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Issue link: https://adp.epubxp.com/i/719781
www.ADandP.media Coleman says that the alternatives are an "enormous naturally aspirated engine" or a highly boosted smaller engine. Clearly the first alternative wasn't in the plans. But he goes on to explain that they wanted the turbocharged engine to feel like a giant, naturally aspirated engine: they didn't want turbo lag, which is the consequence of getting the cycle started of the engine throwing off the exhaust that's used to spin the turbine to produce the air that's forced into the combustion chamber. They essentially created exhaust flow plumbing that at low speeds ports the exhaust gas through a restricted opening that creates more pressure (Coleman likens this to using your thumb to restrict the water coming out of a garden hose). And they also created a 4-3-1 pulse converter manifold that draws the exhaust gas out in a manner that is analogous to the way paint is drawn up and into the airflow of an airbrush. "One dirty secret of turbos," Coleman reveals, "is that they typically don't make the fuel economy numbers that they promise." He explains that the reason this tends to be the case is because under high loads there is a thermal management strategy often employed that is based on injecting additional fuel into the combustion chamber: "Paradoxically, more fuel makes the combustion cooler." It also wastes fuel. However, given the nature of the EPA drive cycle, which is comparatively gentle, that fuel enrichment strategy doesn't come into play, so the EPA numbers for turbo- charged engines are good. But Mazda engineers were working for "real world" performance. So they are using a cooled EGR system to manage the temperature. "It's a well-understood principle," Coleman says. But if the goal is to get good window sticker numbers, then it is irrelevant. The EGR approach allows the use of a 10.5:1 compression ratio. As previously mentioned, the three-row CX-9 is a "family" vehicle. But the Mazda devel- opers discovered something interesting about what people who are looking at vehicles in this category are interested in. It once was that the scales were entirely weighted toward family interests for vehicles like the CX-9, with the individual driver having little consequence. But perhaps it is because of Mazda's own focus on the importance of driving (it will probably be among the last companies to introduce an autonomous car when that time comes), but they determined that people are interested in more of a balance between the individual and the family, so when Julien Montousse set about to design both the interior and the exterior of the CX-9, they worked to address the functional needs of families (ease of access to the third row; the ability to have a child seat in place in the second row while providing access to the third), as well as a sense of performance and fashion: "Compared to the old CX-9," he says, "which was maybe more submissive, this time we wanted it to represent Mazda in a very proud, very stylish manner." And all evidence points to the fact that they delivered. The CX-9 is meant to be the "flagship" for the brand, including the use of Nappa leather on the interior, real aluminum and rosewood. 29 AD&P; ∕ SEPTEMBER 2016 MAZDA CX-9