Introduction to the HKS GT III Turbo Upgrade for the E63

The HKS GT III Turbocharger represents a significant leap in forced induction engineering, designed specifically for high-output applications. When installed on an E63 platform (Mercedes-AMG E63 with the M156 or M157 engine), this turbo can reliably support power levels up to 720 horsepower, transforming the driving character of the car. This comprehensive guide walks through the entire installation process, from preparation through post-installation tuning, with detailed technical notes and safety considerations for both experienced mechanics and serious DIY enthusiasts.

Before beginning, verify that your specific E63 model year and engine variant are compatible with the HKS GT III kit. The installation can be completed in a fully equipped home garage or professional shop, but careful adherence to torque specifications and fluid procedures is critical. For a complete reference, always keep the official HKS GT III product documentation at hand.

Tools and Materials Required

Gather all tools and consumables before starting to avoid interruptions. Beyond standard hand tools, you will need several specialized items. Use the following checklist to prepare your workspace:

  • HKS GT III Turbo complete kit – Verify all gaskets, bolts, and wastegate actuator hardware are included
  • Metric socket set (10mm–19mm) with extensions and universal joints
  • Torque wrench – accurate from 10–120 N·m (for engine and manifold fasteners)
  • Combination wrench set (10mm–19mm, plus offset wrenches for tight spaces)
  • Screwdrivers – flathead and Phillips, magnetic tip recommended
  • Gasket sealant – high-temp silicone based (e.g., Permatex Ultra Copper)
  • New engine oil and coolant – use the exact grade specified for your E63 (typically 0W-40 or 5W-40, MB229.5 approved)
  • Oil catch can – optional but strongly recommended to reduce crankcase pressure and carbon buildup
  • Shop towels, safety glasses, mechanic gloves
  • Thread locker – medium strength (Loctite 242) for exhaust studs
  • Vacuum pump or cooling system pressure tester (for refilling coolant correctly)

If your E63 is equipped with an auxiliary water pump or air-to-water intercooler system, have the necessary hoses and clamps ready. An E63-specific forum or workshop manual can provide fastening locations and routing diagrams tailored to your exact engine code.

Understanding the HKS GT III Turbo

The HKS GT III series uses a ball-bearing center cartridge for rapid spool, a larger compressor wheel than the factory turbo, and a wastegate actuator calibrated for higher boost levels (typically 1.2–1.5 bar). The turbine housing is designed to bolt directly to the stock exhaust manifold on most E63 variants, though some years require an adapter plate. Key specifications include:

  • Compressor inducer: 56 mm – delivers up to 720 whp with proper supporting mods
  • Turbine housing: T25 flange (or T3, depending on kit) – check your kit’s compatibility
  • Oil feed and drain: 3/8″ NPT inlet, AN -10 outlet – verify line sizes match your engine
  • Maximum recommended boost: 22–24 psi (requires high-octane fuel or ethanol blend)

Before installation, inspect the turbo for free rotation and test the wastegate actuator movement. Any axial play exceeding 0.5 mm indicates a defect and should be addressed with the seller immediately.

Pre-Installation Preparations

Proper preparation reduces installation time and prevents common mistakes. Follow these steps before removing any hardware:

1. Park the vehicle on a level surface, disconnect the negative battery terminal, and allow the engine to cool completely (overnight is ideal). Removing the turbo on a hot engine risks warping the exhaust manifold and scalding yourself.

2. Remove the engine cover, air intake ducting, and the air filter box. On AMG E63 models, the air box is secured with multiple 8mm bolts and a few spring clips. Protect the intake ports with clean shop towels.

3. Drain the engine oil and coolant. Removing the lower radiator hose and the oil drain plug simultaneously ensures fresh fluids go in after installation. Do not skip this – residual coolant can contaminate the turbo oil feed line.

4. Detach the battery ground cable and remove any wiring harnesses that cross over the turbo area (e.g., engine harness, knock sensor wires). Label all electrical connectors with tape and marker.

5. Lift the vehicle using jack stands at designated lift points. You will need access from below to disconnect the downpipe and oil drain line.

Step 1: Remove the Factory Turbocharger

1.1 Exhaust Manifold and Turbo Removal

Using a socket wrench, unbolt the exhaust heat shield that covers the turbo. On most E63s, there are four to six 10mm bolts. Set the shield aside. Next, disconnect the oxygen sensors: carefully unscrew them from the downpipe and manifold using an O2 sensor socket to avoid damaging the wires.

Remove the downpipe from the turbo outlet (usually three bolts or V-band clamp). Support the downpipe as you remove it to avoid stressing the exhaust system. Then, unbolt the turbo from the exhaust manifold. The manifold-to-turbo fasteners are often nuts on studs; apply penetrating oil (like PB Blaster) twenty minutes before attempting to loosen them. Use a six-point socket to avoid rounding.

