MAZDA 13B

NZ Performance Car - - Doing It For The Bro -

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.

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