Heizung/Klima: Klima 750

[harrry]

Hallo,

Drehzahlüberwachung??? Der Kompressor hat selber nur einen Anschluß - das ist der für die Magnetkupplung (geschaltetes Plus). Der fahrzeugseitige Stecker hat allerdings 3 Anschlüsse... (aber der Kompressor greift halt nur einen Pol ab)

Der Vergleich Motordrehzahl und Kompressordrehzahl geht auch nicht so einfach, denn die Riemenscheiben sind unterschiedlich groß - demnach unterschiedliche Drehzahlen.

[linma34]

Zitat von harrry

Hallo,

Drehzahlüberwachung??? Der Kompressor hat selber nur einen Anschluß - das ist der für die Magnetkupplung (geschaltetes Plus). Der fahrzeugseitige Stecker hat allerdings 3 Anschlüsse... (aber der Kompressor greift halt nur einen Pol ab)

Der Vergleich Motordrehzahl und Kompressordrehzahl geht auch nicht so einfach, denn die Riemenscheiben sind unterschiedlich groß - demnach unterschiedliche Drehzahlen.

Nochmaler Locksensor ist eine Drehzahlüberwachung für den Kompressor.Im
Kompressor ist ein Hallgeber eingebaut und damit die Drehzahl abgegriffen.
Bei > 30% Drehzahlabweichung,wird mit der Drehzahl verglichen in der DME
schaltet der Locksensor den Kompressor ab.
Das hat nix mit den Riemenscheibendurchmessern zu tun!

[harrry]

Im Kompressor ist KEIN Hall-Geber eingebaut - zumindest nicht bei mir.
Der Kompressor hat genau 1 Anschluß (1 PIN). Das ist der für das geschaltete Plus, welches die Magnetkupplung einrücken läßt.

Der Stecker, der in den Kompressor eingesteckt wird hat allerdings 3 PINs. So ist ja auch der Plan.

Zur Drehzahlüberwachung:
Da die Kurbelwellenriemenscheibe nen anderen Durchmesser als die Scheibe des Kompr. hat, dreht der Kompressor immer im Faktor x anders als der Motor. Dieser Faktor müßte ja dann in dem LOCK-Senosr auch hinterlegt sein. Warum grad 30%??? Wie soll das gehen, daß der Kompressor x% langsamer (schneller geht ja nicht) dreht???
Entweder er dreht oder er ist fest.

Das macht so alles keinen Sinn - und warum auch nur beim 12-Zylinder???

[12Zylinder]

Zitat von harrry

Drehzahlüberwachung??? Der Kompressor hat selber nur einen Anschluß - das ist der für die Magnetkupplung (geschaltetes Plus).

Das ist richtig, zumindest bei Deinem Baujahr!
Wie Du den obigen Links entnehmen kannst, war das jedoch nicht immer so. Früher gab es am Kompressor "drei" Kabel. Einer für das geschaltete Plus, die beiden anderen für den im Kompressor integrierten Locksensor. Dieser war/ist dafür zuständig, die Riemenscheibe bei Kick-Down (Abruf der vollen Leistung) auszukuppeln, sodass der Klimakompressor keine Leistung mehr frisst (mal Laienhaft ausgedrückt )

Der im Klimakompressor eingebaute Locksensor ist später entfallen. Beim Umrüsten auf einen neuen Klimakompressor ohne integrierten Locksensor wird ein anderes Klimasteuergerät benötigt (dieses ist im Bereich des linken Frontlautsprechers im Fußraum angeordnet, siehe dazu auch den dritten Link weiter oben).

Beim umrüsten werden neben dem Klimasteuergerät, dem Adapterkabel (3polig/1polig) auch noch andere Riemenrippen benötigt, da die Riemenscheibe bei den neueren Klimakompressoren einen anderen Durchmesser hat.

Gruss
12Zylinder

[Johan735]

Zitat von harrry

und warum auch nur beim 12-Zylinder???

Weil bei der 12 -zylinder der riemme fur der antrieb von der kompressor ach fur der antrieb von der wasserpumpe ist.

[harrry]

Hallo,

was, wie??? Was hat die WaPu jetzt damit zu tun???

Adapterkabel von 3- nach 1-polig??? Gibt's bei mir auch nicht. In die Buchse (männlich) am Kompressor, paßt der 3-polige Stecker, aber am Kompressor selber ist halt nur ein PIN.
Lastabwurf bei Kickdown macht Sinn.
Dazu braucht man aber auch keine Drehzahlüberwachung am Kompressor.
Vollgas und Plus am Kompressor weg würde reichen...

