Porsche 993 Carrera 4

The 993 was to be the last air-breathing Porsche, and was produced until mid-1997, when it was replaced by the 996. It was available with 2 or 4-wheel drive, wide or narrow body, coupe, cabriolet, targa, Turbo and RS.

The 964 generation inaugurated a new all-aluminum block with a displacement of 3,600 cm3, achieved by a bore of 100 m and a stroke of 76.4 mm. The 993 Carrera’s engine is in fact an evolution of the 964 RS block, whose crankshaft, pistons, connecting rods and valves had been reinforced. The interior of the engine block, without liners, is protected by a layer of Nikasil applied by galvanization. Lubrication is by dry sump, with an oil reservoir positioned in front of the rear wheel. The oil is cooled by a radiator (with fan) located at the front of the car when the temperature exceeds 87°C. Another special feature of this 3L6 is the dual ignition system on each cylinder (which caused some problems in the early days of the 964) and hydraulic valve lash adjustment, which significantly reduces the cost of major overhauls. Ignition and sequential multipoint injection are managed by a Bosch Motronic 2.10 electronic control unit. A completely new feature is the dual catalytic exhaust system. In its first version, the 993 Carrera 2’s engine (type M64/05 for ’94 and M64/06 for ’95) developed 272 hp at 6,100 rpm and maximum torque of 330 Nm at 5,000 rpm.

In 1995, the 993 Carrera 2 underwent a further power upgrade to 285 bhp at 6,100 rpm and 340 Nm of torque at 5,250 rpm (engine type M64 21/22/23/24). These versions are recognizable from the outside by their more rectangular tailpipes. The 13 horsepower gains are mainly due to the Varioram, a Porsche-patented system that adjusts intake manifold length according to engine speed. At 4,850 and above 5,840 rpm, the electronic management system adapts the intake by selecting the ideal pipe for the current rpm and controlling a valve that modifies resonance. The aim is to generate near-optimal tuning of the waves generated by the air flows, and to optimize the filling ratio over a wider range. It’s worth noting that Porsche got rid of the VarioRam on the 996, preferring to modulate plenum volumes to smooth the torque curve (Variocam).

(Variocam). A new hydraulically-operated clutch also makes its appearance, making gear shifting easier.

Alongside these «standard» engines, Porsche offered the X51 engine kit as an option. The first-generation 993 Carrera develops 272 hp. The X51 option gives 285 hp, via a displacement boosted to 3.8 liters, more aggressive camshafts, larger valves, specific pistons, cylinder heads and crankshaft. In 1996, the 993 Carrera adopted the Varioram variable intake system and increased its power output to 285 hp, as if it had adopted the X51 option. But if the power ratings are identical, one cube 3.6 liters and the other 3.8, don’t confuse them! In any case, this new 993 with Varioram can also be fitted with the X51 option. Using the same recipe as before, it offers 300 hp, just like the Carrera RS!