BMW N52B25 Engine

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

N52B25 Specs

Manufacturer  Munich Plant
Also called BMW N52
Production 2005-2011
Cylinder block alloy Aluminium-magnesium
Configuration Straight-6
Valvetrain DOHC
4 valves per cylinder
Piston stroke, mm (inch) 78.8 (3.1)
Cylinder bore, mm (inch) 82 (3.23)
Compression ratio 11
Displacement 2497 cc (152.4 cu in)
Power output 130 kW (177 HP) at 5,800 rpm
150 kW (204 HP) at 6,400 rpm
160 kW (218 HP) at 6,500 rpm
Torque output 230 Nm (170 lb·ft) at 3,500-5,000 rpm
250 Nm (184 lb·ft) at 2,750-3,000 rpm
250 Nm (184 lb·ft) at 2,750-4,250 rpm
Redline 7,000 rpm
HP per liter 69.7
Fuel type Gasoline
ECU Siemens MSV70
Weight, kg (lbs) ~120 (265)
Fuel consumption, L/100 km (mpg)

for E90 325
9.8 (24)
5.5 (42.8)

7.1 (33.1)
Turbocharger   Naturally aspirated
Oil consumption, L/1000 km
(qt. per miles)
up to 1.0
(1 qt. per 750 miles)
Recommended engine oil 5W-30
Engine oil capacity, L (qt.) 6.5 (6.9)
Oil change interval, km (miles)  7,000-10,000
Normal engine operating temperature, °C (F) ~95 (203)
Engine lifespan, km (miles)
-Official information

~200-250 (125-155)
Tuning, HP
-Max HP
-No life span loss


The engine is installed in BMW 323i E90
BMW 325i E90
BMW 523i E60
BMW 525i E60
BMW 523i F10
BMW X3 E83
BMW Z4 E85
BMW Z4 E89

BMW N52B25 engine reliability, problems and repair

It is another 2.5-liter engine from N52 series which also includes N52B30 engine with ordinary layout and 6 cylinders. It appeared in 2005 as an alternative to popular at that time M54B25 engine. Apart from previous version of M series where every new motor reflected evolution of the previous one, new engine turned out to be absolutely new product.
N52 engine is based on revolutionary Aluminum-magnesium cylinder block which is lighter in comparison with the previous version. It is also equipped by new light connecting rods, pistons and modified crankshaft.
New improved Double-VANOS cylinder block head is installed in N52B25. At the same time new Valvetronic lifting system was also added in order to regulate the level of inlet valves. It made it possible to increase power as well as reduce fuel consumption. Variable-length intake manifold DISA is used on the inlet. At the same time injectors are installed in cylinder block head.
Previous engine control unit was replaced by Siemens MSV70.
This engine was used in BMW models with 23i and 25i indexes.
Alternative to N52B25 engine was introduced after 2 years of its production. It was later replaced by N53B25 motor as well as its lighter N53B30 version. Nevertheless, N52 2.5 L has been produced for a long time. Its production was stopped only in 2011.

BMW N52B25 engine modifications and differences

1. N52B25U1 (2005 – 2008) is a basic engine with decreased level of HP with the help of intake manifold. The specifications are as follows: power – 177 HP at 5,800 rpm, 230 Nm of torque at 3,500-5,000 rpm. It was used for BMW models with 23i index.
2. N52B25 (2009 – 2011) was equipped with another intake manifold providing it with the following specs: power – 204 HP at 6,400 rpm, 250 Nm of torque at 2,750 rpm. It was used for BMW models with 23i index.
3. N52B25O1 (2005 – 2009) is the most popular version of engines from the series with the following specifications: power – 218 HP at 6,500 rpm, 250 Nm of torque at 2,750-4,250 rpm. It was used for BMW models with 25i index.

BMW N52B25 engine problems and drawbacks

1. The most common problem in N52B25 is high level of motor oil consumption. This is due to thin oil rings which are carbonized rather fast. At the same time valve stem seals goes out of order rather often. Such problems may occur even after 100,000 km (~60 000 miles) of mileage. The only solution to this problem is replacement of damaged components.
New N52NB25 version did not have such problems. It was firstly introduced in 2007 and has black cap.
2. If you do not solve the problem of oil consumption as soon as possible, it may result in polluted catalysts. It will lead to additional costs of their replacement. Catbeck may turn out to be a good alternative to catalyst.
3. Ticking noise. This problem can occur mostly with engines that have been produced up to 2009. However it does not have any negative consequences for the motor or ride.
4. Rough idle. Such problem is mostly connected with Valvetronic, Vanos valves or flow meter. You should examine all these components.
At the same time overheating is another common problem of this engine. You should always check cooling system and regularly clean radiator. At the same time N52 engine is equipped with not very reliable electric water pump. It needs replacement every 80,000-100,000 km (50,000-60,000 miles) of mileage. You should also add high requirements to oil and fuel.
Is it a good idea to buy N52? No, it isn’t. M54 or N52B30 seem to be more reliable.

BMW N52B25 engine tuning

N52B25 Chiptuning

This engine is rather bad choice when it comes to tuning and upgrades. That is why the best variant is to buy more powerful BMW model. If you still want to experiment with tuning, implementation of chip tuning will be a good idea to increase the level of N52 power.
You will need performance exhaust system and K&N air filter as well as tuned ECU in order to add your engine at least additional 20 HP.
Owners of 23i models are recommended buying intake manifold from N52B25O1 which can be found in 25i models. It will add additional 15-20 HP.

N52B25 Supercharger

If you feel like you need something more in comparison with abovementioned mods, prepare to waste some money and buy supercharger. ARMA supercharger kit will make it possible for the engine to perform up to 300 HP with stock internals. However, it will be cheaper to purchase BMW 35i equipped by N54/N55.


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