The M62 block is unique in that it does not use cast iron liners, which are less able to dissipate heat than aluminum. The aluminum alloy used to manufacture the M62 block contains high levels of silicon (called Alusil). The block is etched to expose the silica, creating a bearing surface in the cylinder. The earlier M60 V8 used Nikasil cylinder wall coating, which was abandoned for Alusil after the adverse effects of burning gasoline containing sulfur in nickel plated combustion chambers were discovered. All M62 engines use Alusil blocks, which is not subject to the corrosion problem associated with Nikasil.
The M62 uses SFI fuel injection, has 4 valves per cylinder with VVT, and features fracture-split forged powder metal connecting rods.
|M62B35||3.5 L (3498 cc/213 in³)||173 kW (232 hp) @ 5700||320 N·m (236 ft·lbf) @ 3300||6200||1996|
|M62TUB35||175 kW (235 hp) @ 5800||345 N·m (254 ft·lbf) @ 3800||1998|
|180 kW (241 hp) @ 5800||345 N·m (254 ft·lbf) @ 3800||1998|
|M62B44||4.4 L (4398 cc/268 in³)||210 kW (282 hp) @ 5700||420 N·m (310 ft·lbf) @ 3900||6100||1996|
|M62TUB44||210 kW (282 hp) @ 5400||440 N·m (325 ft·lbf) @ 3600||1998|
|M62B46||4.6 L (4619 cc/281 in³)||255 kW (342 hp) @ 5700||480 N·m (354 ft·lbf) @ 3700||6500||2001|
|S62B50||4.9 L (4941 cc/301 in³)||294 kW (394 hp) @ 6600||500 N·m (369 ft·lbf) @ 3800||7000||1998|
The M62B44 is a 4.4 L (4398 cc) version with a 92 mm bore and 82.7 mm stroke. Output is 283 hp (210 kW) at 5750 RPM with 310 ft·lbf (420 Nm) of torque at 3900 RPM. In 1998, BMW introduced the M62TUB44 which included the VANOS system and an electronically actuated throttle. The non-VANOS M62B44 had a slightly less restrictive intake manifold (the difference was very similar to the difference between OBD1 and OBD2 M52/S52.)
The M5’s engine starts with an aluminum and silicon alloy Alusil engine block as do all current BMW V-8’s and V-12’s. Cylinder linings are etched after honing to promote oil retention and reduce friction. The S62’s V-8 block shares the M62's basic architecture but with 94.0 mm (3.7 in) cylinder bores vs. the M62's 92.0. The stroke is increased from 82.7 mm to 89.0 mm (3.5 in) significantly improving torque. This results in a displacement of 4941 cc, or approximately 5 liters (301 cu in). The cylinder centers are 98.0 mm apart, leaving only 4 mm of block surface between cylinders. For effective sealing with this tight cylinder spacing, BMW M engineers developed new 3-layer steel head gaskets to help ensure isolation of gasoline, oil and coolant.
Based on the cylinder heads used in other BMW V-8’s, the M5’s heads are re-jacketed for cross-flow cooling, as is customary in M division engines. The intake side of the heads also gets coolant passages. Valve adjustment is not needed, thanks to hydraulic lifters, as fitted on the U.S. spec. E36 M3 inline-6. This is the first European-market M car to use hydraulic lifters.
The air induction system is also unique to the S62. Air is taken in at two points behind the front bumper, passes through two intake silencers and two hot-film air-mass meters, and then flows into the voluminous plenum atop the engine. From there, air courses through 230-mm intake runners (including the throttle housings) to the individual cylinders. The entire assembly of plenum and runners is attached to the throttle housings via a rubber/metal flange (one per bank) that acoustically and thermally decouples the plenum from the engine itself thereby keeping the air charge cooler before it passes into the cylinders.
Admission of air to the cylinders is not through typical "throttle body," but through eight individual throttle butterflies (each 50 mm or 1.97 in. in diameter), one for each cylinder. Individual throttles are a very costly feature and previous large M six cylinder engines powering the M1, M5 and M6 models, all had this feature. However, the S62 is the first BMW engine with electronically actuated individual throttles. Positioned much nearer the cylinders than a single throttle can be, these throttles eliminate air flow “lag times" significantly improving throttle response. Each throttle operates in its own housing, mounted directly above the intake port. The electronic throttle linkage (or so-called “fly-by-wire” system) is actuated by two potentiometers as the driver depresses the accelerator. The driver accelerator inputs are processed by the engine control module and received by a DC servo motor between the cylinder banks. Through a small gearbox, this motor drives a shaft that in turn drives a link to each bank rotating the four throttle butterflies of that bank. These two links rotate the two throttle shafts, connecting via ball joints at cylinders 3 and 6. From these points, the other three throttles of each bank are opened and closed in unison. The servo motor reacts to any pedal movement in 120 milliseconds, so the driver perceives no lag time – only instant throttle response. The M Driving Dynamics Control System, controlled by the Sport button on the dash, provides two settings for throttle response: Normal mode and a quicker Sport mode. In the Sport mode, throttle response is more immediate and linear. In the non-Sport or Normal mode, throttle tip-in is softer and more languid. Additionally, the throttles of cylinders 4 and 8 also have their own feedback sensors to monitor the throttles' operation. If a fault is recognized, the system switches to one of four "limp-home" modes that can allow operation at up to 62 mph.
Bosch Motronic port fuel injection is utilized. Fuel pressure, at up to 5 bar (72.5 psi), varies according to need. Interestingly, the fuel regulator is also plumbed into the fuel filter. Excess fuel delivered to the filter/regulator returns directly to the fuel tank without passing through the fuel lines to the engine compartment and fuel rails. This keeps the excess fuel unpressurized, which thus keeps fuel heating to a minimum.
