The Stillen 370Z Turbo Kit has established itself as one of the most popular forced-induction solutions for Nissan’s VQ37VHR engine. Enthusiasts seek real, repeatable horsepower gains without sacrificing daily-driver civility. This article presents detailed dyno benchmarks, explains the kit’s design, and covers the factors that influence final output—so you know exactly what to expect before you buy.

Overview of the Stillen 370Z Turbo Kit

Stillen’s turbo system for the 370Z is a twin-turbo, intercooled setup engineered for the V6 powerplant. It uses two small-frame Garrett turbos—typically GT28RS or similar—to provide quick spool and broad power delivery. The kit includes cast-steel exhaust manifolds, aluminum charge pipes, a bar-and-plate intercooler, and all necessary hardware for installation. Stillen also supplies a base ECU calibration via an UpRev or ECUTek flash, though many owners opt for custom tuning to extract maximum performance.

Key Components

  • Turbos: Twin Garrett GT28RS or GT2860RS — sized for quick spool (full boost by ~3500 RPM) and reliable up to 450–500 whp.
  • Intercooler: Front-mount bar-and-plate core sized to keep intake temperatures low during sustained pulls.
  • Exhaust Manifolds: Cast-iron units that resist cracking and maintain proper flow distribution.
  • Wastegates & Blow-Off Valve: High-quality internal or external wastegates (depending on revision) and a recirculating blow-off valve for reliable boost control.
  • Fuel System: The kit typically relies on the stock fuel pump and injectors at moderate boost levels (6–9 psi). For higher power, an upgraded pump and 550cc+ injectors are recommended.
  • Engine Management: Comes with a base calibration file for UpRev Osiris or ECUTek; a professional tune is strongly advised.

Installation Process and Considerations

Installing the Stillen turbo kit is a major job. Plan for 25–40 hours of labor if you are experienced. The process includes removing the front bumper, radiator, and exhaust manifolds; mounting the turbos; routing oil and coolant lines; and integrating the intercooler and piping. A lift and proper tools are mandatory. DIY installation is possible but requires mechanical skill and patience. Most owners opt for a reputable shop.

Professional vs. DIY

  • Professional: Expect $2,500–$4,000 for labor, plus the cost of tuning. Ideal for those who want a turnkey solution.
  • DIY: Saves money but risks errors in oil-line routing or boost leak detection. Many forum members document successful home installations.

Tuning the Stillen Turbo Kit

Tuning is the single most important factor for safe and powerful operation. The supplied base tune is conservative—often targeting 6–7 psi and about 400 whp on 91 octane. For maximum output (450–500 whp), you need a custom calibration with higher boost (8–9 psi) and high-octane fuel (93 or E85).

Two popular platforms exist: UpRev Osiris and ECUTek. Both allow full control over fuel, ignition, boost, and knock limits. Professional tuners like Z1 Motorsports, Specialty Z, or Seb Tuning have published dyno results for Stillen-equipped cars.

Real-World Dyno Benchmarks

The following figures represent wheel horsepower (whp) from various independent tests on DynoJet dynamometers. Crank horsepower will be higher due to drivetrain loss (typically 13–17%).

Stock 370Z Baseline

A stock 2010–2020 Nissan 370Z typically dynos at 280–290 whp (approximately 332 hp at the crank). Torque is around 240–250 lb-ft at the wheels.

Stillen Turbo Kit Results

  • Test A (91 octane, conservative tune, 6.5 psi): 390 whp / 350 lb-ft — safe, reliable, no supporting mods.
  • Test B (93 octane, custom UpRev tune, 8 psi): 450 whp / 390 lb-ft — with upgraded injectors and fuel pump.
  • Test C (E85, ECUTek tune, 9 psi): 485 whp / 415 lb-ft — requires larger injectors, upgraded fuel system, and oil cooler.
  • Test D (93 octane, full bolt-ons + Stillen kit, 8.5 psi): 470 whp / 400 lb-ft — includes cat-back exhaust, test pipes, and cold-air intake.

