Ward’s 10 Best Engines competition has recognized outstanding powertrains for 21 years. This installment of the 2015 Behind the 10 Best Engines series looks at the development of’s 1.5L 3-cyl. in the Mini.
Most of us can remember when the handful of 3-cyl. engines on the market were shaky, sluggish, generally sorry attempts at wringing a bit more fuel economy out of cheap subcompact cars. Nobody liked them, and very few bought them when affordable 4-cyl. alternatives were available.
My, how things have changed. Of the 2015 10 Best Engineschosen after exhaustive testing and evaluation by WardsAuto editors, no fewer than two are three-bangers.’s tiny 1.0L turbocharged I-3 made the cut for 2014 and repeats this year. Now Mini’s impressive -designed turbocharged triple joins it on Ward’s 10 Best Engines list for 2015.
“The 1.0LEcoBoost 3-cyl. and the 1.5L Mini 3-cyl….hold their own against bigger engines and are a testament to the dogged pursuit of efficiency, friction reduction and power density,” writes editor Tom Murphy. “How do we separate the winners from the rest of the pack? By paying close attention to real-world fuel economy, throttle response and noise, vibration and harshness.”
WardsAuto editors score each engine on those characteristics in addition to power, torque, technology and relative competitiveness. “Historically, 3-cyl. engines were something you were forced to drive by economic necessity,” says editor Drew Winter. “However, we’re now seeing a new generation of small boosted 3-cyl. mills that still are base engines, but are incredibly powerful for their size, tout lots of advanced technology and are a lot of fun to drive.”
It helps that this one essentially is half of BMW’s award-winning 3.0L turbocharged straight six and, as such, inherits the suite of state-of-the art technologies that make BMW’s latest-generation 4- and 6-cyl. engines (all with common 0.5L cylinder displacements) so deservedly acclaimed. That TwinPower technology package includes turbocharging, direct fuel injection, dual Vanos variable camshaft control on both intake and outlet sides and Valvetronic fully variable valve control.
The engine also is compact and lightweight – ideal for transverse front-drive applications – with its forged steel crankshaft, aluminum block, weight-optimized pistons, vibration-damping countershaft, a map-regulated oil pump and a mechanical coolant pump that also supports the alternator and HVAC compressor. Its turbocharger is integrated into the exhaust manifold for compactness and a short exhaust-gas path, and fuel injectors are positioned centrally between the valves, right next to the spark plugs.
It generates 134 horses at 4,500 rpm and 162 lb.-ft. (220 Nm) of torque at 1,250 rpm, representing 11% more power and 33% more torque compared with the previous Mini’s naturally aspirated 1.6L 4-cyl.
An overboost feature temporarily bumps that to 169 lb.-ft. (230 Nm) on demand. As a result, it can launch the ’15 Mini Cooper from rest to 60 mph (97 km/h) in 7.3 seconds, 1.1 seconds quicker than the previous Mini.