N54 Engine

N54 Engine

N54 engine
The new generation of 6-cylinder petrol engines (NG6) is being continued with an enhancement. With the new turbocharged 6-cylinder petrol engine N54 with direct fuel injection, BMW is once again entering the arena of turbo technology.
Direct fuel injection of the 2nd generation (DI2) is used on the new turbocharged engine. The direct fuel injection (HPI: High Precision Injection) offers additional latitude for defining metering of injection flow volumes and regulating injection duration (multiple injection events, up to 3, depending upon engine rpm and load factor) and in defining mixture distribution within the combustion chamber. This has a positive effect on the power output, engine torque, consumption and pollutant emissions. The mixture cooling by the directly injected fuel means the compression can be increased compared to a turbocharged engine with intake pipe fuel injection. This improves efficiency. The use of direct fuel injection creates a homogeneous mixture formation in the entire combustion chamber. Homogeneous mixture formation means that the fuel-air ratio is regulated stoichiometrically in the same way as for intake pipe fuel injection (Lambda = 1). ("Stoichiometrically" refers to a fuel-air ratio of 14.8 kilograms of air to 1 kilogram of fuel.) The homogeneous mixture formation means that a conventional system for exhaust retreatment can be deployed.
The bi-turbo concept makes an especially important contribution with its substantially quicker response to demand for increased power. Instead of a large exhaust turbocharger, two smaller units each supply three cylinders with compressed air. The major advantage of the smaller exhaust turbochargers is their low mass moment of inertia.
Even the smallest actuation of the accelerator pedal module leads to an immediate pressure build-up in response.
At the same time variable valve timing (double VANOS) provides optimal thermodynamic efficiency, furnishing increased torque at low engine speeds for enhanced flexibility.

Brief component description
The following components of the N54 engine are described:
- Digital Engine Electronics
- Electric fuel pump control unit and electric fuel pump
- High-pressure fuel pump
- Rail with rail-pressure sensor
- Injectors (high-pressure fuel valves)
- Intake-manifold pressure sensor
- Exhaust turbocharger
- Volume-flow-controlled oil pump
- Electric coolant pump
- Variable camshaft control for the inlet camshaft and for the exhaust camshaft "double VANOS"
- Oil condition sensor
- Crankcase made of aluminium

DME: Digital Engine Electronics
There are 3 sensors on the board in the DME control unit (MSD80):
- Temperature sensor
- Ambient pressure sensor
- Voltage sensor

The temperature sensor is employed for calculating thermal conditions of the components in the DME control unit.
The ambient pressure sensor is required to calculate the mixture ratio. The ambient pressure falls the higher you go above sea level. The voltage sensor monitors the voltage supply from Terminal 87.

Electric fuel pump control unit and electric fuel pump
The DME control unit determines the fuel requirement of the engine. The required volume of fuel is sent as a message via the PT-CAN to the EKP (electric fuel pump) control unit. This message is converted by the EKP control unit into an output voltage. This output voltage controls the motor speed of the electric fuel pump. This ensures that the high-pressure pump delivers fuel at the required rate.







The electric fuel pump is an in-tank pump. The electric fuel pump is activated as soon as Terminal 15 is switched on.

High-pressure fuel pump
The high-pressure fuel pump boosts the fuel pressure (range from 50 to 200 bar) and maintains this fuel pressure to the rail. The high-pressure fuel pump is bolted onto the rear end of the vacuum pump. The driveshaft of the high-pressure fuel pump is connected to the driveshaft on the vacuum pump.







The volume control valve controls the fuel delivery pressure in the rail. The volume control valve is activated via a pulse-modulated signal (PWM signal) from the DME control unit. The PWM signal determines the throttle opening while also adjusting the fuel supply to provide the correct delivery rate for the engine's current load factor. In addition, there is the possibility to reduce the pressure in the rail. If a fault in the system is diagnosed, e.g. failure of the high-pressure sensor, the current to the volume control valve is cut off. The fuel then reaches the rail via a so-called bypass valve.







