We’ve been waiting since February to find out which BMW will be the first to carry a four-cylinder engine in the U.S. after over a decade of sixes, and now we know it will be the Z4 roadster.
Officially dubbed the Z4 sDrive 28i, the new entry-level Z4 will go on-sale in the fall with BMW’s brand new 2.0-liter turbocharged four-cylinder engine. The new mill is a melting pot of BMW’s latest technologies, including Valvetronic variable valve timing, Vanos throttle-less intake, direct gasoline injection and a twin-scroll turbocharger. Altogether, they help the engine produce a stout 240 horsepower and 260 pound-feet of torque.
That’s a pretty impressive little motor, considering that the naturally-aspirated inline-six in the current base Z4 produces 255 horsepower and 220 pound-feet of torque. What’s more impressive is that even though the four-cylinder produces 15 fewer peak horsepower than the six, dyno graphs reveal that the four produces more horsepower and torque than the six at any given RPM from idle to 6000 RPM.
On top of it all, the new four-cylinder is smaller, lighter and more compact than the six, so it can be mounted farther back to optimize weight distribution and reduce overall weight slightly. All told, BMW is claiming the four-cylinder will improve fuel efficiency by 20 percent over the old six when mated to an eight-speed automatic transmission. That could mean fuel economy as high as 22 mpg city and 34 mpg highway based on the current six’s 18/28 MPG EPA rating.
What of that sweet-revving inline-six, though? It’s likely going to be phased out as the new turbo four replaces it, not just in the Z4 but other BMWs as well. The turbocharged version of the inline-six isn’t going anywhere, though it will be replaced a few years down the road with a similar but updated version of the engine from the new EfficientDynamics engine family.
We’re eager to drive the new model after our experience with this engine in the updated X1 crossover. In that vehicle, we found the four-cylinder to be torquey and smooth with a strong pull and no noticeably turbo lag. While low-end power was good, we were a bit disappointed that it fell off near redline, where the old inline-six did its best work. In the X1, that’s certainly forgivable, but we hope the Z4 will receive different tuning to reflect its sporting mission.
Unfortunately, BMW laid everything on us today except the price. It will likely remain a mystery until much closer to the on-sale date in the fall. Based on the current base model’s $47,450 starting price, though, we’re guess it will still fall between $45,000 and $50,000.