· Premium Member
2016 BMW 3 Series 340i are arriving at US dealerships now. One of the, if not the biggest change of the 2016 LCI is the replacement of the venerable N55 engine. The N55 has been the heart of the 335i 3 Series from 2009 on. Despite being long in the tooth the engine is much loved and relatively rock solid, the new B58 engine has big shoes to fill.
In a never ending quest for more performance and efficiency the B family of engines was developed. We dive into what makes the B58 3.0 liter TwinPower inline 6 engine special.
BMW B58 Highlights
- 3.0 liter inline 6 cylinder
- Engine codes B58B30M0 (ULEV II) and B56B30M0 (SULEV) - Bx7 engines are diesel
- Single turbo, twin scroll, water to air intercooling
- Forged crankshaft and piston rods
- Intake and exhaust VANOS
- TwinPower Turbo Technologies
- Modular B family design
The B58 6-cylinder engine forms part of the new in-line engine family. The B58 engine features elements including double VANOS, TwinPower exhaust turbocharger technology, indirect charge air cooling that has been integrated into the intake system and a heat management module.
The new engine generation is mainly characterized by lower fuel consumption and fewer exhaust emissions (It complies with Euro 6 in ECE and ULEV II in the US). A characteristic map-controlled oil pump, an injection system with direct rail and electric arc wire injection cylinder bores are used to achieve low fuel consumption. All engines are also equipped with an automatic engine start-stop function and intelligent generator control as a further EfficientDynamics measure. Compared with the N engines (N55/N20), the new B engine generation (B38/B48/B58) demonstrates a considerably higher number of common and interchangeable parts between the diesel (Bx7 models) and gasoline (Bx8) engines.
B58 to N55 Comparison
The B58 engine is the successor to the N55 engine. The following table compares the technical data for both engines. The B58 has more horsepower and torque then the N55.
Notable changes from the N55
- Improvement of Valvetronic - VVT4 with reduced height
- Rear mounted VANOS and timing chain
- Mechanical water pump (N55 is electric)
- Thermostat replaced with heat management module
- Air to water intercooler replaces air to air system
TwinPower Turbo Technologies
TwinPower Turbo is a commonly misunderstood term, often being confused with twin turbo, especially as it was introduced around the time BMW discontinued the twin turbo N54 engine. TwinPower does not mean twin turbo, in BMW nomenclature it is the umbrella term that means the following technologies are used:
- Direct injection
Crankcase / Engine Block Design
The crankcase is a completely new design engineered as both a gasoline and diesel engine in one common part. The closed deck crankcase is equipped with a completely new structure which can be identified by a complex array of ribs on the exhaust and intake side and an additional reinforcement frame on the oil sump side. The structural construction of the B58 include:
- Heat-treated all aluminum crankcase made from AlSiMgCu 0.5
- Electric arc wire-sprayed cylinder walls
- Weight-optimized main bearing cap of crankshaft
- Closed deck design
- Deep skirt
- Oil ducts for the use of a map-controlled oil pump
With the closed-deck design, the coolant ducts around the cylinder are closed from above and provided with coolant bore holes. This design is mainly reserved for BMW diesel engines. Due to the high combustion pressures in the diesel engine, a greater degree of rigidity is required in order that the forces can be safely absorbed. As the gasoline engine uses the same unfinished cast part as the diesel engine, it also benefits from this robust design.
The B58 engine is equipped with a cylinder head featuring transverse flow cooling. In the case of cross-flow cooling, the coolant flows from the hot exhaust side to the cooler intake side. This has the advantage of enabling a more uniform heat distribution to prevail throughout the cylinder head. Loss of pressure in the cooling circuit is also prevented.
Electric arc wire spraying
The cylinder walls of the B58 engine are coated with electric arc wire spray (LDS). In this procedure a conductive metal wire is heated until it melts. The melt is then sprayed onto the cylinder barrels at high pressure. This layer of ferrous material is roughly 0.3 mm thick, extremely wear-resistant and facilitates an efficient transfer of heat from the combustion chambers to the crankcase, and from there to the coolant ducts
Timing Chain, VANOS and Valvetronic Components
click for full diagram
On of the bigger changes on the B58 is the location of the cam shaft timing chain drive. Typically found on the front of the engine, the B family of engines has the chain drive on the transmission side. The inertia of the transmission at this end of the engine significantly reduces the rotary oscillations and also therefore the loads acting on the chain drive.
Note the two different chains that make up the cam drive chain. In the diesel engines, the high pressure fuel pump is driven by this intermediary gear setup. On the gasoline engines the high pressure fuel pump is located on top of the engine so a simple gear transfer sprocket is used.
To facilitate VANOS repairs the VANOS solenoid valve actuators on the B58 are not mounted to the cylinder head, but in the cylinder head cover. Presumably the cylinder head cover (valve cover) can be removed to change the solenoid so the entire engine does not need to be dropped. Additionally the mounting of the VANOS solenoid valve actuators has also changed. They are no longer bolted on, but are attached to the cylinder head cover using a bayonet fitting and retaining clips.