The volume control valve is a component of the high-pressure pump and can be removed during service.

Rail with rail-pressure sensor
In the rail, the compressed fuel is stored temporarily and distributed to the injectors.
The rail-pressure sensor measures the current fuel delivery pressure in the rail.







The fuel pressure reaches the diaphragm with sensor element through the high-pressure connection. The deformation of the membrane is converted via the sensor element into an electrical signal. The evaluating circuit processes the signal and forwards an analogue voltage signal to the DME. The voltage signal rises in linear form with increasing fuel delivery pressure.
The signal from the rail-pressure sensor is an important input signal of the DME for activation of the volume control valve (component of the high-pressure pump). If the rail-pressure sensor fails, the volume control valve is activated in emergency operation by the DME.

Injectors (high-pressure fuel valves)
The injector sprays the fuel into the combustion chamber under high pressure. The injector opens the tip of the nozzle needle outwards and forms a ring gap that is only a few micrometres wide. The ring gap shapes the high precision injection and ensures even, cone-shaped divergence.
The piezo-electric activation has the following advantages compared to activation via solenoid coils:
- improved possibilities for multiple fuel injection due to rapid switching times with very short dead times.
This results in significant improvements with regard to pollutant emission as well as fuel consumption.







A piezo element is an electromechanical converter. The piezo element is a type of ceramic that converts electrical energy directly into mechanical energy (power/travel). The piezo element expands when voltage is applied. This creates the lift of the nozzle needle. To achieve a greater lift, a piezo element can be structured in a number of layers.







Intake pipe pressure sensor
The intake-manifold pressure sensor measures the partial vacuum in the intake system. The intake pipe vacuum is a substitute value for the load signal. The intake-manifold pressure sensor is fitted behind the throttle valve.

Exhaust turbocharger
The engine is equipped with 2 exhaust turbochargers (one exhaust turbocharger at the exhaust manifold for cylinders 1 to 3, one exhaust turbocharger at the exhaust manifold for cylinders 4 to 6). The turbines permit especially high exhaust-gas temperatures (1050 °C technology), leading to a noticeable reduction in fuel consumption particularly at high load. The boost pressure of the exhaust turbocharger is controlled by the DME by means of a bypass valve (wastegate valve). A portion of the exhaust gases is fed via the bypass valve to the turbine. The bypass valves are controlled by the DME electro-pneumaticic pressure converter and can be adjusted to various positions. 2 connection fittings for the engine's cooling circuit and 2 fittings for the lubrication circuit oil circuit are present to support cooling and lubrication in the exhaust-gas turbocharger.







Volumetric flow-controlled oil pump
The engine has a volume-flow-regulated oil pump. This pump supplied exactly the amount of oil necessary to reach the control pressure level. The oil pump is driven by a chain from the crankshaft.

Electric coolant pump
An electric motor drives the coolant pump. The power output of the electric motor (400 Watts) is controlled by a control electronics circuit. This control electronics circuit is connected via the bit-serial data interface with the DME (Digital Engine Electronics). The DME uses the load, operating range and the data of the temperature sensors to determine the required cooling output. The DME sends to the corresponding signals for control of the coolant pump to control electronics circuit. The coolant pump's motor is immersed in flowing coolant. This cools the motor and the control electronics circuit. The coolant also lubricates the bearings of the electric coolant pump.

Oil condition sensor
The oil condition sensor measures the following variables:
- Engine oil temperature
- Oil level
- Engine oil quality

The oil condition sensor sends the recorded measurement values to the DME.

Variable camshaft control for the inlet camshaft and for the exhaust camshaft "double VANOS"
The variable camshaft timing control serves to enhance torque in the lower and middle engine speed range. A VANOS solenoid valve controls a VANOS unit on the intake side and the exhaust side. The VANOS solenoid valves are activated by the DME control unit. The timing of the engine can be influenced using the two variable VANOS adjustment units. A greater valve overlap results in lower amounts of residual gas at idle speed. A recirculation of internal exhaust gas in the partial load range reduces the volume of nitrogen oxide.







