Upgrading your 13B engine with a Garrett GT50 turbocharger is one of the most effective ways to unlock serious horsepower and torque. The 13B rotary engine is renowned for its compact design and high-revving nature, and pairing it with a well-matched turbo like the GT50 transforms it into a monster on both street and track. However, installing a GT50 is not a simple bolt-on affair — it requires careful planning, the right supporting modifications, and meticulous attention to detail. This expanded guide walks you through every critical phase of the installation, from selecting the correct parts and prepping the engine bay to tuning and breaking in the new setup. Whether you’re a seasoned rotary enthusiast or a first-time turbo installer, these steps will help you achieve a reliable, high-performance build.

Understanding the 13B Engine and Garrett GT50 Turbocharger

The 13B is a 1.3-liter twin-rotor Wankel engine produced by Mazda. Its unique rotary design offers a high power-to-weight ratio and exceptional response, but it also has specific turbocharging requirements. The Garrett GT50 turbo (often part of the GTX50 or G Series family) is a large-frame turbo capable of flowing massive air volumes — typically supporting 500-900 horsepower depending on the trim. It features a billet compressor wheel, dual ball bearings, and advanced aerodynamics. This turbo demands proper oil delivery, wastegate control, and intercooling to avoid overheating and oil starvation. Understanding the characteristics of both the engine and turbo is crucial before starting the install.

Before you begin, verify the exact GT50 variant you have (e.g., GTX3576R, G35-900, or GTX4294R). Each has different flange sizes, oil inlet/outlet dimensions, and boost ranges. Consult Garrett Motion’s official documentation for specific specs. Also confirm your 13B is built to handle the power goals — a stock ported 13B may need upgraded apex seals, studs, and a stronger oil pump.

Tools, Materials, and Supporting Parts

Beyond the turbo itself, the installation requires a comprehensive set of tools and ancillary components. Incomplete preparation leads to frustrating delays and potential damage during startup. Use the following list as a minimum checklist:

Essential Tools

  • Complete socket set (metric, 8mm-24mm)
  • Torque wrench (5-150 ft-lb range)
  • Feeler gauges for wastegate setup
  • Oil catch pan and rags
  • Thread locker (Loctite 243 or 271)
  • Boost leak tester
  • Vacuum/pressure gauge

Required Materials

  • Garrett GT50 turbocharger (correct flange for your manifold)
  • Turbo manifold – T3/T4 or divided T4 flange, designed for 13B
  • Wastegate – external (e.g., Tial 44mm or 60mm) with appropriate spring
  • Intercooler – air-to-air; core size at least 24x12x3 for 500+ hp
  • Silicone couplers and T-bolt clamps (all sizes match piping)
  • Oil feed line – -4AN or -3AN with restrictor if needed
  • Oil return line – -10AN or -12AN with proper drain to pan
  • Exhaust gaskets (manifold to turbo, turbo to downpipe)
  • Redundant exhaust studs and nuts (use high-temp anti-seize)
  • Boost controller (manual or electronic)
  • Upgraded fuel pump (e.g., Walbro 450 or AEM 340)
  • Fuel injectors at least 1000cc (for E85) or 750cc pump gas
  • Standalone ECU or piggyback fuel controller (e.g., Haltech, Power FC, Adaptronic)

Note: Some GT50 turbos require a water cooling circuit. If your variant has water ports, you’ll need -6AN water lines and a coolant source (often from the heater hose circuit). Check Garrett’s spec sheet before ordering.

Preparation: Engine Bay and Vehicle Setup

Do not rush into the installation. Proper preparation can save hours of troubleshooting later. Begin by disconnecting the battery (negative terminal) and draining the engine coolant (if your turbo uses water lines). Relieve fuel system pressure by removing the fuel pump relay and cranking the engine until it stalls. Remove the air intake, intercooler piping, and any components blocking access to the exhaust manifold.

Inspect the engine’s overall health. Perform a compression test on both rotors. Low compression (below 90 psi per face) indicates a rebuild may be necessary. Check the oil condition – if it’s black or sludgy, change it and consider using a break-in oil with high zinc content for rotary engines. Install an oil temperature gauge and a wideband air-fuel ratio sensor before startup to monitor vital signs.

If your 13B is originally non-turbo (e.g., 13B-RE from FC or FD), you may need to add an oil supply from the oil pressure sender port or an oil cooler sandwich plate. For turbo models (13B-REW, 13B-RE), the oil supply port is typically available on the engine block near the front cover. Consult a factory service manual for the exact location.

