Adding forced induction to your Subaru BRZ is one of the most rewarding ways to unlock its true potential, and the APS Twin-Scroll Turbo Kit stands out as a refined, high-quality solution. Designed specifically for the FA20 engine, this kit delivers linear, responsive power with minimal lag. While the installation is a serious mechanical undertaking, a methodical, informed approach can save you hours of frustration and prevent costly mistakes. This guide expands on the key steps, covering everything from workspace preparation to post-installation tuning considerations, so you can complete the job with confidence and get the most out of your new turbo system.

Tools, Materials, and Workspace Preparation

Before turning a single bolt, gather all necessary tools and consumables. A well-organized workspace reduces downtime and the risk of losing small parts.

Essential Tools

  • Metric socket set (1/4”, 3/8”, and 1/2” drive) – 10mm, 12mm, 14mm, 17mm, 19mm are most common
  • Combination wrenches (same sizes) and ratcheting wrenches for tight spaces
  • Torque wrench (ft-lb and in-lb ranges) – critical for exhaust manifold studs and turbo fasteners
  • Allen keys (hex) and Torx bits (T30, T40 for various brackets)
  • Pry bars and trim removal tools for plastic clips
  • Jack stands and a floor jack – never rely on a scissor jack
  • Oil catch pan, coolant drain pan
  • Shop towels, brake cleaner, thread locker (medium-strength)
  • Safety glasses, mechanic’s gloves, and a fire extinguisher rated for fuel/electrical

Consumables and Fluids

  • Fresh engine oil (5W-30 or as recommended by your tuner) – 6-7 quarts
  • OEM Subaru coolant or equivalent – approximately 1.5 gallons
  • New gaskets: exhaust manifold gaskets, downpipe gasket, turbo oil return gasket (often included in kit)
  • Copper anti-seize for exhaust fasteners
  • Loctite 567 or PTFE thread sealant for oil fittings
  • Vacuum caps and zip ties for re-routing lines

Set aside a full weekend for the mechanical work, plus additional time for tuning. Having a factory service manual (OEM Subaru or a reliable aftermarket version) on hand is indispensable – it provides torque specs and connector removal procedures. You can find the official Subaru BRZ service manual online for reference.

Pre-Installation Safety and Vehicle Preparation

Park the BRZ on a level, well-ventilated surface. Allow the engine to cool completely – the exhaust manifold and catalytic converter retain heat for hours. Disconnect the negative battery terminal to prevent accidental short circuits and to reset the ECU in preparation for the new tune.

  • Drain the engine oil and remove the oil filter. This makes access to the turbo oil drain port easier later.
  • Drain the coolant from the radiator petcock and also from the engine block drain plug (located on the driver’s side near the oil pan).
  • Remove the front bumper cover, headlight housings (if needed for intercooler piping), and all undertray panels. This opens up the entire front of the engine bay.
  • Label and photograph all vacuum lines and electrical connectors before disconnecting. The FA20 engine has several small coolant hoses that are easy to mix up.

Removing Factory Components

Removing the stock intake and exhaust components is straightforward, but patience pays off when dealing with rusted bolts and heat-shield clips.

Intake System

Remove the airbox assembly, mass airflow sensor (MAF), and the intake tube that connects to the throttle body. The MAF sensor is delicate – store it in a clean, static-free bag. Unclip any wiring harness brackets along the intake path.

Exhaust Manifold and Downpipe

The factory exhaust manifold is integrated with the catalytic converter and comes off as a single heavy piece. Begin by spraying penetrating oil on the six exhaust manifold studs and the downpipe nuts (two at the turbo flange, two at the midpipe).

  • Disconnect the oxygen sensors (O2) – unplug them near the firewall, then unscrew them from the exhaust. A 22mm oxygen sensor socket works best.
  • Remove the heat shield over the manifold. It may require flex-head ratchets and extension.
  • With a long breaker bar, loosen the manifold-to-head nuts. Use a 14mm socket and work from the center outward in a cross pattern to avoid warping the mating surface.
  • Separate the downpipe from the midpipe at the spring-loaded flange. If it’s seized, a small propane torch applied to the nut (not the stud) can help.
  • Lift the entire manifold/downpipe assembly out from the bottom of the engine bay. Be careful not to damage the steering rack boot.

