The Nissan 370Z, equipped with the factory VQ37VHR engine, is a naturally aspirated performer that delivers a thrilling 332 horsepower from the factory. However, the aftermarket community has long recognized this platform's potential for significant power gains through forced induction. For owners seeking to push past the 400 wheel horsepower mark, two kits dominate the conversation: the Greddy Turbo Kit and the Stillen Supercharger. This analysis moves beyond marketing claims, focusing specifically on raw dyno results, power delivery characteristics, and the engineering realities of installing and living with each system.

Forced Induction Fundamentals: Matching the System to the Engine

Before analyzing the specific dyno graphs, it is critical to understand how the VQ37VHR responds to forced air. The high-revving 3.7-liter V6 features a high 11.0:1 compression ratio. This is a crucial variable because high compression ratios amplify the risk of knock under boost, but they also make the engine exceptionally responsive to efficient forced induction.

  • Turbocharging (Greddy): Utilizes exhaust gas velocity to spin a turbine wheel. This creates a natural restriction in the exhaust stream, which can help scavenging at high RPM but creates "backpressure." The big advantage is that the compressor and turbine are not mechanically linked to the engine, allowing for a higher peak efficiency island on the compressor map.
  • Supercharging (Stillen): The Stillen kit uses a Vortech V3 Si centrifugal supercharger, which is belt-driven. It acts like a high-speed air pump. There is no exhaust restriction created by the supercharger itself. The trade-off is that the supercharger consumes parasitic power (typically 40-60 hp) just to spin the impeller, reducing the net gain slightly compared to a turbo of the same boost level.

The fundamental question the dyno must answer is: Which system delivers the most usable torque for the driving environment, and at what cost to the engine's longevity?

Greddy Turbo Kit: Raw Peak Power and the Mid-Range Spike

The Greddy kit for the 370Z is typically a TD05H-18G or TD06-20G setup. This kit is a "hot parts" kit, meaning Greddy provides the cast iron or stainless steel manifold, the turbocharger itself, a wastegate, and the intercooler piping. The owner must supply the intercooler (air-to-air), oil lines, and exhaust downpipe.

Dyno Results: The Peak Numbers

On a conservative 93 octane tune with proper fuel injectors and a fuel pump, the Greddy kit consistently delivers:

  • Peak Wheel Horsepower: 450-480 whp (a net gain of +120 to +150 whp over a stock baseline of 330 whp).
  • Peak Torque: 360-390 lb-ft at the wheels.

The turbo kit wins the "bragging rights" competition on the dyno sheet. The peak numbers are simply higher than the Stillen kit because the VQ37VHR is a fantastic platform for a turbo. The engine can handle the boost without breaking a sweat, provided the tune is not aggressive.

The Real Story: Boost Threshold and Torque Curve

Where the Greddy kit reveals its character is not at redline, but at 3,500 RPM. On a dyno graph, you will see a sharp "knee" in the torque curve around 4,000 to 4,500 RPM. This is the "spool" event. Before this point, the engine is making stock power. After this point, torque rises sharply to a peak around 5,500 RPM before falling off slightly to redline.

This characteristic is excellent for a drag racing or track car where you keep the engine on the boil. However, for street driving or road racing, the sudden onset of torque can overwhelm the tires. The driver must manage the boost threshold. A single scroll turbo like the TD05H will spool later than a twin-scroll setup. The lag is real, but the reward is a violent surge of power that the Stillen kit cannot match at the top end.

Technical Considerations for the Greddy Kit

  • Heat Management: The turbo sits very close to the engine block. Heat shielding of the intake, brake lines, and motor mounts is mandatory.
  • Oil System: The turbo requires a pressurized oil feed and a gravity return to the oil pan. This requires drilling the oil pan for the return line, which is a permanent modification. Oil coking (overheating) is a risk if the car is shut down hot without a turbo timer.
  • Intercooler: An air-to-air intercooler is prone to heat soak at low speeds (stop-and-go traffic), but it has a massive thermal capacity for high-speed pulls.

Stillen Supercharger: Linear Power and Immediate Response

The Stillen kit is the most popular "showroom" upgrade for the 370Z. It is a CARB-legal (EO# D-660-13) system that utilizes a Vortech V3 Si trim supercharger. This is a self-contained unit with an internal oil reservoir, meaning the owner does not need to tap into the engine's oil system for lubrication. The system uses an air-to-water intercooler (charge cooler).

Dyno Results: The Consistent Performer

Dyno results for the Stillen supercharger on a standard VQ37VHR are remarkably consistent:

  • Peak Wheel Horsepower: 410-430 whp (a net gain of +80 to +100 whp).
  • Peak Torque: 320-340 lb-ft at the wheels.

While the peak numbers are 30-50 hp lower than the Greddy kit, the Stillen graph tells a different story about driveability. There is no sharp spike in torque. The curve rises smoothly and linearly from 2,500 RPM to redline. This linear delivery is significantly easier for the chassis and tires to handle.

Why the Dyno Graph Looks Different

The centrifugal supercharger builds boost proportional to engine RPM. At 3,000 RPM, you might only see 2-3 psi of boost. At 7,000 RPM, you see 8-9 psi. This creates a "ramping" torque curve that mimics a larger naturally aspirated engine. The driver does not have to "wait for the boost." The power is directly tied to how hard the engine is working, making it incredibly intuitive for road racing and autocross.

