BMW M20B20Kat engine

M20B20kat is an improved version of the M20B20 power unit, which was created specifically for installation on Bavarian cars of the fifth series. Distinctive features lie in the rade of characteristics. The first fundamental difference is the installation of the Bosh Motronic system. The addition was also a catalytic converter, which was new at the time. This significantly reduced the amount of harmful substances emitted into the atmosphere.

Production of the BMW M20B20Kat inline six-cylinder engine began in 1977. It was recognized to replace inline four-cylinder motors, and was the first engine in the M20 range. You can also meet a modification for 2.3 liters (M20B23), motors for 2.5 liters (M20B25) and the most voluminous power units for 2.7 liters of working volume (M20B27). Such motors were installed on cars with the 20i index.

The engine is based on a cast iron cylinder block, which is covered by an aluminum cylinder head with 12 valves. SOHC 12V system on a single camshaft is used. In the initial versions of the motor began to use a head with an index 200, and on the modifications of M20B20kat began to install the cylinder head 731, providing a larger diameter of valves. The exhaust valves were 34 millimeters, and the intake valves at the same time 40 millimeters in diameter.

The design of the power unit did not provide for the installation of hydraulic compensators, so owners of cars with such motors have to adjust the thermal valve clearances after 10-20 thousand kilometers of mileage. In the drive of the timing mechanism, a belt is used, which must be replaced after 50 thousand kilometers. It is necessary to constantly monitor its condition, otherwise in case of belt breakage you will get bent valves.

The first variations of M20B20 motors provided for a carburetor fuel supply system. The M20B20kat modification began to use electronic injection, allowing to provide more power and the highest degree of fuel combustion. In 1990, this power unit began to gradually displace the new motor from BMW – M50B20.

The M20B20kat modification was produced from 1987 to 1992. It was equipped with Motronic direct electronic injection, providing a compression ratio of up to 8.8 to 1. Maximum power was 129 horsepower, with peak torque of 174 Nm.

M20B20Kat engine specifications

Disadvantages

M20B20kat motors, like all other versions of the M20 range, are very prone to overheating. The cylinder head on such engines is very easy to overheat, which will lead to one thing – it behaves. The cause of this phenomenon may be a malfunction in the standard cooling system. First of all, you need to check the condition of the radiator, and then the operability of the pump and thermostat. Pastels of the camshaft can bring inconvenience to the owners of cars with such motors, which have passed more than 200 thousand kilometers. Detect the malfunction is very simple – it is accompanied by a knock of the camshaft. There is only one way out – the purchase of a new cylinder head.

Cracks in the cylinder head are also a not uncommon problem, often resulting from overheating of the powertrain. The most common location for cracks is in the 4th and 5th cylinders. Treatment should be the same as in the case of wear of the camshaft pastels – buy a new cylinder head. In addition, owners of cars with such motors have to constantly monitor the condition of the belt drive of the timing mechanism. Also do not forget about the tensioner, or rather about its position. If this is not done, the belt can tear, and this leads to bending valves. More rarely, things get even worse – the pistons are destroyed.

Also do not forget that the M20B20kat were developed specifically for the five, so for such a large car the power will be a bit small. And the age of the motor also adds certain inconveniences in the form of breakdowns, so before buying such a car it is worth thinking about.

Maintenance

All engine models of this series, and M20B20kat are characterized by approximately the same requirements in maintenance and selection of lubricants. Semi-synthetic SAE engine oil is best suited for such power units. The optimal viscosity should be 10w-40, 5w-40, 0w-40. In certain cases, it is recommended to use synthetic oils for one change cycle.

First of all, it is worth paying attention to oils produced by Liqui Molly. The lubricant should be replaced after every 10 thousand kilometers of mileage. Consumables are subject to replacement, as well as on other power units. But do not forget that this is a Bavarian motor, so it is necessary to constantly monitor the level of filling fluids, as there is a high probability of failure of the gasket, which begins to skip. But this is not a big disadvantage, as it is always possible to install other gaskets made of higher quality materials.

Chip Tuning

The topic of tuning all cars of the German concern is quite beaten, and there is a huge number of different options to increase the output of Bavarian motors. First of all, it is worth to realize whether it is necessary to do it on such cars. The easiest way to modernize M20B20kat motors is to install a turbo kit, remove the catalytic converter and replace the software. This will make it possible to remove about 200 horsepower of maximum power from the car. Quite a large figure, given the small volume of these powertrains.

Since, cars with such power units under the hood are already about twenty years old, some of their owners are thinking about replacing the motors with newer and more productive ones. The prevalence and reliability of modern BMW and Toyota engines makes them the most suitable option for installation in old cars from the Bavarians. Given the power of some models of modern engines, the working volume of which does not exceed 3 liters, you can install them in the car without much trouble without having to replace the gearbox.

This engine is installed on the following models:

BMW 5-Series (E28)