924:
The Porsche 924 was introduced in 1976 to replace the aging 914. Well, it did not truely replace it, but it filled its place as the entry level Porsche. It came with a 2.0L engine that produced 125hp which was coupled to a 4 speed manual transmission. The engine consited of a cast iron block with an aluminum head. For the time this was quite a competitive sports car. It was introduced to North America as a 1977 model year. However, the North America spec 924 only produced 100hp. This was just too little for US enthusiasts. It was called slow, but at the same time it's handling was held in high regard.
This is because Porsche had been able to give the car a perfect 50%-front/50%-rear weight distribution. Thankfully the power output was raised mid year in 1977 to 115hp. Its power output would remain the same, accept for the Turbo model that was intorduced in 1979 and produced 170hp. The 924 Turbo came standard with 4-wheel discs. Accept in North American where it only came standard with them for 1981 and 1982. A 5 speed manual transmission was also introduced in 1979 for both the Turbo, and Normally Aspirated models. This was quite something and was concidered very fast. The 924 would remain in production until 1983 when it was replaced by the 944 (1982 was the last year of production).
944:
The 944 replaced the 924, but merely supplemented it in Europe. The European 944 produced 163hp and was introduced in 1982. The North American 944 only produced 150hp and was introduced in 1983, however, for the time this was an impressive output. The early 944 was very similar to the 924. It shared the same interior. Also, the suspension and transmission were very similar in design. Like the later 924 Turbos, the 944 came standard with 4 wheel disc brakes. Also like the later 924s, the 944 had a 5-speed manual transmission, and the option to get a 3-speed automatic. Even the chassis was basically the same, with the addition of flared fenders and quarter panels.
The 944 underwent a makeover in the middle year of 1985. The intereor was updated to a more 911 like style. Also, the engine management and suspension were updated. At the same time a turbo model was introduced in Europe. In North America it was introduced as a 1986 model year. The 944 Turbo came with a whopping 217hp. It also came with upgraded brakes and suspension.
In 1987 the 944 underwent yet another suspension change to accomidate and Anti-Lock-Braking system (ABS). In actuallity the design did not change, but the wheel offset changed. In the same year the 944S was introduced. The 944S produced 188hp through the addition of 4-valves per cylinder. Other than that it was a plane old (non-Turbo) 2.5L 944. The 944S would only stay in production for 2 years. Also that year, Porsche introduced the 924S. It was a 924 chassie with a 944 drive train in it.
In 1988 Porsche offered an "S" package for the 944 Turbo. It included a Limited Slip Differential and sport suspension package as standard equipment, while also providing a hourse power boost to 247hp. The 944 Turbo S would become the standard turbo for 1989, which was the last year it was brough into North America. It would continue in production through 1991 in Europe.
In 1989 the 944S2 was introduced. It had a 208hp 3.0L engine that had 4-valves per cylinder. It shared the 944 Turbo suspension and brakes.
968:
The replaced the 944 line of cars in 1992. It was basically a 944 with a few changes. It has different body panels that gives it an appearance closer to the 928. On a technical note, it had a 3.0L engine that produced 236hp. It was based on the 944S2 engine but gained the extra hourse power through the use of Porsche's variable valve timing system called Variocam. Also it was offered with either a 6-speed manual transmission or a 4 speed automatic "tiptronic".
Sadly the 968 left production after the model year of 1995, it left with the other front engine, water cooled Porsche, the 928.
For more information:
The Main 924/944/968 FAQ: http://www.connactivity.com/~kgross/944faq.html