JUN is back on the offensive for 2010! With the world taking an ever-increasing interest in time-attack, they've just completed an extensive rebuild of one of their most legendary machines. Sporting all-new livery and a more focused performance package, the old "Akira Supra" is back with a vengeance. To see what this reloaded contender in the Japanese time-attack scene is packing, we met up with Watanabe-san of JUN literally days after the rebuilt engine was dropped into the chassis. After months in the engine building room, the 2JZ has been tuned for smoother power delivery, ready to impress skeptics who believe the JZA80 isn't cut out for lap time shootouts.
The original version of this car was built under the direction of Susumu Koyama back in 2000 as a fast street/circuit car. It managed to lap Japan's Tsukuba in just over a minute-a very impressive result for its time. It was a year later that the car went through its first makeover, when it was transformed into the JUN Akira Supra for land speed trials at Bonneville in the Nevada desert. It packed a monster 2JZ boosted by twin Trust T78s and a bespoke set of aerodynamic parts to help it penetrate the air more efficiently, all in an effort to help it beat JUN's standing record of 260.809 mph, set by Koyama-san himself with their Z32 300ZX a decade prior. After its failed attempt [see sidebar], the Supra was put away, coming out for the occasional show or exhibition. Until early this year, when the car was put through its second transformation, seen here.
The JUN JZA80 chassis was originally modified to comply with the strict safety regulations for Bonneville's top-speed racers; its shell strengthened with a complex cage to provide extensive roll-over support, which brought the added benefit of chassis stiffening. This time around, Zeal Super Function adjustable dampers and ridiculously stiff springs were fitted all around. The rear suspension member was welded directly to the chassis in true race car style, and all arms and links were replaced with adjustable Ikeya Formula items to enhance alignment tuning. Braking is taken care of with big Alcon four-piston calipers at each corner, mated to two-piece Grex slotted discs and Endless high-friction pads. At the heart of the car is the same 2JZ-GTE used to power the car at Bonneville, though freshly rebuilt with a full JUN 3.2L stroker kit, and fitted with a single Trust T88-34D for fuller and more exploitable power and torque curves (still with an ass-load of peak power). The already ported-and-polished head was fitted with 3SGTE inner shims and valve springs, along with RB26DETT lifters, to allow the engine to rev freely over and over again. A 292-degree exhaust camshaft joins the tuned variable valve timing on the intake side, which helps provide the right combination of low-end grunt and top-end power. In this state of tune, the engine cranks out a respectable 800 whp at just under 7,000 rpm, with a meaty torque curve peaking at 6,300 rpm with a towering 644 lb/ft.
A Trust four-row intercooler, large-diameter Nissan VH45 throttle body, and JUN inlet plenum introduce air to the engine, mixed with the fuel of six Sard 1,000 cc/min injectors fed by twin Bosh fuel pumps and a custom JUN collector tank in the trunk. To handle all the power, the driveline is still running the same Holinger six-speed transmission it has since the Bonneville days, now mated to an HKS triple-plate clutch and TRD limited slip differential downstream.
Outside, the Supra wears the same front bumper JUN originally developed for its initial debut, which shares nothing with the long-nose aero used at Bonneville. Its current piece was designed to direct as much incoming air as possible to its intercooler, custom radiator, and Trust 16-row oil coolers; the Bonneville piece, for the exact opposite reason. To help generate downforce at the front, JUN has added a series of dry carbon canards along with a front lip splitter. And those FRP fender vents are fully functional, helping to rid the engine bay of hot air. The original vented hood is still used for the same reason, easily recognizable with its turbo-clearing driver-side bulge. Fuji Mspec dry carbon doors and a rear hatch serve to further lighten the car, though you might miss them thanks to their meticulous Japanese construction. Active side skirts help give a more aggressive stance and limit airflow entering the car from its sides, but it's the rear additions that really set the car off, starting with the massive Sard adjustable carbon GT-wing sitting high on billet stays, and continuing on down to the carbon rear diffuser and vortex generators borrowed from RE-Amemiya. The Supra sits on 18-inch Yokohama Advan RG wheels at the front, and RGIIs at the rear, all wrapped in sticky M-compound Advan A050 semi-slicks, sized at 265/35/18. To give a more modern feel to the car, JUN has stepped away from its usual yellow and green livery in favor of metallic sand-grey hues, topped off with orange graphics.
Before the JUN Supra hits circuits like Tsukuba and Fuji, it still has to go through a lot of testing and setup to guarantee the best possible performance. Shattering records straight off the bat shouldn't be expected, but it's something JUN's been doing since the beginning-we'd be unwise to expect it not to happen again.
Behind The Build
JUN Auto mechanic
Parts MFG; Engine builders; race prep
"When you have a question about our service and product, please ask freely."
JZA80 Toyota Supra
Output: 800 hp @ 6,900 rpm / 644 lb/ft of torque @ 6,000 rpm
Engine JUN 3,210cc stroker kit: (87mm forged pistons, I-beam connecting rods, 90mm counter-balanced crankshaft), 292-degree/10.8mm lift exhaust camshaft, adjustable cam gear, head studs, stainless steel turbo manifold, intercooler piping, titanium turbo-back exhaust piping, muffler, intake manifold, custom fuel collector tank, racing radiator, electric fans; 3SGTE valve springs, inner shims; RB26DETT valve lifters; Trust T88-34D turbocharger, 2mm metal head gasket, Type-R wastegate, Airinx intake filter, four-row intercooler, 16-row oil cooler; Sard twin catalysts, 1,000cc/min injectors (x6); Nissan VH45 mechanical throttle body
Driveline Holinger six-speed sequential transmission; HKS GD Pro triple-plate clutch; TRD LSD
Suspension Zeal Super Function adjustable coilovers, 25kg/mm front springs, 21kg/mm rear springs; custom Ikeya Formula adjustable control arms/links; Trust front and rear strut tower bars; JUN anti-roll bars
Wheels/Tires Advan RG wheels (18x9.5 front, 18x10.5 rear); Yokohama Advan A050 tires (265/35-18 front and rear)
Brakes Grex 355mm two-piece slotted rotors (front and rear); Alcon four-piston calipers (front and rear); Endless MA22B brake pads (front and rear)
Exterior JUN front bumper, front fenders, side skirts, rear splash skirts, aero hood, carbon fiber rear diffuser, front canards, roof fins, aero mirrors, graphics; Fuji Mspec carbon fiber doors, hatch; Sard GT carbon fiber rear wing
Interior JUN fully spot-welded monocoque, gusseted roll cage, rigid rear suspension member, boost gauge, dash panel, switch panel; Recaro SPG racing bucket seat; Takata harness; Nardi steering wheel; Greddy gauges (oil pressure, exhaust temperature, boost, fuel pressure), Profec B Spec-2 boost controller; Billion variable radiator fan controller
Brought to our shores in 2001 for Bonneville land speed competition, the JUN Supra's most well-known form was that of a sleek, elongated, 1,300hp beast that ultimately topped out at 249.292 mph-an impressive speed, but 11.517 mph slower than the JUN Z32 300ZX clocked in the Nevada desert in August of 1991. Is time-attack this Supra's true calling? JUN is betting on it.