BMW S14

The S14 is the engine of the E30 M3: a 2.3-litre four-cylinder built by BMW M GmbH from 1986
to 1991. It is the only four-cylinder engine ever fitted to an M3, and it was built for one
reason — to make the car eligible to race.

What the S14 is

A 2.3-litre inline-four with two overhead camshafts, four valves per cylinder and four
individual throttle bodies. The S prefix means it was built by BMW M GmbH rather than BMW AG,
and as our guide to engine codes explains, that makes
it a separate engine rather than a tuned version of an ordinary one.

Its construction is unusual even by M standards: a four-cylinder block from BMW’s
M10 family with a four-valve cylinder head derived from the
six-cylinder M88 line — effectively two thirds of a
six-cylinder racing head on a four-cylinder bottom end.

Where it appears in our records

Three specification pages, and the interesting part is not that they
exist but what is in them: four cylinders and 2,300 cc, against six cylinders and 3,000 cc for
the 1995 M3 in the same dataset. The generation change from E30 to E36 is visible in the
government record as a change in cylinder count, which is a cleaner piece of evidence than any
description.

Rated power is absent, as it is for everything before 1998 — United States
certification records did not carry it then, and we hold no brochure of the period.

Why a four-cylinder M3

Group A touring car racing required a manufacturer to build road cars closely related to the
racing version, in quantity. The E30 M3 exists because BMW needed a homologated car, and the
S14 exists because the racing regulations favoured a light, high-revving four over a heavier
six.

Every M3 since has had more cylinders: six in the E36 and E46, eight in the
S65-powered E9x, six again with turbocharging in the
S55 and S58 cars. The four-cylinder M3
was a one-off answer to a rulebook rather than a step in a progression.

How to tell a real E30 M3

The bodywork is different from an ordinary E30 in ways that are expensive to fake — but
the check that cannot be faked at all is the VIN. Cars built by BMW M GmbH carry
WBS as their first three characters rather than the WBA of a BMW AG car, and
our VIN decoder reads that straight out of the number.

A 325i with M3 panels is still a WBA car. Given what E30 M3s are now worth, that is a check
worth two minutes.

What we do not publish

No reliability rating. The NHTSA complaint database records faults against a
vehicle, not an engine, and for a car this old and this rare the surviving record
reflects what owners were still complaining about decades later. We also publish no power
figure, because no source we hold carries one for these years.

Common questions

Which BMWs have the S14?

One: the E30 M3, in the United States from 1989 to 1991. Some European versions and the
homologation specials used higher-output variants of the same engine that were not sold
here.

How much horsepower does the S14 have?

We do not publish a figure. Certification records carrying rated power begin in 1998, seven
years after this engine finished, and our archive holds no brochure covering the E30 M3. What we
can source is the configuration: four cylinders, 2,300 cc.

Is the E30 M3 really a four-cylinder?

Yes, and the EPA record confirms it for every US model year: four cylinders, 2.3 litres. It
is the only M3 that has ever been one.

Is the S14 related to the M10?

It uses the M10 four-cylinder block as its foundation, with an M
division four-valve head on top. They are not the same engine and share little beyond that
starting point.

What replaced the S14?

The S50 six-cylinder in the E36 M3, from 1995 in the United States — visible in our
records as the year the M3 goes from four cylinders and 2.3 litres to six and 3.0.

Sources

Cylinder counts, displacements and model years from EPA fuel economy data, with the source
named on every specification page. Manufacturer identifier decoding from
the VIN structure itself, as described on our VIN decoder page. No
brochure covering the E30 M3 is held in the archive.