Understanding the AEM 60mm Turbo Kit for the GR86

The AEM 60mm Turbo Kit is a comprehensive forced-induction system engineered specifically for the Subaru BRZ / Toyota GR86 platform. It includes a precision-machined 60mm turbocharger, cast-iron exhaust manifold, aluminum intake piping, bar-and-plate intercooler, blow-off valve, and all necessary hardware for a complete install. When tuned correctly, this kit can deliver power gains in the 300–350 wheel horsepower range on pump gas, making it one of the most popular mid-range turbo options for the FA24 engine.

While the kit is designed for a relatively straightforward installation using factory mounting points, the added complexity of a turbo system introduces several potential failure points. This article provides a detailed troubleshooting guide for the most common issues GR86 owners face after installing the AEM 60mm kit, from boost leaks and fuel delivery problems to tuning challenges and cooling system inadequacies.

Common Issues and Troubleshooting Overview

Before diving into specific problems, it helps to understand that most AEM turbo kit issues fall into four categories: air path integrity (leaks), fuel system capacity, tuning calibration, and thermal management. The following sections break down each category with step-by-step diagnostics and fixes.

1. Boost Leaks: The Most Frequent Problem

Boost leaks are arguably the #1 complaint among GR86 turbo owners. Even a small leak at a coupler, clamp, or intercooler end tank can reduce peak boost by 2–5 psi, causing a noticeable loss of power, sluggish throttle response, and potential lean air/fuel mixtures that can damage the engine.

Identifying Boost Leaks

The most reliable method is a professional boost leak test using a smoke machine connected to the intake tract after the turbo. For a DIY approach, you can build a leak tester from a PVC cap and an air compressor schrader valve. Pressurize the system to 15–20 psi and listen for hissing sounds. Common leak points include:

  • Rubber couplers at the turbo outlet, intercooler inlet/outlet, and throttle body.
  • Intercooler end tank seams (especially on used kits where the core may have been damaged).
  • Blow-off valve diaphragm or O-rings.
  • Throttle body gasket or shaft seals.
  • Intake manifold gasket.

Fixing Boost Leaks

Always replace worn silicone couplers with high-quality 4-ply silicone. Use T-bolt clamps instead of worm-gear clamps, as they provide more even clamping force. Torque clamps to manufacturer specs (typically 35–45 in-lbs) – overtightening can deform the coupler. If the intercooler is leaking, consider upgrading to a welded core unit or a bar-plate unit from AEM directly for warranty replacement.

2. Fuel Delivery Problems

The FA24 engine in the GR86 comes with direct injection and port injection on certain markets, but the stock fuel system is not designed for significant boost. Symptoms of fuel starvation include hesitation under high load, lean lambda readings (above 0.85 on a wideband), and eventual misfire or knock.

Diagnosing Fuel Delivery Issues

  • Fuel pressure test: Install a fuel pressure gauge at the rail. At idle you should see ~50–60 psi (depending on regulator). Under full boost, pressure should rise 1:1 with boost (e.g., 15 psi boost = ~65–75 psi rail pressure). If pressure drops instead of rising, your pump or regulator is undersized.
  • Fuel pump current draw: Use a clamp meter to verify the pump draws sufficient amperage (typically 8–12A for an upgraded pump). A failing pump will draw lower current.
  • Injector duty cycle: Log injector duty cycle via your ECU software. If it exceeds 85–90% at peak power, injectors are maxed out.

Solutions for Fuel Delivery

Most GR86 owners with the AEM 60mm kit need at least an upgraded in-tank fuel pump (such as AEM 50-1220 or 340LPH pump) and larger fuel injectors (800cc-1000cc) to support 300+ whp. Keep the fuel lines free of kinks, especially if you reinstalled the factory hard line. Consider adding a fuel flex fuel sensor if you plan to run E85 – the kit’s fuel return system simplifies upgrades. For further reading, check this FT86 Club fuel system guide.

3. Turbo Lag and Throttle Response

The AEM 60mm turbo is a relatively small frame (60mm inducer), so it should spool quickly – typically reaching 10 psi around 3500–4000 rpm. If you experience excessive lag (boost not building until 4500+ rpm), investigate these areas:

Common Lag Causes

  • Exhaust restriction: Cat-back exhaust with too-small piping (under 2.5”) or a clogged catalytic converter. The AEM kit includes a downpipe with a 3” outlet – ensure your exhaust matches that diameter.
  • Boost control issues: If the wastegate actuator is stuck open or the preload is too slack, the turbo will not spool. Check that the actuator arm is properly adjusted – you should feel resistance when the actuator rod is extended.
  • Boost leak (already covered): Even a small leak can dramatically slow spool.
  • Tuning calibration: A conservative tune with overly rich mixture or excessive ignition retard will kill spool. Work with a reputable tuner who understands the FA24’s direct injection behavior.

