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.
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