BMW M52B25 engine

The M52B25 engine is a gasoline motor of the M52 range, which stands out with a working volume of 2.5 liters. The power unit is capable of developing a maximum power of 170 horsepower, which is quite enough for the normal dynamics of cars on which it was installed, and this was BMW third and fifth series.

M52B25 engine specifications

Advantages

The M52B25 engines fitted to the BMW E39 are part of the new M52 powertrain family (it also includes the M52B20, M52B24, M52B28, S52B32). These internal combustion engines were first introduced in 1995, and were intended to replace the 2.5-liter representatives of the M50 family.The geometric component of the bottom end remained unchanged from the previous range. The cast-iron cylinder block was replaced by an aluminum version with a lower weight, which included coating the cylinders with Nicasil. Changes were also made to the pistons and connecting rods. The connecting rods were 140 millimeters long, while the piston had a compression height of 32.5 millimeters.

The intake system has also undergone some changes. The M52B25 was fitted with the same cylinder head as the M50 with Vanos. From this point on, the variable valve timing system began to be used on all powertrain variants. The injectors were installed with a capacity of 190cc.

Since 2000, the technical characteristics of the power units no longer meet the needs of customers, and the motors began to gradually withdraw into the background, and before them appeared six-cylinder engines M54B25, which entailed the complete completion of the process of engine production in 2001.

In 1998, the M52B25 alpina version of the engine was recognized as the best powertrain in the United States for the period 1997-200. The engine lineup was included in the top ten powertrain ranking by the specialist publication Ward’s.

At one time, the differences of M52B25 and their reliability, caused astonishment among specialists. But over time, these engines have become obsolete, as the last version of the engine rolled off the assembly line back in the early two-thousand years.

To date, it is necessary to choose motors with special care, having previously checked all indicators. It is best to buy a motor with low mileage in a contract version, since the reviews about this solution are the most acceptable. This is an old motor, which under certain conditions will not fail its owners.

The repairability of this motor causes the appearance of a twofold situation. In some cases, it is possible to repair the M52B25 with your own hands, but overhaul of the cylinder block will be problematic to perform in our country. The whole point is that it is practically impossible to align the shafts and restore the nickasil coating on the cylinder walls, taking into account modern domestic technological solutions.

Disadvantages

A typical failure of these motors is overheating. Similarly to the power units of the M50 range, M52B25 motors often overheat, which can lead to failure of the cylinder head. In case you have found an increased operating temperature of the engine, it is necessary to clean the radiator, try to eliminate air plugs in the standard cooling system, as well as pay attention to the performance of the pump, thermostat and radiator cap.

Motors can bring problems in the form of increased consumption of lubricating fluid. The piston rings of these power units are very susceptible to wear, so it is possible to replace them if the cylinder walls are still in factory condition. If the cylinder walls are also worn out, you can try to send the engine to the liner. It is also necessary to pay attention to the condition of the crankcase ventilation valve.

The motor may start to trottle and stop revving after 3000, the reason for this is ignition misses. The problem may lie in dirty hydraulic compensators, which leads to a drop in the performance of one of the cylinders and the engine control unit disconnects it. Only replacement of the hydraulic compensators can help in this case, after which everything will work in the same mode.

The oil light may come on while driving. It is worth checking where the dipstick is, if it is not in its usual place, it is worth putting it back and everything will be back to normal. The oil cup may also be out of order. Do not forget to check the oil pump.

The Vanos system can also fail, resulting in a drop in power, unstable operation with constant revs floating, and in rare cases the engine may start to stall. To eliminate such difficulties, you can buy a repair kit and replace it.

Among other things, various sensors can also fail at the most inopportune moment, most often the engine may not start because of a broken crankshaft position sensor, or camshaft. The threads for the cylinder head mounting bolts also leave much to be desired. The thermostat is characterized by a small resource. But the saddest thing is the demanding nature of the fuel used. The working life is lower than that of the previous version of the M50 engines.In addition, it is worth considering the great age of the motors, as well as the nature of all Bavarian internal combustion engines, so buying it is not the best choice.

If an overhaul is necessary, it is better to make a swap to M52B30, or to the power unit M50B25, which differs in the absence of the Vanos system. But if you know what oil to pour how much, then there should not be any special problems.

Technical specifications

The BMW M52B25 powertrain is characterized by an in-line arrangement of six cylinders, which are 84 millimeters in diameter. The exact working volume is 2,494 cubic centimeters, which allowed for lower taxes. The piston strokes 75 millimeters. This makes it possible to provide a compression of 10.5 to one.

For correct operation of the M52B25 engine, it is necessary to use only high-quality high-octane gasoline. Fuel consumption on the highway is up to 9.8 liters per hundred kilometers, and with measured driving in the city you will have to count on 11 liters of 95-grade gasoline per hundred kilometers. Emissions of harmful substances into the environment range from 230 to 252 grams for each kilometer traveled.

The characteristics of the M52B25 allow for a maximum output of 170 horsepower, which the motor develops at 5.5. thousand rpm. Peak torque is 245 Nm and is achieved at 3,950 engine speeds.

Tuning

A banal way to make tuning M52B25 is to install a cold intake manifold from the modification M50B25, and camshafts with a smaller phase, such as 250/250, and a lift of 10 millimeters, while having to make a software change. As a result, it will be possible to remove from the motor up to 220 horses.

You can try to make a stroker, increasing the working volume to the mark of 2.8 liters. For this purpose, you will have to install a special kit. Crankshaft together with connecting rods will have to be installed from M52B28, pistons remain stock, software will also have to be replaced by the version for the 2.8 liter engine. To provide even more thrust it is necessary to install the intake from the M50B25 version, in combination with the exhaust from the S52 motors.

You can try to build an M52B25 turbo. This is done in case the power of the atmospheric motor is not enough. In case you need to make a budget-limited version of modernization, it is suitable to install a Chinese turbo kit based on a Garrett GT35 turbine, or another option, the main thing that the kit included ECU. In this case, the payoff will be much greater than from the installation of a compressor.

If you can find a kit based on the original Garrett GT35, you can get even more power. Then you’ll have to install CP Pistons, which have a compression ratio of 8.5 to 1. The stock connecting rods will have to be replaced with Eagle and ARP bolts will have to be installed, as well as injectors designed for 550cc performance. Such a kit will give the opportunity to develop about 500 horsepower of power.

This engine is installed on the following models:

BMW 3-Series (E36)

BMW 5-Series (E39)