Introduction

Upgrading your vehicle’s turbocharger can unlock substantial power gains, and the Forge Motorsport A45 Turbo Kit is a popular choice for owners of Mercedes-AMG A45 (W176, W177) and CLA 45 platforms. This kit is engineered to replace the restrictive factory turbo with a larger, more efficient unit that increases airflow and boost pressure, resulting in significant horsepower and torque improvements. However, a turbo upgrade is not a simple bolt-on; it requires careful planning, precise mechanical work, and attention to supporting modifications. This comprehensive guide walks you through every stage of installing the Forge Motorsport A45 Turbo Kit, from gathering the right tools to post-installation tuning. Safety, torque specifications, and common pitfalls are emphasized to ensure a reliable, high-performance outcome. Whether you are an experienced DIY mechanic or a shop technician, following these steps will help you complete the installation successfully.

Tools and Materials Needed

Before starting any work, assemble all necessary tools and components. Having everything on hand prevents mid-job delays and ensures you can follow torque specs and fitting instructions precisely.

Required Tools

  • Socket set (metric, 1/4” and 3/8” drive, including deep sockets for hard‑to‑reach bolts)
  • Torque wrench (capable of 10–100 N·m; essential for critical fasteners)
  • Ratchet with extensions and universal joints
  • Combination wrenches (8–19 mm)
  • Screwdrivers (flathead and Phillips)
  • Intercooler piping and silicone hoses (included in the kit)
  • Clamps (t‑bolt or worm‑gear, depending on kit specifications)
  • Oil catch can (optional but recommended for direct‑injection engines)
  • Safety glasses and mechanic gloves
  • Jack and jack stands (or a lift) to access the undercarriage
  • Pry bar and pick set for stubborn hoses and clips
  • Vacuum/pressure tester (to verify boost system integrity after installation)

Kit Contents Check

The Forge Motorsport A45 Turbo Kit typically includes the turbocharger unit, intake and discharge piping, silicone couplers, clamps, gaskets, and hardware. Verify that all components are present against the packing list. Note that the kit does not include engine oil or coolant – you will need fresh OE‑spec fluids for refill. Also check that the turbo is the correct variant for your A45 generation (e.g., early 2.0L M133 vs. later M139).

Preparation Steps

Proper preparation reduces the risk of damage and ensures a smooth workflow.

Work Area & Vehicle Safety

  • Park the vehicle on a level, clean surface. Apply wheel chocks.
  • Disconnect the battery (negative terminal first) to prevent short circuits and accidental airbag deployment.
  • Allow the engine to cool completely – working on a hot turbo can cause burns and warped gaskets.
  • If the vehicle is lowered, raise it on a lift or use jack stands with adequate capacity. Never rely on a jack alone.
  • Drain the engine oil and coolant (if necessary per turbo service procedure). Collect fluids in approved containers.

Preliminary Checks

  • Inspect the engine bay for any pre‑existing oil leaks or damage. Address these before proceeding.
  • Read the installation manual provided with your specific Forge kit thoroughly – torque values and order of assembly may vary.
  • If your vehicle has an aftermarket intake or exhaust, verify that they will be compatible with the new turbo location and piping.
  • Label and photograph all connections, vacuum lines, and electrical connectors for easy reassembly.

Supporting Modifications

Installing a larger turbo without upgrading fueling, intercooling, or engine management can lead to severe engine damage. Forge Motorsport recommends at minimum a high‑capacity intercooler, a larger intake system, and a professional ECU tune (e.g., via Cobb Accessport or ECUTek). The oil catch can is highly advised to reduce carbon buildup on intake valves – a common issue on GDI engines after turbo upgrades.

Removing the Stock Turbo

Removing the factory turbo requires patience and careful disassembly. Work systematically to avoid breaking brittle plastic connectors or stripping bolts.

Step 1 – Remove Engine Covers and Intake Tract

  • Detach the engine beauty cover by pulling it upward at the mounting points.
  • Disconnect the MAF sensor and air intake duct. Unclip the air filter box and remove it.
  • Remove the resonator and any attached brackets.

Step 2 – Drain Coolant and Oil Lines

  • Place a drain pan under the coolant line to the turbo. Loosen the clamp and disconnect the hose. Be careful – coolant may still be hot.
  • Similarly, disconnect the oil feed and return lines. Cap them to prevent debris ingress.
  • On many A45 engines, the oil drain line is located underneath the turbo; you may need to access from below.

