The Nissan 370Z, powered by the VQ37VHR engine, has long been a favorite among driving enthusiasts for its balanced chassis, high-revving character, and robust aftermarket support. While the stock 332 horsepower is respectable, the true potential of this platform is unlocked with forced induction. The Stillen Supercharger kit stands out as one of the most refined and widely adopted supercharger systems for the 370Z, enabling owners to achieve 550 horsepower on pump gas—a figure that transforms the car’s personality without sacrificing daily drivability. This article provides a comprehensive look at the components, tuning, performance metrics, and real-world considerations behind this impressive 550-horsepower milestone.

The VQ37VHR Engine: A Strong Foundation

Before examining the supercharger system, it’s essential to understand the engine it sits upon. The VQ37VHR is a 3.7-liter V6 that debuted in the 2009 370Z and later appeared in the Infiniti Q50, Q60, and other models. It belongs to Nissan’s renowned VQ family, known for its smoothness, durability, and willingness to rev. Key design features that make it an excellent candidate for forced induction include:

  • Variable Valve Event and Lift (VVEL): This continuously variable valve timing system allows precise control of intake valve duration and lift, optimizing both low-end torque and high-rpm power. The VVEL system is robust enough to handle the increased air volume from a supercharger without requiring internal engine modifications—at least at the 550-horsepower level.
  • High Compression Ratio: The VQ37VHR features a compression ratio of 11.0:1. While this is higher than many traditional forced-induction engines, modern standalone tuning and high-octane fuel allow supercharger kits like Stillen’s to work safely with the factory compression, provided the tune is conservative.
  • Dual Overhead Camshafts: DOHC design with 24 valves ensures efficient airflow, and the variable timing on both intake and exhaust cams helps spool the supercharger quickly.
  • Forged Connecting Rods and Crank: The VQ37VHR uses forged connecting rods and a forged crankshaft from the factory. These components are strong enough to safely handle up to about 600 wheel horsepower on pump gas—beyond that, upgrading to forged pistons becomes necessary.

One common point of concern is the factory rod bolts. At power levels approaching 550 horsepower, many experienced tuners recommend upgrading the rod bolts to ARP hardware for added safety margin, especially if the car will see track use or aggressive tuning. Still, many street-driven examples run reliably on stock internals at this power level with a conservative tune.

The Stillen Supercharger Kit: Engineering and Components

Stillen’s supercharger kit for the 370Z has been in development for over a decade and has gone through multiple revisions. The current generation is known for its reliability, ease of installation, and complete package. The kit includes the following major components:

  • High-Efficiency Twin-Screw Supercharger Unit: The heart of the system is a twin-screw (roots-type) supercharger, specifically a Lysholm-style unit. This design provides instant boost response and excellent low- and mid-range torque, making the car feel significantly faster on the street compared to a turbocharged setup that may lag.
  • Custom Cast Aluminum Intake Manifold: This replaces the factory intake manifold and integrates the supercharger discharge. The design is optimized for even air distribution across all cylinders.
  • Air-to-Water Intercooler System: To keep intake air temperatures in check, the kit uses an air-to-water intercooler (heat exchanger) with a dedicated water pump and front-mounted radiator. This system is highly effective and shortens the intake path, improving throttle response.
  • Upgraded 550cc Fuel Injectors: The factory injectors are insufficient for the extra fuel required at 550 horsepower. Stillen includes higher-flow injectors (typically 550 cc/min or larger) to support the increased fuel demand. Many installers later upgrade to 650 cc or 1000 cc injectors for future flexibility.
  • High-Flow Fuel Pump (Optional but Recommended): The factory fuel pump can keep up at 550 horsepower, but upgrading to a Walbro 255 lph or equivalent is common to ensure consistent fuel delivery, especially if running a return-style fuel system.
  • Tuned ECU Calibration via UpRev or ECUTek: The kit includes a base tune loaded on an UpRev or ECUTek platform. However, a professional dyno tune is strongly recommended to dial in the air-fuel ratios, ignition timing, and boost levels for the specific fuel and local conditions. UpRev and ECUTek are the two most popular tuning solutions for the VQ37VHR.

