V6 REVAMP

After the body changes, Maezuka’s attention shifted back to engine development. It made sense to stick to familiar territory, so he began by supercharging the VQ37 engine with an HKS GTS7040 supercharger. After exploring the engine’s capabilities with one supercharger, he decided to take aim at running a 1:50 or better at Fuji Speedway. But the Z34 would need more power, so Maezuka proposed the incorporation of a second supercharger. However, having pushed the stock VQ37 engine to its limits, reinforcement of the rotating assembly was essential in order to safely and reliably produce higher horsepower levels. To this end, the block received an upgraded rotating assembly composed of low-compression CP Pistons and Carrillo connecting rods. The cylinder heads remained unchanged, save for upgrading the exhaust cams with a set of 272-degree JUN AUTO bump sticks. According to Maezuka, changing the intake cams proved a complicated project due to the complexities of the VVEL system.

BOOST CRAZE

With the block fortified, Maezuka implemented his twin supercharger plan, mounting a second GTS7040 supercharger on the opposite side of the engine. A longer serpentine accessory belt replaced the original, now driving both superchargers. The compressors feed into a Revyou front-mount vertical flow intercooler that chills the air charge before it flows through the stock throttle bodies and into the Revyou custom intake plenums for distribution to the cylinders. With each supercharger capable of supporting up to 400 PS (approximately 394 hp) feeding each bank of cylinders, significantly greater horsepower figures could be realized.

CONTROL FACTOR

Having the right hardware under the hood prompted improvements to the Z34’s software program in turn. With dual SARD 265-lph pumps in the tank supplying a six-pack of SARD 900 cc/min injectors, adjustments to the ECU was a must for proper air/fuel delivery at the target boost pressure of 17.5 psi. Utilizing open-source reflash software, the fuel and ignition tables were optimized for the second supercharger. Maezuka stated that, once refined, the Z34 produced 739.5 whp and 622 lb-ft of torque to the wheels as measured on a Bosch dynamometer.