The 4S is a 1.8 L (1,838 cc), a narrower bore version of the 3S (82.5 x 86.0 mm). This was essentially a multi-valve, twin cam replacement for the 1.8-litre 1S series, with parallel differences as those between the 2S and 3S. There were both 4S-Fi (central point fuel injection) and 4S-FE (multi-point fuel injection) versions.
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