Overview: The GTX2860R Gen II Upgrade for the A45 AMG

Upgrading the turbocharger on your Mercedes-AMG A45 (M133 engine) is one of the most effective ways to unlock substantial horsepower gains without replacing the entire engine. The Garrett GTX2860R Gen II represents a significant evolution in turbocharger technology, offering improved aerodynamics, faster spool, and higher flow capacity compared to the stock unit. This comprehensive guide walks you through the complete process of installing this turbo on your A45, from preparation and removal through tuning and testing. Whether you're a DIY enthusiast or a professional technician, these steps ensure a safe, reliable, and high-performance outcome.

The Garrett GTX2860R Gen II uses advanced billet compressor wheels and a low-inertia turbine design, reducing turbo lag while supporting up to approximately 450 horsepower on the M133 platform when paired with proper fueling and tuning. It replaces the factory BorgWarner K04-style turbo, providing better mid-range torque and higher peak power without sacrificing daily drivability. Before beginning, verify that your A45 is in good mechanical condition—address any oil leaks, cooling system issues, or existing boost leaks first.

Tools and Materials Required

Below is a comprehensive list of items you will need. Having everything on hand before you start will minimize downtime and prevent frustration.

  • Garrett GTX2860R Gen II turbocharger (specific A45 application kit, includes gaskets and hardware)
  • Complete turbo installation gasket set (manifold gasket, turbo-to-downpipe gasket, intake gaskets)
  • New OEM oil feed and return line gaskets or O-rings
  • Silicone coolant hoses and hose clamps (if not included in the kit)
  • Torque wrench (range 10-80 Nm recommended)
  • Socket set (metric: 8mm, 10mm, 13mm, 15mm, 18mm)
  • Combination wrenches (10mm, 13mm, 17mm, 19mm)
  • Swivel-head ratchet and extension bars
  • E-Torx sockets (E10, E12, E14) for manifold bolts
  • Pickle fork or ball joint separator (for wastegate linkage)
  • Oil drain pan, shop towels, and degreaser
  • High-temperature anti-seize compound (copper or nickel-based)
  • Thread-locking compound (medium strength, Loctite 243)
  • New engine oil (5W-40 or as recommended by your tuner)
  • Coolant (MB 325.0 spec or equivalent)
  • Safety glasses, gloves, and a fire extinguisher (nearby)

Recommended optional tools: vacuum pump for coolant refill, boost leak tester, and a scan tool to read/clear codes.

Preparation and Safety

Workspace Setup

Park the A45 on a level concrete surface, engage the parking brake, and chock the wheels. Disconnect the negative battery terminal (using a memory saver is recommended to preserve ECU adaptations). Allow the engine to cool completely—hot components can cause severe burns and make fasteners harder to remove.

Remove the engine under-tray (several 8mm and 10mm bolts) to access the turbo area. Jack up the front of the car and support it securely on jack stands if you need additional clearance—the A45 has a tight engine bay, and working from below will be necessary for oil and coolant line access.

Inspect the Existing Setup

Before starting the removal, check the stock turbo and related components for any signs of failure such as oil leaks, shaft play, or cracked housings. Verify that the wastegate actuator holds vacuum and operates smoothly. This is also a good time to inspect the condition of the intake hoses, intercooler connections, and the PCV system—replace any worn components now to prevent future issues.

Removing the Original Turbocharger

This is the most labor-intensive part of the installation. Work methodically and label all connectors and vacuum lines as you disconnect them. Take reference photos of the belt routing and wiring harness routing around the turbo area.

Step 1: Drain Coolant and Oil

To avoid a mess when you disconnect the turbo coolant lines, drain the cooling system into a clean container. Open the radiator drain plug and the engine block drain (located near the turbo). Also, drain the engine oil if you plan to replace it—which is strongly recommended. Removing the oil allows you to disconnect the oil feed and return lines without spilling leftover oil into the engine bay.

Step 2: Remove the Air Intake System

Unclip the intake duct from the turbo inlet and remove the air filter box to gain room. Disconnect the MAF sensor wiring and set the duct assembly aside. The A45 uses a plastic intake manifold—be careful not to crack any vacuum ports.

Step 3: Disconnect Oil and Coolant Lines

Use a 13mm wrench on the banjo bolts of the oil feed line. The oil return line is a larger banjo usually secured with a 17mm bolt. Discard the copper washers and replace them with new ones from your gasket kit. For the coolant lines, carefully release the spring clamps or remove the bolts holding the hard lines to the turbo. Expect some residual coolant to drip—place towels underneath.

