JWT Stage 2 Turbo Kit: A Quantum Leap for the Infiniti G37

The Infiniti G37, equipped with the naturally aspirated VQ37VHR engine, is a formidable platform from the factory. Its 3.7-liter V6 delivers 330 horsepower to the crank, providing a solid foundation for luxury sport coupe and sedan enthusiasts. While the stock car offers a satisfying balance of comfort and performance, many owners inevitably crave more power. The JWT (Jim Wolf Technology) Stage 2 Turbo Kit has emerged as a premier solution, unlocking a reliable and substantial increase to over 400 wheel horsepower. This comprehensive guide explores what the JWT Stage 2 kit entails, the engineering behind the gains, installation considerations, and how to maximize your G37’s potential after the upgrade.

The jump from 330 horsepower at the crank to 400+ horsepower at the wheels represents a transformative change in the vehicle's character. This is not a minor modification; it is a complete forced-induction system designed to integrate seamlessly with the G37’s electronics and drivetrain. Understanding the components, tuning strategy, and supporting modifications is essential for any owner considering this upgrade.

What Sets the JWT Stage 2 Turbo Kit Apart

Jim Wolf Technology has a long-standing reputation for producing high-quality, performance-tested hardware for Nissan and Infiniti vehicles. The Stage 2 kit is specifically engineered for the VQ37VHR engine, moving beyond generic universal turbo kits that require extensive fabrication. JWT’s kit is a complete, bolt-on system that includes all necessary components for a turnkey installation when performed by a qualified shop.

The “Stage 2” designation indicates a focus on substantial power gains while retaining street drivability and reliability. Unlike stage 1 kits that might use smaller turbos and conservative tuning, the Stage 2 kit employs larger turbochargers and a more aggressive tune, targeting the 400-450 wheel horsepower range on pump gas. This level of power positions the G37 squarely in the realm of serious performance, rivaling modern sports cars while retaining its luxurious interior and daily-driver comfort.

Core Components of the JWT Stage 2 System

The kit’s effectiveness stems from the careful integration of each component. Here is a detailed look at what’s included:

  • Precision Turbochargers: The heart of the system is a pair of journal-bearing or optional ball-bearing turbochargers, typically sized to spool quickly (full boost by 3500-4000 RPM) yet support airflow for 450+ wheel horsepower. The specific model varies by production run, but JWT usually selects Garrett or similar high-reliability units.
  • Cast Exhaust Manifolds: Unlike thin-wall tubular manifolds that can crack over time, JWT uses thick-wall cast stainless steel manifolds. These provide durability and optimal exhaust flow to the turbos while minimizing heat soak.
  • High-Flow Intercooler: A large air-to-air intercooler is included, sized to cool the compressed charge air effectively. Lower intake air temperatures prevent detonation and allow the engine to run more aggressive timing, directly translating to power and safety.
  • Fuel System Upgrades: To support the increased air volume, the kit includes larger fuel injectors (typically 550-650cc) and a high-flow fuel pump. These ensure the engine receives adequate fuel under boost without leaning out.
  • Engine Management & Tuning: The Stage 2 kit comes with a JWT-tuned ECU (Engine Control Unit) or, more commonly, inclusion of a JWT reflash and a programmable piggyback or standalone unit like Uprev Osiris or Cobb Accessport. The provided base tune is safe and drivable, but dyno tuning is strongly recommended to dial in air-fuel ratios and timing for your specific setup and fuel.
  • Exhaust System: A custom downpipe and full 3-inch exhaust system, or adapters to connect to the existing cat-back, are provided. The exhaust must flow freely to minimize backpressure and support the turbochargers’ output.
  • All Necessary Hardware: The kit includes all gaskets, hoses, clamps, piping, intercooler brackets, and hardware. This eliminates the need for sourcing miscellaneous parts, making the installation process far more straightforward.

