The GReddy Tuner Kit is a well-regarded upgrade for the Subaru BRZ equipped with the FA20 engine, offering significant gains in throttle response, horsepower, and overall driving engagement without the complexity of a full turbo or supercharger system. This kit integrates a high-flow intake pipe, a performance air filter, a blow-off valve, and a programmable ECU tuner module that allows you to remap the factory engine control unit. When installed correctly, the GReddy Tuner Kit transforms the BRZ's naturally aspirated character into something sharper and more responsive, especially in the mid-range where the FA20 can feel flat from the factory. This comprehensive guide will walk you through every step of the installation, from gathering the right tools to verifying that the system is running at peak performance. Whether you are a seasoned DIY mechanic or a first-time tuner, careful attention to detail is paramount to ensure a safe and effective installation.

Before starting, it is essential to understand the tools and workspace required. The installation is moderate in difficulty and can be completed in a well-equipped home garage using a lift or sturdy jack stands. You will need a socket wrench set with metric sockets (10mm, 12mm, 14mm are most common), a set of flathead and Phillips screwdrivers, a torque wrench capable of delivering inch-pounds for small bolts and foot-pounds for larger fasteners, a pair of pliers or hose clamp pliers, and a trim removal tool if you need to access the ECU harness under the dashboard. Safety glasses, mechanic's gloves, and a fire extinguisher are non-negotiable items to have nearby. Additionally, have a clean workspace free of debris and a well-lit area where you can keep all small hardware organized. The GReddy kit itself should include the intake pipe, air filter, blow-off valve with associated vacuum lines and fittings, the ECU tuner module, a wiring harness with piggyback connector, and instructions specific to the 2013-2020 Subaru BRZ (and Scion FR-S/Toyota 86).

Tools and Parts Required

  • GReddy Tuner Kit (model specific to FA20 BRZ/FR-S/86)
  • Metric socket set (10mm, 12mm, 14mm) with ratchet and extensions
  • Flathead and Phillips screwdrivers
  • Torque wrench (inch-pound and foot-pound ranges)
  • Jack and two jack stands or a four-post lift
  • Trim removal tool (for ECU harness panels)
  • Hose clamp pliers or standard pliers
  • Safety glasses and mechanic's gloves
  • Shop towels and a vacuum or brush for cleaning the engine bay
  • Dielectric grease for electrical connections
  • Optional: Scan tool or OBD-II reader for monitoring after installation

Preparation and Safety

Begin by parking the vehicle on a level surface and allowing the engine to cool completely. A hot engine can cause burns and make plastic components brittle, increasing the risk of breakage. Disconnect the negative battery terminal using a 10mm socket and isolate the cable to prevent accidental contact. Then raise the front of the car using a jack and secure it on jack stands placed at the designated lift points under the front pinch welds or subframe. Never work under a vehicle supported only by a jack. Once the car is safely raised, remove the factory engine undercover if equipped (usually held by 10mm bolts or push pins) to give yourself access to the lower intake tract and blow-off valve area. Take a moment to inspect the existing intake system for any signs of oil leaks, loose clamps, or debris that may interfere with the new installation. A clean engine bay is easier to work on and helps prevent foreign objects from entering the intake during the swap.

Step-by-Step Installation

Removing the Stock Air Intake System

The factory intake system on the BRZ FA20 includes an airbox, a resonator chamber, and a rubber intake tube connecting to the throttle body. Start by loosening the hose clamp that secures the intake tube to the throttle body using a flathead screwdriver or a 7mm socket. Then disconnect the mass air flow (MAF) sensor wiring harness by pressing the tab and pulling it free. The MAF sensor is mounted on the intake tube near the airbox. Next, remove the bolts or clips holding the top of the airbox (usually three 10mm bolts). Lift the airbox lid and pull out the stock air filter. With the filter removed, you can unfasten the lower portion of the airbox by removing any additional bolts or screws. The intake tube itself can then be pried off the throttle body; it may require a gentle twisting motion. Finally, disconnect any small vacuum lines or breather hoses attached to the intake tube. On some BRZ models, there is a PCV hose that connects to the intake pipe near the throttle body. Remove it entirely and set all stock components aside. Be careful not to drop any fasteners or small parts into the engine bay.

