S3 vs S4 Engine

The 928 S4 EZK module will not work with the 1985 - 1986 Porsche 928. The 1985 - 1986 engines do not have the provisions for spark knock sensors and the cam position sensor that the EZK requires. The wiring harnesses are different, the 1985 - 1986 use a 25 pin connector to the module, the 1987 and newer use a 35 pin connector.

Remember that the Rest of the World (i.e., non-USA) market could choose the 16-valve or 32-valve engines in '85, and perhaps '86. Those last 16-valve engines are neat pieces, and very desirable.

To add a bit more detail on Wally's comment, the 5-liter 32 Valve 928 motor for ROW was an option in markets that gave incentives for running lead free gas that was just coming on the market in some areas of Europe/world at the time. Those 928 ROW cars fitted with the 32 Valve motor had CATs .... it was the same engine as used for the US market.

The ROW 928s for 1984 - 1986 were 16 valve 4.7 liter motors fitted with LH and EZF spark control but no CATs.

BTW - On the '85 and '86 models only, there is an "octane loop" on the cable from the EZF ECU connector. This is a single wire loop, with a connector in the middle. This wire should NOT be connected! When the wire is connected, it retards the timing three degrees to allow for poor grade gasoline. Connecting the wire will cost a few hp and mpg...