CAUTION: Do not mix up the VANOS adjuster units.

The VANOS adjustment units for the inlet and exhaust camshafts have different adjusting paths. If the VANOS adjustment units are confused, bottoming valves can lead to engine damage. The installation side is engraved on the front of the VANOS adjustment unit.

Crankcase made of aluminium
A split crankcase made of aluminium is used on the engine. To increase the rigidity, the lower part is designed as a bed-plate construction.

System functions
The following system functions are described:
- Charging pressure control
- Engine ventilation
- Engine cooling
- Volumetric flow-controlled oil supply
- Supply of fuel in line with requirements
- System protection

Charging pressure control
The boost pressure of the exhaust turbocharger is controlled by the DME by means of a bypass valve (wastegate valve). The bypass valves are activated via the electro-pneumatic pressure transducer by the DME (map-controlled).
In addition to the bypass valves, 2 blow off valves are fitted. Without the compressor bypass valves the turbochargers would have to work against the backpressure induced by the closed throttle valve. When the throttle valve closes the increase in manifold pressure causes the compressor bypass valves to open. When opened, the blow off valves connect the inlet side of the compressor with the exhaust side of the compressor. This prevents excessive ram pressure.







Engine ventilation
The engine ventilation is pressure-controlled. Depending upon the pressure levels in the intake manifold and the boost pressure, air is discharged either through a 6-channel distributor into the intake tracts or into the fresh-air intake duct on the intake side of the turbocharger (cylinders 4 through 6). The distributor rail is integrated in the cylinder head cover.







Two valves are fitted for engine ventilation.
- Non-return valve with pressure limitation
The non-return valve with pressure limitation regulates the flow depending on the applied intake pipe vacuum and controls the introduction of the blow-by gases into the inlet ports. As of a defined boost pressure, the non-return valve closes with pressure limitation.
- Non-return valve to the fresh air pipe
The 2 fresh air pipes are arranged after the intake muffler. Each of the 2 fresh air pipes connects the air filter to an exhaust turbocharger. In the fresh air pipe, the air cleaned in the air filter is transported to the compressor. As of a defined boost pressure, the prevailing partial vacuum in the fresh air pipe opens the non-return valve. The blow-by gases are vented into the fresh air pipe to the exhaust turbocharger (cylinders 4 to 6).
The ventilation connection to the fresh air pipe has an engine ventilation heating system based on the PTC principle (positive temperature coefficient). The engine ventilation heating is activated via terminal 87.

Engine cooling
For the cooling system with electric coolant pump, the possibilities of the conventional cooling system are exploited. The heat management determines the current cooling requirement and regulates the cooling system accordingly.
The following components are influenced by the heat management:
- Electric coolant pump
- Characteristic map thermostat
- Digital engine electronics (DME)

The cooling output of the system is adapted by means of a freely variable volumetric flow of the coolant.







The heat management determines the current cooling requirement and regulates the cooling system accordingly.
Under certain circumstances, the coolant pump can even be switched off completely, for example to accelerate heating of the coolant in the warm-up phase. If the engine is not running but very hot, the coolant pump will also work while the vehicle is out of use. The cooling output can be requested independent of the engine speed.
The heat management now means that, over and above the map thermostat, various characteristic maps can be used for control of the coolant pump. In this way, the engine control unit can adapt the engine temperature to the driving characteristics.

The engine control unit (MSD80) regulates the following temperature ranges:
- 108 °C = Economy mode
- 104 °C = Normal mode
- 95 °C = High mode
- 90 °C = High mode and regulation by the characteristic map thermostat

Example: If the engine control unit detects the economical operating range "Economy" due to the driving characteristics, the DME regulates to a higher temperature (108 °C). In this temperature range, the engine is operated with a relatively fuel requirement. The friction inside the engine is reduced at higher temperature. The temperature increase thus favor the lower fuel consumption in the low load range.
In the mode "High and control by the map thermostat", the driver wants to use the optimized power output development of the engine. To allow this, the temperature in the cylinder head is lowered to 90 �C. This reduction leads to better cylinder filling, which increases the torque of the engine. The engine control unit can now regulate to a certain operating range adapted to each driving situation. This means is it possible to influence consumption and power output by means of the cooling system.

