Understanding the Audi RS5 2.9TT and Its Performance Potential

The Audi RS5 (B9 generation) houses a 2.9-liter twin-turbo V6 (code EA839), a powertrain shared with the RS4 and Porsche Panamera 4S. This engine delivers impressive factory outputs of 444 hp and 442 lb-ft of torque, but it is widely known for its tuning headroom. With the right aftermarket parts, owners have consistently reached 550-600 whp on stock internals and upgraded fuel systems. Understanding the engine’s architecture—particularly the hot-vee layout, where twin turbos sit in the valley between cylinder banks—is crucial before any disassembly. The intake and exhaust paths are compact, meaning clearance is tight, and careful planning saves hours of frustration.

Before upgrading, review your RS5’s service history. Oil changes at 5,000-mile intervals with 0W-30 or 5W-40 full synthetic oil are critical because these engines suffer from carbon buildup on intake valves (direct injection). Installing an oil catch can early can mitigate this. Also, note that the ECU is locked on later models; some tuning solutions require bench unlocking or sending the ECU to a specialist. Plan for this in your timeline and budget.

Essential Tools for a Successful DIY Installation

Rushing tool preparation leads to stripped bolts, broken plastic clips, and safety hazards. Invest in quality tools that will last beyond a single project. Below is an expanded list with specific recommendations.

Socket and Torque Wrench Requirements

Use a metric socket set from 6mm to 19mm. ¼-inch drive for small fasteners (interior trim, sensors) and ⅜-inch or ½-inch drive for suspension and engine components. A torque wrench (beam-style or click-type) is non-negotiable for critical fasteners like subframe bolts, lug nuts, and turbo oil lines. Example: Audi specifies 18 Nm for the oil drain plug and 120 Nm for wheel bolts. Over-tightening can crack aluminum housings.

Specialty Tools for the 2.9TT

  • VAG-compatible scan tool – VCDS or OBDeleven for resetting adaptations and reading fault codes after installation.
  • Pickle fork or ball joint separator – Necessary for suspension work like lowering springs or sway bars.
  • Turbo blanket and heat shield tools – High-temp silicone tape and a set of long-reach needle-nose pliers to route wires around hot surfaces.
  • Oil filter wrench – Cup-style socket (36mm or 32mm depending on oil cooler) to avoid slipping.
  • Trim removal kit – Non-marring plastic pry tools to pop clips on the underbelly pan and fender liners.

Also, have a good floor jack (3-ton capacity minimum) and a pair of jack stands rated at 6 tons. Never work under a vehicle supported only by the jack.

Selecting the Right Performance Parts for Your Goals

Not all bolt-on parts deliver equal gains. Choose components that work together as a system. For example, an open intake without a corresponding tune can trigger MAF errors, while downpipes with no software adjustment will leave the check engine light on. Evaluate each part based on your target power level, budget, and daily drivability requirements.

Intake and Induction Upgrades

Cold-air intake kits from Eventuri, MST Performance, or Unitronic improve airflow and reduce intake air temperatures (IAT). Look for kits that retain the factory MAF housing size to avoid scaling issues. Some intakes also require removal of the engine cover, which may change engine bay acoustics. Pair a high-flow intake with a larger intercooler if you live in a hot climate.

Exhaust and Downpipes

Catted downpipes (e.g., from RedStar, Wagner Tuning, or Milltek) are the biggest single gain for the 2.9TT, freeing up to 40-50 whp when tuned. Choose HJS 200-cell catalytic converters to avoid stench and pass visual inspections. Catless downpipes offer max flow but are illegal on public roads in most areas. For the cat-back section, consider valves for noise control; brands like AWE and Akrapovic offer well-engineered systems.

Intercooler and Cooling

Factory intercooler heat soaks quickly during back-to-back pulls. Upgraded units (e.g., Wagner Tuning, SRM, or Forge) feature larger cores and improved charge piping. A front-mount intercooler (FMIC) replaces the factory unit and reduces IAT by 30-50°F under sustained load. This is essential for cars running a stage 2 tune.

