N62B48
The N62B48 engine is an increased displacement variant of the N62B44. The following components have been modified for use in the E53 X5 4.8is
- Intake Silencer
- Cylinder Head
- Engine Block
- Crankshaft
- Pistons and connecting rods
- Lubrication System
- Exhaust System
- Engine wiring harness
Intake Silencer
On account of the higher intake capacity at high engine speeds the flow characteristics of the intake silencer have been optimized for the N62B48 and the silencer has been additionally equipped with a second intake snorkel. This intake snorkel is active in the area of the righthand fog light. The second intake snorkel does not have a negative effect on the fording depth. The second intake snorkel draws in additional air only when the engine is running at high load and speed. The main volume of air is drawn in via the sound absorption cover (3).
Scheme 1390
Cylinder Head
The cylinder heads of the N62B48 are variants of the N62B44. Due to the higher stress load, the cylinder heads on the N62B48 are made from a stronger aluminum-silicon alloy. The combustion chamber diameter in the cylinder head has been adapted to the larger cylinder bore of the N62B48. The flange pattern of the exhaust manifolds on the cylinder heads has been changed in line with the new exhaust manifolds. Due to the close proximity to the hood, a heat shield has been mounted over the new exhaust manifolds on the cylinder heads.
Secondary Air System
The N62B48 is no longer equipped with a secondary air system so that the secondary air duct in the cylinder head is also rendered unnecessary. This modification has been made possible by using an optimized catalytic converter coating.
Cylinder Head Gasket
The cylinder head gasket has been adapted to the larger combustion chamber diameter. For the N62B48 it is identified by two 6 mm holes on the left next to the BMW part number.
Engine Block
Compared to the N62B44, the diameter of the cylinder bores in the N62B48 have been increased by 1 mm to 93 mm.
The crankshaft bearing caps feature apertures (1) for the purpose of improving ventilation lengthways in the crankcase and reducing pump and splashing losses in the crankcase.
Scheme 1391
Crankshaft
For strength reasons, the crankshaft material in the N62B48 has been changed from lamellar graphite to steel. The journal width of the crankshaft has been adapted to the modified connecting rods and therefore reduced from 42 mm (N62B44) to 36 mm (N62B48). To increase the displacement, the stroke of the crankshaft journals has been increased from 82.7 mm to 88.3 mm.
Pistons and Connecting Rods
The pistons have been adapted to the increased cylinder bore diameter. The connecting rods of the N62B44 feature an asymmetric form. The connecting rods are symmetrically formed on the N62B48. The symmetrically formed connecting rods permit a more uniform force application.
Consequently, it has been possible to reduce the width of the connecting rods from 21 mm (N62B44) to 18 mm (N62B48), matching the width of the crankshaft journals. In view of the higher mechanical loads in the big-end bearing, different bearing shells are used on the bearing cap and rod sides in the N62B48. Glyco 199 (sputter bearings) are used on the connecting rod end in the N62B48. These bearings are very important as the bearing shells on the connecting rod end are subject to high pressure loads.
Glyco 81 (three-component bearings) are fitted on the bearing cap end to withstand the tensile loads that occur at this point.
Exhaust System
The flow characteristics of the exhaust system have been optimized for the N62B48. The pipe diameter has been widened.
Exhaust Manifold
The exhaust manifolds have been newly developed for the N62B48 and are designed as 4-2-1 exhaust manifolds. The newly developed form prevents residual gasses entering the combustion chamber, thus improving the cylinder charge and the torque progression in the lower engine speed range.
Scheme 1392
Catalytic Converters
The catalytic converters feature an optimized catalytic coating. This coating has a faster response characteristic and higher temperature resistance. The faster response characteristic of the catalytic converters renders the secondary air injection after starting the engine unnecessary on the N62B48.
N62TU
The N62 engine is replaced by the N62TU engine as of April 2005. The N62TU engine features changes from its predecessor in the following areas
- Air intake duct
- Differentiated intake system (DISA)
- Crankshaft
- Oil dipstick
- Oil pump
- Inlet and exhaust valves
- Spark plugs
- DME 9.2.2
- Secondary Air System
Air Intake Duct
The N62B48TU engine has a greater displacement and thus a larger air requirement. Due to the new lower profile hood design of the 7 series, a new air intake ducting is required. A larger, two-channel air intake duct is therefore used.
