BMW M20B20LE engine

M20B20LE engines are a modification of the M20B20 power units, which were developed specifically for installation in BMW cars in the E30 body. Their cylinder block had a reduced mass, and the cylinder head itself was also different. New intake and exhaust manifolds were also installed. The main distinguishing feature of the intake and exhaust manifolds is the adaptation to the installed LE system.

The basic M20B20 engines provide for the installation of six cylinders arranged in a single row. These engines run on gasoline and are equipped with a single camshaft. In the range of M20 engines, this modification of the power unit is the smallest, because its working volume is only two liters. The most voluminous is the extreme modification of engines, providing 2.7 liters. For the development of M21 series engines, which became legendary engines from the Bavarians, it was used as a base line.

The impetus for the start of assembly of M20B20LE engines was the growth of consumer demand in 1970. At that time, the Germans needed inline six-cylinder engines, but with small displacement. To this day, these engines remain the smallest of all six-cylinder engines.

The powertrains are slightly different from the M30 lineup models. The main distinguishing features are the following factors:

• The timing chain drive was replaced by a classic belt drive.
• Instead of the usual 100 millimeters in diameter cylinders, 91 millimeters were used.
• Changes were also made to the tilt angle, which differed by 10 degrees, and was only 20.

Also, the M20B20LE power units were equipped with a lightweight steel cylinder block. The cylinder head was made entirely of aluminum and was also lightweight. The head accommodated a single camshaft to ensure optimum output from the two valves on each cylinder.

The first cars had electrically driven fans as an aid to the cooling system. After minor changes, a thermo clutch was introduced in 1979. The carbureted version of the motor was replaced in 1981, and it was replaced by an injector. Bosh K-Jetronic was used as the system for injection and fuel mixture supply. During the same period, the cogs on the camshaft were also replaced. In order to ensure that there was no hum while the engine was running, it was decided to replace the teeth with a rounded version. The maximum compression ratio of these powertrain models reached 9.9:1. Thanks to the installation of the LE-Jetronic system, it was also possible to reduce the maximum speed to 6,200 rpm.

In 1987, the first and only replacement of the equipment responsible for injection and fuel supply with Bosh Motronic took place. Thanks to the replacement, the compression ratio was slightly reduced to 8.8:1. Peak power of such motors was up to 127 horsepower, while the maximum torque reached a rather high figure of 174 Nm.

M20B20LE engine specifications

Disadvantages

Without the traditional faults for engines from the Bavarians did not do without in this case. Overheating of M20B20LE motors very often accompany the owners of cars with them under the hood. The cylinder head in these engines often overheats, as a result of which it begins to lead. Often this happens due to the failure of elements of the standard cooling system. It is necessary to immediately pay attention to the formation of air plugs in the system, the operability of the thermostat. It is also worth checking the pump and standard radiator.

The camshaft pastels can also suffer from a short period of operation. Often, this problem is faced by owners of cars with a mileage of more than 250 thousand kilometers. It is very easy to diagnose the malfunction, as a knock in the area of the camshaft begins to be noticed. Repair the motor in such a case can only be done by buying a new cylinder head. Cracks in the cylinder head are also not an uncommon problem. This is a typical fault for the entire series of M20B20 engines, and the M20B20LE is no exception to the rule. The most common cause is engine overheating. Cracks usually form in the 4th or 5th cylinder. Troubleshooting is also extremely simple, but costly – buying a new cylinder head.

This is not the end of the problems for owners of vehicles with these power units. It is necessary to constantly monitor the condition of the timing belt and check the position of the tensioning roller. Do not neglect this, because if the belt breaks while driving, the valves will bend for sure. In the worst case, the pistons may also be damaged, which will increase the cost of repair.

The M20B20LE motors are quite old, so they have already had a fair amount of wear and tear. This means that age-related sore spots can be added to the typical malfunctions. Therefore, welding these engines into other cars is not a wise decision, and buying cars powered by motors of this series is not worth it at all.

Chip Tuning

M20B20LE engines are not characterized by great power due to their small displacement, so owners of such motors have long worked out a huge number of options aimed at increasing power and output. Increasing the working volume is the best option that provides maximum efficiency. Since the cylinder block on power units with a working volume of 2.3 liters and on M20B20LE engines has the same height, it is not difficult to add 300 cubes. To do this, you will have to go to the store for a flywheel, connecting rods with pistons and crankshaft from the M20B23 engine. A new gasket under the cylinder head, liners and rings, as well as the mounting bolts themselves will also need to be purchased new. This will be inexpensive, and for a small amount of money, motor owners will be able to increase their horsepower to 150 horsepower.

With the same set of spare parts from the M20B25 version, the displacement can be expanded to two and a half liters. But the highest point is to build a 2.8-liter version with components from the M20B28 engine. Here you can not do without turning to a turner, as you will have to bore the cylinders to 84 millimeters. Crankshaft must be purchased from the M20B28 engine. The connecting rods can be left standard, but you need to trim them by three millimeters. Pistons will have to be purchased from the M20B25 version with a catalytic converter. You will also have to get a new flywheel from the M20B20 Carb motor. Such power will not be able to cool with a standard radiator, so you will have to replace it with a more productive one. This will make it possible to get the M20B28 variant with a higher power figure. The camshaft will also have to be replaced and a new intake and exhaust manifold will have to be installed.

But do not forget that you will have to bore the cylinder block, which will reduce the thickness of its walls. This will affect the engine life only in a negative way. Such motors with increased working volume rarely go more than 20 thousand kilometers.

You can try to build a turbo version of the engine. To realize such an idea, you will have to buy a turbo kit based on Garrett GT30 or T04E turbos. Standard pistons should be changed to forged pistons together with connecting rods, which will provide compression ratio up to 8.5. Without replacing the standard cylinder head gasket with a metal version will not do without. The standard injectors will also have to be replaced with 440cc injectors, and the fuel pump will be installed Walbro 255 lph. Additional sensors to monitor various indicators will also be required.

Building such a version of the motor on the basis of an enlarged engine with 2.8 liters will give the opportunity to get about 400 horsepower. Such a power unit will go very fast, but its service life will be extremely low.

This engine is installed on the following models:

BMW 5-Series (E28)