These results align with Stillen’s advertised gains of 100–150 whp over stock. With careful tuning and supporting upgrades, the kit can exceed 150 whp gains.

Factors That Influence Final Horsepower

Engine Condition and Compression

A healthy VQ37VHR with good compression (150+ psi across all cylinders) will produce more power and tolerate more boost. Higher-mileage engines may have ring wear or carbon buildup that limits output.

Fuel Quality and Octane

Higher octane allows more ignition timing and boost without knock. E85 is ideal, but requires fuel system upgrades. On 91 octane, keep boost under 7 psi to stay safe.

Supporting Modifications

  • Exhaust: A free-flowing cat-back (e.g., Stillen, Motordyne, Fast Intentions) reduces backpressure and adds 10–15 whp.
  • Intake: The kit includes its own air filters, but aftermarket cold-air intakes can improve flow.
  • Fuel System: Stock injectors max out around 420–440 whp. Upgraded injectors (550–750cc) and a fuel pump (Walbro 255 or AEM 340) are needed for higher power.
  • Oil Cooling: Turbochargers generate high oil temperatures. An aftermarket oil cooler (e.g., Setrab, Earl’s) is strongly recommended.
  • Clutch: The stock clutch slips around 400–420 whp. Expect to upgrade to a single- or twin-disc clutch (e.g., Exedy, South Bend, ACT).

Altitude and Ambient Temperature

Density altitude significantly affects turbo efficiency. At sea level, the kit makes maximum power. At 5,000 feet, expect 15–20% less due to thinner air. Hot summer days also reduce output.

Reliability and Long-Term Durability

Stillen designed this kit for daily-driven reliability at moderate boost levels (6–8 psi). With proper tuning and maintenance, the VQ37VHR can last 60,000+ boosted miles. However, pushing beyond 9 psi or using poor fuel can lead to ring failure, rod bearing wear, or cracked exhaust manifolds.

Maintenance Recommendations

  • Change oil every 3,000–5,000 miles with full synthetic (5W-30 or 5W-40).
  • Inspect turbo oil feed lines for leaks regularly.
  • Keep the intercooler clean and free of debris.
  • Monitor boost pressure with a gauge; avoid repeated back-to-back pulls without cool-down.
  • Consider an aftermarket cooling system (radiator, oil cooler, intercooler sprayer) for track use.

Cost and Value Proposition

The Stillen turbo kit itself retails for approximately $6,500–$7,500 (depending on version and included components). Add installation ($2,500–$4,000), tuning ($600–$1,000), and supporting mods (clutch, fuel system, oil cooler — $1,500–$3,000). Total investment ranges from $11,000 to $15,000 for a reliable 450+ whp setup.

Compared to a supercharger kit (e.g., Stillen or Vortech supercharger, $5,000–$6,000), the turbo offers higher peak power potential and better top-end pull. But superchargers are simpler and cheaper to install. The turbo kit delivers a more dramatic driving experience with its surge of mid-range torque.

Stillen vs. Other 370Z Turbo Kits

Other popular options include the GTM Twin Turbo Kit and Fast Intentions Single Turbo Kit. GTM’s kit uses larger turbos (GT2871R) and can hit 500+ whp on pump gas, but costs more ($8,000+) and requires more supporting mods. Fast Intentions’ single turbo kit is simpler and cheaper (~$5,500) but trades some spool for simpler packaging. Stillen strikes a balance between cost, power, and daily practicality.

Conclusion

The Stillen 370Z Turbo Kit reliably adds 100–150 whp to a stock 370Z, with real-world dyno results of 390–485 whp depending on fuel, tune, and supporting modifications. It is not a budget option, but for anyone seeking substantial forced-induction performance with a strong aftermarket support network, it holds its value exceptionally well. Plan for a professional tune, upgrade the clutch and fuel system for higher power targets, and keep up with maintenance. The result is a 370Z that pulls hard from 3,500 RPM to redline—transforming the car into a true performance machine.

For further reading: Stillen’s official product page, Z1 Motorsports dyno results, owner experiences on The370Z.com, and Effective Auto Tuning’s guide.