BMW M40B16 Engine (Design, Issues & Tuning)

Updated: Nov 23

BMW created the M40B16, a SOHC straight-four petrol engine, between 1987 and 1994. It has a displacement of 1.6L producing between 98-102hp and 141-143nm depending on the version.


This engine has a bore of 84 mm and a stroke of 72 mm. It was used in the following cars.


  • 1988-1994 E30 316i

  • 1990-1994 E36 316i

  • 1992-1993 Bertone Freeclimber 2


BMW M40B16 engine

Design

The manufacturer started making the 1.6-liter M40 series engine (official name M40B16) in 1988. This little engine was developed using the M40B18 engine, which has a 1.8-liter displacement and a longer stroke.


The cylinder block of this engine is made of durable cast iron. The 1.6l M40 engine employs the same connecting rods despite having a shorter stroke crankshaft than the M40B18 (the length is 140 mm).


To keep the compression ratio at the desired level, there are new pistons with a different form. It  has a different intake manifold, throttle body, spark plugs, and ECU.


The cylinder head is made of aluminium. It has an eight-valve SOHC head with internal hydraulic tappets and lifters. Exhaust valves have a diameter of 36 mm, whereas intake valves are 42 mm in size.


The M40 camshaft has a duration of 244 degrees (single pattern), and the valve lift is 10.6 millimetres. A timing belt drives the camshaft.


It isn't as reliable as it might be. The belt has a short lifetime due to its low width. Every 25,000 miles, it is advised that the timing belt be changed. There is also a substantial risk of valves bending.


The engine was utilised in BMW 16i models until 1994, when it was superseded by the M43B16 engine, which debuted in 1993.


Specs

  • Manufacturer: Steyr Plant

  • Production years: 1987-1994

  • Cylinder block material: Cast Iron

  • Cylinder head material: Aluminum

  • Fuel type: Gasoline

  • Fuel system: Fuel injection

  • Configuration: Inline

  • Number of cylinders: 4

  • Valves per cylinder: 2

  • Valvetrain layout: SOHC

  • Bore: 84.0 mm

  • Stroke: 72.0 mm

  • Displacement: 1596 cc

  • Type: Four-stroke, naturally aspirated

  • Compression Ratio: 9:1

  • Power: 102 hp at 5,500 rpm

  • Torque: 105 lb-ft (143 Nm) at 4,250 rpm

  • Firing order: 1-3-4-2

  • Engine oil weight: 0W-30, 0W-40, 5W-30, 5W-40, 10W-40, 15W-50

  • Engine oil capacity: 4.0L

  • Oil change interval: 9,000 miles (15,000 km) or 12 months

  • Applications: BMW 316i E30, BMW 316i E36


Problems & Reliability

BMWs M40 series' engines are all relatively good. The lifespan is between 180,000-200,000 miles.


The M40B16 does have several drawbacks, such a timing belt that can be unreliable. The age of this engine is its main weakness. Most of them require the rebuilding or replacement of a few aged components, and all BMW parts are pricey.


Common Issues

The M40B16 has some common issues, as listed below.


  • Timing belt problems: A thin timing belt causes expedited wear of the belt.

  • Cylinder head oil flow: All frictional engine parts in the cylinder head will wear down more quickly as a result of restricted cylinder head oil flow, necessitating more frequent engine maintenance. Regular oil changes and the use of stop-start oil may help.

  • Overheating: The deterioration of plastic flanges may lead to coolant loss and overheating as well as overheating.

  • Issues with efficiency and power: This common issue is caused by the lambda sensor failing.


Changes & Updates

From 1988 through 1991, M40B16 was used. This engine is a non-catalytic base modification. The engine produces 102 horsepower at 5,500 rpm and 105 lb-ft (143 Nm) torque at 4,250 rpm.


A new version of M40B16 with a catalyst was released in 1991. It has 100 horsepower at 5,500 rpm and 104 lb-ft (141 Nm) at 4,250 rpm, which is slightly less power and torque.


Tuning

Although the M40B16 is a well-rounded engine, modifying it may not be the greatest decision because it does not respond to tuning as well as other engines.


However, there are three main paths for modification if you want to optimise this engine.


  1. Increasing the stroke will increase displacement

  2. By widening the bore, further increase displacement

  3. Forced induction techniques like turbocharging


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