BMW S14 M-Tech Four Cylinder Engines

BMW S14 engine

Nice clean S14., lovely.


In 1986 BMW wanted to go racing with the E30 three series, for this they needed an engine and a car that could be homologated. The answer was the S14 and the E30 M3 - a legendary combination.

Initially the S14 was a 2.3 litre, four cylinder 16 valve. This was a problem for markets with high car tax for engines over two litres such as Italy, so a special 320iS was produced to avoid the taxes.

The demands of the racing team mean that more power was required, the answer was a 2.5 litre S14 for the final E30 M3 Evo 3 / Sport Evolution version.

Sadly no cars were ever produced in right hand drive with the S14. Production ceased in 1991 when the E36 replaced the E30, the new model would have a six cylinder M engine and the early racing E36s used an adaption of the M42 four cylinder.

Incidentally, it's called the S14 as from inception to prototype Paul Rosche and his team built it in only 14 days. God made the earth in half that time but he didn't have to worry about the camshaft profiles.

BMW S14 engine

S14 components, note the two part cylinder head.


The S14 was two thirds of an S38 six, so much so that the prototype used an S38 head with two cylinders removed and plate welded across the end! The S38 was a fantastic engine with excellent pedigree. It had been fine tuned both on the road and in racing, there could be no better parent for the new four cylinder engine. I won't repeat the S38 design here so check out the S38 page

S14s had a double row timing chain which was highly durable so long as the chain tensioner didn't fail. They had Motronic fuel injection which is a great system, well proven.

The 1988 Evo 2's S14 produced more power by virtue of a different camshaft profile and revised intake ports. A higher compression ratio was used and the exhaust had larger diameter tubes. Some versions had a catalytic converter.

On the 1989 2.5 the webs between each cylinder bore are a mere 4.5mm thick (same as on S38 3.8), but this was enough and the block is very strong.

To this day an incredible number of after market S14 upgrades are available. Many go further than the factory race team did in the 80's!

BMW S14 engine

S14s for road and track.


Code Size Power
Made Bore x
Timing Weight
VANOS Used in
S14 2.0
189 @ 6900
200 @ 6750
215 @ 6750
235 @ 7000
155 @ 4900
177 @ 4600
181 @ 4750
177 @ 4750
87 - 90
86 - 88
88 - 89
89 - 90
Chain 106 No 320iS
E30 M3
Evo 2
Evo 3


BMW S14 engine

S14 race engine with carbon fibre intake.


BMW used a variety of timing chain tensioners over the years. The S52 tensioner is a good upgrade to avoid chain and sprocket wear.

Leaks from the oil filter manifold aren't uncommon but are easy to fix.

These engines used shims of variable thicknesses to set the valve clearances, a task which must be performed periodically. When the clearances are set you need a supply of these shims, this very much limits the number of garages that can do the work.

On Motronic engines the distributor and rotor arm must be in good condition as these are vital to correct ignition timing, there is no vacuum advance or similar mechanism. A worn set can cause poor economy and a lack of high end power.

The throttle bodies need to be synchronized, ideally using vacuum gauges.

A rubber gasket links the intake manifold to the head, each gasket section covers two cylinders. These can fail causing a vacuum leak.