Glossary - Subaru and VW terminology:
AVCS - Subaru’s variable valve timing system, which alters the phasing of the inlet cams hydraulically - as used on some STi turbo’s and Japanese spec Legacy Lancaster 2.5 quad cam models (->1999)
Bellhousing – a term for a removable housing around the clutch on a manual gearbox, around the torque converter on an automatic gearbox, or around the flywheel / torque converter drive plate on an engine. Typically a casting, vaguely bell shaped. Starter motors are often attached to the bellhousing, on the transmission side in both VW and Subaru terms.
Boxer – Subaru’s overhead cam engine, first fitted in 1990, was called ‘Boxer’ by Subaru (confusing as all their horizontally opposed engines are ‘boxer’ engines – it’s a generic term for horizontally opposed).
Closed Deck - the stronger Subaru engine blocks in which the cylinder liners are more rigidly attached to the surrounding water jacket in the cylinder head flange area - as used in all(?) Subaru turbo engine. Closed deck blocks were originally an homologation only feature, as fitted to Japanese spec 280 bhp Impreza’s
DOHC - Double Overhead Cam - giving four cams in a horizontally opposed engine (Quad Cam) - as used in most Subaru Turbo’s and all EJ25’s --> 2000
Dual Mass Flywheel - a type of flywheel where the rotating mass is split into two pieces. These are joined by a damping mechanism to disperse torsional vibration from the crank shaft. As used on naturally aspirated EJ 20 and EJ 25 Subaru engines from about 1998 ->. Unfortunately the dual mass flywheels are not as strong as the single mass equivalents.
EG33 - Subaru designation for the 3.3 litre engine from the SVX
EJ22 (or 16, 18, 20, or 25) - Subaru designation for the 1990 -> flat four range, the two digits indicating the engine capacity.
EZ30 (or EZ30R) - Subaru designation for the 2000 -> flat six three litre engine. EZ30R is the 2004 --> version, and has many minor differences from the EZ30
H4 – Subaru terminology for their horizontally opposed four cylinder engines.
H6 – Subaru terminology for their horizontally opposed six cylinder engines.
MYXX - Subaru terminology for model year is MY followed by the last two digits of the year - e.g. MY98 = 1998 model year. Useful as it avoids confusion with registration year.
Open Deck - the more easily manufactured but less strong design of join between the cylinder liners and the surrounding water jacket - as used in most naturally aspirated Subaru engines
Pull Clutch - A clutch in which the centre of the diaphragm spring needs to be pulled away from the crank shaft to disengage drive. Allows a higher torque capacity for the same pressure plate diameter As used on all Subaru Turbo’s (and Porsches)
Push Clutch - A clutch in which the centre of the diaphragm spring needs to be pushed towards the crank shaft to disengage drive. Standard on most cars, including all naturally aspirated Subaru’s and VW’s
SOHC - Single Overhead Cam - i.e. twin cam in a horizontally opposed engine
Syncro - the VW invented viscous coupling, two differential four wheel drive system used on T25 from 1986 --> 1992 - developed on Bay Windows for a military contract in the 1970’s
T25 - UK terminology for a Vanagon / T3 / Wedge, etc. - from the ‘025’ part number prefix
T3 - European name for a T25 / Wedge / Vanagon etc. - Why do they call them ‘T3’s? isn’t the type the is a Fastback / Squareback / Nothcback?
Transaxle - a combined gearbox and final drive, particularly where the final drive unit sits between the engine and gearbox. As used in all rear engined VW’s
Vanagon - US name for a T25 / T3 / Wedge, etc.
VSS - Vehicle Speed Signal. A signal with a frequency proportional to the vehicle speed. Used by many but not all Subaru ECU’s, and all Subaru speedometers and odometers
VVT - Variable Valve Timing
Wasserboxer - the water cooled VW flat four engine, infamous for having steel cylinder head studs going through the coolant, which rust and snap
WBX - short for ‘wasserboxer’, the water cooled VW flat four engine, infamous for having steel cylinder head studs going through the coolant, which rust and snap
Water Manifold - Subaru engines have a manifold on the top of the engine which combines the hot coolant exiting from each half of the engine into a single pipe (to the radiator)