Subaru Impreza WRX STI Engine History

The introduction of the Impreza line began with Subaru in 1993. Subaru’s main goals when producing this vehicle were to help fill a gap in the small car market initially; later in its life Subaru changed its goals to become dominant in rally race scenes. The power to weight ratio of the Impreza when a combination of the fairly small, light chassis and the boxer styled four cylinder Subaru engine made it instantly successful in the rally races. Each year brought new revisions to the Subaru engines, ramping up power while still keeping the lighter chassis making it a dominating force when on the track.

The first versions of the Impreza were offered in either front wheel drive or an all wheel drive configuration. It was available in either a four door sedan or a five door station wagon/estate. Initially the Subaru engine offered was a 1.8 flat 4 cylinder known as the EJ18. This was followed quickly with the addition of the 1.6 litter version. Subaru chose to stay with the same basic design of the engine known as the flat four cylinder (or boxer) engine as they believed that by keeping the engine on a low centre of gravity, in line with the transmission, minimised body roll as compared to vehicles with offset engines. Another bonus to this design is that it also eliminated the need for a weighted counter rotating crankshaft. Since each piston is counter weighted by the opposing piston directly opposite while the engine is running. The 1.6 and 1.8 engines were dropped from production in 1996 and replaced with the now common 2.0 litre.

Subaru then introduced the STI(Subaru Technica International) version of the Impreza into the Japanese Domestic Market or JDM as it is more commonly known, in 1994. The STI was an upgraded version of the Impreza WRX models currently available. The STI came equipped with performance tuned suspensions, engines and transmissions. The STI was immediately successful in rallies and was sought after by street racers. There was even an option to order special RA (Race Altered) versions direct from the manufacturer which were modified by being lighter in weight, having reduced sound proofing, manual window mechanisms, omitting the air conditioning and coming equipped with more robust engines, shorter gearing and driver controlled center differentials.

The Impreza model received an external facelift in 1997, this was followed by an internal redesign incorporating the more advanced dashboard from the Forester in 1998. Further upgrades were found on the European models in 1999-2000. These upgrades included making parts from the STI range standard, front brake callipers were now four pot with 294mm brake discs, wheels were upgraded from 15 inch to 16 inch, they added vented rear disc brakes, a firmer suspension and bucket seats.

The beginning of 2001 saw the introduction of the second generation of the Subaru Impreza. The body style was larger, safer, more refined, the suspension was stiffer and more responsive. Many Subaru owners use nicknames for their vehicles based on the headlights they came with. In 2002-2003 the headlights became known as “bug eyes”, these were followed in the 2004-2005 “crocodile eye” versions also known as “blob eyes” and then finally in 2006-2007 the headlight configuration was to be known as “hawk eyes”.
The engines and body styles available through the years are as follows:

1993-2001

Body Style Available:

1. door coupe
2. door sedan
3. door estate

Engines Available:

1. 1.8 110hp
2. 2.0 turbo 208-280hp
3. 2.2 145hp
4. 2.5 155hp

2002-2007

Body Style Available:

1. door sedan
2. door estate

Engines Available:

1. 1.5 125hp
2. 2.0 125hp
3. 2.5 165hp
4. 2.5 173hp
5. 2.0 turbo 227hp
6. 2.5 turbo 300hp

2008-Present

Body Style Available:

1. door sedan
2. door estate

Engines Available:

1. 1.5 107hp
2. 2.0 150hp
3. 2.5 170hp
4. 2.5 turbo 224hp
5. 2.5 turbo 265hp
6. 2.5 turbo 305hp
7. 2.0 turbo diesel 148hp