Scheme 1393
Differential Intake Air System (DISA)
The previous fully variable intake system is no longer used in the N62TU engine. A new two-stage intake system (DISA) is used instead. The previous intake manifold was made from magnesium, the new intake is manufactured from glass fiber reinforced plastic.
There are two servomotors which provides a 2-stage (long/short) function of the intake manifold runners. Due to the increased displacement and engine power, the fully variable intake system is no longer needed.
Scheme 1394
Scheme 1395
In the intake system a sliding sleeve (3) is located at the intake manifold for each cylinder. The displacement of the sleeves determines whether the intake passage is long (1) or short (2). At idle a long intake passage is set (torque setting).
From 4700 RPM, the sleeves are pushed back and a short intake passage is thereby set (power setting). When there is no flow, the sliding sleeves remain in their respective position.
Varying the intake passages controls the pressure wave in the intake manifold in such a way as to produce a boost effect in the high RPM range. The sliding sleeves are driven by a servomotor assigned to each cylinder bank. The two servomotors together with the differential pressure sensor form a single component.
The 12V servomotors are actuated by the ECM via a PWM signal. While the sliding sleeves are open (power setting), the servomotors are actuated with a 5 % PWM signal in order to hold the sleeves in their open position.
The servomotors do not have position feedback. The sleeves can be inspected visually through the throttle valve opening. The sleeves are opened and closed once when the ignition is turned on. This prevents the sleeves from seizing during extended operation in the torque setting.
The bores for the fuel injectors and the connections for crankcase and tank ventilation are located on the intake system as well.
The following illustrations show the sliding sleeves of the intake runner in their respective positions. The first illustration (1) shows the intake sleeves closed (long runner). This setting is for low RPM to create higher torque.
The second illustration (2) shows the intake sleeves open (short runner). This setting is for high RPM which takes advantage of the pressure wave effect for increased power.
Scheme 1396
Scheme 1397
Due to the increased demands, the N62B48TU engine has a steel crankshaft. In the interests of reducing power loss (oil churning losses in the crankcase), the crankpin width has been reduced from 42 mm to 36 mm. The connecting rods are adapted accordingly.
Oil Pump
The geometry of the oil pump is specifically adapted. Oil churning losses in the crankcase are further reduced by the modified design of the oil deflector.
Oil Dipstick
The E65 Facelift model series is equipped with an electronic oil level display. The engine oil dipstick has a modified handle in black. This eliminates the need for the customer to check the engine oil level twice.
Scheme 1398
Inlet and Exhaust Valves
The stem diameter has been reduced from 6 mm to 5 mm. The moving masses reduced in this way result in a higher RPM capability.
Spark Plugs
The previous surface-gap spark plugs with 2 ground electrodes have been replaced by spark plugs with the spark position brought forward and a hook electrode.
This enables better ignition of the fuel/air mixture. In the new spark plugs the center electrode is made of platinum (replacement interval: every 100,000 miles).
Digital Motor Electronics (DME)
The N62TU engine is equipped with DME ME9.2.2. The functions of the ME 9.2.2 are carried over from the previous ME 9.2 of the N62 engine.
The pin assignment of the ME 9.2.2 has not changed in relation to the ME 9.2.1. An ME9.2.2 control unit and a VALVETRONIC control unit are used to run the N62TU.
The following changes have been made
- New processor (clock frequency 56 MHz)
- Lambda oxygen sensor LSU 4.9
- Hot-film air-mass meter HFM 6
- Software for electronic oil level measurement.
Lambda Oxygen Sensor
An LSU 4.9 oxygen sensor is used as the control sensor for each cylinder bank. Compared with the LSU 4.2 oxygen sensor previously used, the LSU 4.9 oxygen sensor reaches operational readiness twice as fast.
Full operational readiness is reached after 10 seconds (LSU 4.2 = 20 seconds). This rapid starting capability is made possible by the use of a smaller ceramic element. The outer dimensions of the oxygen sensor remain unchanged.
The previous opening for the supply of ambient air (reference air measurement) has been dispensed with. The new sensor differs from the LSU 4.2 in that a porous layer permeable by air is used instead of a reference air channel. The function stays the same. The ambient air is directed to the measuring element via the connecting cable.
Hot-film Air-mass Meter (HFM)
The HFM 6.4 is used in the N62TU engine. The sensor signal is already digitized in the HFM 6.4. The digitized signal is sent to the ECM (DME).