Engine and Transmission Software

Tuning is the heart of any performance upgrade. Off-the-shelf (OTS) tunes from Unitronic, APR, Integrated Engineering, or 034Motorsport are popular and well-tested. For custom tuning, consider a remote tuner like Custom Code or EPL. Ensure the tune supports your specific octane level (91, 93, or E85). A stage 1 tune alone provides 480-500 hp on pump gas, while stage 2 with downpipes and intercooler reaches 530-550 hp.

For reference, 034Motorsport provides detailed data logs and dyno charts for their RS5 2.9TT packages (see their product page). Always compare multiple tuners before purchasing.

Preparation: Workspace, Safety, and Vehicle Readiness

Preparation separates a smooth weekend project from a nightmare. Follow these steps before turning a single wrench.

Workspace Setup

  • Work in a well-ventilated garage or on a clean, level concrete driveway. Lay down cardboard or a tarp to catch fluid spills.
  • Charge your battery before beginning – many modern cars need stable voltage during disconnections to prevent CAN bus errors.
  • Have a fire extinguisher rated for Class B (flammable liquids) and a first aid kit nearby.

Vehicle Prep

  • Cool the engine completely before working near exhaust components. Aluminum expands and can cause gasket misalignment if hot.
  • Disconnect the battery negative terminal and wait 10 minutes for capacitors to discharge.
  • Remove the under-engine cover (belly pan) – it hides many bolts and you’ll need access for oil changes and intercooler work.
  • Take reference photos of wire harness routing, especially near the turbo area. This saves time during reassembly.

A helpful tip: label all connectors with painter’s tape and a marker. The ECU connectors, camshaft sensors, and turbo oil lines are easy to mix up.

Step-by-Step Installation Guide for Common Performance Parts

Below is a general sequence that applies to most bolt-on upgrades. Always refer to the manufacturer’s instructions first, as torque specs and procedures vary.

Installing an Aftermarket Cold-Air Intake

  1. Disconnect the MAF sensor electrical connector. Press the release tab firmly to avoid breaking the clip.
  2. Loosen the hose clamps connecting the factory intake tube to the turbo inlet. Use a long extension and universal joint for the hidden clamp.
  3. Remove the stock air box by pulling upward – it is held by two rubber grommets. Do not force it; twist slightly to break the seal.
  4. Transfer the MAF sensor into the new intake tube. Ensure the orientation matches the airflow arrow on the sensor.
  5. Install the new intake heat shield and filter per kit instructions. Tighten hose clamps to 4-5 Nm max; overtightening can crack plastic.
  6. Reconnect the MAF sensor and double-check all connections. Start the engine and listen for whistles or unmetered air leaks.

Recommended: spray a little soapy water on the couplers after startup to verify no leaks.

Downpipe Installation (Critical Clearance Area)

  1. Apply penetrating oil (e.g., Kroil or PB Blaster) to all downpipe-to-turbo flange bolts the night before. Let it soak.
  2. Remove the front wheel on the driver side for better access to the lower bolts. Remove the fender liner if needed.
  3. Unbolt the factory downpipes from the turbochargers. These bolts are tight (typically 30-35 Nm with thread locker). Use a 10mm 12-point socket.
  4. Separate the downpipe from the cat-back exhaust section. The slip joint may corrode; use a rubber mallet to carefully tap it apart.
  5. Remove the passenger side downpipe first (it clears the engine mount tensioner). The driver side may require lifting the engine slightly (support with a jack under the oil pan – use a block of wood).
  6. Install the new downpipes with new gaskets. Apply anti-seize to the flange studs and torque to the spec provided by the manufacturer.
  7. Connect the downstream O2 sensor. Some tunes disable the rear sensor; but if not, you may need a spacer to avoid a CEL.