Installing the GReddy Intake Pipe

With the stock intake completely removed, prepare the GReddy intake pipe for installation. The pipe is typically made of polished aluminum or silicone-reinforced rubber, with pre-installed MAF sensor bungs and vacuum ports. Apply a small amount of dielectric grease to any electrical connectors that will be reused, particularly the MAF sensor connector. If the GReddy pipe requires repositioning the MAF sensor, carefully remove the sensor from the stock housing using a small screwdriver (usually held by two screws) and install it into the provided bung on the new pipe. Be sure the sensor is oriented correctly according to the flow arrow marked on it. Slide the included silicone coupler and T-bolt clamp over the throttle body end of the pipe, then attach the pipe to the throttle body hand-tight. Align the pipe so that it clears the radiator fan shroud, alternator, and power steering lines. Once positioned correctly, tighten the T-bolt clamp to the specified torque (usually 30-40 inch-pounds) using a torque wrench. Then secure the other end of the intake pipe—this may connect to a lower tube or directly to the air filter—using the provided clamps. If your kit includes a recirculation or intake tube for the blow-off valve, install that now as well.

Mounting the GReddy Performance Air Filter

The air filter supplied with the GReddy kit is a high-flow, oiled or dry cotton unit that requires proper seating to avoid unfiltered air entering the engine. Slide the air filter onto the end of the intake pipe or onto a connecting tube, ensuring the filter's opening fits snugly over the pipe. Use the provided worm gear or spring clamp to secure the filter. Tighten the clamp only enough to hold the filter without crushing its mounting ring; overtightening can distort the filter housing and cause air leaks. For oiled filters, allow any excess oil to settle before installation—over-oiling can contaminate the MAF sensor. Position the filter so it is not touching any hot engine components or rubbing against the bodywork. Many installations place the filter in the lower front area behind the bumper cover for cooler air. If your kit includes a heat shield, attach it now to reduce heat soak.

Installing the GReddy Blow-Off Valve

The blow-off valve (BOV) in this kit is typically a vent-to-atmosphere type that releases boost pressure during throttle lift-off. Locate the factory recirculation hose that runs from the intake pipe to the turbocharger compressor bypass valve (on naturally aspirated cars, this BOV is actually a diverter valve; the GReddy kit often replaces it). Remove the existing hose and fit the GReddy blow-off valve using the supplied mounting bracket and hardware. Install a vacuum line from the BOV's top port to a manifold vacuum source—many installations tap into the intake manifold vacuum port located near the throttle body. Ensure the vacuum line is routed away from hot surfaces and moving parts. Secure all connections with zip ties if necessary. The BOV should be mounted in a stable location where it does not vibrate loose. Verify that the valve's spring tension is appropriate for the expected vacuum level; for a NA FA20, the stock spring is usually sufficient. Do not overtighten the mounting bolts as the BOV housing may be aluminum.

Connecting the GReddy Tuner Module to the ECU

This is the most critical electrical step. The GReddy tuner module is a piggyback device that intercepts signals between the ECU and various sensors to modify ignition timing, fuel maps, and other parameters. Locate the ECU under the dashboard on the passenger side (or behind the glove box). You may need to remove a cover panel (held by clips or a few bolts) to access the ECU connectors. Disconnect the two main ECU harness connectors: the black 80-pin connector and the gray 60-pin connector. The GReddy kit includes a pass-through harness that splices between the ECU and the factory connectors. Plug the GReddy harness' male ends into the ECU, then plug the factory connectors into the GReddy harness' female ends. Ensure each connector clicks securely. Route the tuner module's cable to a convenient location (e.g., under the dash or in the glove box) where it can be accessed for programming. Connect the module's power and ground as per the instructions—often via tapping into a switched 12V source and a clean chassis ground. Use crimp connectors and heat shrink for a weatherproof connection. Double-check all connections before reconnecting the battery.