Step 4: Unbolt the Turbo from the Exhaust Manifold

Remove the heat shields covering the turbo (usually two separate pieces held by 10mm bolts). Then, access the four M8 nuts (or studs) securing the turbo to the exhaust manifold. These are often tight due to heat cycling; use penetrating oil and let it soak for 10 minutes if needed. A swivel-head ratchet and a deep socket are helpful here.

Step 5: Disconnect the Downpipe and Wastegate

Unbolt the downpipe from the turbo housing (three 13mm nuts at the flange). Lower the downpipe carefully—it is heavy and often hangs on the subframe. Next, remove the wastegate actuator rod from the wastegate arm by using a small pick or pliers to unclip the C-clip. The stock actuator is vacuum-operated; disconnect the vacuum line as well.

Step 6: Remove the Turbo

With all connections freed, lift the old turbo up and out of the engine bay. It may require some gentle maneuvering—rotate the compressor housing to clear the firewall and the block. Compare the old turbo to the new Garrett unit to ensure the coolant and oil port locations are similar (they should be, as the GTX2860R Gen II is a direct-fit upgrade for the A45). Note the orientation of the water ports.

Installing the Garrett GTX2860R Gen II Turbo

Carefully unpack the new turbo. Inspect the compressor and turbine wheels for any shipping damage. Rotate them by hand—they should spin freely with minimal resistance. Apply a few drops of clean engine oil to the oil feed port and rotate the shaft to pre-lube the bearings.

Step 1: Prepare the Mounting Surface

Clean the exhaust manifold flange and the turbo mating surface with a gasket scraper and brake cleaner. Remove any remaining gasket material. Install the new manifold-to-turbo gasket (supplied in the kit or as an OEM part) without any sealant—the metal embossed gasket provides sealing through compression.

Step 2: Mount the Turbo

Position the Garrett GTX2860R Gen II onto the manifold studs. Ensure the oil drain port faces downward and the coolant ports are oriented to match your lines. Hand-tighten the nuts, then torque them in a diagonal pattern to 25 Nm (or per manufacturer spec). Use a thin film of anti-seize on the stud threads to prevent galling of the stainless steel nuts.

Step 3: Reconnect Oil and Coolant Lines

Fit the oil feed line with new copper washers on both sides of the banjo fitting. Torque the banjo bolt to 30 Nm. For the oil return, use a new gasket or O-ring and tighten carefully—overtightening can crack the turbo housing. Reinstall the coolant lines with new O-rings or silicone hoses as needed. Ensure all connections are free of leaks by later pressure testing.

Step 4: Attach the Downpipe

Use a new turbo-to-downpipe gasket. Raise the downpipe into position and loosely thread the three 13mm nuts. Once aligned, torque them to 40 Nm in sequence. Check that the downpipe does not contact the subframe or any other components—if it does, you may need to loosen and realign.

Step 5: Reinstall the Intake System

Connect the intake duct to the compressor outlet using a high-quality silicone coupler and T-bolt clamps (the stock rubber hose may be too restrictive for the increased airflow). Install a new air filter if your existing one is old. Make sure all clamps are tight, but avoid overtightening to prevent damaging the plastic intake.

Wastegate and Boost Control Connections

Understanding the Wastegate Setup

When upgrading to the GTX2860R Gen II, you will need to adjust the wastegate actuator. The Garrett kit typically includes an adjustable actuator pre-set for your target boost pressure (often around 1.5 bar). However, you must connect the boost reference line correctly. Run a 4mm silicone line from the compressor housing boost port to the top port of the wastegate actuator. Some tuners recommend a line from the intake manifold for a more direct pressure reference, but the compressor housing port works well.

Setting Actuator Preload

With the actuator attached, adjust the rod length so that the wastegate flap is closed when the actuator is at rest (no vacuum). There should be a small amount of preload—typically 1-2 mm of additional rod length past the point where the flap just closes. Use threaded adjusters and a C-clip to secure the rod to the wastegate arm. An incorrect preload can cause boost spikes or slow spool.

Boost Control Solenoid

The A45's factory boost control solenoid can be reused if it is in good condition. However, many upgraded setups benefit from a dedicated 3-port electronic boost control solenoid (such as a MAC valve) for more precise boost control. Connect it according to your ECU tune’s instructions—usually a ground, 12V, and a signal wire. Ensure the wiring is routed away from exhaust heat and moving parts.