Außerdem würde nen Lastabwurf bei nem 6-Zylinder mehr Sinn machen...

Vllt. weiß ja Erich etwas?
Gab es mal einen Kompressor mit einem integr. E-Motor für Standkühlung für den Export??? Das würde Sinn ergeben...

[SALZPUCKEL]

Zitat von harrry

Hallo,

was, wie??? Was hat die WaPu jetzt damit zu tun???

Der Kompressor wird von dem gleichen Riemen angetrieben wie die WaPu.
Wenn der Kompressor durch defekt blockieren sollte, würde der Keilriemen fliegen gehen und damit die Wasserpumpe ausfallen.

Gruß Wolfgang

[harrry]

DAS klingt logisch!
Stimmt, beim R6 (M30) hat der Klimakompr. nen eigenen Keilriemen.

[Erich]

Zitat von harrry

Vllt. weiß ja Erich etwas?
Gab es mal einen Kompressor mit einem integr. E-Motor für Standkühlung für den Export??? Das würde Sinn ergeben...

Gab/gibt es meines Wissens auch nicht fuer Japan/Australien oder andere Heisslandausfuehrungen. Da ist nur die Standlueftung fuer den Innenraum standardmaessig verbaut am 750.
weitere Aenderungen fuer Motorkuehlung: andere Riemenscheibe fuer hoehere Drehzahl, dann gab/gibt es noch eine Visko-Heisslandausfuehrung, Motoreol in Japanausfuehrung ist 0.75 Liter mehr durch groesseren Motoroelkuehler.
Dann gibt es noch einen anderen Temperaturschalter fuer Stufe 1 und 2 fuer den Zusatzluefter, die schalten dann frueher hoch, und es gibt andere Thermostate. Alles aus dem Ersatzteilkatalog ersichtlich.

[Erich]

MODEL: 750iL
BMW has developed a completely new, light alloy engine which becomes the premier engine of the new 7-Series. Designated the M70, this development demonstrates many advances in modern engine engineering. A broad power band and smooth operation are assured as the new V-12 produces 295 horsepower and the torque output is rated at 450 Nm. The compact, high performance engine radiates a balanced functional design. In addition to the impressive visual appearance, the new V-12 maintains a power-to-weight ratio of 1.77 lbs/hp. From the beginning of development, fuel economy and emission control were assigned high priorities, resulting in a combination of V-12 performance with economical operation and low emissions.
Additional technological refinements include individual cylinder bank management, precise electronic throttle operation and hot wire air flow sensing. Maintenance has been reduced with the employment of self-adjusting valves and drive belts. The M70 is equipped with a powerful 2.2kW gear reduction starter motor which provides easy starting at all temperatures. Smooth running is enhanced with the use of small, lightweight pistons which limit the oscillating mass. Further, the strong drop-forged crankshaft with twelve counterweights and the unitized engine/transmission assembly reduce vibration and resonance.
The M70 exemplifies quiet operation resulting from the use of self-adjusting valves, more precise internal clearances, optimized timing chain tensioning and a silent oil pump. These noise reduction features combine with unique laminated metal/fiber/metal cylinder head covers and oil pan which act as sound barriers.

The lightweight aluminum crankcase is manufactured hypereutectically. That is to say, special measures are employed during the formation, casting and cooling which promote torsional resistance and dimensional stability. The crankcase is symmetrical and can be machined to accept the starter motor on either side to accommodate market demands of left- or right-hand drive. The cylinder banks are arranged in a 60°V configuration with a constant cylinder center-to-center distance of 91 mm. Cooling is achieved with horizontal coolant flow. The cast iron main bearing caps, which are heat treated, are fastened to the crankcase with four bolts (arrows). Two are attached parallel to the vertical axis and two parallel to the cylinder axis. This patented configuration promotes bottom end stability and strength. During crankcase formation, a concentration of silicon crystals is maintained in the cylinder bore areas. Special cylinder wall treatment and honing produces a wear resistant silicon surface that, in combination with metal-coated pistons, provides minimal wear and long life. The drop forged steel crankshaft has excellent torsion resistant qualities and is supported in seven main bearings. Connecting rod journals are spaced 1200 apart with two counterweights per journal. The axial thrust bearing is now located at the No. 7 bearing position for improved vibration damping. Similar to the M21 design, all bearing shells are triple layered. The main bearing shells conform to the triple classification. The connecting rods are made of drop forged steel and are similar to the M20 type. The center to center distance is 135mm, however, unlike the M20, the big end is machined asymmetrically. The special machining allows two rods to run on one journal, thus there is an "installed direction" requirement. The connecting rod bearing shells conform to the double classification. Vibration is held to a minimum with short 60° ignition intervals and the use of low mass, light alloy pistons. The pistons have a 0.1mm ferrous coating which provides a highly compatible operating surface for use in aluminum/silicon cylinders. The combustion chamber bowl is located eccentrically to concentrate the air/fuel charge central to the spark plug. Correct wrist pin off-set is maintained with the use of
different pistons for each cylinder bank. The top and intermediate rings are compression rings having plain and tapered faces respectively. The oil control ring has a rubber-lined spring with a bevelled face for good oil control.
Cylinder heads are manufactured of die cast aluminum and
are identical for both banks. Cylinder head gaskets in various thicknesses are available so that combustion chamber volume uniformity can be maintained. The intake and exhaust valves are arranged in a 14° V-configuration and operated by overhead camshafts which are supported in seven bearing journals each. Camshaft lubrication is pressure fed at the journals and with overhead oil pipes providing spray oil to the camshaft lobe/rocker contact area. This valve arrangement in conjunction with the piston bowl forms a compact combustion chamber with excellent cylinder filling and evacuating characteristics. Low valve mass and dual valve springs insure reliable opening and closing between the short ignition periods. Due to the offset of the cylinder heads, the camshafts are of unequal length. The longer shaft is used in the left cylinder head.
1. Ball pin type hydraulic tappet
2. Cast rocker arm
3. Thrust guide pad

The operation of the self-adjusting valve clearance system is based on engine oil pressure hydraulics. Clearances are taken up as oil pressure enters the hydraulic tappet through the oil feed bore (arrow) and internal one-way valve. The hydraulic pressure acts on the adjusting piston which is displaced to reduce any nonspecified clearance.

1 Bleeder bore
2 Oil supply chamber
3 Oil supply bore
4 Piston
5 Body
6 Ball valve
7 Tappet pressure chamber
8 Return spring

Engine start-up and shut-down present thermal changes that require compensation. The hydraulic tappet reacts to these thermally caused dimension changes by bleeding tappet pressure back into the supply chamber when necessary. The hydraulic tappet is biased in the "clearance reduce" phase with the help of an internal return spring. Replacement hydraulic tappets are supplied with full oil supply chambers, therefore, proper functioning after installation is assured. Specific procedures must be followed concerning hydraulic tappet spare parts storage, or oil leakage will occur. Please follow instructions on tappet package. The twin camshafts are driven with a single row chain which operates in conjunction with low noise plastic guide tubes and tensioning rails. The camshaft drive chain lash is controlled with an automatic hydraulic tensioner.

The individual cylinder banks receive precisely balanced air charge delivery from two symmetrical intake plenums which have equal length ram intake runners. The fuel injectors are mounted in the inlet flanges. Elastic sealing plates are used to attach the plenum assemblies to the cylinder heads. This feature acts as a sound barrier and limits vibration to the electronic throttle valve assemblies. Each intake plenum chamber is equipped with a fast acting, electronic throttle valve assembly. Hot wire air flow sensors are used in conjunction with Digital Motor Electronics for measurement of physical air mass. Precise and rapid load sensing allows improved adaptation to changing engine operating conditions. The crankcase ventilation system vents crankcase vapors direct to the intake plenum to prevent oil mist contamination. After engine shutdown, the air flow sensing wire is superheated to vaporize any contaminants which may have adhered during the previous engine operating period. The DME 1.2 Engine Management System represents a further development in Motronic engine control. DME 1.2 is actually two individual Motronic six cylinder engines which share a common crankshaft. Precise balance and synchronization is achieved with the employment of a third management system - EML. In addition to throttle synchronization, EML provides failsafe throttle operating programs, maximum RPM and vehicle speed limits and cruise control operation. For complete DME information, see TRI 12 01 87 (2083).

For complete EML information, see TRI 12 02 87 (2087). Each cylinder bank has it's own secondary ignition distributor and high tension cables. All secondary wiring is routed and protected in a special plastic conduit developed for this purpose. The oil pump is an Eaton Rotary type of tandem design. The front segment is the primary pump which provides high pressure lubrication for all internal engine components. The rear segment operates as a scavenger pump insuring an adequate oil supply for the primary pump under all operating conditions. The scavenger pump draws oil from the rear of the crankcase via a snorkel tube and delivers the oil to the primary pump pickup.
correct hydraulic tappet operation requires engine oil which
is free of all air bubbles. A special oil deflector (windage
tray), located in the oil pan, defoams the oil and limits splash oil precipitation. The engine oil pan is constructed of two sections. The upper section is cast aluminum and incorporates strengthening ribs at strategic attachment points. This feature creates a "unitized" engine and transmission assembly which reduces flex, vibration and noise. The oil pan sump cover, like the cylinder head covers, is constructed of laminated metal-fiber-metal material which acts as a sound barrier.

The easy access oil filter is mounted on the left inner fender. Features include large diameter hoses to insure ample oil flow and an anti-drain back valve. Thermostatic oil cooler control is located in the lower section. At a temperature threshold of 95°C, engine oil is directed to the external oil cooler for additional heat dissipation.
Lubrication oil routing - Engine cross section
Lubrication oil routing - Main oil gallery
Schematic Presentation of Oil Circuit

1 Oil pan
2 Oil intake, primary oil pump
3 Primary oil pump with relief valve (4 bar, activation via filtered oil pressure)
4 Oil filter (filter cartridge bypass valve-2.2 bar, one-way check valve, oil pressure switch, oil cooler valve-activated at 95° C)
5 Filtered oil, main gallery
6 Crankshaft main bearings
7 Connecting rod bearings
8 Piston pins (oil spray)
9 Cylinder wall surfaces (oil spray)
10 Oil feed bores in crankcase (cylinders 1 - 6 and 7 - 12)
11 Oil feed bores in cylinder heads
12 Oil gallery
13 Oil spray pipes for cam lobe lubrication
14 Camshaft bearings
15 Hydraulic tappets
16 Timing chain lubrication (oil splash)
17 Rocker arm thrust (guide) pads (oil splash)
18 Oil supply for hydraulically-damped chain tensioner
19 Oil drain bore
20 Oil intake, snorkel
21 Oil pump, scavenger

The cooling system is a high volume design flowing symmetrically through both cylinder banks. The compact aluminum cross-flow radiator with a high ratio of fins and tubes has excellent heat exchanger qualities.
Cooling system flow to the radiator is regulated with an 800 C thermostat. A ball type valve (arrow) in the thermostat plate allows air bubble bleeding following cooling system service.
1. Radiator
2. Return
3. Feed
4. Thermostat
5. Water Pump
6. Right Cylinder Head
7. Left Cylinder Head
8. Connecting Pipe
9. Expansion Tank
10. Heater Core
11. Auxiliary Water Pump


All accessory component rotary drive is accomplished with two poly-V type drive belts. Once correctly installed the belts are self-adjusting with automatic hydraulic tensioners (arrow) and thus are maintenance-free.

Component Drive Distribution:
Belt #1: Water pump, cooling fan and air conditioner compressor
Belt #2: Alternator, hydraulic fluid pump
A special lock sensor control unit monitors the A/C compressor speed in relationship to engine RPM. In the unlikely event of A/C compressor seizure, the lock sensor system will immediately de-energize the compressor clutch, thus insuring uninterrupted water pump/fan operation. The four exhaust down pipes of the exhaust assembly are mounted with spring loaded ball flanges (arrows). This arrangement insures positive sealing and tends to release any trapped stress. The four 63mm stainless steel down pipes are of a balanced configuration and limit flow restriction. Further, the pipes are insulated to minimize thermal loss from the exhaust manifolds to the dual 3-way catalysts.

Exhaust system layout
Engine side view left (cylinders 7-12)
Engine side
Engine side view right (cylinders 1-6)
Engine number location (right side, front)
Engine power and torque curves


Technical Data
Design 60° V, twelve cylinders
Displacement 4987.5 cc
Stroke 75 mm
Bore 84 mm
Power 295 hp/220 kW
at engine speed 5200 rpm
Max. torque 450 Nm
at engine speed 4100 rpm
Max. permissible engine speed 6000 ± 40 rpm
Constant engine speed 5900 rpm
Compression ratio 8.8 to 1
Combustion chamber volume53.3 cc
Compression pressure 10 to 12 bar
Piston running clearance 0.01 to 0.034 mm
Valve diameter
Intake valve 42 mm
Exhaust valve 35 mm
Valve clearance self-adjusting, hydraulic
Oil pressure 4 bar
Oil volume 6.5 ltr. (+1 ltr. for oil filter and 1 ltr. for oil cooler)
Ignition Digital Motor Electronics, 30 kV system
Firing order 1-7-5-11-3-9-6-12-2-8-4-10
Distributor 2 high tension distributors
Spark plugs F8 LCR (Bosch)
Electrode gap 0.7 ± 0.1 mm
CO level Max. 0.7 ± 0.5% by volume
Idle speed 700 rpm
Fuel injection DME M1.2 with hot wire air flow sensors
Fuel grade 87 AKI (91 RON)

GROUP 11 11 01 87 (2080) Montvale, NJ December 1987
Engine Technical Dept.