Installation: What to Expect

Installing a twin-turbo system on a modern V6 engine is a significant project. The JWT kit is designed to be more “bolt-on” than a custom fabrication job, but it is still an intensive process. JWT estimates the installation time at 20-30 hours for an experienced mechanic. Key steps include removal of the front bumper, radiator, intake, exhaust manifolds, and stock exhaust; fitting the turbo manifolds and turbos; routing oil and coolant lines; installing the intercooler and charge pipes; fitting the new fuel injectors and pump; and finally, installing the exhaust system.

While a skilled DIYer with proper tools and a lift can tackle this, most owners delegate the installation to a performance shop familiar with Nissan VQ engines. Improper installation—such as misaligned oil drains, insufficient coolant routing, or loose charge pipes—can lead to premature turbo failure or boost leaks. A professional installation ensures the system is safe and performs as intended.

Post-Installation Tuning Is Critical

Even though the JWT Stage 2 kit includes a base tune (usually via a reflashed stock ECU plus a separate boost controller or piggyback device), each engine and fuel type (91 octane, 93 octane, or E85) requires individual calibration. The base tune is a conservative starting map. A proper dyno tune will maximize power, adjust for altitude, and address any idiosyncrasies in your specific G37. Expect to spend an additional 2-4 hours with a tuner operating software like Uprev or EcuTek. The final result—a smooth, linear power delivery and safe air-fuel ratios—justifies the extra cost and effort.

Measurable Performance Gains: From 330 to 400+ Wheel Horsepower

Let’s be clear about the numbers: Factory Infiniti G37s deliver approximately 270-285 horsepower at the wheels on a chassis dyno (depending on transmission and drivetrain loss). The JWT Stage 2 kit, with proper tuning, reliably produces 400-430 wheel horsepower on 93 octane fuel. This represents a gain of roughly 130-150 wheel horsepower, which is a massive increase in power density.

Acceleration, Trap Speeds, and Real-World Impact

With 400+ wheel horsepower, a G37 coupe can run the quarter-mile in the high 11-second range at 117-120 mph, compared to the stock mid-13-second range. 0-60 mph times drop from 5.2 seconds to under 4.0 seconds with proper traction (sticky tires and launch control are essential). The mid-range punch is even more transformative: from 60-100 mph, the JWT Stage 2 equipped G37 pulls with authority, making highway passing effortless.

On a road course or canyon road, the increased power requires composure and smooth throttle inputs. The torque curve becomes fatter and peaks earlier, pulling hard from 3500 RPM to redline. However, the stock suspension and brakes quickly become limiting factors (discussed below).

Boost Pressure and Power Curve

The twin turbos typically run 9-12 psi of boost on pump gas, with peak torque arriving around 4000 RPM and holding strong to 6500 RPM. The power curve is broad and progressive, not peaky. JWT’s tuning prioritizes drivability, avoiding a violent surge of boost that could upset the chassis. The result is a car that feels naturally aspirated below 3000 RPM and then pulls with increasing urgency as revs climb—a very rewarding character.

Essential Supporting Modifications for Safety and Reliability

Doubling the power output of any engine places stress on drivetrain components, cooling systems, and chassis dynamics. Owners planning a JWT Stage 2 kit should budget for these supporting upgrades to ensure the car remains reliable and enjoyable.

Cooling System Upgrade

Increased boost generates additional heat. At minimum, upgrade to a larger aluminum radiator (e.g., Koyo, Mishimoto) and consider an oil cooler. The added intercooler does reduce intake air temperature, but the engine itself runs hotter under sustained load (track days, mountain runs). An upgraded radiator and high-flow thermostat prevent coolant temps from creeping into dangerous territory.

Clutch Upgrade (Manual Transmission)

The factory clutch is not designed to hold 400+ lb-ft of torque. At the first serious pull, the stock clutch will slip. A heavy-duty single disc or a twin-disc clutch (e.g., Competition Clutch, SPEC, ACT) is mandatory for manual transmission cars. Owners of the 7-speed automatic (7AT) should consider a transmission cooler and a performance torque converter (or an upgraded valve body) to handle the power, though the 7AT is quite durable at this power level with proper maintenance.

