Stroking the bunny: Ben Wilkinson’s Rocket Bunny S15 drift monster

When making the step up from Pro-Am to the Demon Energy D1NZ Pro series, Benjamin Wilkinson wanted to make a statement to establish himself as a serious contender, retiring his old, well-used S13. In its place, is his new Rocket Bunny S15, powered by a monster RB32DET–and–four-speed Jerico dogbox combination. It’s a car you can’t walk past without a second look. If you did, you’ll have been unaware of just what had simultaneously graced you with its presence and threatened to steal your daughter’s innocence. But that’s alright — you’ll have learned by the end of this article.

Stroked RB engines are only now becoming more popular with the average import owner. It’s a process more akin to something that you might find in our sister NZV8 magazine, but it really does make a lot of sense. When competition demands higher power figures, more torque, and response, how do you keep a deteriorating 30-year-old engine reliable? This was the issue facing Ben and his team after their previous RB30DET S13 continued to snap cranks, costing more than its fair share of time and money. The solution? Take one RB30E block, throw a Nitto Performance Engineering 3.2-litre stroker kit into it, bolt an RB26DETT head on top, and hang a BorgWarner EFR 9180 turbo off the side — that’s how you get the job done.

The Nitto Performance Engineering 3.2-litre stroker kit gives you an increased stroke, a forged billet steel crank, one-piece forged–billet steel I-beam connecting rods, and a JE/Nitto forged piston set with upgraded thick-wall gudgeon pins and premium ring sets. Proven in drag racing, drifting, and circuit racing applications, the kit frees up the revs while maintaining bulletproof reliability. Having already run Nitto parts in the previous build, Ben knew the stroker kit would make all the difference in creating a monster powerhouse. He told us, “We needed something strong, reliable, and to also make a lot of power. I have always run Nitto pistons and rods, and there has never been any issues, so I decided that, in the long run, going with the company’s 3.2-litre stroker kit, we could get more torque and response while still being able to rev the engine and make good power.” 

Opting for the classic RB26/30 package, a collection of Tomei parts was fitted to the RB26DETT head to open it right up — including Tomei Procams, Tomei solid lifters, Tomei Type B valve springs, Tomei 1mm oversized intake valves, and Supertech oversized exhaust valves — with that mentioned BorgWarner EFR 9180 67mm strapped to the BDMotorsport exhaust manifold. The turbo is the biggest, baddest, highest-flowing turbo in the EFR family, with an airflow of 94 pounds per minute. The same turbo is run by three-time World Time Attack Championship (WTAC) champion Tilton Racing, 2012 WTAC champ Nemo Racing, and Honda’s IndyCar team. It’s a turbo that redefines what 67mm turbos are capable of — which probably explains the package’s ability to produce 480kW (644hp) on ‘low boost’ (16psi).

However, when you’re wanting to make a big splash, having monster power figures is only half of the equation. The other side of things is having a car that looks badass … so, might we add that the car is also the first genuine Rocket Bunny Pandem–kitted S15 in the country? Kei Miura’s Rocket Bunny designs are arguably some of the most well-known bodykits and have gained a worldwide fan base due to their huge over-fenders, hard body lines, and deleted-bumper accenting. Naturally, the more popular models, particularly for the Silvia family, have been imitated and become readily available to Joe Public. But Ben didn’t want to have any of this and didn’t want to be dealing with shoddy kits that never fit right and fall off every second run. Unlike most kits — which rely on hand-shaped clay or urethane — every Rocket Bunny aero kit is designed from a full-vehicle laser scan that creates 3D digital rendering of the stock vehicle.

Taking inspiration from his background in the Japanese classic car culture, Miura-san reinvents the overall image of modern vehicles with old-school design cues. Nobody in New Zealand had used the S15 kit up until this point, and Ben wanted to seize the opportunity to be the first, so that’s exactly what he did. It’s the true markings of a madman, choosing to run a kit like this in a sport that promotes close proximity and more than occasional door rubbing — and that’s exactly what Ben has done.