The air-to-water intercooler is a major advantage here. Air-to-water systems have a lower thermal mass than air-to-air units but are incredibly efficient at absorbing heat for short bursts. They do not experience the same "heat soak" at low speeds that an air-to-air unit faces, though extended pulls can heat the water loop, requiring a heat exchanger with a strong electric pump.

Technical Considerations for the Stillen Kit

  • Installation: This is a major advantage. The kit bolts onto the front of the engine. No oil pan drilling is required. A skilled DIYer can install this in a weekend.
  • Belt Drive: The supercharger is driven by a dedicated belt. Belt slip at high RPM is a known issue on high-boost builds (over 10 psi), requiring a larger crank pulley or a cogged belt system.
  • Drivetrain Wear: Because the torque curve is linear, it is easier on the transmission and differential. The sudden shock of a turbo hitting boost can break axles; the Stillen delivers torque smoothly.

Head-to-Head Dyno Comparison: Area Under the Curve

When comparing dyno sheets, the "Peak Number" is a marketing metric. The true measure of performance is Area Under the Curve (AUC).

  • Greddy Turbo (AUC): The AUC is heavily skewed to the mid-to-upper RPM range. Below 4,000 RPM, the torque line sits close to stock. Above 4,500 RPM, it explodes upward. The total AUC is very high because the peak torque spike creates a huge "hump" in the middle of the graph.
  • Stillen Supercharger (AUC): The AUC is more evenly distributed across the entire RPM band. It makes significantly more torque than the turbo from 2,500 to 4,000 RPM. This makes the car feel faster in daily driving. However, the total area under the curve is typically slightly less than the turbo kit because the peak is lower.

The Verdict: If your driving involves rolling starts at 60 mph, the turbo will win. If your driving involves corner exits at 40 mph or traffic, the supercharger is the faster car in the real world.

Critical Factors Influencing Final Dyno Numbers

No two dyno sheets look exactly the same. The following factors play a massive role in the final output of both the Greddy and Stillen kits.

Fueling and Tuning Platform

Both kits require a custom tune. The VQ37VHR is notoriously difficult to tune due to the VVEL (Variable Valve Event and Lift) system. Most tuners prefer the ECUTEK suite over older UpRev options because it offers better control over the VVEL mapping.

  • Fuel Injectors: The stock 380cc injectors are insufficient for either kit above 430 whp. Upgrading to 550cc or 600cc injectors is mandatory for the Greddy kit.
  • Fuel Pump: The stock fuel pump can handle the Stillen kit at 8 psi, but the Greddy kit requires a stronger pump (Walbro 450 or similar) to maintain fuel pressure under high boost.

A poorly tuned Stillen kit results in a lean condition at high RPM. A poorly tuned Greddy kit results in a huge spike in torque that destroys the clutch. Investing in a professionally dyno-tuned ECUTEK map is the single most important factor for reliability.

Supporting Modifications: The Bottleneck

A dyno chart is only as good as the "breathing" components attached to the engine.

  • Exhaust: The Greddy turbo kit requires a 3-inch exhaust to prevent boost creep. The Stillen kit benefits heavily from long-tube headers and a 3-inch system. A restrictive exhaust can rob either system of 20-30 whp.
  • Cooling: Both systems generate massive heat. An upgraded CSF or Koyo radiator, a Setrab oil cooler, and transmission cooler are mandatory investments if you plan to track the car. The Stillen kit's heat exchanger location is critical; mounting it in front of the radiator can cause overheating in traffic if not properly ducted.
  • Clutch: The stock clutch slips around 380 whp. The Greddy kit absolutely requires a twin-disc clutch (like the Competition Clutch or OS Giken). The Stillen kit can sometimes survive on a heavy-duty single disc, but a twin disc is recommended for longevity.

Installation, Maintenance, and Total Cost of Ownership

The purchase price of the kit is just the entry fee. The installation and hidden costs are where the two systems diverge significantly.

  • Installation Cost: The Stillen kit is $1,500 to $2,000 for professional installation. The Greddy kit often runs $3,000 to $5,000 due to the complexity of the oil lines, downpipe fabrication, and heat management.
  • Maintenance: The Stillen supercharger requires a belt change every 60,000 miles. The oil in the Vortech head unit is self-contained and needs changing every 30,000 miles. The Greddy turbo requires much more frequent oil changes (every 3,000 miles) to prevent oil coking in the turbo bearings.
  • Smog Checks: The Stillen kit is CARB-legal for plug-and-play street legality. The Greddy kit (and most turbo kits) will require a visual inspection removal or a "sniffer test" failure in strict emissions states (California, New York, etc.).

Which Forced Induction System is Right for Your 370Z?

This is not a contest of which kit "makes more power." It is a contest of which kit fits the driver's objective.

  • Choose the Greddy Turbo Kit if: You are building a dedicated track weapon, drag car, or highway monster. You want the highest possible peak numbers and are willing to manage the lag, heat, and maintenance to get them. You are not concerned about emissions compliance.
  • Choose the Stillen Supercharger if: You want a reliable, daily-drivable street car that feels faster than stock everywhere in the rev range. You want a linear, predictable powerband for road racing or canyon carving. You need a kit that will pass a visual smog inspection and requires minimal maintenance.

Both the Greddy Turbo Kit and the Stillen Supercharger are exceptional pieces of engineering that fundamentally transform the Nissan 370Z. The Greddy kit delivers the adrenaline rush of a violent, peaky power band. The Stillen kit delivers the surgical precision of perfectly linear, immediate torque. The correct answer depends entirely on whether you want to conquer the dyno graph or conquer the apex.