Disconnect the oil feed line at the top of the turbo and the return line at the bottom. Have a drain pan ready – old oil will pour out. Remove the coolant lines from the water jacket (if water-cooled). Slide the turbo off the manifold studs and remove it. Inspect the manifold surface for cracks or warping; if found, resurface or replace before proceeding.

1.2 Inspect and Clean Manifold Flange

Once the stock turbo is off, clean the manifold flange thoroughly with a razor blade and non-residue solvent. Remove all old gasket material. Any debris left behind will cause a boost leak or damage the new turbo’s gasket. Apply a thin layer of high-temp gasket sealant to both sides of the new exhaust gasket.

Step 2: Install the HKS GT III Turbo

2.1 Mount the Turbo

Place the new HKS GT III turbo onto the manifold studs. Ensure the oil drain port faces downward (typically at a 45-degree angle) and that the compressor outlet aligns with the charge air pipe routing. Hand-tighten the mounting nuts, then torque to the specification in the HKS manual (usually 30–35 N·m for M8 studs). Use thread locker on the studs to prevent loosening from vibration.

Next, install the wastegate actuator bracket and actuator. Adjust the actuator arm length so the wastegate valve closes fully at zero boost. A general rule: preload the wastegate spring by turning the rod end until you feel slight resistance, then lock the jam nut. Check the actuator travel with a vacuum pump if available.

2.2 Connect Oil and Coolant Lines

Install the oil feed line from the engine block to the turbo’s oil inlet (usually a 90-degree fitting). Use a new copper or aluminum crush washer at every connection. Torque banjo bolts to 25–30 N·m – overtightening can crush the banjo fitting and restrict oil flow. For the oil drain, connect the return line to the side of the oil pan. If no drain exists, you may need to weld a -10 AN bung to the pan; alternatively, use a return line to the factory drain plug location with a T-fitting.

Attach the coolant feed and return hoses. Use constant-tension spring clamps (not standard worm-gear clamps, which can loosen with thermal cycles). Purge the cooling system by filling the radiator and running the engine with the cap off to remove air pockets.

Step 3: Reconnect Piping and Electrical Components

3.1 Charge Air and Exhaust Connections

Reconnect the charge air pipe from the turbo compressor outlet to the intercooler (or to the intake manifold on some setups). Use silicone couplers and stainless T-bolt clamps. Tighten to 4–5 N·m – overtightening can crush the hose bead. Connect the exhaust downpipe to the turbine outlet, applying a new gasket. Torque the downpipe bolts to 40 N·m.

If your kit includes a blow-off valve (BOV), install it on the charge pipe between the turbo and throttle body. Route the BOV vacuum line to a manifold pressure source (not a boost reference after the throttle). This prevents compressor surge.

3.2 Reattach Sensors and Harnesses

Reconnect the oxygen sensors to the new downpipe (if using your original downpipe, note that bungs may need relocation). Plug in all previously disconnected electrical connectors: camshaft position sensors, knock sensors, and the engine harness that crosses the turbo area. Secure all wiring away from hot turbo surfaces using heat-sleeving or zip ties.

Step 4: Install Supporting Components for 720 HP

Achieving 720 horsepower requires more than just the turbo. The stock fuel system will be insufficient.

  • Fuel injectors: Upgrade to 1,000 cc/min or larger (e.g., Bosch EV14 or Injector Dynamics). Must be compatible with your ECU and fuel type.
  • High-flow fuel pump: A Walbro 525 or equivalent in-tank pump (or a surge tank setup for continuous supply).
  • Intercooler: Stock intercooler will heat-soak quickly. Upgrade to a larger air-to-air or a dual-core unit with properly ducted airflow.
  • Intake plumbing: Replace restrictive factory air intake with a 4" cold-air kit and high-flow filter.
  • Engine management: A standalone ECU or piggyback tuning device (e.g., Haltech, Motec, or Cobb Accessport with custom tuning) is mandatory for boost control, fuel mapping, and ignition timing.

Install these components per the manufacturer’s instructions. For fuel injectors, replace O-rings and use assembly lubricant. After installing the fuel pump, perform a flow test to verify adequate pressure at the rail (target 3.5 bar at idle, 4.5 bar at full boost).

Step 5: Refill Fluids and Perform Leak Checks

Pour new engine oil (use the viscosity recommended by HKS, typically 5W-40 synthetic) and fill the cooling system with the correct MB coolant mixed 50/50 with distilled water. Start the engine and let it idle for one minute, then shut off. Check the oil level and top up as needed.

Inspect all turbo connections for leaks: oil feed and return, coolant lines, charge pipes, and exhaust. Use a spray bottle of soapy water on boost-related connections while the engine runs at fast idle (1500 RPM) – bubbles indicate a leak. Tighten or replace clamps as required.