While the manifold is off, inspect the exhaust port gaskets and replace them if they show signs of leakage. Clean the cylinder head mating surfaces with a plastic scraper – metal scrapers can gouge the aluminum.

Additional Components

Remove the oil cooler lines (if equipped) and the factory oil filter housing adapter if the APS kit includes a remote oil filter mount. Also remove the coolant expansion tank bracket to make room for the turbocharger.

Installing the APS Twin-Scroll Turbo Kit

With the engine bay cleared, you can begin installing the turbo assembly. The APS twin-scroll design uses a divided manifold that separates exhaust pulses from cylinders 1-2 and 3-4, providing faster spool and better transient response than a standard single scroll.

Manifold and Turbo Mounting

  • Install the new exhaust manifold gaskets onto the cylinder head studs. Use a light smear of copper anti-seize on the stud threads, not on the gasket itself.
  • Place the APS manifold onto the studs. If the kit includes a separate wastegate mounting bracket, install that now. Hand-tighten the manifold nuts (14mm) in a cross pattern, then torque to 25 ft-lb. Re-torque after a short heat cycle.
  • Prepare the turbocharger by spinning the compressor wheel to confirm free rotation. Apply a thin film of clean engine oil to the oil feed port – this prevents a dry start.
  • Mount the turbo to the manifold using the supplied gasket and hardware. Tighten the turbine housing bolts to the spec provided in the kit (typically 30-35 ft-lb).
  • Install the upgraded oil drain fitting (usually a -10 AN or -12 AN) into the turbo center section. Apply thread sealant to the fitting, but keep it off the first two threads to avoid contamination.
  • Attach the wastegate actuator to the turbo's compressor housing. Connect the actuator rod to the wastegate arm and adjust the preload per the instruction manual – typically 2-3 threads of visible rod before the clip is installed.

Downpipe and Exhaust System

Connect the APS downpipe to the turbo exhaust outlet using the supplied gasket. Use new, high-temperature lock nuts (copper or nickel-plated) and torque to 25 ft-lb. The downpipe will usually drop down and connect to the factory cat-back exhaust via an adapter – this is a good time to upgrade to a 3-inch cat-back if desired. Ensure the downpipe does not contact the steering shaft or front subframe. A slight bend clearance tool can help you check.

Front-Mount Intercooler (FMIC) and Charge Piping

Most APS twin-scroll kits include a bar-and-plate front-mount intercooler. Mount the intercooler core behind the bumper beam using the supplied brackets. Route the charge pipes from the turbo compressor outlet to the intercooler, then from the intercooler to the throttle body. Use silicone couplers and T-bolt clamps – snug them to 35-40 in-lb; overtightening can deform the pipes.

  • If the kit includes a blow-off valve (BOV), mount it on the charge pipe before the throttle body. Recirculating (plumb-back) valves are recommended for MAF-based tuning to avoid rich spikes.
  • For boost reference, T into the intake manifold vacuum line (the one that runs to the factory EVAP solenoid). Connect this hose to the wastegate actuator top port.

Oil and Coolant Lines – Precision Routing

Proper oil and coolant line routing is the most critical aspect of the installation – mistakes here can destroy the turbo in minutes.

Oil Feed

The APS kit usually taps into the engine block's oil galley plug (located behind the alternator, using a 1/8” BSP or NPT fitting). Remove the plug, apply thread sealant to the supplied banjo bolt or adapter, and install the feed line. Run the -3 AN or -4 AN braided line up to the turbo inlet, avoiding the exhaust manifold and steering shaft. Use zip ties to secure the line at 6-inch intervals.

Oil Drain

The oil drain line must be downhill from the turbo to the oil pan. Most kits provide a -10 AN or -12 AN hose that connects to a bung welded into the oil pan. You will need to drill and tap the pan or install a pre-welded replacement pan. If drilling, remove the pan completely to keep metal shavings out of the engine. Tap the hole, clean thoroughly, and install the -10 AN weldless bulkhead fitting or a threaded bung. Route the drain line with a gentle, continuous slope – no loops or low spots. Use two wrenches to tighten the AN unions.

Coolant Lines

The turbocharger’s water-cooled center section requires coolant flow. The kit includes a T-fitting that splices into the heater core return hose (located at the firewall). Connect the coolant feed hose to the lower port on the turbo, and the coolant return hose to the upper port. After installation, bleed the cooling system by running the engine with the radiator cap off and adding coolant until the thermostat opens and bubbles cease.

Final Connections and Wiring

Reconnect all sensors and harnesses that were removed:

  • Plug in the MAF sensor (now located on the intake pipe after the air filter).
  • Reconnect the front and rear oxygen sensors. The rear sensor may need to be relocated further downstream using a supplied bung – ensure it is at least 18 inches from the turbo outlet to avoid heat damage.
  • Connect the boost controller solenoid (if using an electronic boost controller). Wire it to a 12V switched source and to the ECU boost control output, per your tuner’s recommendation.
  • Install the new intake pipe and cone filter. Ensure the filter is at least 12 inches from the turbo inlet to allow proper airflow.

Double-check all hose clamps, AN fittings, and electrical connections. No loose wires should touch the downpipe or manifold. Use heat-shrink loom on any exposed wiring near heat sources.

First Start and Test Procedure

Before starting the engine, prime the turbo oil system. Disable the fuel pump and ignition by pulling the fuel pump relay and ignition fuse. Crank the engine for 10-15 seconds – this builds oil pressure and pushes oil through the turbo feed line without starting the engine. Reconnect the relay and fuse.

  • Start the engine and let it idle. Immediately check for oil and coolant leaks. Look at the turbo drain and feed lines, drain plug, and water hoses.
  • Monitor oil pressure with a gauge (if installed) or through the factory oil pressure sensor via an OBD2 scanner. Pressure should reach 30-60 psi at cold idle.
  • Check the turbo for unusual noises – whining, grinding, or chirping indicates a problem. If the turbo sounds clean, let it idle until the coolant temperature reaches 180°F.
  • Perform a boost leak test. With the engine off, plug the intake pipe and pressurize the charge system to 10-15 psi using a boost leak tester. Listen for hissing. Fix any leaks before driving.
  • Take a short, low-load test drive of 5-10 miles, keeping boost below 5 psi. Vary RPM and avoid hard acceleration. Return and check for leaks again.

Tuning and Break-In Considerations

The APS twin-scroll kit requires a custom ECU tune. Do not drive the car on a stock tune – the extra airflow will cause lean conditions and catastrophic engine damage. Work with a professional Subaru tuner (e.g., Delicious Tuning, Crawford Performance, or a local dyno shop).

  • Use a base map provided by the kit manufacturer or tuner for initial start and idle.
  • Plan for a dyno session or remote e-tuning with data logging. Wideband oxygen sensor (AFR) readings should be confirmed.
  • Break in the turbo and new oil seals: drive the first 200 miles with occasional full-boost pulls (up to 8-10 psi) followed by cool-down coasting. Avoid prolonged idle and sustained high boost.
  • After break-in, switch to a full synthetic oil and change the oil filter. Check the turbine shaft play – a small amount of axial play (0.001-0.002”) is normal; excessive radial play indicates a problem.

Conclusion

Installing the APS Twin-Scroll Turbo Kit on your Subaru BRZ is a demanding but highly rewarding project. The kit’s engineering reduces many common headaches, but the quality of the installation ultimately determines reliability and performance. By following this expanded guide, you’ll have a solid roadmap: from selecting the right tools and safely removing factory parts, to precision routing of oil and coolant lines, to the critical first start and tuning phase. Take your time, torque everything to spec, and don’t skip the oil prime step. With a proper tune, your BRZ will deliver a linear, responsive powerband that transforms the driving experience – exactly what the FA20 engine deserves.