Higher gas prices and fuel economy standards are once again downsizing automotive design. But this time around, it’s not so much the size of the car but the size of the engine that’s shrinking. But, leave it to BMW to have us actually looking forward to driving a 4-cylinder where once a six held court. It’s their first four banger available here in over a decade; and it’s in the Z4!

While an inline-6 is synonymous with BMW performance for us here in the States; around the world, BMW 4-cylinder power has been commonplace for years. And, with the 2012 BMW Z4 sDrive28i, it’s our turn again. But, the engine in question is a far cry from our last BMW 4-cylinder. Named TwinPower, it’s a 2-liter with one, twin scroll turbo where each side of the manifold is fed by a pair of exhaust runners. All of that plumbing makes for 240-horsepower and 255 pound feet of torque. And, as is usually the case when a turbo-4 replaces a natural-6, horsepower is down, but torque is up. 

Our car’s 6-speed manual transmission is standard, but an 8-speed automatic is an option. At our test track, the Z4 sprang off the line with little turbo lag on its way to 60 in 5.6-seconds, only about a half second slower than the Z4 twin-turbo six we tested in 2009. But, our 4’s power actually builds faster to a plateau, and stays fairly flat all the way to the 7,000 RPM red-line. The shifter is oddly rubbery, but still precise, as you make your way through the first 3 gears to the end of the quarter mile in 14.3-seconds at 97 miles-per-hour.

There’s a fairly aggressive exhaust note and things can get a little rough at the top of the rev-band, but for the most part it’s pretty smooth for a I4. And, believe it or not, this engine actually improves handling, as well. It takes 40-pounds off the front end, and sits further back towards the vehicle’s center, evening out weight distribution, resulting in a quicker turn-in and better balance overall. The double-wishbone-front and central- arm-axle-rear suspension remain unchanged; and provided a solid and relatively flat trip through the cones.

Styling is also unchanged, which is okay by us, as the long hood, short rear deck has perfect proportions and enough angles to keep things interesting. If you didn’t already know that it was a convertible, you’d have a hard time telling as the Z4’s hard top blends in seamlessly with the rest of the car. Open-air motoring is just the push of a button away; however, as the 2-piece aluminum top quickly folds into the trunk. 

Whether top up or top down, the Z4 has a very solid, but pleasant ride. Driving Dynamics Control, with three settings, adjusts damping as well as throttle and steering response, and stability control thresholds. Braking performance is excellent, bringing our Z4 to a halt from 60 in just 116-feet. 

Being a proper roadster, there are only seats for two, and everything in the cockpit is definitely driver oriented. Seats are snug and well bolstered. Everything seems put together very well, and our car sports body color matching yellow trim throughout. Trunk space is good for a roadster at 8 cubic-feet, and about half of that when the top is stowed.  

Government Fuel Economy Ratings for our manual with automatic start-stop are 22-City and 34-Highway. We averaged 30.5 miles-per-gallon of Premium. The Energy Impact Score is better than average, consuming 12.7-barrels of oil per year while emitting 6.9-tons of CO2.  

The Z4 sDrive28i is the new base model in the Z4 line-up starting at $49,525. Since that’s pretty pricey you might want to consider skipping TwinPower for now, and save over ten grand with the 1-Series Convertible. 

Still, BMW has big plans for the TwinPower four. Look for it to spread across the BMW line-up all the way up to the 5-series. And, when it comes right down to it, does it really matter what’s under the hood? What matters to us is hitting the start button, nailing the throttle, and having something thrilling happen. And in that regard the 2012 BMW Z4 sDrive28i certainly delivers.