In our first car, the Sky-D was paired to Mazda's revised six-speed manual that's lighter and more compact than the previous gearbox. Mazda also sought to mimic the feel of an MX-5 Miata shifter by shortening throws by five millimeters and reducing shift effort by a little more than one pound. More significant, though, is the shift pattern that's tighter with less side-to-side slop in each gear. Even though we were shifting with our left hand (the prototypes were right-hand-drive cars), it's clear that the new stick offers more precise, better-feeling throws.
Along with 310 lb-ft of torque, the Mazda diesel has one other surprising spec: 5200 rpm. That's the redline of the new engine, which is about 700 rpm higher than that of the typical four-cylinder diesel. On the road, the torque and redline serve harmoniously, creating an engine that has much more flexibility than Volkswagen's 2.0-liter diesel with 140 hp and 236 lb-ft of torque. With Mazda's 2.2-liter, you can comfortably cruise with significantly less shifting, accelerating easily in higher gears and staying in each gear longer. We were already in the left lane when we hit our first stretch of derestricted autobahn. Rather than dropping to fourth gear, we simply left the transmission in sixth and planted the accelerator. The engine pulled strongly and linearly until the 6 found its top speed just north of 130 mph with 600 rpm still available on the tachometer.
Choose to row through the gears, though, and the diesel will charm you with smooth acceleration that lives up to the Zoom-Zoom promise. With the Sky-D, there isn't a performance or refinement penalty for choosing the more efficient engine. The two turbochargers provide thrust throughout the entire rev range that channeled through a sensual six-speed. It's quiet too. The diesel is just marginally louder than today's direct-injected gas engines and these prototypes don't have the meticulous application of insulation like the production vehicles will.