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Motoring Contributions

A showcase of independent motoring journalism and automotive travails

Xedos-9 Miller: The Mazda engine with a stupid name you didn't know about

The Mazda Xedos-9 is a car that, truth be told, I had all but forgotten ever existed until today. Unfortunately, I'm an engine geek and an interesting power plant can result in otherwise deathly dull vehicles becoming objects of my fleeting affection.

I had cause to look up the Miller Cycle and discovered that Mazda put the concept into production in the mid-90's in its KJ-ZEM engine.

Unlike other specific-output increasing engine technologies, borne of Japan's displacement-based vehicle tax, Mazda's Miller engine wasn't utilised in vehicles as exciting as Honda's VTEC or even their own Wankel Rotary efforts. Xedos was Mazda's, ultimately doomed, answer to Toyota's Lexus luxury brand and its smooth-but-dull model line-up (the Xedos-9 and smaller Xedos-6) faded into the wallpaper of the 1990s automotive scenery.

The engine itself is a 2.3L Supercharged V6, with power output boosted to that of a contemporary 3.0L V6 thanks to the use of the Miller Cycle. In basic terms, the intake valves stay open into the first 30% of the engine's compression stroke - resulting in reduced compression energy losses. The resultant deficit in charge air and compression ratio is made up using a twin-screw supercharger, thus increasing the efficiency and specific power output of the engine.

Whilst this may not be that exciting to most people, surely the appeal of owning a supercharged V6 is universal? Especially since Xedos-9 Millers come loaded with all the toys you'd expect in a Japanese "luxury" barge (in Japan, luxury = buttons) and can be had for shed money these days. Despite the relatively complex engine, they enjoy a good reputation for reliability and ride quality - if not dashing good looks and seat-of-the-pants driving thrills.

I love a quirky engine, and I applaud Mazda for not only trying something different, but also turning it into production reality. Perhaps if it had been placed in something more exciting, the concept would still be around today. To me, it seems to be less flawed as a design than Mazda's Wankel engine, and that survived to 2012 - largely because of a cult following and attractive packaging.

I'd have bought a Xedos-9 Miller today if I had the space to store it - mainly just so I could say I drive a supercharged V6 and listen to it whine as I cruise to work in '90s faux-opulence. I doubt the desire will extend beyond the next few days but at the minute it represents an interesting diversion into a corner of motoring history I never knew existed.

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