It’s a big step up from Pro-Sport (previously Pro-Am) in the Demon Energy D1NZ Pro series, but Ben is happy with how the season has gone thus far: “It has been a great season. We managed to qualify ninth in Tauranga against some strong competitors. Last year, in Pro-Am, we finished in the top four at Pukekohe and qualified first a couple of times. We’re aiming to get back to that.” Issues with the car saw practice cut short for round four at Hampton Downs Raceway and eventually forced the team to pull out from battles. “On Saturday, we struggled with a miss issue that was caused by fuel, followed by a small selector problem,” said Ben. The team’s luck unfortunately didn’t improve from there, as he went on to tell us: “The clutch gave way in Sunday morning practice. We managed to fix that, thanks to the crew and Cole Armstrong, who helped out with a replacement clutch, then an axle snapped in the parade run. We got another axle right before the five-minute call for battles, but, when we went to scrub the car, the axle free-spun in the hub.”

The team remains confident about pulling out a solid finish to the season, and has already started planning (or “dreaming”, as Ben put it) for the future, with hopes to incorporate a NOS injection system, a sequential six-speed gearbox, and a Winters Performance Quick Change rear end. Anything seems to be possible with this team.

2001 Nissan Silvia S15

Heart

• Engine: Nissan RB32DET, six-cylinder, 3200cc
• Block: Nissan RB30E block, Nitto Performance Engineering 3.2-litre stroker kit, Nitto pistons, Nitto rods, Nitto crank, Nitto head gasket
• Head: RB26DETT head, Tomei Procams, Tomei solid lifters, Tomei 1mm oversized intake valves, Supertech 1mm oversized exhaust valves, Tomei Type B valve springs
• Intake: Four-inch air
• Exhaust: Four-inch stainless-steel, BDMotorsport manifold
• Turbo: BorgWarner EFR 9180
• Wastegate: Turbosmart 60mm
• BOV: Turbosmart
• Fuel: MagnaFuel 2000hp main pump, two Carter pickup pumps, Injector Dynamics ID2000 injectors, Aeromotive A1000 fuel-pressure regulator 
• Ignition: AEM smart coils, custom MSD leads
• ECU: Link G4 Extreme 
• Cooling: Fenix radiator, Davies Craig electric water pump, oil cooler mounted under car

Driveline

• Gearbox: Jerico Revision 4 four-speed dogbox
• Clutch: Tilton twin-plate
• Flywheel: Custom flywheel
• Diff: R32 GTS-4 R200, GT-R 6×1 axles

Support

• Struts: Tein Super Drift coilovers, (F) Tein 8kg springs, (R) Tein 4kg springs
• Brakes: (F) R33 GT-R Brembo calipers, Wilwood pedal box; (R) R33 GTS-25T main calipers, R33 GT-R Brembo secondary for OBP Motorsport hydraulic handbrake
• Other: TDP steering kit, adjustable camber, toe, and traction arms; BDMotorsport strengthened subframe
• Shoes
• Wheels: (F) 18×9.5-inch Work Emotion CR 2P, (R) 18×10.5-inch Work Emotion CR 2P
• Tyres: (F) 235/40R18 Westlake Sport RS, (R) 265/35R18 Westlake Sport RS
• Exterior
• Paint: GT-R black, gold pearl flakes 
• Enhancements: Rocket Bunny Pandem S15 bodykit, livery by Redline Signwriters 

Interior

• Seats: Racetech bucket, Racetech safety harnesses
• Steering wheel: Racetech
• Instrumentation: Racepak dash

Power

• Power: 480kW (644hp) at the wheels on 16psi boost

Driver profile 

• Driver/Owner: Benjamin Wilkinson 
• Age: 23
• Location: Auckland
• Occupation: Insurance retainer 
• Build time: Seven months
• Length of ownership: One year
• Thanks: Pak’nSave Botany, Moa Brewery, Joe’s Mechanical Services, BDMotorsport, Infinity Autoworks, Tommy at Redline Signwriters, Kouki Apparel, Henderson Automotive, GDS Automotive, Nitto Performance Engineering, Westlake Performance Tyres, Advance Auto Tyres, Luxury Sports, Penrite Oil, Mothers car care, and Kicker audio. Plus, we can’t forget all our friends, family, and supporters out there 

This article originally featured in NZ Performance Car Issue No. 233. You can pick up a print copy or a digital copy of the magazine below: