BMW M43B18 Engine

  1. Specifications
  2. Overview, problems
  3. Performance tuning

M43B18 Specs

Manufacturer Steyr Plant
Also called BMW M43
Production 1992-2001
Cylinder block alloy Cast iron
Configuration Straight-4
Valvetrain SOHC
2 valves per cylinder
Piston stroke, mm (inch) 81 (3.19)
Cylinder bore, mm (inch) 84 (3.3)
Compression ratio 9.7
Displacement 1796 cc (109.6 cu in)
Power output 85 kW (115 HP) at 5,500 rpm
Torque output 168 Nm (124 lb·ft) at 3,900 rpm
Redline 6,200 rpm
HP per liter 64
Fuel type Gasoline
Fuel system Bosch Motronic 1.7.1
Weight, kg (lbs) ~133 (293)
Fuel consumption, L/100 km (mpg)

for E36 318i
11.0 (21.4)
6.2 (37.9)

7.9 (29.8)
Turbocharger Naturally aspirated
Oil consumption , L/1000 km
(qt. per miles)
up to 1.0
(1 qt. per 750 miles)
Recommended engine oil 0W-30
Engine oil capacity, L (qt.) 4.0 (4.2)
Oil change interval, km (miles) 7,000-10,000
Normal engine operating temperature, °C (F) 90-95 (195-203)
Engine lifespan, km (miles)
-Official information

300+ (185)
Tuning, HP
-Max HP
-No life span loss


The engine is installed in BMW 318i E36
BMW 518i E34

BMW M43B18 engine reliability, problems and repair

M43B18 is 4-cylinder straight engine from M43 series as well as M43B16 and M43TU. This motor was produced in 1992 as replacement to already existing M40B18. The main difference between M43B18 and M40B18 includes practically the same block of cylinders, lighter crankshaft which now has only 4 counterweights in comparison with 8 units on the previous version. Pistons have also been changed. Compression ratio was increased up to 9.7.
Cylinder head was changed a lot. It was modified to fit new timing chain. It proved to be more reliable in comparison with timing belt. Chain needs replacement every 180,000 miles (300,000 km) of mileage. Diameter of valves is the same. Diameter of inlet valves is 42 mm while outlet valves are 36 mm in diameter. Hydraulic lifters are also the same. Stock camshaft specs are as follows: duration 244/244 deg, lift 10.6/10 mm. Variable-length intake manifold DISA is also used on M43B18. It made it possible to increase the rate of rpm on low and high revolutions. Ignition system was also modified.
This engine was mainly used in BMW 18i models.
N42B20 was produced in 2001 as replacement of M43B18.

BMW M43B18 disadvantages and problems

1. Oil leaking. This problem is rather common for M43 engines. Valve cover is leaking in the majority of cases. All you need is to buy new valve cover gasket, PCV valve and sealant.
2. M43 engine knocking, crackling and noise. This problem is mainly connected with DISA valve. You need to purchase DISA valve repair kit and use it for intake manifold repairing.
Knocking of hydraulic lifters occurs rather seldom.
At the same time some problems are equal to BMW M40B18 engine. They include acceleration problems, rough idling, overheating. HERE you can learn more about them.
However they are not the main disadvantage for owners of this engine. The main problem of M43 is its low power. The rate of HP is so low that even lighter BMW E36 modification is very slow. The driving is extremely dull.
Summing up we should say that in spite of all above mentioned BMW M43 has enough level of reliability and lifespan. On the other hand available versions of the engine have already expired level of durability and you should not expect smooth ride without any problems.
Is M43 worth buying for your BMW? No, it isn’t. You’d better opt for 6-cylinder BMW M50 engine.

BMW M43 engine tuning

M43B18 Stroker

The easiest and most reliable way to increase HP rate of M43 engine is to make it from M43B18 into M42B18 using special stroker kit. HERE you can find detailed guide.
That section also includes tutorial how to install turbocharger on your M40 engine. The same operations can be done for M43 motor. You only need to purchase forged piston for compression ratio up to 8.5.