On the M54, the double-VANOS's oil-pressurized pistons rotate both the intake and exhaust camshafts within a range of 40 degrees and 25 degrees, respectively. Since then, the engine has acquired a few tweaks, including twin cams, multivalve heads, an aluminum block, Nikasil-coated cylinder liners, and variable valve timing that BMW calls VANOS for "Variable Nockenwellen Spreizung." According to our Microsoft translator, that means "variable knockwurst splicer" and not "variable camshaft adjustment" as the press kit would have us believe. The M54, as the new engine is dubbed at Bimmer Central, employs basically the same architecture that debuted on BMW's original small six-banger in 1977, which didn't migrate to these shores till 1984. And order returns to BMW's nomenclature, as a car with the 2.5 will be labeled properly as a 325, not a 323 as last year. To be clear, every horse in the growing 3-series corral, including the wagons, coupes, sedans, convertibles, and their all-wheel-drive variants, will still offer the 2.5 (it will be the only choice in the wagon). Thanks to the intake finagles shared with the 3.0-liter, the base 2.5-liter six also gets a 14-hp jolt to 184 hp. Happiness through better breathing, in other words. Another 57 percent comes from fiddling with the profiles of the twin-chamber intake-manifold and exhaust ports, and the rest comes from changes in the cam profiles. BMW says the added cubes only account for about 30 percent of the power spike over the 2.8-liter engine, which made 193 hp and 206 pound-feet, compared with the 330i's 225 hp and 214 pound-feet. The blip in displacement is courtesy of a stroke increase of 5.6 millimeters to 89.6mm.
The most obvious difference between the base 330i and 328i is the additional $590 that buys you six 496.5cc cylinders instead of six 465.5cc cylinders.
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