Minimizing Turbo Lag

Consider installing a boost controller (manual or electronic) to optimize wastegate duty cycle. For daily driving, maintaining a 10–12 psi spring in the wastegate and letting the ECU handle boost control works well. If you track the car, invest in a quality electronic boost controller like the Turbosmart e-boost2 for progressive boost ramping.

4. Overheating: Cooling System Upgrades

Adding a turbocharger increases heat rejection significantly – the intercooler dumps heat into the air stream, and the turbo itself radiates heat. The GR86’s stock radiator and oil cooler are marginal for naturally aspirated use; under boost, coolant temperatures can easily exceed 220°F (105°C) on track days, leading to power reduction or engine damage.

Identifying Overheating

  • Coolant temperature gauge climbing above 210°F during hard driving.
  • Fan cycling continuously after shutdown.
  • Radiator cap blowing off or coolant overflow tank filling rapidly.
  • Engine pulling timing (visible in ECU logs via reduced ignition advance).

Cooling System Upgrades to Consider

For street driving with occasional pulls, a high-pressure radiator cap (1.3 bar) and proper coolant mix (30% coolant, 70% distilled water + water wetter) may suffice. For track use or hot climates, install:

  • An aluminum radiator with at least 40mm core thickness (e.g., Koyo or CSF).
  • An oil cooler (thermostatic sandwich plate, 19-row or larger).
  • Upgraded electric fans (e.g., Spal) to move more air at low speeds.
  • A hood vent or louver kit to relieve underhood pressure.

Monitor engine temperatures via an aftermarket gauge or OBD-II logger. The AEM kit itself comes with a slim fan shroud that fits the stock radiator, but upgrading is recommended for sustained high-load use. For more detail, refer to CSF’s GR86 cooling page.

Additional Troubleshooting Areas

5. Oil Feed and Drain Issues

The AEM kit uses a sandwich plate on the oil filter housing for the oil feed line. Common failures include:

  • Restricted oil drain line (routing too high, kinked, or too small diameter). This causes oil smoking from the turbo seals.
  • Oil supply hose leaking if the AN fittings are not sufficiently tightened.
  • Oil pressure dropping: verify with a mechanical gauge. If pressure falls below 10 psi at idle hot, the oil pump may be unable to supply both the engine and turbo. Consider a higher-volume oil pump gear upgrade.

6. Tuning and ECU Calibration Pitfalls

Running the AEM 60mm kit without a proper tune is dangerous. The kit requires a standalone ECU or a flash tune for the factory ECU (e.g., ECUTek, Cobb Accesstuner). Issues arise when:

  • The base map supplied by AEM (if any) is too conservative or too aggressive for your specific fuel quality.
  • Fuel trims are not adjusted for larger injectors, causing idle surging or rich misfire.
  • Boost control tables are not calibrated, resulting in boost spikes or overboost.
  • Knock detection thresholds are not set correctly – the FA24 is sensitive to knock and will pull timing aggressively, making the car feel slow.

Always find a tuner who has experience with the FA24 turbo. Read community feedback on GT86.org for tuner recommendations.

7. Wastegate and Boost Control

The AEM kit uses an internal wastegate. Problems include:

  • Wastegate creep (boost rising above target under load) – check that the wastegate port is not too small or the actuator is weak.
  • Boost spikes (sudden overboost) – usually due to boost controller setting or spring rate mismatch.
  • No boost at all – wastegate arm disconnected or jammed open.

Check wastegate movement by removing the actuator rod and ensuring the flapper valve moves freely. Replace the actuator if it leaks air when pressurized.

Preventive Maintenance and Long-Term Reliability

Once you’ve resolved initial issues, establish a maintenance schedule:

  • Change oil every 3,000 miles using 5W-30 full synthetic. The turbo places extra thermal load on the oil.
  • Inspect all couplers and clamps every 5,000 miles – retighten T-bolts as needed (they can loosen with thermal cycling).
  • Replace spark plugs every 15,000 miles; use colder heat range (NGK LFR7AIX or equivalent) to prevent pre-ignition.
  • Flush coolant annually if using water-based mix.
  • Log fuel trims and boost levels periodically with your tuning software to catch drift early.

With careful attention to these details, the AEM 60mm Turbo Kit can transform your GR86 into a reliable 350+ whp street machine. The key is systematic diagnostics and not ignoring small symptoms – a boost leak today can become a bent rod tomorrow if left unaddressed.