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175 bolt-on horsepower. Who wants it? Any street-performance car could benefit from the simplicity of bolt-on power. It’s the least complex and typically reliable instant gratification that can be enjoyed after putting in some effort in the garage at home. So how can bolt-ons make 175 horsepower?

For the fans of Nissan’s latest Z, the 370Z or Z34, a forced-induction solution that caters to a broad audience would be just what the doctor ordered. However, options in the Z34 community have been thin, with only a few tuners venturing under the hood of the more-compact engine bay of the 370Z. But despite the challenge, a forced-induction system would add an entirely new dimension to an already competent machine.

Back To The Drawing Board GReddy led the way with a turbo system for the 350Z at a time when designing bolt-on turbo systems for normally-aspirated platforms was still cost prohibitive. When the 370Z hit our shores in 2009, GReddy was once again among the few on the leading edge to offer a twin-turbo system for the Z34. Development of the system revolved around GReddy’s tuner turbo systems. Although the manifolds, turbochargers and wastegates interchange between the various generations of VQ engine, the VQ37VHR requires the use of engine-specific wastegate adapters, downpipes and hard pipe plumbing.

Modularity = Quick Development

The VQ37-powered platforms had been available for a relatively short time; fortunately, the interchangeability of the components between the VQ family of engines saved precious development time. Leaving the factory longblock unchanged, fitment of the manifolds and turbochargers began. GReddy’s durable, cast ductile-iron manifolds channel exhaust gasses into the turbine inlets of the TD06SH-20G turbochargers. These particular turbos offer a balance of response and peak power potential for streetability and high performance. VQ37-specific wastegate adapters enable the use of the GReddy Type-T external wastegates to regulate boost pressure set by the PRofec B-Spec2 electronic boost controller. Stainless downpipes (that eliminate the catalytic converters) route spent gasses through a Turbo Ti-C dual exhaust.

Two Paths

The turbochargers send the compressed intake charge through the GReddy Type-29 R-Spec intercooler before reaching the throttle bodies. The VQ37VHR features a similar dual-path intake tract to the VQ35HR, which employs a separate throttle body for each bank of cylinders and distributes air to the intake ports through Nissan’s nylon intake system. Since nylon does not heat soak like metals do, it in turn does not transfer heat to the intake charge either. Cooler air entering the combustion chambers equates to greater air density and greater power potential.

Special Delivery

Forced-induction will almost immediately overtax the stock fuel system, prompting improved fuel delivery improvements. Six RC Engineering 440 cc/min injectors receive a steady supply of fuel from GReddy fuel rails equipped with a fuel return. Employing a fuel return system ensures that the injector farthest from the point that enters the fuel rail does not lean out from fuel starvation under extreme duty cycles. Regulating fuel delivery on modern drive-by-wire engines has also become tricky business, since many factory engine-management systems are networked throughout the car. GReddy’s pre-programmed eManage Ultimate piggyback enginemanagement computer was selected for its tuning flexibility and simplicity. By supplementing the factory ECU, the eManage Ultimate enables customization of fuel and ignition tables in addition to monitoring and tuning other features like variable cam timing. With the Z strapped to SP Engineering’s Dynojet dynamometer, the boost pressure was set to a conservative 7 psi. This was done to ensure reliable performance from the factory rotating assembly. Once tuned, the Z spun the rollers to the tune of 453.4 horsepower and 344 lb-ft of torque.

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