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1993 Mazda RX-7 - Rocket Bunny Widebody & LS-Powered

Modernizing Mazda’s legendary RWD coupe

Aaron Bonk
Feb 9, 2015
Photographer: Ginash George

The early '90s were a special time for anybody who cared about going fast. The shackles once placed upon the auto industry were letting go, which meant that all of a sudden 1993 had a whole lot more going for it than flannel shirts and America Online trial CDs. By the mid-1990s, the American auto landscape was riddled with all sorts of Japanese performers. No high school boy's bedroom wall poster ensemble was complete without Toyota's Supra, Acura's NSX, Nissan's 300ZX, Mitsubishi's 3000GT VR-4 and, despite it having one of the shortest production runs of the bunch, Mazda's third-generation Mazda RX-7.

1993 mazda RX7 GM LS1 engine 06 Photo 2/11   |   Hard to beat 451hp and 421 lb-ft of torque from this reliable LS1.

The RX-7's turbocharged rotary engine demanded respect while also causing fear. The car's lines, however, while two decades later, hid its age well. Such is obvious for Scott Sengpiel, who's admired the factory-turbocharged chassis since its creation but has since gone on to replace its temperamental Wankel engine with eight cylinders worth of American intensity. "The car doesn't look 21 years old, and I love that," he says. "People come up to me all the time, asking what it is, and when I [tell them] what year it is, they're shocked."

Mazda's third-time RX-7 may be old enough to buy beer, but its near-perfect balance and affinity for grip don't care about its age. The engine, however, can wane fast and hard. At just 85,000 miles, Sengpiel's was on its fourth, which is why the swap was planned even before settling on a particular car. "I've always wanted to do a V8, and this was the perfect chassis for it," he says. "I bought the car intending on putting the LS in there because of its potential, its reliability, and its [ability to make] big power at a low cost."

1993 mazda RX7 rocket bunny widebody aero kit 02 Photo 6/11   |   One of the first Rocket Bunny FDs to hit the States—damn, it looks good!

The party starts with the 5.7-liter small-block sourced from 1998-2002 versions of Chevrolet's Camaro SS. Sengpiel, whose background is arguably more Mitsubishi than Mazda, ditched the car's turbocharged heritage early on and instead relegated the LS1 to naturally aspirated status. Here, the cylinder heads have been modified by Racing Head Service and feature oversized valves and Comp Cams valvetrain that are orchestrated by one of the company's street cams stuffed inside the block. The rest of the all-aluminum V8's internals remains mostly stock, while outside the intake and exhaust tracts have been updated with higher-flowing pieces. The result: 451hp and 421 lb-ft of torque.

Consider Sengpiel's affinity for the racetrack and the eight pistons underneath the hood and it's easy to dismiss any sentiments he may have toward an RX-7 that looks as good as it is quick. Your dismissal would be wrong, though, and that's mostly because of the Rocket Bunny aero package that made its RX-7 debut on his chassis but also because of the car's remarkably tidy engine space. "I built the car to be a really fun street car, race it in an HPDE [high-performance driving event], and then drive it home," Sengpiel says after explaining why he put so much effort into how the car looks. "I take a lot of my inspiration from the pro touring guys who are building really clean, old cars," he says. "But before I do anything on the car, I come up with a plan on how I want it to function and then how I want it to look."

1993 mazda RX7 sparco EVO II seat 04 Photo 10/11   |   1993 Mazda RX-7 - Rocket Bunny Widebody & LS-Powered

Bad things rarely happen when you allow form to follow function. Up front, the detailed wiring harness and thorough ensemble of AN plumbing don't just look nice, they allow the engine to be pulled and set aside in less than two hours, which is a good thing for Sengpiel, who does most of the work himself. He did, however, leave the bodywork to the professionals and the wiring to Jordan Innovations. "Wiring has always been a trouble area for me," he admits, "so I decided to hand it off to Jeff Jordan." Everything else underneath the hood is all Sengpiel, though; he's even building an entirely new engine to replace the LS1 on his own, this time an LSX that he says will be good for about 600whp.

What Sengpiel wants out of his RX-7 isn't all that different than what the original buyers of the 1990s were looking for: a purpose-built performer that can be abused whenever and wherever he pleases. A dedicated track car this isn't and, despite the aero package and attention to detail, a fancy-pants showpiece, it most certainly is not. To that end, Sengpiel simply says, "I really want people to know that this car was built with the intention of being a street car that is raced. It doesn't sit in the garage only to come out for parking lot shows." All of that is entirely okay and, if you ask the 1990s, its ensemble of Japanese sports car heritage is better for it.

1993 mazda RX7 volk racing ZE40 wheel 08 Photo 11/11   |   Matte blue gunmetal on the new Volk Racing ZE40s are sex!
By Aaron Bonk
408 Articles
1993 Mazda RX-7 - Rocket Bunny Widebody & LS-Powered
Tuning Menu
Owner: Scott Sengpiel
Hometown: Milwaukee, WI
Occupation: Snap-On Marketing Specialist
Power: 451hp; 421 lb-ft of torque
Engine: GM LS1 engine transplant; RHS cylinder heads, 1mm oversized titanium valves; Comp Cams street cam, dual valve springs, hardened push rods, Ultra Gold rocker arms, hydraulic rollers; C5-R Corvette oil pump, hardened timing chain; Improved Racing oil baffle pan, oil cooler bypass; ARP rod bolts, main studs, head studs, crankshaft bolt; coated long-tube headers; FAST 92mm throttle body, intake manifold; LS7 injectors; Aeromotive fuel pressure regulator; Bosch 044 fuel pump; Arc Asylum stainless-steel exhaust; Turn One power steering pump; Samberg Performance radiator, intake; MSD 8.5mm spark plug wires; Jordan Innovations engine and chassis wiring harnesses; Earl's oil cooler; Accusump oil accumulator; Rawsomotion oil catch can
Drivetrain RPM Level V Tremec T56 transmission; ACT twin-disc clutch, lightweight flywheel; ARP flywheel and pressure plate bolts
Footwork & Chassis: TEIN Flex coilovers; SuperPro bushing system; On Point Motorsports front sway bar with Arc Asylum mounts; Tanabe rear sway bar; Improved Racing rear sway bar endlinks
Brakes: Project Mu four-piston calipers, rotors, pads; Wilwood proportioning valve; Lil Joe steel-braided and hard lines
Wheels & Tires: 18x10.5" +28 front, 18x12" +20 rear Volk Racing ZE40 wheels; 275/25 R18 front, 315/35 R18 rear Nitto NT05 tires
Exterior: KC Customs Graphite Metallic Silver paint; Rocket Bunny widebody aero kit; FEED-style carbon-fiber hood; Seibon carbon-fiber trunk lid; RE Amemiya HID headlights; shaved antenna, rear side markers, engine bay
Interior: Sparco EVO II seats, four-point harnesses, R 345 steering wheel; Arc Asylum custom harness bar; custom Speedhut instrument cluster; Pioneer AVIC head unit
WWW: compcams.com; mackin-ind.com; nittotire.com; sparcousa.com; tein.com

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