BMW M42 Engine (M42B18)

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

M42 Specs

Manufacturer Munich Plant
Also called BMW M42
Production 1989-1996
Cylinder block alloy Cast iron
Configuration Straight-4
Valvetrain DOHC
4 valves per cylinder
Piston stroke, mm (inch) 81 (3.19)
Cylinder bore, mm (inch) 84 (3.3)
Compression ratio 10
Displacement 1796 cc (109.6 cu in)
Power output 103 kW (140 HP) at 6,000 rpm
Torque output 175 Nm (129 lb·ft) at 4,500 rpm
Redline 6,400 rpm
HP per liter 78
Fuel type Gasoline
Fuel system Bosch Motronic 1.7
Weight, kg (lbs)
Fuel consumption, L/100 km (mpg)

for E36 318is
10.9 (21.6)
6.4 (36.8)

7.7 (30.6)
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.) 5.0 (5.3)
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 318is E30
BMW 318is/ti E36

BMW M42B18 engine reliability, problems and repair

BMW M42 is a 4-cylinder straight engine which was developed on base of M40B18. The main difference between two motors is the fact that new version has more efficient aluminum 16-valve cylinder head. It uses two camshafts as well as optimized combustion chambers. M42 is still equipped with hydraulic lifters. Diameter of inlet valves is 33 mm, while outlet valves are 30.5 mm in diameter. Camshafts specs are as follows: duration 240 deg, lift 9.7 mm.
In addition this engine has different crankshaft, lighter pistons and connecting rods which are 140 mm length. Intake and exhaust manifolds have been improved. Stock M42 injectors – 192 cc.
Engine has a very reliable timing chain.
This engine was mainly used for BMW 18is models. They were mainly produced for the US market.
M42 was replaced in 1992 by new 1.9-liter M44B19 engine which was under the bonnet of BMW 318is models.

BMW M42B18 disadvantages and problems

Speaking about common problems, M42 has malfunctions equal to M40B18. The only thing which is out of any questions is timing chain. It proved to be rather reliable and has no drawbacks. You can learn more about BMW M42 problems HERE.

BMW M42 engine tuning

M42 NA. Stroker. ITB

Successful tuning of BMW M42 should start with purchasing of M50B25/M54B30. If you still want to improve your M42 motor, then you need to buy Dbilas camshafts with duration 264 or 272 deg. In addition you will also need to buy stronger springs, cold air intake, performance exhaust system and ECU modification to suit all these upgrades.
Such modifications will provide us with extra 30 HP and sag and low rpm. If you need to obtain even more HP, you can buy individual throttle bodies and add productive camshafts and cylinder head porting.
Our M42 will eventually become more powerful but at the same time more expensive for maintenance and rather uncomfortable for city driving.

M42 Turbo

M42 turbocharging has been implemented for many times already. If you want your engine serve as long as possible, you will need forged pistons and connecting rods (CR ~8.5). Next stage is purchasing of turbo kit Garrett GT28/TD05 with intercooler, 630 cc injectors and performance exhaust system 2.5”.VEMS will be a perfect suit as ECU. You will get about 280-300 HP under low pressure. However you should note that such project can be rather expensive. That is why it may be better to purchase M50/M54 engine at once.