Interestingly, the intercooler sits directly on top of the valve cover. Mazda argues the cooler intake charge resulting from direct injection still meets efficiency targets with the intercooler in this location. It's no secret this positioning also significantly reduces flow through the core, makes packaging the engine easier and production cheaper.
But efforts were made to get air through the intercooler. A trick, two-piece ram-air duct supplies fresh high-pressure air at speed. The intercooler is housed in a box, which seals against molded plastic ductwork attached to the underside of the hood. Ram air nostrils draw air from under the leading edge of the hood.
The exhaust note is well tuned inside the cabin, but from the outside sounds like a linebacker exhaling through a cocktail straw--backpressure in D flat. Engineers hinted the engine endured extended bouts with more than 15.6 psi during testing with no ill results; a stiffer block, forged crankshaft and steel connecting rods offer proper credentials.
There is certainly power to be had from uncorking the exhaust. But once power figures start growing, the issue of whether the aftermarket can meet the challenge of a necessary bump in fueling, given the complexity of the ultrahigh-pressure direct-ignition fuel system, remains. In a direct injection engine, the injectors can only fire during the compression stroke vs. constantly in an engine with port injection, which may explain some of the softness we felt after 6000 rpm as injectors struggled to inject more fuel in less time.
Our best advice is to use conventional auxiliary injectors in the manifold for added fueling once beyond the capacity of the DI system. Combine those with a front-mount intercooler and larger turbo and you'll have a legitimate powertrain capable of serious numbers.
Mazda gets big kudos for its newly developed six-speed manual transmission whose compact three-shaft design keeps dimensions equal to those of the five-speed model. Double- and triple-cone synchronizers, some of which are made from high-carbon steel, combine to create smooth and positive shift action. Wide gear ratios take advantage of the engine's prodigious torque output and provide decent fuel economy, in the neighborhood of 27 mpg on the highway. Mazda worked with LUK to create the Active Torque Split All-Wheel-Drive System that uses an electro-mechanical clutch pack with a water-cooled "power take-off unit" to feed up to 50 percent of torque to the rear wheels. The system uses sensors that measure g-forces, yaw, throttle position, wheel speed and steering position to apportion torque. It features three automatic modes, which are not manually selectable: Normal, Sport and Snow. Under normal driving conditions, 100 percent of engine output is fed through the front axles. Start making lateral demands and the Sport mode instructs a three-piece rear-drive shaft to twist into a Tochigi-Fuji manufactured rear limited-slip differential (the same type found in the RX-8). The sport mode is smart enough to hold the 50/50 split through the exit of a corner to aid in rotation. The front differential is open. In Snow mode, the clutch pack locks torque split at 50/50. Chassis rigidity was increased by 50 percent over the Mazda6's, whose chassis is no Gummy worm. High-tensile steel was added to areas like the cross member, cowl and rear diagonal braces, with increased numbers of joints and gussets. This extra bracing, combined with the all-wheel-drive system, adds around 330 pounds; the car should arrive at around 3,500 pounds.
Increased rigidity pays dividends in ride and especially in high-speed stability, one of the Mazdaspeed6's strengths. We whipped through a lane-change chicane on the back straight at stupid velocities with utmost confidence. Monotube, rather than twin-tube dampers, feature larger diameter shafts and more aggressive valving controls springs that are 25 percent stiffer in the front and 37 percent in the rear. Anti-roll bar diameter increased by 1mm in the front and 2mm in the rear, and front lower wishbones and rear multilink bushings use harder durometer rubber. The installation of the AWD system necessitated a slightly higher ride height than the standard 6.
The TI circuit was soaked during the morning session, which tested the 215/45-18 Bridgestone Potenzas as much as the car's AWD system. Mounted on 18x7-inch wheels, the tires get fully utilized. While the car isn't necessarily undertired, it feels like more rubber would be a plus. In the wet, the Mazdaspeed6 employed understeer as its primary defense against excessive speed. No matter how hard and sideways we threw the car into a corner, mashing the power just encouraged safe understeer. We were told wet handling will be adjusted to make the car more driveable.
When faced with a dry track, the Mazdaspeed6 demonstrated an entirely different character. It was drawn toward the apex by the gentle persuasion of a left foot on the brake pedal, and all that torque made it easy to stream out of corners both fast and slow. We didn't experience as much power-on rotation as we expected given the torque split and rear limited-slip.
Although the car features an electronic throttle, there is no penalty for overlapping the throttle and brake pedal. The Mazdaspeed6 is a comfortable, willing partner that's happier to help you safely exit a compromising corner rather than punish you for a talent deficit.
Single-piston calipers remain at all four corners, but discs have grown to a healthy 12.6 inches in the front and 12.4 inches in the rear. ABS remains standard. The Mazdaspeed6 had no problem hauling down repeatedly from license-revoking velocities, but the cars we drove were fitted with prototype track-duty pads that will be available through Mazdaspeed. We'll have to wait for a production car to pass final judgement.
Aesthetic enhancements, just like the mechanical bits, are integrated: All the sheet metal forward of the A-pillar is new. The fenders are flared to fit larger rollers, and the hood is 45mm taller to fit the top-mount intercooler. A new rear bumper incorporates the dual exhaust tips and even a functional diffuser; a mild spoiler sits on the trunk.
The Mazdaspeed6 looks both aggressive and elegant, exactly the duality that defines the car's essence. Still, with this much body revision we can't help but question whether cost savings were realized in production by the top-mount intercooler.
Inside the car, three-way power semibucket seats are more supportive than those in the regular 6, but still need additional bolstering, especially in the shoulder area. Upmarket touches include an adjustable tilt-and-reach steering wheel, chrome-ringed gauges, new center console and upgraded soft-touch materials.
The Mazdaspeed6 should be in showrooms by the end of April. Expect a price tag starting in the neighborhood of $28,000. Mazda has a successful habit of entering niches it creates itself or convinces us we need, and no one dares enter the STi-vs.-EVO fray, including Mazda. The Hiroshima-based manufacturer hopes its blend of serious performance, sophistication and affordability offer an enticing alternative to a segment dominated by BMWs, Audis and Mercedes, and perhaps to those for whom the edge on the rally-bred monsters is too hard.
We look forward to time with the Mazdaspeed6 on the street. You can expect a road test soon.