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Sacrilege? Nathan Champman’s SR20DET-Powered Mazda RX-7

26 February 2014


Nathan Champman’s SR20DET-Powered Mazda RX-7 is bound to ruffle a few feathers.

Nathan Champman’s SR20DET-Powered Mazda RX-7 is bound to ruffle a few feathers.

Based out of Christchurch, 22-year-old mechanic Nathan Chapman has long had a love affair with two particular types of car — Mazda RX-7s and Nissan Silvias. He’s owned a few of both since first getting his licence as a

teenager, but until recently he never once thought he’d be able take both those loves and mash them into one beautiful machine.

“I’d had a few FD3S RX-7s in the past, and this 1992 Mazda RX-7 was the third,” Nathan says. “I rebuilt it from scratch with a 13B turbo power plant, but I got caught skidding it on the street, so to be mature I sold the running gear on Trade Me and the body to a friend, Scott McElroy.”

With his newly acquired sense of maturity, Nathan left his Mazda days in the past (or so he thought), and decided to take his love of drifting to the track where it rightfully belongs, acquiring himself an S13 Nissan Silvia to use in the local drift series, Drift South.

He tells us: “I bought the S13 not going. It was completely original at the time, and I built that up to daily drive and compete in on the weekends.” After a few successful events, the Silvia’s SR20DET unexpectedly melted a piston, spelling the end of Nathan’s attack on his local track, Ruapuna’s Mike Pero Motorsport Park in Christchurch.

Instead of letting the meltdown keep him from the track, Nathan saw it as an opportunity to do things right, if a little differently, when his old RX-7 shell came back up for sale.

He says: “I was already rebuilding the SR20 with forged internals when I saw that Scott wanted to sell the FD, so I put two and two together — I’ve always loved RX-7s and the SR20 motor, so it was a match. In the drifting scene you see heaps of Silvias, Skylines, and Cefiros with all sorts of engine swaps. I always want to be different; it’s a way to get noticed and may even help with sponsorship later on. If I kept playing around with my S13, it would just be another S13, and I probably wouldn’t be talking to you about a magazine feature right now. I Googled the SR20DET–RX-7 combination and could only find a few pics here and there — mainly just pro drifter James Deane from Ireland, who has been running one for a while in competition. Otherwise, there was nothing else good out there, so I wanted to do it right.”

The RX-7 had received a little love in the time it had spent apart from Nathan, though much of it would eventually be redone: “Scott had caged the car thanks to Paul Tomlin at Surfab, and had begun setting the engine bay up to take a Toyota 1JZ-GTE straight six-cylinder. I think he probably realized just how much work was involved and decided he couldn’t commit, so I got it back.” The Mazda returned to Nathan’s possession complete with the custom widebody kit, though a lot of time has since been spent reworking it to get everything fitting right.

Now it was back in the home garage, and between Nathan and his good friend and fabrication guru Ryan Scott of Corona Customs, work began on fitting the small, lightweight four-cylinder, now running forged internals, into an engine bay it was never meant to go near.

“Fitting the motor was a very long and stressful process,” Nathan admits. “I never wanted to touch the firewall at all, but because of the height of the motor and the steering rack being at the front of the subframe in an RX-7, we had to mount it behind the rack, which led to firewall modifications. With custom subframes fabricated, the motor was dropped into its new home and fitted with a nice array of bolton modifications, including a Kinugawa TDO6 20G turbo sitting on a custom steampipe manifold, capable of supporting somewhere over 300kW at the rear 18×10.5-inch Cosmis Racing wheels once the Link G4 has been tuned [sadly this couldn’t happen before issue 206 went to print].”

Though many will probably question how this new engine, vastly different in shape and size to the factory 13B rotary, will affect the handling characteristics of the RX-7, Nathan isn’t worried: “Being an alloy block and sitting back a bit more, I’m sure it will handle well. I have talked to a few experienced people about the swap and they all think it will be OK; we will see soon enough.”


After spending a whole lot of time and money completely gutting, painting, fitting out the interior, rewiring the entire car, and respraying the newly customized and straight body, Nathan is tantalizingly close to the moment he can finally get his Frankenstein machine on the dyno for a proper full-power run. The question is, once it’s all ready to go and hitting both the street and circuit (that’s right, like the S13 before it, this car will be street legal in time for summer), what kind of reception does Nathan think his car will receive? Of course, a four cylinder in an RX-7 is sacrilege to many, but Nathan says: “There hasn’t been as much hate as I expected — so far, anyway. Most people are all about it. I do know there will be a bit of hate, I don’t really mind as long as they realize and appreciate the amount of hours and work that has gone into this. In the end, it’s not like I’m anti-rotary — I’ve owned three in the past — I just figured it was time to do something different.”

Though it certainly is different, it’s important to remember that even if this RX-7 had a conventional rotary power plant, it would still be a car worth noticing. Great build quality, nice tidy finishing touches, and super-aggressive looks make this machine one of the best and most interesting southern rides to hit the tracks and streets of the South Island this summer. We’re certainly looking forward to seeing, and hearing, this unique machine come race day!