Electrical and ECU Considerations

Upgrading to a GT50 turbo necessitates major fuel and timing changes. The stock ECU cannot handle the airflow or boost pressure. Install a standalone ECU such as a Haltech Nexus, Motec M130, or a rotary-specific unit like the Microtech LT10S. You’ll also need a map sensor capable of reading 3-5 bar (depending on boost target). Wire the ECU’s boost control output to the wastegate solenoid (if using electronic boost control). Have a professional tuner prepare a base map to safely start the engine.

Removing the Existing Turbo or Manifold

If you already have a turbo system installed, removal is mostly reverse of installation. But if the 13B is naturally aspirated, you’re removing the stock exhaust manifold and intake hardware. For either scenario, follow these steps:

  1. Disconnect the battery and drain coolant if water lines are present.
  2. Remove the air filter box, intake ducting, and intercooler piping.
  3. Unbolt the exhaust downpipe from the turbo (or exhaust manifold if NA). Support the exhaust system with a jack stand.
  4. Disconnect the oil feed and return lines at the turbo. Place a drip pan underneath to catch oil residue.
  5. If water-cooled, disconnect the coolant lines (be ready for coolant spillage).
  6. Remove the turbo-to-manifold bolts (usually 10-12mm studs with lock nuts). Use penetrating oil if rusted.
  7. Carefully lift the turbo out of the engine bay. Rotate it to clear the intake manifold and frame rails.
  8. Unbolt the old manifold from the engine. Clean the exhaust ports thoroughly; use a rotary wire brush or new surface gaskets.

Tip: While the manifold is off, inspect the exhaust ports for carbon buildup. Clean them with a soft wire brush and solvent. Also check for warped flanges; minor warping can be machined flat.

Installing the Garrett GT50 Turbo

Mounting the Manifold and Turbo

  • Install the new turbo manifold onto the 13B exhaust ports. Use new copper or MLS exhaust gaskets. Apply anti-seize to all manifold studs. Torque in stages: first to 20 ft-lb, then final to 35-40 ft-lb (follow manufacturer recommendations).
  • Mount the wastegate to the manifold’s designated flanged port before installing the turbo on the manifold. This is easier with the turbo off. Use the included gasket and high-temp thread locker.
  • Place the GT50 turbo onto the manifold’s T4/T3 flange. Ensure the oil drain is oriented downward (preferably between 5 and 7 o’clock). Rotate the compressor housing as needed for intercooler piping.
  • Bolt the turbo to the manifold with new lock washers. Torque to spec (typically 30-40 ft-lb for 10mm studs). Do not over-torque; the cast iron can crack.
  • Attach the exhaust downpipe. Use a flexible coupling or V-band if possible to reduce stress from engine movement. Ensure the wastegate dump tube is routed away from the downpipe (or re-merge after the turbo).

Oil and Water Line Installation

The GT50’s ball bearings are sensitive to oil pressure. Too much oil pressure can blow out the seals; too little can cause failure. Use a restrictor if your 13B’s oil pressure exceeds 80 psi after the turbo (common on rotary engines). A -3AN feed line with a 0.040″ restrictor is typical. Connect the feed line to the engine’s oil supply port (usually at the front cover or oil filter sandwich plate). Secure all fittings with proper wrenches, avoid over-tightening.

For the oil return, use a -10AN or -12AN line (large diameter) with minimal bends. Gravity drain is essential — the return must go to a location above the oil level in the pan. If your oil pan has only a return port below the oil line (unlikely on 13B pans), install a return fitting on the pan’s side at least 2 inches above the oil level. Some aftermarket pans have dedicated turbo drain ports. Use a high-quality rubber hose rated for oil, or wrap stainless braided hose with heat protection near the exhaust.

For water-cooled variants: Connect -6AN lines from the turbo’s water inlet to the coolant return (e.g., heater core outlet pipe) and the outlet to the water pump or radiator. This ensures constant coolant flow. Use hose clamps to prevent leaks under boost.

Wastegate Setup and Boost Control

The external wastegate (e.g., Tial 44mm) must be plumbed correctly for consistent boost. Mount the wastegate as close to the turbo as possible. Connect the wastegate’s boost reference line to a pressure source on the compressor cover or intercooler piping (not directly at the turbo outlet, as that can cause surge). The signal line should be -4AN or 1/8″ NPT. If using a boost controller, tee into this line.

Set the wastegate spring to your minimum boost level. Common springs: 7 psi, 10 psi, 14 psi. For a GT50, a starting boost of 10-12 psi is safe for break-in. After the engine is tuned, you can increase boost using an electronic controller. Ensure the wastegate’s actuator arm is adjusted to apply preload (about 1/16″ gap before it starts to open). Refer to the manufacturer’s manual for precise gap specification.