Suspension and Brakes

With more power, the car’s weight transfer and stopping distances change significantly. Upgraded coilovers or at least performance springs/dampers are recommended to control body roll. Upgraded brake pads, high-temperature fluid, and stainless steel lines are a minimum—consider a big brake kit (e.g., StopTech, Brembo) if you intend to drive aggressively on track. The stock braking system will fade quickly with repeated high-speed stops.

Drivetrain Bushings and Mounts

Under hard acceleration, the rear differential and engine can twist, causing wheel hop and inconsistent traction. Polyurethane or solid differential bushings, engine mounts, and transmission mount help keep the driveline geometry stable. This improves launch traction and reduces driveline shock, protecting the transmission and axles.

Cost-Benefit Analysis: Is the JWT Stage 2 Worth It?

The JWT Stage 2 turbo kit is a premium product, and the total investment is significant. Expect to spend $8,000-$10,000 for the kit alone, plus $4,000-$6,000 for professional installation, tuning, and supporting modifications (clutch, cooling, suspension upgrades). This can quickly total $15,000-$20,000 on top of the purchase price of the G37 itself.

For that investment, you get a car that accelerates as hard as a brand-new $80,000 sports car while retaining near-stock reliability and driveability. When properly built, these turbo G37s are daily-driven vehicles that make over 100,000 miles with routine oil changes and maintenance. The aftermarket support for the VQ37VHR is mature, with replacement parts readily available. In contrast, swapping an engine or supercharging with less comprehensive kits often yields lower peak power and poorer durability.

Common Questions and Considerations

Will a JWT Stage 2 Turbo Kit Affect Engine Reliability?

The VQ37VHR engine is robust and has been pushed to well over 600 wheel horsepower with built internals. At the 400-450 wheel horsepower level, the stock bottom end and cylinder heads are reliable, provided tuning is correct and cooling is adequate. The biggest reliability risk comes from poor installation, detonation from bad fuel/tuning, or insufficient oiling. JWT’s kit includes high-quality oil and coolant lines, and the tune is designed with a safety margin. Many owners report tens of thousands of trouble-free miles.

What About Exhaust Sound and Smell?

The JWT Stage 2 kit will change the exhaust note. The turbochargers act as mufflers, so the overall volume is surprisingly civilized at partial throttle. Under boost, you get a deep, authoritative bellow mixed with turbo whistle. Wastegate dump tubes (if equipped) add a raspy note under full load. Expect a noticeable smell of fuel and hot oil in the engine bay after hard driving, which is normal for any turbocharged vehicle.

Are There Alternatives to the JWT Stage 2 Kit?

Competing products include GTM (Greasemonkey) turbo kits, Stillen supercharger kits, Topgunz turbo kits, and various custom setups. The Stillen supercharger is simpler and cheaper but caps out at around 380-400 wheel horsepower. GTM’s kit can make more power but requires more fabrication and has less comprehensive support. The JWT Stage 2 occupies a sweet spot of proven hardware, good documentation, and strong customer support from a well-established vendor.

Final Thoughts: The G37 as a Turbocharged Performance Legend

The Infiniti G37 with a JWT Stage 2 turbo kit is a deeply satisfying vehicle. It transforms a comfortable grand tourer into a genuine 11-second quarter-mile machine without sacrificing the amenities that make it a daily driver. The key to success lies in respecting the process: budget for proper installation, invest in supporting mods, and commit to professional tuning.

For enthusiasts who want a car that can dominate a highway pull, carve through mountain roads, and then comfortably cruise home, this upgrade delivers in spades. It is not the cheapest path to power, but it is one of the most reliable and rewarding for the VQ37 platform. With careful planning and execution, your G37 can become a turbocharged legend that stands out in any crowd.

For further reading, visit the official Jim Wolf Technology product page for the latest kit specifications: JWT G37 Turbo Kits. See owner experiences and dyno results on forums such as MyG37.com. For tuning software options, explore Uprev or EcuTek.