Introduction

The Audi RS5 2.9TT is a formidable performance machine, but even the factory engineering leaves room for improvement. One of the most effective upgrades for sustained power output is a high-quality intercooler system. The Wagner Tuning intercooler kit for the RS5 2.9T delivers significantly denser intake air, reduces charge air temperatures, and minimizes heat soak during aggressive driving. This guide provides a detailed, step-by-step walkthrough for installing these intercoolers on your Audi RS5, covering tools, removal of factory components, proper installation, and post-installation testing. By the end, you will have a cooler-running, more consistent powertrain ready for track days or spirited back-road driving.

Why Upgrade the Intercoolers on the RS5 2.9T?

The factory intercoolers on the B9 RS5 (2018+) are compact air-to-water units located in the front bumper area. While adequate for normal driving, they become a bottleneck under sustained boost. Heat soak occurs quickly during repeated hard pulls, causing the engine computer to reduce timing and boost pressure to protect the engine. This results in a noticeable loss of power after just a few acceleration runs. Upgraded intercoolers from Wagner Tuning feature larger cores, improved fin density, and superior pressure drop characteristics. They maintain lower intake air temperatures (IATs) even in hot weather, allowing the ECU to keep the engine running at peak power for longer periods. The result is more consistent performance, reduced knock risk, and a solid foundation for further modifications like tuning and larger turbos.

For a deeper look at intercooler theory and the specific benefits of uprated units, check out this Wagner Tuning product page for technical diagrams and flow data. Also refer to the B9 RS5 community discussions on forums such as Audizine for real-world owner feedback.

Tools and Materials Needed

Before beginning the installation, gather the following items. Having everything on hand will prevent interruptions and ensure a smooth process.

  • Wagner Tuning intercooler kit (includes two intercoolers, mounting brackets, and new o-rings)
  • Socket set with extensions (metric: 8mm, 10mm, 13mm, 15mm, 18mm)
  • Torque wrench (range 5–25 Nm for plastic clips; 25–50 Nm for intercooler bolts)
  • Flathead screwdriver (medium, for hose clamp springs)
  • Phillips screwdriver (#2, for under-shield screws)
  • Trim removal tool set (plastic pry bars to prevent paint damage)
  • Jack and jack stands or ramps (to access under-bumper fasteners)
  • Coolant catch pan (the intercooler system is part of the engine’s water cooling circuit)
  • Cooling system cleaner and distilled water (optional, for flushing)
  • Shop towels and clean rags
  • Safety glasses and gloves

If you plan to reuse the factory coolant, ensure you have enough container capacity (approximately 2 litres for the intercooler loop). Otherwise, G13 or G12evo coolant concentrate and distilled water can be used to fill the system afterward.

Preparation Steps

Proper preparation reduces the risk of damaging trim, causing leaks, or introducing dirt into the coolant system.

  • Park the RS5 on a level surface and engage the parking brake. Chock the rear wheels for extra safety.
  • Disconnect the negative battery terminal using a 10mm socket. This prevents any accidental electrical shorts while working near the front bumper sensors and radiator fans.
  • Allow the engine to cool completely. The coolant system in the RS5 remains hot for hours after driving. A warm engine can cause burns and improper seal seating.
  • Remove the key from the ignition and store it safely. The B9 platform’s electronic parking brake and cooling fans may operate unexpectedly if the key is nearby.
  • Jack up the front of the vehicle and support it on jack stands. Set the parking brake and chock rear wheels. You will need clearance to access the lower belly pan and intercooler drain plugs.

Draining the Intercooler Coolant Loop

The factory intercooler circuit is a dedicated air-to-water system separate from the engine radiator loop. However, it shares coolant and the expansion tank in the engine bay. To avoid spills:

  • Locate the coolant expansion tank on the passenger side of the engine bay. Place a catch pan under the vehicle near the passenger-side intercooler.
  • Remove the pressure cap slowly to release any residual pressure.
  • Underneath the car, remove the lower belly pan (torx T25 or T30 screws, plus a few push pins).
  • Identify the drain port on each factory intercooler (lowest point). Place the catch pan and loosen the drain plug using an appropriate hex or Allen key. Allow the coolant to drain completely.
  • If the coolant is clean, you may reuse it after filtering through a fine mesh. Otherwise, dispose of it properly and use fresh coolant during reassembly.

