The Nissan 370Z (Z34) is a modern sports car icon, and its VQ37VHR engine responds exceptionally well to forced induction. For owners looking to unlock serious horsepower, selecting the right turbo kit is the single most important decision. Three names consistently dominate the conversation: JWT (Jim Wolf Technology), Injen, and TopSpeed. This comprehensive comparison breaks down the features, power gains, and real-world character of each kit to help you make an informed choice for your budget and performance goals.

Turbocharging the VQ37VHR: Understanding the Platform

The 3.7-liter VQ37VHR is a high-revving, durable engine with an aluminum block and heads. Its variable valve event and lift (VVEL) system presents specific tuning challenges and opportunities. Adding a turbo kit is the most effective way to substantially increase horsepower, moving from the stock ~330 hp to well over 500 whp at the wheels. However, the addition of forced induction places significant stress on the engine’s fuel system, cooling system, and drivetrain. Whether you choose a kit from JWT, Injen, or TopSpeed, understanding the holistic needs of the vehicle is key to building a reliable, powerful 370Z.

JWT Turbo Kit: The Complete Plug-and-Play Package

Jim Wolf Technology (JWT) has been a cornerstone of Nissan performance since the days of the original Z cars. Their 370Z turbo kit is widely regarded as one of the most complete and refined options on the market. Designed for enthusiasts who want OE-like drivability with dramatic power gains, this kit emphasizes integration and reliability.

JWT Kit Hardware and Components

The JWT kit is engineered around a high-quality Garrett Motion turbocharger, typically the GTX3071R or GTX3576R. This ensures robust build quality and excellent turbine efficiency. The kit includes a cast exhaust manifold, a stainless steel downpipe, a high-flow catalytic converter, and an aluminum intercooler with polished piping. Notable features include a TiAL Sport wastegate and blow-off valve, which are industry standards for consistent boost control.

  • Turbocharger: Garrett GTX3071R/GTX3576R (ball-bearing)
  • Intercooler: Custom bar-and-plate core with mandrel-bent piping
  • Wastegate/BOV: TiAL Sport QRJ/Atmosphere
  • Fuel System: 550cc injectors (optional upgrade available)
  • Exhaust: 3-inch stainless steel downpipe and high-flow cat

Power Gains and Tuning with JWT

On pump gas (93 octane), the JWT kit reliably produces between 420 and 470 wheel horsepower, depending on the specific turbo wheel and supporting mods. With E85 or race fuel, output can climb past 520 whp. JWT includes a custom ECUTEK tune via a handheld flash tool, which integrates seamlessly with the factory ECU. This preserves VVEL control and cold start characteristics, making the car feel nearly stock in traffic while delivering ferocious power at wide-open throttle.

The JWT Difference

The primary advantage of the JWT kit is its polish. It is a CARB-compliant package (EO number D-670) for those in California, a major differentiator. The driving experience is refined, with linear power delivery and strong reliability. However, this integration comes at a higher upfront cost, and JWT kits often have longer lead times due to their high demand and meticulous assembly process.

Injen Turbo Kit: Precision Engineering for Reliable Gains

Injen Technology is best known for its award-winning intake systems, but their 370Z turbo kit represents a serious step forward in their engineering capability. The Injen kit focuses on efficiency and mid-range power, making it an excellent choice for daily-driven cars that see occasional track use.

Injen Kit Hardware and Components

The core of the Injen kit is their proprietary SES (Single Entry System) manifold and a high-efficiency turbocharger. The kit uses lightweight, polished aluminum piping for the intercooler and intake tracks, reducing under-hood heat soak. Injen’s intercooler is specifically designed for the 370Z’s front end, maximizing airflow without requiring extensive bumper trimming.

  • Turbocharger: Precision Journal Bearing (or Garrett upgrade)
  • Intercooler: High-flow stepped core design
  • Wastegate/BOV: Injen-sourced high-flow units
  • Fuel System: High-flow fuel injectors and adjustable fuel pressure regulator
  • Piping: Mandrel-bent 6061 aluminum with polished finish

Power Gains and Tuning with Injen

The Injen kit targets a safe and reliable power band. On stock internals and pump gas, owners typically see 370 to 410 wheel horsepower. This is a lower peak number than some competitors, but the torque curve is very strong, providing excellent responsiveness from 3,000 to 6,500 RPM. The kit comes with Injen’s proprietary tuning solution or can be paired with an external device like UpRev or ECUTEK for fine-tuning. Injen’s focus on cooling efficiency makes this a very reliable setup for extended driving sessions.

The Injen Advantage

The Injen kit is often considered the best value proposition for the 370Z. It delivers a substantial horsepower increase with high-quality components at a more accessible price point. The install is well-documented, and the kit supports future upgrades well. If your goal is a strong, reliable 400 whp daily driver, the Injen kit is a top contender.

TopSpeed Turbo Kit: Maximum Performance for the Track

TopSpeed Motorsports has built a reputation for creating some of the highest-performing 370Z builds in the country. Their turbo kit is designed for one primary purpose: maximum power output. This is the choice for owners who are building a dedicated race car or a weekend warrior that demands respect.