Engine oil thermostat
The engine oil thermostat is located at the oil filter.







The engine oil thermostat opens or closes depending on the temperature. However, it never closes completely; it has a minimum flow through to the engine oil cooler. Up to an engine oil temperature of 110 °C, the engine oil thermostat is closed. The supplied engine oil flows via the engine oil thermostat back into the oil return through the bypass circuit. This ensures faster warming up of the engine. As of an engine oil temperature of 110 °C, the engine oil thermostat opens and reduces the aperture in the short circuit. This increases the oil flow rate in the line to the engine oil cooler. As of approx. 125 °C, the thermostat is fully opened.

Volumetric flow-controlled oil supply
The volume-flow-regulated oil pump (pendulum slide cell pump) supplies exactly the amount of oil necessary to reach the control pressure level.
The oil pressure that is applied across the control line on a control piston with oblique thrust surface (hinged bracket) counteracts the force of a compression spring. If the oil requirement of the engine rises, the pressure in the lubricating system falls and thus also at the control piston. The oil pump raises the delivery volume and sets up the previous pressure conditions. When the oil requirement of the engine falls, the pump regulates a lower delivery volume according to the position of the control piston.







The oil condition sensor indicates the engine oil temperature and oil level to the DME control unit. To calculate the oil level, the DME control unit calculates the time it takes to heat up and cool down the engine oil. The oil pressure switch indicates the oil pressure. The DME control unit activates the warning and indicator lamp in the instrument cluster via the PT-CAN (red: oil pressure low; yellow: oil level low)


Supply of fuel in line with requirements







According to system pressure applied between the fuel pump and high-pressure pump, the fuel low pressure sensor sends a voltage signal to the engine control unit (DME control unit). The system pressure (fuel low pressure) is determined with the fuel low pressure sensor before the high-pressure pump.
The DME control unit runs a continuous comparison between the specified pressure and actual pressure. If there is a deviation between the specified pressure and actual pressure, the DME control unit increases or decreases the voltage for the electric fuel pump, sent as a message across the PT-CAN to the EKP control unit. The EKP control unit converts the message into an output voltage for the electric fuel pump. These regulates the required delivery pressure for the engine (or high-pressure pump).
In the event of a signal failure (fuel low pressure sensor), with terminal 15 On the electric fuel pump is operated with pre-control. If the CAN bus fails, the electric fuel pump is operated via the EKP control unit with the prevailing on-board supply voltage.

Discontinuation of the fuel low-pressure sensor
On the E89, the fuel low-pressure sensor has been discontinued.
The high-pressure pump raises the fuel pressure from 50 to 200 bar. The high-pressure line delivers the fuel to the rail. In the rail, the fuel is stored temporarily, then distributed to the injectors. The rail-pressure sensor measures the current fuel delivery pressure in the rail. When the volume control valve in the high-pressure pump opens, the excess fuel delivered is returned to the inlet. If the high-pressure pump fails, restricted driving is possible.

System protection
If the temperature of the coolant or of the engine oil becomes excessive during engine operation, certain functions in the vehicle are influenced in such a way that the engine cooling has more energy available.

The measures are divided into 2 operating modes:
- Component protection
Coolant temperature between 117 °C and 124 °C Engine oil temperature between 150 °C and 157 °C
Action: e.g. power reduction of the climate control (up to 100 %) and of the engine
- Emergency
Coolant temperature between 125 °C and 129 °C Engine oil temperature between 158 °C and 163 °C
- Action: e.g. power reduction of the engine (up to approx. 90 %)

Notes for Service department

General notes

WARNING: Always ensure that the engine is cold before working on the fuel system.

At coolant temperatures above 40 °C, fuel can emerge at high speed when the injectors are loosened.
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