The valve overlap times have a significant impact on the characteristics of the engine. An engine with smaller valve overlap therefore tends to have a high maximum torque at low engine speeds but the maximum power which can be achieved at high engine speeds is low. The maximum power achieved with a large valve overlap on the other hand is higher, but this is at the expense of the torque at low engine speeds. The VANOS provides a solution. It makes a high torque possible in the low and medium engine speed range and a high maximum power in the higher engine speed ranges. A further benefit of the VANOS is the option of internal EGR. This reduces the emission of harmful nitrogen oxides NOx, particularly in the partial load range
The Valvetronic has been further developed for use in the new Bx8 engines. A distinguishing feature of the VVT4 is the Valvetronic servomotor is located outside of the cylinder head. Valvetronic comprises a fully-variable valve lift control and a double VANOS. It operates according to the principle of throttle-free load control. With this system, a throttle valve is only used to stabilize the engine operation at critical operating points and to ensure a slight vacuum for the engine ventilation. A very small vacuum can be produced in the intake pipe by slightly tilting the throttle valve, which allows treated blow-by gases to be introduced into the intake port during naturally-aspirated engine operation.
By reworking the Valvetronic, it has been possible to significantly reduce the installation space. A considerable height advantage has been gained by swapping round the intake camshaft and the eccentric shaft. The new position of the intermediate lever and gate simplifies the application of force in the cylinder head.
click for full diagram
In order to protect components from overheating damage, the engine oil as well as the transmission fluid are cooled using coolant. A mechanical coolant pump makes its return to the engine and is used to circulate the coolant. An electric fan is used to assist the radiator output.
The heat produced by the turbocharger is absorbed by the coolant which is supplied via a coolant connection on the exhaust turbocharger. When the motor is not running, post-cooling of the exhaust turbocharger is possible with the assistance of an electric coolant pump (20 W). This prevents a build-up of heat in the area of the exhaust turbocharger.
Heat management module
The conventional thermostat in the B58 engine is replaced by a so-called heat management module. The heat management module is electrically operated. In contrast to a map controlled thermostat with expansion element, there is no direct, physical connection to the coolant temperature. The opening cross-sections of the various cooling ducts can be variably opened and closed using a rotary valve. The Digital Motor Electronics (DME) require elements including the coolant temperature from the coolant temperature sensor and the material temperature of the cylinder head from the component temperature sensor to correctly position the rotary valve.
Warm-up and cooling of the engine and the supply of additional ancillary components can be implemented as required and therefore the fuel consumption is reduced.
Air to Liquid Intercooling
In the B58 engine the charge air intercooler has been integrated into the intake plenum (integrated, indirect charge air cooler - ILLK). The compressed air flows through the charge air intercooler in several plates, around which the coolant flows.
The benefits of integrated air to liquied intercooling include:
- Lower charge air volume between compressor and intake valve
- More even temperature distribution within the intake ports
- Increased performance due to higher intake pressure
- Improved response characteristics due to the use of a smaller turbocharger
- Reduction in consumption by modifying the ignition point and transmission ratio
The exhaust turbocharger of the B58 engine is a twin-scroll turbocharger (6 in 2 exhaust manifold). To facilitate a fast and direct response, the exhaust flows from cylinders are merged and routed to the compressor via two separate channels. This principle is referred to as pulse turbocharging.
The exhaust manifold of the 3rd and 4th cylinder and the turbocharger housing form one single cast steel part which cannot be replaced individually. The exhaust manifolds of the 1st and 2nd cylinders and the 5th and 6th cylinders consist of multiple parts. They consist of stainless steel exhaust manifold pipes which have been formed by applying internal pressure and feature forged stainless steel flanges that are welded on as well as an expansion compensation unit made of a nickel and chrome alloy installed between the turbine housing and the exhaust manifold. The expansion compensation units compensate for material expansion and contraction as a result of both low and high temperatures between the turbine housing and the exhaust manifold and safeguard tension-free connections. The expansion compensation units are welded to the turbine housing and the exhaust manifold and cannot be replaced individually.
A blow-off valve is not used in current models. Pressure peaks, caused by sudden load shedding due to the inertia of the turbine of the exhaust turbocharger, can be avoided by careful tuning of the Digital Motor Electronics software. With foresighted charging pressure control, pressure peaks can be predicted and reduced by quick adjustment of the electrically-adjustable wastegate valve. Assisted by a delayed load control of the Valvetronic (in the minimum lift direction) or the throttle valve (in the closed direction), the remaining charge air which is produced can be routed to the exhaust emission system via the engine. This form of control thus prevents the exhaust turbocharger shaft from being exposed to excessive torsional stress due to high pressure peaks.
An electrically controlled wastegate valve controls the charging pressure control in the B58 engine.