For the cooling system, use a pressure tester to pressurize to 1.4 bar (20 psi). Hold pressure for 10 minutes – a drop of more than 0.1 bar indicates a coolant leak. Address immediately to prevent overheating.

Step 6: Reconnect Battery and Initial Startup

Reconnect the battery terminal. Before cranking, prime the turbo by pouring a few ounces of fresh oil into the turbo oil inlet (this prevents dry start damage). Crank the engine without starting (disable fuel pump relay or remove fuel pump fuse) until oil pressure registers on the gauge – about 10 seconds. Then enable fuel and start the engine.

Let the engine warm to operating temperature (coolant 90°C, oil 80°C). Listen for abnormal noises: grinding, whistling, or rattling. Inspect the exhaust for smoke or unusual odors. If all is normal, take a short test drive staying below 3,000 RPM and 5 psi of boost for the first 50 miles to allow the turbo to break in.

Step 7: Professional Tuning – The Essential Final Step

Running the HKS GT III turbo without proper engine calibration is dangerous. The increased airflow will cause extremely lean air-fuel ratios, potentially melting pistons. Do not exceed half throttle until the vehicle is tuned. Schedule an appointment with a reputable tuner experienced in AMG engines and aftermarket turbos. A dyno tuning session typically takes 3–6 hours and includes:

  • Base maps: idle, cruise, and low-load fuel trims
  • Wide-open throttle (WOT) pulls at various RPM points to achieve target air-fuel ratio (11.5–12.5:1 on pump gas)
  • Boost control calibration – set to a safe level (e.g., 20 psi) with a gradual taper at higher RPM
  • Ignition advance optimization (knock sensor monitoring)
  • Transmission shift points and line pressure adjustments (if using automatic)

After tuning, the E63 should produce approximately 720 horsepower at the crank (around 600–620 whp depending on drivetrain losses). For reference, the stock E63 S produces 603 hp, so this upgrade represents a substantial gain.

Post-Installation Checks and Break-In Procedure

For the first 500 miles after tuning, vary engine RPM and avoid sustained high boost. Perform three full cooling cycles (hot to cold) to seat the piston rings and turbo bearings. Check all fluid levels weekly. After 1,000 miles, change the oil and filter – the new turbo may shed manufacturing debris into the oil. Use the same high-quality synthetic oil as the initial fill.

Monitor oil consumption: 1 quart per 1,000 miles is acceptable; more indicates excessive blow-by or a turbo seal issue. If you notice blue smoke from the exhaust during deceleration, inspect the turbo oil drain seal and crankcase ventilation system.

Common Pitfalls and Troubleshooting

  • Boost creep: Wastegate port is too small. Solution: ensure wastegate valve opens fully at 10–12 psi of actuator pressure. If problem persists, port the turbine housing wastegate hole by 1–2 mm.
  • Oil leak from compressor side: Crankcase pressure too high (plugged PCV system). Install an oil catch can with a one-way valve.
  • High intake air temperatures (IAT): Intercooler insufficient or heat soak. Upgrade intercooler core and ensure ducting seals around the radiator.
  • Check engine light (CEL) for post-cat O2 sensor: The new downpipe may lack a catalytic converter. Install a mini-cat or have the tuner delete the rear O2 monitoring.

If you encounter persistent issues, consult the HKS GT III FAQ page or reach out to a dedicated AMG performance forum for model-specific advice.

Performance Expectations and Reliability Considerations

With the HKS GT III turbo installed and properly tuned, an E63 will experience a transformed powerband: boost arrives around 3,000 RPM and pulls hard to redline. Expect 0–60 mph times in the mid-2-second range with traction, and quarter-mile times in the low 10 seconds at 135+ mph. The turbo’s ball-bearing core spools noticeably faster than the stock unit, reducing lag.

However, reliability demands diligent maintenance. Shorten oil change intervals to 3,000–5,000 miles with high-quality synthetic. Use a boost controller with safety features (overboost protection, wastegate fail-safe). Monitor engine parameters with a gauge or data logger – EGT, AFR, and boost pressure. HKS recommends using a turbo timer to let the turbo cool after hard driving. For longevity, reduce boost to 18 psi on 93 octane fuel; use high-octane (100+) or ethanol for the full 720 hp potential.

Consider upgrading the engine internals if you plan to track the car frequently – the M157 has proven strong up to 750 whp, but forged pistons and rods become prudent beyond that level. For most street-driven E63s, the HKS GT III with a conservative tune provides a durable and exhilarating upgrade.

Final Words

Installing an HKS GT III turbo on your E63 is a rewarding project that dramatically elevates performance. By carefully following each step, using quality tools, and securing professional tuning, you can achieve a reliable 720 horsepower build. The key is patience – do not rush the break-in or skip the leak tests. Keep the vehicle’s supporting systems in good health, and enjoy the newfound power every time you press the throttle.