Why the Garrett GTX3584RS Kit Stands Out for the Porsche 718 Cayman

The Porsche 718 Cayman, with its mid-engine layout and razor-sharp handling, is already a benchmark in the sports car segment. However, the factory turbocharged flat-four engines—whether the 2.0-liter in the base model or the 2.5-liter in the S and GTS—leave measurable headroom for increased output. For owners seeking a significant leap in power without sacrificing daily drivability, the Garrett GTX3584RS turbocharger kit has emerged as the premier upgrade. This article provides a detailed, technical breakdown of the kit, its performance gains, installation requirements, and essential supporting modifications.

Understanding the Garrett GTX3584RS Turbocharger

The Garrett GTX3584RS is part of Garrett Motion’s GTX Gen II series, designed to bridge the gap between fast-spooling street turbos and high-flow race units. Its designation—GTX3584RS—indicates a 58mm inducer on a GTX frame with an RS (Race Series) compressor wheel. Key engineering highlights include:

  • Dual Ball Bearing Center Section: Garrett’s proprietary dual ball bearing cartridge reduces rotational friction by up to 50% compared to journal bearings, enabling faster spool and improved transient response.
  • Extended-Tip Technology (ETT): The compressor wheel’s extended tips push the flow range wider, increasing surge margin and peak efficiency. This translates to higher airflow at low RPM without compromising top-end power.
  • Cast Inconel Turbine Wheel: The turbine wheel is cast from Inconel 713C, a nickel-based superalloy that withstands extreme exhaust gas temperatures (EGTs) and resists creep, ensuring long-term reliability under high boost.
  • Integrated Boost Control Solenoid: The kit includes a plug-and-play electronic boost control solenoid that interfaces with the factory wiring, allowing precise boost management via the ECU.

For the 718 Cayman, the GTX3584RS is typically paired with a CNC-machined billet compressor housing and a custom cast exhaust manifold that replaces the OEM unit. The result is a turbocharger capable of flowing enough air to support over 500 wheel horsepower (whp) on pump fuel, with safe limits extending beyond 600 whp on ethanol blends.

Performance Benefits: Beyond the Numbers

Upgrading to the GTX3584RS kit transforms the 718 Cayman’s power delivery. The factory turbo on the 2.5-liter engine peaks around 3,500 RPM and runs out of steam after 6,500 RPM. The GTX3584RS shifts the power band upward while maintaining excellent mid-range torque. Real-world gains include:

  • Peak Horsepower Increase: With a proper tune, the 2.5-liter engine gains 120–160 whp over stock, pushing total output to 450–500 whp (depending on fuel and supporting mods). The 2.0-liter benefits even more proportionally, gaining 100–130 whp.
  • Torque Delivery: The dual ball bearing design allows the turbo to spool by 3,200–3,400 RPM, delivering 380–420 lb-ft of torque by 3,800 RPM and holding strong past 6,000 RPM. This creates a broad, usable power plateau ideal for street and track use.
  • Throttle Response: Reduced rotating inertia and low friction bearings mean the turbo responds nearly instantly to throttle inputs, eliminating the ‘laggy’ feel often associated with larger turbos.
  • Thermal Efficiency: Garrett’s ETT compressor operates in the 78–80% efficiency island, meaning lower intake air temperatures (IATs) compared to less efficient turbo designs. Cooler IATs reduce the risk of detonation and allow more aggressive timing.

It is important to note that these gains require calibration. The stock ECU must be tuned to deliver appropriate fuel, ignition, and boost targets. Without tuning, the larger turbo will either underperform or overboost dangerously. A quality tune from a reputable shop like Integrated Engineering or Drift Shop is mandatory.

Supporting Modifications: Building a Complete System

Installing the GTX3584RS kit alone is not enough. The increased airflow demands complementary upgrades to ensure reliability and extract maximum performance. Essential supporting modifications include:

Fuel System Upgrades

The stock high-pressure fuel pump (HPFP) and injectors are maxed out around 400 whp. For the GTX3584RS, you need:

  • Upgraded HPFP: A Nelson Racing Engines or FCP Euro high-flow HPFP ensures sufficient rail pressure at high RPM.
  • Larger Injectors: Bosch 1050cc or 1300cc injectors (or equivalent) are necessary to maintain proper air-fuel ratios under boost.
  • Flex Fuel Sensor (Optional): If running E85, a flex fuel sensor and controller allow the ECU to automatically adjust for ethanol content, increasing octane and enabling higher boost.

Cooling System Upgrades

Higher boost generates more heat. Upgrade the intercooler and charge air cooling system:

  • Front-Mount Intercooler (FMIC): A larger core (like those from Do88 or BMP Performance) reduces IATs by 30–50°F compared to the OEM side-mount intercooler.
  • Oil Cooler: A larger oil cooler or an additional remote cooler helps manage engine oil temps during extended hard driving.
  • High-Flow Water Pump: Upgrading the water pump (e.g., Alveo Racing) improves coolant flow.