If you wish to flush the system, use a dedicated cooling system cleaner following the product instructions. Flushing ensures no debris remains that could clog the new Wagner Tuning units.

Removing the Factory Intercoolers

Accessing the stock intercoolers requires removing the front bumper cover. On the B9 RS5, this is a straightforward procedure but requires care with the many clips and connectors.

Front Bumper Removal

  • Remove the wheel arch liner screws on each side (Philips and 8mm). Pull back the liner to expose the bumper mounting bolts.
  • Remove the front upper grille trim (pry out carefully with trim tools).
  • Unclip the lower grille panels and remove the fog light surrounds if equipped.
  • Disconnect all electrical connectors: fog lights (if present), parking sensors, and the front camera (if equipped).
  • Remove the bolts securing the bumper to the fenders and the lower bumper support. Typically four 8mm or 10mm bolts per side, plus bolts along the lower edge.
  • With a helper, gently pull the bumper cover outward away from the clips. Lay the bumper on a padded surface to avoid scratching.
  • Remove the upper crash bar and bracket assembly (four bolts each side) to gain clear access to the intercoolers.

Factory Intercooler Removal Steps

  • With the crash bar removed, locate the two intercoolers – one behind each side’s bumper opening.
  • Disconnect the coolant hoses from the intercooler. Use a flathead screwdriver to release the spring clamps (or use pliers for squeeze-style clamps). Have a rag ready to catch any residual coolant.
  • Remove the bolts securing each intercooler to the chassis mounts. On the RS5, the factory intercoolers are held by two 10mm bolts and two 13mm bolts per side.
  • Shimmy the intercooler out through the lower opening. It may require tilting it to clear the lower crash bar tube.
  • Repeat for the other side.

Inspect the factory intercoolers for any oil residue or debris. If present, it may indicate a small boost leak or crankcase ventilation deposit. Address any underlying issues before installing the new intercoolers.

Installing Wagner Tuning Intercoolers

The Wagner Tuning units are direct-fit replacements but feature a larger core and more robust construction. Follow these steps carefully to ensure a proper seal and secure mounting.

Pre-Installation Checks

  • Compare the new intercoolers to the removed factory units. Confirm the hose connection angles align with the factory piping.
  • Inspect the provided o-rings and silicone couplers (if included). Lubricate with a thin layer of coolant or silicone grease to ease assembly.
  • Clean all mounting surfaces on the chassis using brake cleaner and a lint-free towel.

Mounting the New Intercoolers

  • Position the Wagner intercooler into the same location as the factory unit. It will sit behind the bumper opening with the hose outlets oriented towards the engine.
  • Insert the mounting bolts (provided or reused from factory) and hand-tighten them. Do not torque yet.
  • Ensure the intercooler sits flush against the rubber isolators. The core should not touch any metal chassis parts to avoid vibration wear.
  • Torque the bolts to the manufacturer’s specification: typically 20 Nm for M8 bolts. Use a torque wrench to prevent over-tightening and stripping aluminum threads.
  • Repeat for the second intercooler.

Connecting the Coolant Hoses

  • Attach the factory coolant hoses to the Wagner intercooler’s fittings. Push until you feel the o-ring seat, then secure the spring clamp.
  • If the Wagner kit includes new silicone hose sections, replace the factory rubber hoses as per the instructions. Typically this requires cutting the factory clamps and installing new unions.
  • Double-check that all clamps are fully engaged and seated in the groove. A loose clamp will result in a coolant leak under pressure.
  • Inspect the hose routing to ensure no kinks or contact with sharp edges.

