Porsche executives soon recognised the need for a higher performance version of the 924 that could bridge the gap between the basic 924 and the 911’s. Having already found the benefits of turbochargers on several race cars and the 1975 911 Turbo, Porsche chose to use this technology for the 924, eventually introducing the 924 Turbo in 1978.
Porsche started with the same Audi sourced 2.0 L I4, designed an all new cylinder head which was hand assembled at Stuttgart, dropped the compression to 7.5:1 and engineered a KKK K-26 turbocharger for the car. With 10 psi boost, output increased to 170bhp. The 924 Turbo engine weighed about 65 lb (29 kg) more, so front spring rates and anti-roll bars were up-rated and revised. Weight distribution was now 49/51 compared to the original 924 figure of 48/52 front/rear.
In order to help make the car more functional, as well as to distinguish it from the naturally aspirated 924, Porsche added a NACA style duct in the hood and air intakes in the badge panel in the nose, 15 inch alloy wheels, four wheel disc brakes with five stud hubs and a five speed transmission. Forged 16 inch flat wheels from the 928 were also available as an optional extra.
Internally, Porsche called it the 931 (left hand drive) and the 932 (right hand drive). These designations are commonly used by Porsche enthusiasts worldwide.
The turbocharged engine allowed the 924’s performance to come surprisingly close to that of the 911 SC 180bhp, thanks in part to a lighter curb weight, but this intern also brought reliability problems.
Intense heat in the engine bay lead to short turbocharger life and turbo related seal and seat problems. To fix the problems, Porsche released a revised 924 Turbo series 2 (although the badge still read 924 Turbo) in 1981. By using a smaller turbocharger running at increased boost, slightly higher compression of 8:1 and an improved fuel injection system with DITC ignition triggered by the flywheel, reliability improved and power rose to 177bhp.
Production of the 924 Turbo ceased in 1982 except for the Italian market which lasted until 1984. This is due to the restrictions on engines larger than 2 litres, putting the 2.5 litre 944 into a much higher tax category.