The Stillen kit is designed to produce approximately 8–9 psi of boost on pump gas. At this boost level, the engine reaches the 550 horsepower mark at the crank (roughly 470–480 wheel horsepower on a chassis dyno). The system is CARB-approved for 49-state emissions compliance, which is a significant advantage for owners in regulated markets.

Reaching 550 Horsepower on Pump Gas: The Tuning and Supporting Mods

While the Stillen kit itself is capable of producing the power, achieving a reliable 550 horsepower on 91 or 93 octane pump gas requires careful tuning and often a few additional supporting modifications. Here are the key factors that influence the final output:

Fuel Quality and Octane

Pump gas in the United States typically ranges from 91 octane (western states) to 93 octane (eastern states). The higher the octane, the more ignition timing and boost can be safely run. Many tuners report that 93 octane allows a little extra power—sometimes 10–20 wheel horsepower—over 91 octane at the same boost level because they can run more aggressive timing without knock. To run 550 crank horsepower safely on 91 octane, the tune must be slightly conservative, often reducing timing a degree or two compared to a 93-octane tune.

Fuel System Upgrades

The factory fuel system includes a returnless fuel line. While it can feed the 550cc injectors at 550 horsepower, the fuel pressure tends to drop at high rpm under boost. Many successful builds add a boost-a-pump (voltage controller) or switch to a return-style system with a larger pump and adjustable fuel pressure regulator. DeatschWerks and Radium Engineering offer popular in-tank pump upgrades and fuel rail kits for the 370Z.

Exhaust System

The Stillen kit is designed to work with the factory exhaust manifold and catalytic converters, but upgrading the exhaust system unlocks additional power. A good cat-back exhaust (2.5-inch or 3-inch) reduces backpressure and allows the engine to breathe better. Test pipes (decats) or high-flow catalytic converters free up even more power, but they may cause emissions test failures in some states. Many 550-horsepower builds include a full exhaust system, including aftermarket headers (like PPE Engineering or Z1 Motorsports headers) to maximize the flow. Headers alone can add 15–20 wheel horsepower to the kit.

Intercooler Efficiency

While Stillen’s air-to-water system is effective, heat soak can become a factor on hot days or during repeated pulls (like road course or autocross). Some owners upgrade to a larger heat exchanger reservoir or an auxiliary radiator to keep intake air temperatures consistent. Running a water-methanol injection kit can also help cool the air and suppress detonation, allowing more aggressive timing.

Clutch and Transmission

At 550 horsepower, the stock clutch becomes a weak point. The 370Z’s factory single-mass flywheel and clutch will slip under hard acceleration. Most builders upgrade to a heavy-duty clutch (like the Competition Clutch Stage 4, Exedy Hyper Single, or South Bend Stage 3) that can handle the torque. The stock six-speed manual transmission (CD00A) is generally durable at this power level, but the syncros can wear faster with aggressive shifts. An upgraded differential bushing and stronger axles (often from Z1 Motorsports or Driveshaft Shop) are recommended for drag racing or abuse.

Performance Metrics: Real-World Numbers

When properly tuned and supported, a 370Z with the Stillen supercharger achieves impressive performance figures. Actual results vary based on altitude, temperature, and the specific combination of parts. Commonly reported metrics include:

  • 0–60 mph: 3.4–3.6 seconds (AWD or well-prepped surface)
  • Quarter-Mile: 11.2–11.6 seconds at 120–125 mph trap speed
  • Top Speed: 165–175 mph (limited by gearing, not power)
  • Dyno (Wheel Horsepower): 470–490 whp with standard 91–93 octane tune
  • Torque: Approximately 400–420 ft-lb at the wheels

For comparison, a naturally aspirated 370Z typically dynos around 275–285 whp and runs the quarter-mile in the high 12-second range at 108–110 mph. The supercharger transforms the car from a quick sports car into a legitimate supercar fighter in terms of straight-line acceleration.

