VANOS is a combined hydraulic and mechanical camshaft control device managed by the car's DME engine management system.

The VANOS system is based on an adjustment mechanism that can modify the position of the intake camshaft versus the crankshaft. Double-VANOS adds an adjustment of the intake and outlet camshafts.

VANOS operates on the intake camshaft in accordance with engine speed and accelerator pedal position. At the lower end of the engine-speed scale, the intake valves are opened later, which improves idling quality and smoothness. At moderate engine speeds, the intake valves open much earlier, which boosts torque and permits exhaust gas re-circulation inside the combustion chambers, reducing fuel consumption and exhaust emissions. Finally, at high engine speeds, intake valve opening is once again delayed, so that full power can be developed.

VANOS significantly enhances emission management, increases output and torque, and offers better idling quality and fuel economy. The latest version of VANOS is double-VANOS, used in the new M3.

Here's how it works:

In overhead cam engines, the cams are connected to the crankshaft by either a belt or chain and gears. In BMW VANOS motors there is a chain and some sprockets.

The crankshaft drives a sprocket on the exhaust cam, and the exhaust cam sprocket is bolted to the exhaust cam. A second set of teeth moves a second chain that goes across to the intake cam. The big sprocket on the intake cam is not bolted to the cam, for it has a big hole in the middle. Inside the hole is a helical set of teeth. On the end of the cam is a gear that is also helical on the outside, but it's too small to connect to the teeth on the inside of the big sprocket. There is a little cup of metal with helical teeth to match the cam on the inside and to match the sprocket on the outside. The V (Variable) in VANOS is due to the helical nature of the teeth. The cup gear is moved by a hydraulic mechanism that works on oil pressure controlled by the DME.

At idle, the cam timing is retarded. Just off idle, the DME energizes a solenoid which allows oil pressure to move that cup gear to advance the cam 12.5 degrees at midrange, and then at about 5000 rpm, it allows it to come back to the original position. The greater advance causes better cylinder fill at mid rpm for better torque. The noise some people hear is the result of tolerances that make the sprocket wiggle a bit as the cup gear is moved in or out.

Double VANOS

Double-VANOS (double-variable camshaft control) significantly improves torque since valve timing on both the intake and outlet camshafts are adjusted to the power required from the engine as a function of gas pedal position and engine speed.

On most BMW engines that use a single VANOS, the timing of the intake cam is only changed at two distinct rpm points, while on the double-VANOS system, the timing of the intake and exhaust cams are continuously variable throughout the majority of the rpm range.

With double-VANOS, the opening period of the intake valves are extended by 12 degrees with an increase in valve lift by 0.9 mm.

Double-VANOS requires very high oil pressure in order to adjust the camshafts very quickly and accurately, ensuring better torque at low engine speeds and better power at high speeds. With the amount of un-burnt residual gases being reduced, engine idle is improved. Special engine management control maps for the warm-up phase help the catalytic converter reach operating temperature sooner.

Double-VANOS improves low rpm power, flattens the torque curve, and widens the powerband for a given set of camshafts. The double-VANOS engine has a 450 rpm lower torque peak and a 200 rpm higher horsepower peak than single-VANOS, and the torque curve is improved between 1500 - 3800 rpm. At the same time, the torque does not fall off as fast past the horsepower peak.

The advantage of double-VANOS is that the system controls the flow of hot exhaust gases into the intake manifold individually for all operating conditions. This is referred to as "internal" exhaust gas re-circulation, allowing very fine dosage of the amount of exhaust gas recycled.

While the engine is warming up, VANOS improves the fuel/air mixture and helps to quickly warm up the catalytic converter to its normal operating temperature. When the engine is idling, the system keeps idle speeds smooth and consistent thanks to the reduction of exhaust gas re-circulation to a minimum. Under part load, exhaust gas re-circulation is increased to a much higher level, allowing the engine to run on a wider opening angle of the throttle butterfly in the interest of greater fuel economy. Under full load, the system switches back to a low re-circulation volume providing the cylinders with as much oxygen as possible.


Original Text: http://www.bmwworld.com/technology/vanos.htm

BMW M54 Engine

In an era of V-6 designs, why a straight-six?