Reassembly and System Refill

Now it’s time to put everything back together and refill the coolant.

Reassembly Steps

  • Reinstall the crash bar and upper bracket assembly. Torque the bolts to 45 Nm.
  • Carefully align the front bumper cover and snap it back onto the clips. Reinstall all bolts and screws.
  • Reconnect the wheel arch liners and all electrical connectors.
  • Lower the vehicle from jack stands.

Refilling the Intercooler Circuit

The intercooler coolant loop must be filled and bled to remove air pockets.

  • Ensure the drain plugs on the intercoolers are tightened (torque to 10 Nm if metal plugs).
  • Use a funnel to pour coolant into the expansion tank (marked with the intercooler symbol). Use G13 or G12evo mixed 50/50 with distilled water.
  • Fill until coolant reaches the "MAX" line. Replace the cap.
  • Start the engine and let it idle. The electric intercooler pump will activate once the engine reaches a certain temperature (or if you turn on the AC and rev the engine). You can speed up bleeding by operating the pump using a diagnostic tool or by performing a quick drive around the block.
  • After the engine has run for a few minutes, check the expansion tank level and top off as needed. Air may escape, causing the level to drop.
  • Repeat the idling and topping process until the level stabilizes. The system should be free of air pockets.

Post-Installation Testing and Performance Verification

Before taking the car on a spirited drive, perform the following checks:

  • Leak test: While the engine is running, inspect all hose connections and drain plugs for any coolant seepage. Use a flashlight to look at the intercooler cores – they should be dry.
  • Boost leak test: If you have access to a boost leak tester, pressurize the intake system to check for leaks at the intercooler hoses. This is not strictly necessary but recommended if you notice any power loss.
  • Monitor IATs: Use an OBD-II scanner or a performance app to watch intake air temperatures during an easy drive. You should see IATs drop faster than before after a pull, and they should remain lower in stop-and-go traffic.
  • Test drive: Take the car on a mix of city and highway roads. Perform a few full-throttle accelerations from 60–120 km/h (40–75 mph) and note the engine response. The upgraded intercoolers shine during repeated pulls; you should not feel power fade after the second or third run.

If you encounter any error lights (e.g., coolant level low, or boost pressure fault), double-check the intercooler pump fuse (located in the engine bay fuse box). The pump may have become unplugged during the bumper removal. Also verify that all harnesses for the intercooler thermostat and pump are properly connected.

For further verification, you can measure charge air temperature with a data logger. Many RS5 owners have reported a drop of 15–20°C in IATs after installing Wagner intercoolers. You can find documented results on Integrated Engineering’s blog and videos from 034Motorsport.

Common Pitfalls and Troubleshooting

  • Reusing factory gaskets: The new intercoolers come with fresh O-rings. Do not reuse the old ones; they may have hardened and cause leaks.
  • Over-tightening clamps: Spring clamps are self-adjusting; do not replace them with worm-gear clamps unless specified. Overtightening can collapse the hose barb.
  • Not bleeding the coolant properly: Air in the intercooler circuit reduces cooling efficiency and may trigger a check engine light. Use the full bleed procedure outlined above.
  • Rushing the bumper removal: The B9 bumper has multiple brittle clips; taking it slowly with proper trim tools will prevent broken tabs that lead to rattles.

Conclusion

Installing Wagner Tuning intercoolers on your Audi RS5 2.9TT is a highly rewarding DIY project that delivers measurable performance gains. By lowering intake air temperatures and combating heat soak, the upgraded intercoolers allow the engine to maintain peak power output for longer durations, whether you are on a track, a mountain pass, or simply enjoying a fast highway entry. This installation guide, based on proper procedures and attention to detail, will help you complete the job with confidence. The result is a cooler, more consistent, and more reliable Audi RS5 that is ready to take on any challenge. For further technical support, refer to Wagner Tuning’s official installation manual or join the RS5 owner community on Facebook for tips from experienced owners.