Featured in NZ Performance Car Issue No. 214, Willy Cate’s NB MX-5 is the product of an unfortunate failure. After only 800km of driving, it ran a big-end bearing. Instead of sinking a replacement into the bay, Willy opted to chase more power via a 13B rotary sourced from an S5 RX-7.
“I have had rotaries before this — always loved the noise, smell, and how good they go for the size,” explains Willy. “It actually fitted up pretty easy. Nothing really needed to be modified to make it fit, besides the subframe.”
The motor itself is dimensionally small and able to be sunk low and deep into the engine bay for good balance, weighing in at 150kg. Willy used a tube Flyin’ Miata V8 conversion subframe, chopped off the V8 mounts to be replaced by custom units, and made a new sump to suit. Most of the other components were altered simply for more engine power or to make it look the way he wanted.
The factory five-speed box was retained, with the use of an S2 RX-7 bellhousing and modified input shaft, which offers long gearing — 80kph in second–type stuff — although Willy admits that they don’t last long behind the 13B. He’s now onto his seventh example, so recommends looking into something a touch stronger. He’s backed his with a Cusco two-way limited-slip differential (LSD) for the track work it sees.
“Overall, it’s lighter, but hard to say if it handles better. In my opinion, they should have come out factory like this. I would definitely do it again, although with a better gearbox — I would love an HGT,” he says.
Willy’s example is far from stock, with 48mm D-port peripheral ports and Sinco inlet manifold with a 50mm EFI Hardware throttle body atop — good for 190kW at the rears.