The S62 is BMW’s first V-8 engine equipped with Double VANOS; a system that steplessly varies the timing of both intake and exhaust valves of both cylinder banks. The VANOS acronym refers to variable cam control or variable valve timing which in German is VAriable NOckenwellen Steuerung. While current BMW 2.5 and 2.8 liter 6-cylinder engines also have the Double VANOS system, the 4.4 liter M62 V-8 has a Single VANOS system that steplessly varies only intake valve timing. Double VANOS is employed for the first time on a BMW V-8 with the introduction of the S62 engine. In addition to enhanced low to medium engine speed torque, the advantages of VANOS include:
As on other BMW engines, the VANOS mechanisms are located at the front of the cylinder heads. The 1450 psi of hydraulic pressure used to actuate VANOS is produced by two dedicated oil pumps; one for each cylinder head. Valve timing is varied over a range of 60 degrees in terms of crankshaft rotation with a wider adjustment range than that of other BMW engines.
A forged five-main bearing crankshaft with counterweights receives Mallory metal plugs for extremely fine balance. Connecting rods are forged as one piece. The caps are then fracture split for the best possible fit when being installed. Balancing pads are also placed on both small and large ends of the rods.
Piston design is unique to the S62 motor. For optimum power output, the engineers designed specifically shaped cutouts in the piston crowns for the intake and exhaust valves. This requires a different piston design for each cylinder bank, rather than the usual identical design for all pistons. The pistons are fitted with valve reliefs, and each is cooled by two upward-firing oil jets per cylinder. The oil jets are indexed to oil pressure; when pressure reaches 2.5 bar (36 psi), they begin operating. This level of oil pressure is a good indication of higher-than-average load and rpm. Oil cooling is provided by two separate oil passages in the crankcase. The compression ratio is 11.0:1, 10% higher than for the 4.4-liter V-8 and thus contributing to the engine's high power and torque output.
Given the 45 degree cant (from vertical) of the cylinder banks and the M5's cornering capability of over 1g, natural return of oil to the sump might have been inadequate during extreme cornering. Thus the M engineers devised a unique system to ensure effective engine lubrication at all times. In addition to the main oil (pressure) pump, there are two scavenging (suction) pumps, one for each cylinder bank. In normal and light cornering conditions, oil from the heads and main bearings flow back into the semi-dry sump at the rear of the engine via the two suction pumps. In hard cornering (0.9g or more), the Dynamic Stability Control system's lateral-g sensor switches magnetic valves to reroute oil extraction points to alternate locationsthe outer sides of the heads and sump—preventing a backup of oil collecting in the outside of the head thus avoiding potential oil starvation. This system remains active even if the driver switches off the Dynamic Stability Control.
The oil level (sump capacity of 7 liters or 7.4 quarts) and temperature are monitored by a thermal sensor. A warning appears in the Check Control display if the oil level falls below a certain point. An oil-temperature gauge replaces the fuel economy gauge in the tachometer face. Oil is cooled by a coolant-oil heat exchanger, the first ever used on a gasoline engine.
The V-8's two cylinder heads are modified to provide efficient coolant flow across the head and the coolant passages are enlarged. Coolant is circulated by a larger water pump with a capacity of 380 liters per minute (83.6 gallons/min.). Improvements in radiator efficiency negated any reason to enlarge it for the M5.
Other significant features of the cylinder heads include hollow camshafts of nodular cast iron for reduced inertia and long life. The S62's 35-mm intake and 30.5-mm exhaust valves are shared with the M62 engine, but valve timing is specific to this engine. The intake cam profiles yield 10.32 mm (0.410 in.) valve lift and 252 degrees total duration and the exhaust cam profiles yield 10.2 mm (0.400 in.) lift and 248 degrees duration, with Double VANOS shifting their timing to vary overlap. As in other current BMW V8 and 6-cylinder engines, the valves are actuated by no-maintenance bucket-type hydraulic lifters.
In place of the M62 engine's simplex roller chain driving both intake camshafts, the S62 employs a heavier-duty duplex (double roller) chain driving each intake camshaft. As in the M62, two secondary simplex (single-roller) chains then drive the exhaust camshafts from the intake camshafts.
Exiting the engine through double-wall stainless-steel exhaust headers (as on the M62 engine), exhaust gases then flow through one tri-metal catalytic converter per cylinder bank. There are four oxygen sensors: two ahead of the converters and two behind. A pressure-equalizer balance pipe connects the two exhaust streams behind the converters, enhancing low-speed torque and contributing to the engine's wonderful exhaust note. Aft of the catalytic converters, the full dual exhaust system includes two resonators and four mufflers that end in four stainless-steel outlets.
The variable tachometer warning zone innovation reminds drivers that a cold engine (especially a high-performance one) should be treated with care. When the engine is first started, the tachometer's warning zone (indicated by orange LEDs) begins at 4000 rpm. As the engine warms, LEDs are extinguished to lift the limit in increments of 500 rpm until the warning field begins at its normal 6500 rpm. The actual rpm limit is 7000.
In summary, when compared to 4.4-liter M62 power plant fitted to the E39 540i, the S62 V8 engine has been extensively modified by BMW M in the following areas:
The S62 engine produces 400 hp (DIN) or 394 hp (SAE) (294 kW) at 6,600 rpm and 369 ft·lbf (500 N·m) of torque at 3,800 rpm. It is easily identified by its large central intake velecity stack chamber cover that carries the "M" logo and is further inscribed with "BMW M Power" against a simulated carbon fiber background.