ECU Tuning and Calibration

With the hardware installed, the tuner module must be programmed to match your specific vehicle and modifications. The GReddy kit typically comes with a base map designed for the BRZ FA20 with intake and exhaust modifications. If you are running the kit only with the intake and blow-off valve (no other modifications), the base map may be sufficient, but a custom tune is highly recommended for optimal performance and safety. You can use a laptop with the GReddy software (if provided) or take the car to a professional tuner who specializes in FA20 engine management. The calibration process involves logging data (air/fuel ratio, ignition timing, knock counts, throttle position) and adjusting the fuel and timing maps accordingly. For DIY tuning, consider using an OBD-II data logger and reviewing the logs during a test run. A custom e-tune from a reputable company like Delicious Tuning or EcuTek can provide a safe, tailored calibration. Never run the car hard on a base map without verifying that fuel trims are within acceptable ranges. Pay close attention to any knock sensor activity; if the engine pings, immediately stop and reduce timing.

Post-Installation Checks and Testing

After completing the hardware installation and loading a base or custom tune, perform a thorough pre-start inspection. Reconnect the battery (positive first, then negative). Turn the ignition to the ON position without starting the engine, allowing the fuel pump to prime and the ECU to power up. Listen for any electrical shorts or unusual noises. Start the engine and let it idle for a few minutes. Check for vacuum leaks by spraying a small amount of carb cleaner or using a smoke machine around all intake connections and the blow-off valve base plate. A change in idle speed indicates a leak. Also, inspect the blow-off valve operation—at idle, the valve should be closed; if it is open, the vacuum line may be misrouted. Rev the engine gently and listen for the BOV venting (a "psshh" sound) when you lift off the throttle. If you hear compressor surge or fluttering, the spring tension may need adjustment. Monitor the MAF sensor values and fuel trims using a scan tool if available. They should stabilize within a few minutes. Finally, take the car for a short conservative test drive. Accelerate gradually, then perform a few moderate throttle lifts to verify BOV operation. Gradually increase manifold pressure as you gain confidence. After the test drive, recheck all fasteners and hose clamps while the engine is cool. Some hot tightening may be required.

Common Pitfalls and Troubleshooting

  • Air leaks: The most frequent issue after intake installation. Ensure all silicone couplers are aligned and tightened evenly. Use a torque wrench on T-bolt clamps (25-35 in-lbs) to avoid crushing the rubber.
  • MAF sensor contamination: If the air filter is over-oiled, oil residue can coat the MAF sensor wire, causing erratic readings. Clean the MAF sensor with an electronics cleaner if necessary.
  • Check engine light (CEL): A lean or rich code may appear if the tune is not matched properly. Recheck vacuum hoses and the BOV spring. Use a code reader to diagnose and reflash if needed.
  • BOV not venting: Verify vacuum source is connected to a manifold vacuum port, not a boost-only port. The FA20 intake manifold has a dedicated vacuum nipple near the throttle body.
  • ECU communication error: Ensure the piggyback harness is fully seated into both the ECU and factory connectors. Inspect for bent pins.
  • Idle fluctuations: After a new tune, the ECU may need to relearn its idle trim. Allow the engine to idle for 10 minutes with all accessories off, then perform a few drive cycles.

Conclusion

Installing the GReddy Tuner Kit on your Subaru BRZ FA20 is a rewarding project that enhances both performance and driving pleasure. By following this detailed guide and taking the time to verify each step, you will have a properly functioning system that delivers improved throttle response and horsepower gains typically in the range of 15-25 wheel horsepower when combined with a quality tune. Remember that the engine management portion is just as important as the physical install—do not skip the tuning step. For additional resources and community support, refer to the GReddy official product page for kit-specific documentation, the FT86 Club forum for shared installation experiences, and this comprehensive video walkthrough (example link) for visual guidance. Always prioritize safety, torque specifications, and proper fuel quality to keep your FA20 running strong for miles to come.

Note: The links provided are for informational purposes and were accurate at the time of writing. Always verify compatibility with your specific vehicle model year.