Exhaust System

The factory exhaust backpressure becomes a bottleneck above 400 whp. A full 3-inch exhaust system with high-flow catalysts or catless downpipes is recommended. Brands like Akrapovič and SoyLent Racing offer systems that mate directly with the GTX3584RS turbine outlet.

Intake and Charge Piping

The stock airbox and intake tract are restrictive. A cold air intake with a larger MAF housing (or MAF-less speed-density tune) is necessary. Silicone charge pipes with reinforced couplers prevent blow-off under high boost.

Installation Overview

Installing the GTX3584RS kit requires moderate mechanical skill, specialized tools (torque wrenches, E-torx sockets, and a lift or jack stands), and familiarity with the 718’s mid-engine layout. Below is a high-level step-by-step summary:

  1. Preparation: Disconnect the battery, drain the cooling system, and remove the engine under-panel for access.
  2. Remove Stock Turbo: Unbolt the factory turbo from the exhaust manifold, disconnect oil and coolant lines, and slide the turbo out through the top or bottom of the engine bay (clearance is tight).
  3. Install New Manifold: Replace the OEM exhaust manifold with the kit’s precision-cast or tubular manifold. Use new gaskets and torque to spec.
  4. Mount GTX3584RS: Attach the turbo to the manifold, ensuring proper alignment of the oil drain and coolant fittings. Garrett’s kit includes AN fittings and braided lines for simple connection.
  5. Connect Intake and Exhaust: Install the compressor outlet pipe to the intercooler, and connect the turbine outlet to the downpipe. Use supplied V-band clamps.
  6. Plumb Oil and Coolant: Connect the oil feed line to the engine block, the oil drain to the pan, and the coolant lines to the engine’s coolant circuit. Purge the oil system before first start.
  7. Boost Control Install: Wire the included boost control solenoid between the ECU and the turbo’s wastegate actuator. Configure the solenoid on a dyno or with a simulation.
  8. Reassemble: Refill coolant, reconnect battery, and check for leaks. Prime the oil system by cranking with the fuel pump fuse removed.

The entire job typically takes 8–12 hours for an experienced DIYer, or 6–8 hours at a specialist shop like Burns Stainless or ESX Motorsports.

Tuning for Optimal Performance

Post-installation, the 718’s ECU must be reflashed to match the new turbo’s flow characteristics. Tuning options include:

  • Piggyback Tunes: Units like the Cobb Accessport V3 offer base off-the-shelf (OTS) maps for the GTX3584RS, but custom tuning is strongly advised for safety and maximum power.
  • Full ECU Remap: Shops such as Drift Shop and Integrated Engineering provide remote tuning services. They will log cruise, WOT, and temperature parameters, then adjust boost targets, fuel maps, and ignition timing.
  • Dyno Tuning: A dyno session on a Mustang or Dynojet ensures accurate air-fuel ratios (target 11.5:1 under boost) and peak boost (22–27 psi depending on fuel). Expect 450–500 whp on 93 octane and 500–560 whp on E85.

Tuning also involves setting boost by gear, launch control, and throttle mapping. Well-calibrated tunes retain factory cold start and emissions compliance (if applicable).

Cost Considerations and ROI

The GTX3584RS kit itself retails for approximately $3,200–$3,800, depending on package inclusions (manifold, downpipe, lines, solenoid). Complete supporting modifications add $2,000–$4,000 (fuel system, intercooler, exhaust, intake). Tuning costs range from $500 (remote OTS maps) to $1,500 (custom dyno tuning). Total investment: $5,700–$9,300. In return, the 718 Cayman gains power levels rivaling the GT4 or even the 911 Turbo S in straight-line performance, with retained mid-engine handling. For many owners, the per-dollar power increase is unmatched in the Porsche aftermarket.

Alternatives and Comparison

Other turbo upgrades exist for the 718, such as the Garrett G25-550 or Precision 5858. The G25-550 spools slightly faster but tops out around 480 whp. The Precision 5858 is more affordable but lacks the advanced ball bearing and ETT technology, leading to slightly slower response. The GTX3584RS strikes the best balance of spool, power ceiling, and reliability for a street-driven 718 that also sees track use.

Conclusion

The Garrett GTX3584RS kit is the definitive turbocharger upgrade for the 718 Cayman, unlocking dramatic horsepower and torque gains while maintaining drivability. By pairing it with necessary supporting modifications and a professional tune, owners can transform their Cayman into a 500+ whp mid-engine monster capable of thrilling performance on road and track. Whether you choose to install the kit yourself or enlist a specialist, the result is a vehicle that outpaces its factory-rated potential with confidence and longevity.