TopSpeed Kit Hardware and Components

The TopSpeed kit is centered around a large-frame turbocharger, often the Garrett GTX3582R or a Precision Gen2 equivalent. It features equal-length stainless steel exhaust manifolds, which are critical for minimizing back pressure and spooling the large turbine quickly. The intercooler core is massive, and the piping is typically 2.5 to 3 inches in diameter to support high-volume airflow.

  • Turbocharger: Garrett GTX3582R / Precision 6266
  • Intercooler: Oversized bar-and-plate core
  • Wastegate/BOV: Turbosmart Comp-Gate 45mm / Race Port
  • Manifolds: Equal-length, schedule-40 stainless steel
  • Exhaust: 3-inch V-Band downpipe (no catalytic converter option)

Power Gains and Tuning with TopSpeed

This kit is built to hit 450 to 550 wheel horsepower on pump gas and can exceed 650 whp on race fuel or E85 with built internals. The power delivery is more aggressive, with noticeable lag until the large turbo spools, followed by a violent surge of acceleration. Tuning must be done in person or by a very experienced remote tuner, utilizing ECUTEK or a standalone AEM Infinity ECU. The TopSpeed kit requires serious supporting modifications to be reliable, including a built short block, upgraded clutch, and complete fuel system.

The TopSpeed Difference

The TopSpeed kit is not for the faint of heart. It is a high-power, high-maintenance system designed for experienced enthusiasts. The street manners are compromised compared to JWT or Injen, but the outright power potential is unmatched. If a 9-second quarter-mile or a dedicated track monster is your goal, TopSpeed is the kit to beat.

Head-to-Head Comparison: JWT vs. Injen vs. TopSpeed

Choosing between these three kits comes down to a trade-off between refinement, cost, and raw power. Here is how they stack up in key categories.

Power Ceiling and Drivability

  • JWT: High ceiling (500+ whp) with excellent low-end torque and daily drivability. The best overall balance for a street car.
  • Injen: Medium ceiling (400+ whp) with a very strong mid-range. Extremely responsive and smooth for daily driving.
  • TopSpeed: Very high ceiling (650+ whp) with peaky, track-focused power delivery. Requires higher RPMs for maximum thrust.

Kit Completeness and Tuning

  • JWT: Most complete. Includes a custom ECUTEK flash tune. Truly plug-and-play.
  • Injen: Good completeness. Relies on an external tuning solution or their included module. Easier to install than TopSpeed.
  • TopSpeed: Focused on hardware. Tuning is up to the owner. Requires professional dyno tuning and often an upgraded ECU (AEM or Haltech).

Value and Long-term Reliability

  • JWT: High initial cost. Excellent long-term reliability if maintenance is followed.
  • Injen: Best value. Lower initial cost with solid reliability at its target power level.
  • TopSpeed: Moderate initial cost for the kit, but high total build cost due to required supporting mods. Reliability is dependent on the quality of the supporting build.

Essential Supporting Modifications for a 370Z Turbo Build

No matter which turbo kit you choose, the bottleneck of any VQ37VHR build is the fuel system and clutch. You cannot safely run boost on the stock fuel system or drivetrain components.

Fuel System Upgrades

Stock injectors and fuel pump will not support boost. You need at minimum a set of 740cc to 1000cc fuel injectors and a separate fuel pressure regulator. Upgrading to a Walbro 450 or AEM 340 lph fuel pump is mandatory. For those running E85, a flex fuel sensor and return-style fuel system are highly recommended to take full advantage of the octane.

Clutch and Driveline

The stock clutch slips around 400 wheel torque. A sprung-hub single disc clutch (like a Competition Clutch or South Bend) is ideal for daily drivers in the 400-500 whp range. For builds over 500 whp, a twin-disc clutch is required to handle the torque without excessive pedal effort.

Cooling and Heat Management

Forced induction generates significant heat. An oil cooler (Setrab or Earl’s) is essential to maintain oil temperatures. Upgrading to a larger aluminum radiator (Koyo or Mishimoto) and a high-flow thermostat will help keep coolant temperatures stable during spirited driving.

Professional Dyno Tuning

The single most critical step in any turbo build is the dyno tune. A reputable tuning shop like Specialty Z or Admin Tuning can dial in the air/fuel ratios and ignition timing to ensure the engine lives a long life. Never rely on a "base map" for extended driving. A proper tune using ECUTEK or UpRev is worth every penny for safety and performance.

Conclusion: Selecting the Right Kit for Your Goals

There is no single "best" turbo kit for the Nissan 370Z, but there is a best kit for your specific driving style and budget.

If you want a refined, go-to-market street car that passes emissions and feels like an OEM upgrade, the JWT Turbo Kit is the gold standard. Its integration and drivability are unmatched for a 470 whp street car.

If you are looking for the best balance of price and performance with a focus on reliable daily driving, the Injen Turbo Kit offers incredible value and a strong power band that makes the VQ37VHR feel alive.

If you are a track enthusiast or power junkie chasing 600+ horsepower, the TopSpeed Turbo Kit provides the foundation needed to build a high-horsepower monster capable of competing with exotics.

Before making a purchase, spend time on forums like The370Z.com and consult with experienced builders at Z1 Motorsports. Your budget should account for the kit plus the necessary supporting modifications, labor, and professional tuning. A well-planned build will provide years of reliable, adrenaline-filled driving.