Step 3 – Disconnect Electrical Connectors and Vacuum Lines

  • Unplug the wastegate actuator connector and the boost pressure sensor (if present).
  • Remove any vacuum hoses from the factory boost control solenoid. Mark them with tape for later reconnection.
  • Detach the oxygen sensor connector from its bracket – you do not need to remove the sensor unless replacing the downpipe.

Step 4 – Unbolt the Turbo from Exhaust Manifold and Downpipe

  • Access the turbo mounting bolts. These are typically M8 or M10 and extremely tight – use a penetrating spray and wait 5 minutes.
  • Support the turbo with a jack or block to prevent it from falling once the last bolts are removed.
  • Remove the downpipe bolts from the turbine outlet. You may need to loosen the exhaust hangers to gain clearance.
  • Carefully lift the turbo out of the engine bay. Avoid damaging coolant and oil lines that remain attached to the engine block.

Discard the old gaskets – always replace them with new ones from the Forge kit.

Installing the Forge Motorsport A45 Turbo Kit

With the stock unit out, clean the mounting surfaces thoroughly. Any debris or old gasket material can cause leaks.

Step 1 – Prepare the New Turbo

  • Inspect the turbo for any shipping damage. Rotate the compressor wheel by hand – it should spin freely without rubbing.
  • Pre‑fill the turbo’s oil feed port with clean engine oil. This prevents dry start wear.
  • Apply a thin layer of high‑temperature anti‑seize on the exhaust manifold studs (if re‑using) or the new studs provided.

Step 2 – Mount the Turbo to the Exhaust Manifold

  • Position the new gasket against the exhaust manifold flange.
  • Carefully place the turbo onto the studs. Check that the oil drain faces downward and the coolant ports align.
  • Hand‑tighten the mounting nuts, then torque them to the manufacturer’s specification (typically 25–30 N·m for M8, 35–45 N·m for M10). Use a torque wrench – overtightening can strip threads or warp the flange.
  • Reattach the downpipe to the turbine outlet with a new gasket. Torque to 40–50 N·m, depending on kit documentation.

Step 3 – Connect Coolant and Oil Lines

  • Attach the coolant feed and return hoses. Use new O‑rings if supplied. Tighten clamps securely.
  • Connect the oil feed line to the turbo. Most Forge kits use a banjo fitting; ensure the copper washers are correctly placed and the banjo bolt is torqued to 20–25 N·m.
  • Reconnect the oil drain line from below the vehicle. Verify the hose is not kinked and the clamp is tight.

Step 4 – Reattach Intake and Actuator

  • Install the intake pipe from the new turbo to the air filter housing. Secure with the silicone coupler and clamps.
  • Plug the wastegate actuator connector. If your kit includes an upgraded electronic boost control solenoid, mount it in a location away from heat sources.
  • Reconnect vacuum lines per your labeling. Mistake here can cause overboost or underboost.

Connecting the Intercooler and Charge Air Piping

Forge Motorsport often supplies a front‑mount intercooler with their turbo kit, or a larger charge air cooler that replaces the factory unit. Proper intercooler installation is critical for intake air temperature management and boost pressure retention.

Intercooler Mounting

  • If you are using the Forge intercooler, position it in front of the radiator. It may require removing the bumper cover for best access.
  • Secure the intercooler using the brackets and hardware provided. Ensure it is centered and not contacting the radiator core.
  • Tighten all bolts to moderate torque (10–15 N·m) – enough to prevent movement but not so much as to deform the end tanks.

Charge Pipe Routing

  • Install the hot‑side charge pipe from the turbo compressor outlet to the intercooler inlet. Use the supplied silicone couplers and t‑bolt clamps.
  • Install the cold‑side charge pipe from the intercooler outlet to the throttle body. Ensure all connections are fully seated before tightening clamps.
  • Important: Double‑check that all couplers are free of oil residue and that clamps are placed over the barbed ends of the pipes. A boosted leak at 20+ psi can cause significant power loss.
  • If your kit includes a blow‑off valve or diverter valve, mount it according to instructions – typically on the cold side pipe.

Optional: Oil Catch Can Installation

To mitigate carbon buildup on the intake valves, install an oil catch can in the PCV line. Mount it securely to a chassis ground point. Route the PCV outlet from the valve cover to the can’s inlet, and the can’s outlet to the intake manifold nipple. Ensure the hoses are not kinked and use grommets to prevent chafing.

