The Bosch K-Jetronic injection system was larger and re-calibrated to suit the higher output. It blew through a cast pipe up and over the head via the throttle chest horizontally into the intake manifold, which turned the flow down and back again into the ports on the upper side of the engine.Īs on the 911 Turbo, an exhaust waste gate was used to limit the output of the exhaust turbine in addition, to improve throttle response, a Porsche 930 blow-off valve between the pressure and inlet sides of the inlet system relieved back pressure which otherwise slowed down the turbine undesirably when the throttle was closed momentarily.
The German-made KKK exhaust turbocharger sat low down near the front under the lee of the heavily inclined engine - it lay, exhaustdown, at 50 deg to the horizontal - taking air from the Bosch K-Jetronic flap valve box and air filter assembly which was mounted transversely across the front of the engine. The cylinder head was entirely new, aluminium alloy as before but with different combustion chambers, recessed valves, 3mm larger exhaust vaIves, sparking plugs with platinum silver electrodes moved across to intake side, and the usual lower compression ratio necessary for any supercharging - this was partly done with different pistons - 7.5 instead the 924's 9.3-to-1 the effective maximum compression at 0.7 bar (10.15 psi) supercharging pressure was 10.8-to-1.
iron-block engine's capacity remained the same and its bottom end was deemed strongenough to be left unaltered, there were considerable changes elsewhere. But the 924's chassis was always cring out for more power - so how did the 2 litre cope with 10 psi of turbocharger boost?Īlthough the 1984 c.c.
Of course the engineers went to work on that engine so that, by the time it was installed in the engine bay of the 924, there was little resemblance. THE 924 HAD A HUMBLE BEGINNING when you consider the donk was derived from the 2 litre unit used in a Volkswagen van.
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