Understanding the VQ37VHR Engine

The VQ37VHR is a 3.7-liter V6 engine that debuted in the Nissan 370Z in 2009. It features dual overhead cams, variable valve timing on both intake and exhaust (VVEL), and a 7500-rpm redline. In stock form, it produces around 332 horsepower at the crank and 270 lb-ft of torque. The engine is known for its high-revving nature and smooth power delivery, but its factory tuning leaves significant headroom for upgrades. Key design aspects include a cast-iron block, aluminum cylinder heads, and a high-flow intake manifold. However, the VQ37VHR has limitations: restrictive exhaust manifolds, mild factory cam profiles, and a conservative ECU calibration that prevent it from reaching higher output without modifications. The VVEL system adds complexity but also enables precise control for tuning.

The Path to 500+ Horsepower

Achieving over 500 horsepower from the VQ37VHR requires a coordinated set of modifications. The two most impactful upgrades are camshaft replacement and ECU tuning, but they cannot work in isolation. Supporting mods like exhaust, intake, fuel system, and often forced induction are necessary to reach this target. A naturally aspirated build with aggressive cams, ported heads, headers, and a full exhaust can approach 400-450 whp (wheel horsepower). To break the 500 whp barrier, forced induction—either a supercharger or turbocharger—is almost mandatory. This article focuses on the core combination of camshaft upgrades and ECU tuning, while also covering the essential supporting modifications needed for a reliable 500+ HP setup.

Camshaft Upgrades for the VQ37VHR

Stock camshafts on the VQ37VHR are designed for a balance of power, emissions, and idle quality. Upgrading to performance cams allows for increased valve lift and duration, which directly improves the engine's ability to move air. This translates to higher peak horsepower and torque, especially in the upper RPM range. A good set of cams can add 30-50 horsepower at the wheels when paired with proper tuning.

Types of Performance Camshafts

Camshafts for the VQ37VHR come in various profiles:

  • Street/Stage 1 cams: Mild lift and duration (around 0.500" lift, 260° duration). These maintain good idle quality and low-end torque, suitable for daily drivers. They pair well with a tune and basic bolt-ons to reach 400+ HP.
  • Stage 2 cams: More aggressive (0.530" lift, 270°+ duration). These shift the power band higher but may cause a slightly rougher idle. They require upgraded valve springs and retainers to prevent float at high RPM.
  • Race/Stage 3 cams: Extreme profiles (0.560" lift, 290°+ duration) for track-only applications. They sacrifice low-end torque and drivability for top-end power, and often require oversized valves and port work.

Selecting the Right Camshaft

When choosing camshafts, consider:

  • Intended use: Street driving favors milder profiles; track use can tolerate more aggression.
  • Complementary mods: Aggressive cams need upgraded springs, retainers, and possibly the VVEL system to be recalibrated.
  • Brand reputation: Popular options include Z1 Motorsports, Jim Wolf Technology (JWT), and Kelford. Z1 offers custom-grind options for specific power goals.
  • Installation expertise: Cam replacement requires precise timing and shimming; professional installation is recommended.

Proper installation is critical. The VQ37VHR uses chain-driven camshafts, so timing must be set exactly to prevent piston-to-valve interference. Always replace the timing chain, tensioners, and guides when swapping cams.

ECU Tuning for Maximum Performance

After installing performance camshafts, the ECU must be reprogrammed to take full advantage of the increased airflow. The stock ECU's fuel and ignition maps are calibrated for the factory cam profiles. Without tuning, the engine will run lean, misfire, or knock under load. Tuning optimizes air-fuel ratios (targeting 12.5:1 for naturally aspirated, 11.5:1 for forced induction), adjusts ignition timing to maximize power without detonation, and recalibrates VVEL to match cam timing changes.

ECU Tuning Methods

  • ECU Reflash: The most common approach. A tuner modifies the factory ECU's software using tools like UpRev or ECUTek. The ECU is removed, read, and rewritten with custom calibration. This retains all factory features (cruise control, AC, OBD-II) and is cost-effective. For the VQ37VHR, UpRev is widely used and allows full control over fuel, timing, and VVEL.
  • Standalone ECU: Units like Haltech, Motec, or AEM replace the factory ECU entirely. They offer unlimited adjustability, data logging, and support for advanced features like boost control or nitrous. However, they require full wiring and a skilled tuner, and cost significantly more.
  • Piggyback Tuning: Less common today. A device intercepts sensor signals to modify outputs. Limited control and reliability issues make this a poor choice for high-power builds.

Professional dyno tuning is strongly recommended. The tuner will run the car on a dynamometer, adjusting parameters to achieve safe and maximum power. For a 500+ HP build, expect multiple pulls and careful monitoring of exhaust gas temperatures, knock sensors, and air-fuel ratios. ECUTek is a popular choice for forced induction VQ builds due to its advanced features like launch control and flex-fuel support.

Supporting Modifications for 500+ HP

Camshafts and tuning alone cannot deliver 500+ HP. The following mods are essential:

Fuel System Upgrades

Stock fuel injectors (typically 320 cc/min) are insufficient for 500 HP. Upgraded injectors (600-1000 cc/min) and a higher-flowing fuel pump (e.g., Walbro 255 or 450 lph) are required. A return-style fuel system with a regulator may be needed for forced induction.

Exhaust and Intake

A high-flow exhaust system (long-tube headers, test pipes, and a free-flowing catback) reduces backpressure and helps the engine exhale. A cold-air intake improves inlet airflow. For forced induction, a larger intercooler and blow-off valve are added.

Forced Induction

To reach 500 whp reliably, a supercharger kit (e.g., Stillen, Vortech) or a turbo kit (e.g., GTM, TurboInspired) is typical. These add 6-10 psi of boost, requiring all the above mods and a stronger clutch, oil cooler, and possibly a built bottom end (forged pistons, rods) to handle the extra stress. Many owners install a Concept Z Performance fuel system kit alongside their boost setup.

Cooling and Reliability

Higher power generates more heat. An upgraded radiator, oil cooler, and sometimes a transmission cooler are necessary. For track use, consider a larger auxiliary cooler. Also, upgrade the clutch and flywheel to handle the increased torque. A lightweight flywheel improves throttle response but may increase noise.

Practical Considerations

Budget for a 500+ HP build can exceed $10,000 to $15,000 including labor. Camshafts ($800–$1500), tuning ($500–$1500), and supporting mods add up quickly. Expect the car to be less streetable—rougher idle, stiffer clutch, and more noise. Emissions compliance may be affected; check local laws. Always document modifications and consult with a reputable shop experienced with VQ builds. Regular maintenance like oil changes with high-grade synthetic oil becomes even more critical.

Conclusion

Upgrading the 370Z's VQ37VHR to 500+ horsepower is a rewarding, demanding project. Camshaft upgrades unleash the engine's breathing potential, while ECU tuning ensures the entire system works in harmony. Combined with forced induction, fuel system upgrades, and proper cooling, you can build a reliable, high-output machine. Work with experienced professionals, prioritize quality parts, and enjoy the transformation of your 370Z into a track-capable, street-legal powerhouse.