Intercooler and Intake Piping

An inefficient intercooler will quickly lead to high intake temps and detonation. Mount a bar-and-plate intercooler in front of the radiator. For a 13B with GT50, a core roughly 28x12x4 inches is adequate for 600-700 hp. Use 3″ or 4″ aluminum piping. Cut and weld the piping to fit your engine bay. Use silicone couplers with T-bolt clamps at each joint. Keep the path from turbo to intercooler as straight as possible.

For the intake side, run a 4″ or 5″ pipe from the turbo compressor inlet to a high-flow air filter (e.g., K&N conical or a screened velocity stack). Place the filter in a cold air location, away from the exhaust. Include a blow-off valve (e.g., Tial Q or HKS SSQV) on the intercooler piping before the throttle body. Set the BOV spring to hold boost without leaking.

Fuel System Upgrades

The 13B rotary relies on precise fuel delivery. The GT50 will demand far more fuel than the stock pump and injectors can provide. Install a high-flow in-tank fuel pump (minimum 450 Lph) along with a surge tank or inline pump if exceeding 600 hp. Replace the fuel filter (use a 10-micron filter). Upgrade injectors to 1000cc-2000cc (low impedance with resistor pack for RX-7s, or high impedance for newer ECUs). Consider switching to E85 for better detonation resistance — this will require even larger injectors and upgraded fuel lines.

Rewire the fuel pump with a relay kit directly from the battery to supply full voltage. Verify fuel pressure at idle (typically 43 psi with vacuum reference). Install a fuel pressure gauge in the engine bay for easy monitoring.

Initial Start, Break-In, and Tuning

Before firing the engine, prime the turbo’s oil system. Disconnect the fuel pump relay (or injector harness) and turn the engine over with the starter until oil appears at the turbo’s oil drain. Reconnect. Check for any oil or coolant leaks. Start the engine and let it idle at around 1000-1200 rpm. Listen for strange noises (whistling, grinding, exhaust leaks). Let it run for 15-20 minutes while checking temperature and oil pressure. The GT50’s ball bearings will need a break-in period of about 500 miles of gentle driving with varying rpm (avoid sustained high boost). Change the oil and filter after the first 100 miles.

Proper tuning is non-negotiable. A base map from a reputable tuner will get you running, but final tuning on a dyno is essential to optimize timing and fuel for the rotary’s apex seal protection. Rotary engines are prone to detonation damage; lean conditions can crack rotors or destroy seals. Trust a rotary specialist for the dyno session. Aim for an air-fuel ratio of 11.5-12.0:1 at full boost on pump gas (richer for E85). Adjust timing to avoid knock.

Common Pitfalls and Troubleshooting

  • Oil leaks from turbo drain: Use a larger return line and ensure gravity drain. If the engine has high blow-by, add a crankcase vacuum pump.
  • Boost creep: The wastegate may be too small or the exhaust pressure too high. Upgrade to a 60mm wastegate or use a divided manifold.
  • Turbo surge: Occurs if the compressor is too large for the engine’s airflow. A recirculating blow-off valve or a smaller compressor trim helps.
  • High intake temps: Check intercooler efficiency. Consider a water/methanol injection kit.
  • Engine dies on deceleration: Check for vacuum leaks in wastegate line or BOV (open during vacuum causing rich condition). Adjust BOV spring.

Always have a fire extinguisher mounted in the vehicle during first startup and subsequent testing.

Maintenance Recommendations

After the break-in, stick to a strict maintenance schedule. Rotaries are hard on oil; change it every 2000-3000 miles with a quality synthetic (e.g., Castrol 10W-60 rotary oil). Inspect the turbo for shaft play every oil change. Clean the air filter and intercooler core annually. Check all silicone hoses for cracks. Keep an eye on exhaust leaks at the manifold gaskets – thermal cycling can loosen bolts. Re-torque manifold nuts after the first 500 miles.

Conclusion

Installing a Garrett GT50 turbo on your 13B engine is a rewarding project that delivers breathtaking performance when done right. The key is methodical planning: gather all tools and supporting parts, prep the engine and ECU, follow precise mounting procedures for the turbo, wastegate, and intercooler, and never skip the tuning phase. Respect the rotary’s unique characteristics — with proper oil supply, fuel delivery, and boost control, your GT50-equipped 13B will run reliably and pull hard through every gear. For in-depth specifications, always refer to Garrett’s G-Series technical page and engage with the rotary community on forums like RX7Club for model-specific advice.