI Water Air Intercooler The type of intercooler fitted to the 165, 185 CS/RC and the 205. Same as a WTA
WI Water Injection Sprays a very fine mist of water into the intake manifold to cool the intake air temperatures. Mainly used to help prevent detonation

The 205WRC was fitted with a deactivated WI system, click here for an article

WOT Wide Open Throttle When your foot is flat to the floor this signal is sent from the Throttle Position Sensor to the ECU to indicate that the throttle body is fully open
WRC World Rally Champ This is normally used to denote the special version of the 205. This is also known as the "Group A" variant in countries outside of the UK

Click here for an article showing some of the special features of the ST205WRC

WTA Water To Air Type of intercooler used on the 165, 185CS, 185RC and the 205 GT4s.

Click here for some pictures