Final Assembly and Checks

Now it’s time to button everything up and prepare the vehicle for its first start.

Step 1 – Reassemble Engine Bay

  • Reinstall the air filter box, intake duct, and MAF sensor. Connect the sensor wiring.
  • Replace the engine cover if it still fits – some aftermarket intercooler piping may require trimming or removal.
  • Secure all wiring harnesses away from the turbo and exhaust – use zip ties or heat‑shielding as needed.

Step 2 – Refill Fluids and Bleed Cooling System

  • Refill the engine with the correct grade of oil (typically 5W‑40 or 0W‑40 for high‑output AMG engines).
  • Refill the cooling system with the specified coolant mixture. Start the engine with the radiator cap off, wait for the thermostat to open, then top off as air purges.
  • Do not run the engine without oil – the turbo will fail instantly.

Step 3 – Reconnect Battery and Check for Leaks

  • Reconnect the battery (positive first, then negative).
  • Prime the oil system by unplugging the fuel pump relay and cranking the engine for 10 seconds (or use a second person to operate the starter while you listen for oil flow).
  • Re‑plug the fuel pump relay and start the engine. Let it idle – listen for any unusual whistling (boost leak) or knocking (detonation).
  • Inspect all turbo connections, coolant hoses, and oil lines for leaks. Tighten clamps if needed.

Step 4 – Test Drive and Data Logging

  • Take a gentle test drive under light load for the first 5–10 miles. This allows the turbo to break in and the ECU to adapt.
  • Monitor boost pressure via a gauge or OBDII scanner. The Forge kit typically targets 20–25 psi with a proper tune.
  • Check for error codes. Common post‑install codes include P0299 (boost under) or P0234 (boost over) if the tune is not loaded yet.
  • Do not perform a full‑throttle pull until a professional tune has been applied – the factory ECU cannot compensate for the increased airflow and will run dangerously lean.

Common Pitfalls and Troubleshooting

Even experienced installers encounter issues. Here are solutions to the most frequent problems.

  • Boost leak after installation: Re‑check all coupler clamps and intake pipe connections. A leak will cause a high‑frequency whistle and low power. Use a smoke tester or pressure tester.
  • Oil leak from turbo: Verify the oil drain line is not kinked and the gasket is correctly seated. A blocked drain can cause seal failure.
  • Engine runs rough or stalls: Air mass meter misalignment or vacuum line error. Confirm MAF orientation and re‑connect all hoses.
  • Overboost condition: Wastegate actuator rod may be too short or the boost control solenoid miswired. Adjust rod length per Forge instructions (typically 1–2 turns out from full tight).
  • Coolant leak: Inspect the coolant line banjo or quick‑connect fittings; sometimes O‑rings are displaced during installation.

If you encounter persistent issues, consult the Forge Motorsport official support or visit dedicated AMG forums such as Mercedes-AMG for community advice.

Post‑Installation Tuning and Next Steps

A larger turbo is only as good as the engine management that controls it. After confirming mechanical integrity, you must install a custom tune. Many tuners offer off‑the‑shelf maps for the Forge A45 kit, but a dyno tune is safer. During tuning, key parameters such as fuel injector duty cycle, ignition timing, and boost target are adjusted. Expect power outputs of 400–450 horsepower on pump fuel and 450–500 on race fuel with supporting mods. Do not skip the tune – running stock software will likely cause engine failure within minutes.

Maintenance and Long‑Term Care

After installation, follow a more frequent maintenance schedule. Change engine oil and filter every 5,000 miles using a high‑quality full synthetic. Inspect the turbo inlet and charge pipes for debris at each service. Clean the oil catch can every 3,000 miles. Monitor boost pressure and intake air temperatures through a gauge or logging tool. With proper care, the Forge Motorsport A45 Turbo Kit can provide reliable, exhilarating performance for many miles.

Conclusion

Installing the Forge Motorsport A45 Turbo Kit is a rewarding upgrade that dramatically transforms your AMG A45’s character. By following this step‑by‑step guide – from careful preparation and methodical removal of the stock turbo to precise installation, intercooler plumbing, and essential tuning – you can achieve a safe, powerful build. Always refer to the official Forge instructions and torque specifications, and never compromise on quality tools or fluids. The result is a daily‑drivable car with track‑ready performance that turns heads and delivers adrenaline every time you press the throttle.

For further reading, explore ECU tuning options for the M133/M139 engine and Cobb Accessport support for AMG platforms.