The laws of physics; a straight-six power unit offers the optimum physical configuration for a six-cylinder engine.
The near perfect inner balance of the straight-six means an absence of free mass forces.
The straight-six does not require balance shafts and elaborate engine mounts to overcome the inherent vibrations of other designs.
With valve drive systems becoming more complex, there are engineering advantages in having only one cylinder head and only one valve train.
The Design of the Straight-Six

More power, more fuel economy. Here's how:

The M54 has an aluminum crankcase with cast cylinder liners. The engine size has been increased from the 2.8 liters of the M52 model to 3.0 liters by increasing the cylinder stroke from 84.0 to 89.6 mm. With the increase in engine size, engine power has been increased from 142 kW/193 hp to 170 kW/231 hp. The increase in the opening period of the intake valves resulted in an increase of 3.5 kW/4.8 hp in engine output. The intake and exhaust manifolds have been streamlined. This improvement contributed 16 kW/22 hp to the increase in engine output. Other refinements result from reducing piston friction and cutting back the engine's idle speed.
Electronic Throttle Butterfly

The throttle butterfly has now been replaced by a fully electronic version.

The system recognizes the gear in which the car is driving and is thus able to activate an individually programmed throttle butterfly control line for each gear. Cruise control has been integrated within the electronic throttle butterfly. Since there are no conventional mechanical linkage bars, there is a reduction of gas pedal forces. The phrase "step on the gas" takes on a whole new meaning! The controls stored within the engine management system have increased to over 600 different operating modes.
Engine Reliability

The M54 is the most reliable BMW engine ever built. Here's why:

The camshaft chain drive and the V-belt drive are maintenance-free and designed for the life of the engine.
Valve clearances are kept consistent throughout the entire running life of the engine by a self-adjusting hydraulic valve clearance mechanism. There is no need to adjust valve clearances, ever.
There is no need to reset the clutch since it is self-adjusting.
The air filters and spark plugs only have to be replaced after 100,000 km or 62,000 miles.
The oil in the transmission and final drive is a lifetime filling not requiring any replacement.
There is no need for any particular running-in service.
The BMW Service Interval Indicator informs the driver of the remaining distance until the next oil change. You no longer have to change the oil after a fixed, rigid mileage.
The engine is able to adjust automatically to all fuel grades between 87 and 98 octane.
Anti-knock control automatically adjusts the engine's running conditions to the respective fuel grade and quality.
Please note that the engine's maximum output is only achieved when running on 98 octane premium fuel.

Specifications of 3.0L

Configuration - Straight-six
Market launch Year 2000
Max output kW/bhp 170 / 231 at 5900 rpm
Max torque Nm(lb-ft) 300 (221) from 3500-4750 rpm
Combustion process - Intake manifold injection / throttle control / lambda = 1.0
Capacity, effective cc 2979.3
Compression ratio - 10.2
Bore / stroke mm 84 / 89.6
Crankcase material - Aluminum (AISi9Cu3) with cylinder liners
Height of cylinder block mm 211.0
Distance between cylinders mm 91
Topland mm 7
Main bearing diameter mm 60.0
Conrod bearing diameter mm 45.0
Conrod length mm 135, crack technology
Cylinder head material - Aluminum ((AISi6CU4)
Camshafts - 2 chain-driven camshafts running in 7 bearings and with ultra-fine balance
Camshaft adjustment - Hydraulically infinitely variable phase adjustment of the intake and outlet camshafts
Valve drive Cup tappets with hydraulic valve play compensation
Valve diameter intake/outlet mm 33.0 / 30.5
Valve shaft diameter intake/outlet 6.0 / 6.0
Valve angle intake/outlet 20 o 15' / 19 o 15'
Max valve lift, intake mm 9.7
Max valve lift, outlet mm 9.0
Opening period, intake o CS 240
Opening period, outlet o CS 244
Intake angle range o CS 86 - 126, infinitely variable
Outlet angle range o CS 80 - 105, infinitely variable
Intake manifold - Two-chamber resonance intake system with additional turbulence unit
Engine weight according to BMW standard kg / lb 170 / 375
Engine management / fuel supply - Siemens MS43 / sequential multipoint injection / fully electronic throttle butterfly adjustment / additional turbulence system adjuster
Fuel grade RON 87 - 98 (rated output with 98 ROM fuel)
Certified emission standard - EU 4 / ULEV
Exhaust system - Shell manifold with three-way main catalysts close to the engine; additional secondary air injection in some markets


Original Text: http://www.bmwworld.com/engines/m54.htm