2012 BMW Z4 sDrive 28i: First Drive - Motor Authority
The venerable BMW inline six-cylinder is, and has long been, one of our favorite engines. That's right: The turbo four-cylinder in the 2012 Z4 sDrive 28i is a worthy replacement to the naturally-aspirated inline six. How can a tiny 2. 0-liter turbo be anywhere near as much fun as a 3. 0-liter inline six--especially in a luxury sport roadster. The answer comes, as it usually does with BMW, in the engineering. Strapped to the exhaust side of the little four-banger is a very, very compact exhaust manifold with a small but punchy twin-scroll turbo bolted alongside. The manifold gathers alternating cylinders to direct exhaust gas pulses to two different points along the twin-scroll turbine path, helping to spool the compressor that much more quickly. All of that torque means that even though the four-cylinder turbo serves up about 15 fewer peak horsepower, there's more area under the curve, which translates to more power at any given engine speed except for the last 1,000 rpm or so--and that... And despite the extra hardware on the four, the engine itself comes out about 45 pounds lighter than the six, though most of that weight is found again with higher standard equipment levels across the range. Source: www.motorauthority.com
