Under these lean-run conditions, the overall air/fuel ratio can be as lean as 65:1, compared to the ideal 14.6:1. The drawback of super-lean mixtures is high EGTs and NOx emissions. Stratified-charge mode isn't offered on North American vehicles, because of the high NOx emissions from such a lean mixture. While there are special catalysts to scrub NOx, these catalysts are poisoned by excess sulfur impurities in North America's fuel. European fuel has a low sulfur content.
Although direct injection isn't something the aftermarket can retrofit or modify for larger fuel needs, as newer cars all begin to adopt DGI technology, engine tuners will soon be able to take advantage of this system for cleaner, more powerful and fuel-efficient modified cars.
E is for throttleMazda has also sprung a surprise with the effective use of an electronic throttle. While we whine about e-throttles being slow to respond, it is used in the MS3 to control torque. Knowing that too much torque (even with a limited-slip diff) can hurt a front-driver, Mazda engineers have developed a reduced boost management strategy for first, second and third gears.
While it's not a new idea (plenty of European vehicles with winter traction systems employ it), the MS3's torque management is independent of the Dynamic Stability Control (DSC) system and is fairly transparent-even in aggressive driving with the DSC off. On track, there's little sensation of throttle interruption when turning into a low-speed corner at neutral throttle. Only as the throttle is fed in after the apex do you feel how much power has been restrained; the front wheels start pulling the car further into the turn even as the steering is being unwound.
Like most modern turbo cars, the MS3 uses an electronic solenoid to limit overall boost pressure. Where wheelspin is an issue, like powering out from a tight corner, the e-throttle will limit boost. And since torque is multiplied by the gearing, the amount of it getting to the ground is dramatically different for each gear. Mazda actually developed separate calibration maps for first, second and even third gear with different spool-up characteristics and thus different powerbands. Depending on the gear, throttle position, steering angle and wheel speed, the butterfly is regulated accordingly. This turns out to be a smoother and more efficient way to control power and small amounts of boost, since the wastegate isn't blowing off the precious exhaust energy that keeps the turbo spooling.
Getting your hands on itThe difficulty in getting our aftermarket paws on this technology isn't in the hardware. Like electronic fuel injection and ABS, DGI and e-throttles will be everywhere in a couple of years. The hard part is for ECU hacks to decipher the cryptic stock tuning that allows engine tuners to do their magic. But just imagine teaching your turbocharged Scion tC gear-based boost/traction control, or getting 40mpg without melting pistons. Tuners like Cobb have already moved in that direction with their e-throttle Subaru ECU reflash.
Autobahn Attack: 155mph In The Mazdaspeed3He won't get out of my way. Clearly he thinks I can't go any faster, despite the fact I'm two feet off the bumper of his 5 Series at 130mph. I toy with passing on the right, again, but I've already felt weighty glares of several outraged German motorists and my co-driver just informed me it's a 1200 Euro ticket if the polizei catch me.