Driving Experience: From Street to Track

The Stillen supercharged 370Z delivers a driving experience that is both exhilarating and surprisingly refined. One of the standout qualities is the linear power delivery—the twin-screw supercharger builds boost immediately, so there is no noticeable lag. From 2,000 rpm, the engine feels stronger than stock, and by 3,500 rpm the boost is fully available, pulling hard to the 7,500 rpm redline.

On the street, the car is perfectly manageable. The throttle response remains crisp, and the car can be driven smoothly in traffic without the on/off nature of some big single-turbos. The extra low-end torque means you don’t have to downshift as much on the highway, and passing maneuvers are effortless. The supercharger whine is audible but not intrusive—it adds mechanical character without being obnoxious.

On a road course, the 370Z’s chassis responds well to the extra power, but heat management becomes a concern. The air-to-water intercooler system can heat-soak after several hard laps, causing the ECU to pull timing. Upgrading the cooling system (larger heat exchanger, oil cooler, and auxiliary radiator) helps maintain consistent performance. Also, the brakes need upgrading—the stock Akebono brakes are adequate, but fade can set in quickly. Many owners install a dedicated brake cooling duct kit and a higher-performance pad.

For drag racing, the 370Z with this supercharger is capable of consistent 11-second passes. The key to good ETs is a sticky tire (like a drag radial) and the right launch technique. The stock final drive ratio (3.69:1) works well, but some owners swap to a 3.91 or 4.08 differential for even quicker acceleration.

Potential Challenges and Reliability Considerations

While the Stillen supercharger is one of the most reliable forced induction kits for the 370Z, no system is without its risks. At 550 horsepower, the following points deserve attention:

Engine Internals

As mentioned, the factory forged rods and crank are strong, but the rod bolts are the weak link. Many tuners recommend upgrading to ARP rod bolts as a proactive measure. Stock pistons are cast aluminum and can crack under heavy detonation, but with a proper tune and good fuel, 550 horsepower is within their safe window. If you plan to push past 550 crank HP, forged pistons are mandatory.

Heat Soak

In hot climates or during track sessions, the intake air temperature can rise, causing the ECU to pull timing. A larger intercooler heat exchanger, a bigger coolant reservoir for the intercooler system, and a high-speed fan can help keep temperatures in check. Some owners also wrap the exhaust manifold and supercharger tubing to reduce radiant heat.

Maintenance

Supercharged engines require more frequent oil changes (every 3,000–4,000 miles with a high-quality synthetic). The supercharger unit itself should be checked for drive belt tension and coupler wear every few years. The air-to-water intercooler system should be flushed and refilled with distilled water and coolant additive annually to prevent corrosion.

Warranty Implications

Installing a supercharger voids the Nissan factory powertrain warranty. Stillen offers a limited warranty on the kit itself, but the engine and transmission fall outside that. Buyers should budget for potential repairs, or consider a pre-purchase inspection by a specialist.

Conclusion: Is the Stillen Supercharger the Right Choice?

For 370Z owners seeking a significant power increase without compromising daily drivability, the Stillen supercharger kit is one of the most compelling options on the market. Reaching 550 horsepower on pump gas is not just a marketing claim—it’s a proven result with proper tuning and support. The kit’s CARB certification, comprehensive component list, and long track record make it a reliable choice compared to custom turbo builds that often require more fabrication and trial-and-error tuning.

However, it is not a cheap upgrade. The kit itself costs around $6,000–$7,000, plus installation (2–3 days of labor), tuning ($500–$800), and the necessary supporting mods (clutch, exhaust, fuel system, cooling). A complete build can easily total $10,000–$12,000. But for the enthusiast who wants a fast, well-mannered, and reliable supercharged 370Z, the investment pays off in smiles per mile.

If you are considering this path, we strongly recommend consulting with a reputable tuner who has experience with the VQ37VHR and the Stillen kit. Z1 Motorsports is a well-known resource for parts and tuning, and the 370Z Forums offer a wealth of owner experiences and dyno results to help guide your build.