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Engine code

IA Technical Bulletin

BMW S14 Engine Guide

Engine: S14

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The S14 is BMW's four-cylinder engine for the E30 M3. BMW's parts catalog also lists it in the E30 320is.

The US-market M3 carries the 2,302 cc version. BMW's workshop data lists engine codes B20, B23 and B25 for the S14 family. This guide sticks to what BMW documents show for the US-market M3.

Quick read

Ownership position: Not established yet. We are still researching this engine.
Reliability: Not established yet. The only BMW-side document we found for the US M3 is a cooling-system recall.
Cost to own: Not established yet.
Power potential: Not established yet.
Main watch item: Cooling system, per NHTSA recall 93V015000 for the M3.

S14 At a Glance

Question	Practical answer
Sold in US-market BMWs?	Yes, in the E30 M3.
Where you find it (US)	E30 M3 two-door, built 03/1987 to 12/1990.
Displacement	2,302 cc, 93.4 mm bore, 84.0 mm stroke.
Factory output, catalyst version (the US M3 is a catalyst car in BMW's parts data)	143 kW at 6,750 rpm and 230 Nm at 4,750 rpm with catalytic converter.
Oil capacity	4.4 liters with filter change.
Timing drive	Double timing chain.
Main watch item	Cooling system. See Known Failure Points.

Technical Specifications

Rows below apply to the standard M3 version of the S14 unless a row says otherwise.

Specification	Detail
Configuration	Inline four-cylinder, double overhead camshafts.
Displacement	2,302 cc
Bore x stroke	93.4 mm x 84.0 mm
Compression ratio	10.5:1
Valves	BMW's parts catalog lists 8 intake valves and 8 exhaust valves per engine for the US M3.
Output without catalytic converter	147 kW at 6,900 rpm and 245 Nm at 4,750 rpm.
Output with catalytic converter (US-market M3)	143 kW at 6,750 rpm and 230 Nm at 4,750 rpm.
Output converted to horsepower	143 kW is about 192 hp.
Compression pressure	10 to 11 bar minimum, about equal across cylinders.
Engine oil capacity	4.4 liters with filter change.
Engine oil grade	BMW of North America's oil chart (SI B11 01 15, February 2017) lists 5W-30 LL01 or 0W-30 LL01FE for all BMW gasoline engines of model year 2011 and older; it does not name the S14 by code.
Oil pressure	1.0 bar minimum at idle at operating temperature, 4 bar regulated.
Thermostat opening temperature	80 degrees C.
Valve clearance, intake and exhaust, cold	0.26 to 0.35 mm at a coolant temperature of 35 degrees C or less.
Coolant capacity	Not established.
Firing order	1-3-4-2, per BMW's Engine Technology training chart.
Engine management	Not established.

Factory Deep Dive

Block and head

BMW lists the S14 cylinder bore at 93.40 mm for the standard size. Over-size bores are listed at 93.60 mm and 93.80 mm. BMW's catalog also carries a cylinder head gasket and a full cylinder head gasket set for the US M3, covered in Service Parts.

Valvetrain

The S14 uses a double timing chain. BMW lists two different camshaft part numbers for the US M3, one for each camshaft.

Variants

BMW's workshop data lists a 1,990 cc version for the 320is with 141 kW at 6,900 rpm.
A separate M3 entry marked E 2 lists 11.0:1 compression and 162 kW at 6,750 rpm.
Wikipedia lists a 2,467 cc S14B25 for the Evolution III M3 at 175 kW.

None of these three is in BMW's US-market catalog records for the E30.

Service Parts at a Glance

Numbers below are current BMW part numbers as of the parts catalog data we read (data date 2019-12-12). Check fitment against the car before you order.

Part	BMW part number	Note
Oil filter	11 42 1 258 038	Current number. Supersedes 11 42 1 258 039.
Spark plug (4 per engine)	12 12 9 061 882	Four per engine. Also supersedes older 12 12 1 311 928.
Ignition coil	12 13 1 286 087	Same number also fits the US E28 M5 and E24 M6.
Air filter element	13 72 1 278 138	Supersedes 13 72 1 271 254.
Thermostat (80 C)	11 53 1 315 537	Replaces 11 53 1 309 786 and 11 53 1 311 654.
Water pump, exchange unit	11 51 1 315 211	Replaces 11 51 1 312 574 and 11 51 1 310 672.
Timing chain	11 31 1 403 081	Double chain. Also fits the US S38 cars.
Cylinder head gasket	11 12 1 316 714	1.82 mm thickness per the catalog.
Cylinder head gasket set	11 12 1 316 992	Includes head gasket 11 12 1 316 714.
Fuel injector (4 per engine)	13 64 1 273 272	Same number also fits the US E28 M5 and E24 M6.

Known Failure Points and Service Items

We list only items a recall, bulletin or BMW document backs. Other S14 problem lists are not established yet.

01 Cooling system pressure and the heater core

NHTSA recall 93V015000, received 1 February 1993, covers the M3 for model years 1988 through 1991. NHTSA's recall summary says a coolant system malfunction can sharply raise coolant temperature and system pressure. NHTSA lists coolant hose leaks, a leaking radiator or expansion tank, a hose coming off a fitting, and a cracked heater core end piece as results.

The dealer remedy was a thermostatic bypass valve for the heater core and a new-design radiator cap. Watch for vapor fogging on the inside of the windows, coolant leaking at the heater core area, and a hose that has come off its fitting. Whether a given car had the remedy done is not something this guide can tell you.

Other S14 failure points: not established yet. We are still researching this engine.

Reliability Verdict

Not established yet. We are still researching this engine. No BMW document we opened gives a reliability verdict, failure rate or mileage figure for the S14.

Power Potential

Not established yet. We are still researching this engine. The factory figures are in Technical Specifications.

Cost of Ownership

Not established yet. We are still researching this engine.

Common Questions

What BMW has the S14 engine?

The US-market E30 M3 has the S14, built 03/1987 to 12/1990 per BMW's parts catalog. BMW's catalog also lists the S14 in the E30 320is, which is not in its US-market records.