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Old 11-15-2006, 03:27 PM
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BMW X5 #2

X5 3.0si: The latest edition of BMW’s trademark inline-6 makes the most accessible X5 even more appealing

BMW’s newest 6-cylinder engine makes its debut in the X5 3.0si. This aluminum/magnesium composite inline-6 features the latest engine technology from the company whose middle name is “motor.”Almost all vehicle manufacturers of 6-cylinder engines have adopted the V-6 format, whose compactness is advantageous in small or midsize cars with front-wheel drive. By contrast, BMW’s inline 6-cylinder engines are brilliant for their smoothness and sound, and treasured for these attributes. An increase in fuel efficiency and even tighter control of emissions were also set as goals for this BMW engine generation.

Compared to the previous X5 3.0i model’s engine, the new motor achieves notable progress on all fronts:

Greater power, 260 hp vs. 225 hp – a very impressive 86.8 hp/liter.

Greater torque, 225 lb-ft. vs. 214, and stronger torque characteristics across the broad range of engine speeds. Appropriately for a substantial SAV, the new engine attains its maximum torque at just 2750 rpm.

Higher revving ability. The “redline” is 7000 rpm, vs. 6500 for the previous engine. This allows the X5 driver to “wind out” the engine for maximum acceleration and exciting sound.

Superior fuel efficiency. Even though performance is enhanced, EPA mileage ratings are significantly improved; the city value increases by 1 mpg, the highway by 2, compared to the ’06 X5 3.0i with automatic transmission.

Reduced weight – 22 lb. less. Had BMW engineers developed the previous engine to meet their goals, it would have added about 30 lb. – and thus would have weighed fully 52 lb. more than the new engine actually does.

More compact – Because there is just one external drive belt, vs. the previous two, overall engine length is about an inch shorter. This frees space for other vehicle attributes customers value, such as climate control, passenger’s-side airbag, a capacious glove compartment or impact-absorption capabilities.

The benefits are all part of a concerted effort to make across-the-board improvements in engine performance. These are the result of an array of changes in the new design over the previous inline-6.

Much of the weight saving, for instance, is the result of the new engine’s aluminum/magnesium architecture. The engine consists of three major components, a magnesium-alloy [1] bedplate, magnesium-alloy upper crankcase and a silicon-impregnated (Alusil) aluminum-alloy insert. The first two magnesium castings create an extremely rigid, lightweight engine block. The aluminum-alloy insert provides the actual cylinder bores, much like the Alusil crankcase in the X5 4.8i’s V-8 engine. Other weight savings come from such items as new, hydro-formed hollow camshafts, plastic camshaft cover, thinner exhaust header flanges and an aluminum cam-chain tensioner.

Obviously, the adoption of the Valvetronic system plays an important part. Valvetronic varies valve lift to control engine power, dispensing with a conventional throttle. The
2nd-generation system includes a number of minor alterations from the original design, introduced in 2002 in BMW’s V-8 and V-12 engines. More rigid reciprocating parts allow a 500-rpm increase in engine redline, while an increase in valve lift improves top-end performance. The added rigidity also permits faster opening of the intake valves, so they are effectively open longer. Phasing of the two intake valves—where one opens sooner than the other—improves low-load efficiency and cylinder filling.

Complementing these changes, a new intake system features 3-stage induction, which spreads the torque band across a wider rpm range. Likewise, an altered combustion chamber shape and a wider range of variability in the double VANOS
[2]valve-timing system also play a role in the power and efficiency improvements. Further modifications, such as all-new engine electronics and higher fuel-injection pressures, increase the accuracy of ignition timing and fuel delivery.

Additional increases in overall efficiency also add a portion of the N52’s performance improvement. Seemingly minor items, such as an electric water pump, variable-volume oil pump and new oil/coolant heat exchanger all provide small improvements, making the new inline-6 more powerful and more fuel efficient. Compared to its most recent predecessor, the new engine delivers a tangible performance boost: 0-60 mph in
7.8 sec. vs. 8.3 for the ’06 X5 3.0i with automatic transmission. The new 6-speed automatic also plays a role in this stronger performance.

[1] – All magnesium castings in the block assembly are actually a magnesium-aluminum alloy, as pure magnesium would not have sufficient strength for these applications.

[2] – VANOS = VAriable NOckenwellen Steuerung = variable camshaft control, or variable valve timing.
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Last edited by Vaigra; 11-15-2006 at 03:31 PM.
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