Automotive Engineer

Hybrids and electric vehicles are probably the best route to carbon emissions reductions for most OEMs in the mid-term. But, right now, most consumers buy vehicles powered by internal combustion only. 

So if, like Mazda, you are a relatively small player in a very tough global industry, it makes sense to improve the basics first and add electrification later. The firm’s strategy is to replace its gasoline and diesel engine families with lighter, more efficient ones. And to do the same with manual and automatic transmissions. And then fit these powertrains, together with lighter, stiffer chassis, into lighter, stiffer bodies. That’s a lot all at once. Perhaps the biggest change is the common vehicle architecture that Mazda will use for all vehicles. Applied to the next-generation C/D-segment Mazda6 sedan, the body-in-white features a fifth more high-strength steel, is almost a third stiffer and is 8%, or 20kg, lighter. 

There are three load paths to improve front-impact performance. And because the main longitudinal members in the underframe are straight and formed in one piece, instead of sub-assemblies with several bends, the structure is simpler and easier to make. The reason why Mazda didn’t adopt the concept sooner is also simple. 

“The body is connected to just about every other component in the vehicle so up until now we’ve had to make some sacrifices to ensure that everything fits together,” says Masanobu Kobashi, head of Mazda’s body technology development department. “This time we’ve renewed everything – the whole vehicle. We worked together to make sure that we optimised everything so that we could have our structurally optimised body. 

“For example, until now, in order to house the existing engines we had to have a curvature in the frame. However, because we renewed the engines too it meant that we could reach the ideal solution – we got a straight frame this time.” 

Although the body is still a complex welded assembly, the idea of closed ring sections helps to improve structural integrity. The B-pillars, hot-stamped from 1,500MPa steel, are connected to crossmembers in the upper and lower body sections.