Final Assembly and Checks

Reinstall Heat Shields and Undertray

Refit any heat shields you removed, using new stainless steel bolts if the originals are rusted. Do not skip the heat shield above the turbo—it protects the hood and wiring harness from radiant heat. Reinstall the engine under-tray.

Fill Fluids and Bleed the System

Fill the engine with fresh oil (approx. 5.5 liters with filter). Pour coolant slowly into the reservoir, then use a vacuum coolant filler if available to purge air pockets. Otherwise, run the engine with the reservoir cap off until the thermostat opens and coolant circulates, topping up as bubbles disappear.

Reconnect Battery and Perform Initial Start

Reconnect the negative battery terminal. Before starting, prime the turbo's oil system by cranking the engine with the fuel pump fuse removed (or coil packs disconnected) for 10-15 seconds. This ensures the turbo bearings receive oil immediately upon startup. Reconnect the fuse or coils, then start the engine. Let it idle for 5 minutes, checking for oil leaks, coolant leaks, and unusual noises. Listen for a smooth spool with no rattling or scraping.

Testing, Tuning, and Achieving Peak Performance

Critical: ECU Tuning Required

Installing the Garrett GTX2860R Gen II without a corresponding ECU remap is dangerous. The stock fuel maps, ignition timing, and boost control parameters are designed for the smaller factory turbo. Running the new turbo on the stock tune can cause severe detonation, excessively high exhaust temperatures, and potential engine damage. You must have a custom tune written by a reputable tuner experienced with the M133 engine. This tune will adjust fuel injection timing, boost targets (typically 21-24 psi), and throttle mapping.

Test Drive and Data Logging

After the tune is loaded, take the car for a gentle test drive, gradually increasing load. Monitor critical parameters such as boost pressure, air-fuel ratio (target 11.5-12.0 under full load for pump gas), and intake air temperatures. Use a scan tool or a dedicated smartphone app to log data. A typical GTX2860R Gen II A45 will reach full boost by 3500-3800 RPM and pull strongly to redline. If you notice boost spikes, surging, or detonation, stop driving immediately and consult your tuner.

External resource: For detailed tuning parameters and community-recommended tuners, the BenzWorld A45 forum is an excellent source of real-world data. Additionally, Garrett’s official website provides technical specifications for the GTX2860R Gen II that can help you verify your setup.

Boost Leak Testing

Even small leaks will cost power and spool. Build or purchase a boost leak tester that connects to the turbo inlet. Pressurize the system to 20 psi and listen for hissing. Common leak points are the intercooler couplers, throttle body gasket, and the crankcase ventilation system. Seal any leaks with new o-rings or clamps.

Maintenance Considerations After Installation

The GTX2860R Gen II is a robust unit, but it requires proper care to last. Use high-quality full-synthetic oil (5W-40 meeting MB 229.5 or Rennsport) and change it every 5,000 miles (or more frequently if you track the car). Allow the turbo to cool after hard driving before shutting off the engine—a turbo timer is optional but helpful. Inspect the wastegate operation and boost hoses every 10,000 miles. Consider upgrading the intercooler to keep intake temperatures in check, especially in warmer climates or for sustained high-load driving.

Expected Performance Gains

On a properly tuned A45 with the GTX2860R Gen II, expect peak power in the range of 400-450 horsepower at the wheels (depending on fuel octane and supporting mods). Torque will also increase significantly, often exceeding 400 lb-ft. The power delivery is broader than the stock turbo, with usable boost from 3000 RPM and stronger top-end pull. Many owners report a 0-60 mph time improvement of 0.4-0.6 seconds without other modifications, though actual results vary based on traction and tuning.

Conclusion

Installing the Garrett GTX2860R Gen II turbo on your A45 is a rewarding project that transforms the car’s character without requiring extensive fabrication. By following the detailed steps above—from careful removal of the original unit to precise installation, wastegate setup, and professional tuning—you can enjoy a significant, reliable power increase. Remember that the key to success lies in preparation, attention to torque specs, and never skipping the tune. With the right approach, your A45 will deliver thrilling performance that rivals more expensive sports cars while retaining daily drivability.

For further reading and to verify specific torque values for your model year, refer to the official Mercedes-Benz technical documentation (available through subscription or dealer) or a trusted factory service manual. Another helpful community resource is the A45/CLA45 Forum where members share installation tips and dyno results.