Warning: The upstream O2 sensors are fragile. Unclip them before removing the downpipe to avoid snapping the wire.

Intercooler Swap

  1. Remove the front bumper cover. This takes ~20 minutes on an RS5; look for bolts inside the wheel arches and under the headlights.
  2. Drain coolant from the intercooler circuit if it’s an air-to-water system (factory is water-to-air). Some aftermarket intercoolers are direct fit air-to-water; others replace the entire system with an air-to-air setup.
  3. Disconnect the charge pipes from the factory intercooler. Expect some coolant spill; have a drain pan ready.
  4. Remove the factory intercooler bracket bolts and lift the unit out from the top or bottom depending on access.
  5. Install the new intercooler, reuse the OEM rubber mounts if included, and secure brackets. Reconnect charge pipes using new O-rings (lube with silicone grease).
  6. Refill coolant and bleed the system per Audi procedure. Start engine, let it idle to normal operating temp, and check for leaks.

For a detailed guide with torque specs, see this Audizine write-up.

Testing and Tuning After Installation

Mechanical installation is only half the battle. Proper testing ensures parts function and that the vehicle is safe.

Initial Checks

  • Scan for fault codes with VCDS or OBDeleven. Clear any soft codes from disconnecting the battery.
  • Check fluid levels: oil, coolant, power steering (if applicable), and brake fluid.
  • Start the engine and let it reach operating temperature. Monitor oil pressure and coolant temperature on the dash.
  • Drive gently for 5-10 miles to allow the ECU to relearn idle and fuel trims. Avoid hard acceleration until the tune is flashed.

Data Logging and Fine-Tuning

Once the tune is installed (via a handheld flasher like Unitronic Uniconnect or ECU bench flash), do a few low-load data logs. Key parameters: boost pressure, IAT, fuel trims (STFT and LTFT), and knock correction. Aim for IAT below 130°F at the end of a third-gear pull. If fuel trims exceed ±10%, you may have a vacuum leak or MAF scaling issue.

Many tuning companies offer free support if you email logs. For example, Integrated Engineering provides a log review service (contact their support team).

Common Mistakes to Avoid

Even experienced DIYers make errors. Here are pitfalls specific to the RS5 2.9TT.

Improper Bolts and Torque

Using generic hardware from a bin often yields wrong thread pitch or tensile strength. Always use the bolts supplied with the parts – often they are 10.9 or 12.9 grade. Over-torque on aluminum threads (e.g., the turbo to downpipe flange) can strip the threads, requiring a helicoil repair.

Ignoring Boost Leaks

After installing new charge piping or intercooler, a small boost leak causes significant power loss. Harbor Freight sells a handy boost leak tester kit. Pressurize the system to 20 psi and listen for hisses. Common leak points: throttle body coupler, intercooler end tanks, and diverter valve O-rings.

Forgetting to Update Tune

Installing hardware without a compatible tune wastes potential. For instance, downpipes with a stock map will still request the same boost targets. Worse, lean conditions can occur because the MAF calibration shifts. Flash the correct tune before your first spirited drive.

Skipping Coolant Bleed

The 2.9TT intercooler system has a specific bleed procedure: open the bleeder screw at the top radiator hose, fill coolant slowly, and rev engine to 3000 rpm in neutral to purge air. Neglecting this leads to air pockets, high IAT, and possible engine knock.

Conclusion

DIY installation of performance parts on your Audi RS5 2.9TT is a rewarding path that saves significant labor costs and deepens your understanding of the car. With proper tools, careful planning, and a methodical approach to each step—from selecting matching components to data-logging the final tune—you can achieve 100+ horsepower gains safely. Start with a stage 1 tune to feel the delta, then add downpipes and intercooler for maximum effect. Remember to cross-reference all torque specs from the official Audi repair manual (available through erWin) and to log every session. By avoiding rushed work and common mistakes, you’ll build a reliable, fast RS5 that truly delivers.