Understanding the RS5 2.9 TT Turbo System

The Audi RS5 equipped with the 2.9-liter twin-turbo V6 (EA839 engine) represents a benchmark in compact performance engineering. Factory-rated at 444 horsepower and 443 lb-ft of torque, this powerplant relies on two small, quick-spooling turbochargers mounted in the engine valley. These turbos feed compressed air into the intake system, enabling the engine to produce significantly more power than a naturally aspirated equivalent. However, the high heat and rotational speeds—often exceeding 150,000 RPM—place immense stress on the turbocharger bearings, seals, and turbine wheels. Over time, oil coking, contamination, or simple fatigue leads to performance degradation, oil leaks, or shaft play. Understanding the turbo system's operation and failure modes is essential for any RS5 owner considering a rebuild or upgrade.

The 2.9TT employs a "hot-vee" layout, with both turbos sitting in the engine's valley between the cylinder banks. This design reduces lag by keeping exhaust paths short and improves packaging. The turbos are water-cooled and oil-lubricated, with electronic wastegate actuators for precise boost control. Each turbo features a small turbine housing that allows rapid spool but can become a restriction when chasing high horsepower. For enthusiasts aiming at 550–700+ wheel horsepower, the stock turbos often become the limiting factor, making a rebuild with upgraded internals or a complete changeover to larger units a popular path.

Why Rebuild Instead of Replace?

When turbos fail or show wear, owners face a choice: purchase brand-new factory units (often $2,500–$4,000 each), source low-mileage used parts, or rebuild the existing turbos. Rebuilding offers several advantages:

  • Cost savings: A quality rebuild typically runs $1,200–$2,500 per turbo, compared to $3,000+ for new OEM units. The total rebuild cost for both turbos often lands between $2,400 and $5,000, depending on parts and labor included.
  • Upgrade opportunity: Rebuilding allows installation of upgraded bearings (e.g., ceramic ball bearings), billet compressor wheels, or ported housings. These modifications can increase flow capacity and spool characteristics without swapping to a completely different turbo kit.
  • Preserving originality: For owners who want to keep the vehicle's VIN-matched components or avoid aftermarket turbo kits that require significant fabrication, rebuilding the factory units retains the original mounting and plumbing.
  • Quality control: A reputable turbo rebuild shop can balance the rotating assembly, check clearance, and use modern seal technology that sometimes surpasses OEM durability.

However, rebuilding is not always the right choice. If the turbo housing is cracked, the shaft is bent, or the turbine wheel is damaged beyond reasonable repair, replacement becomes necessary. Additionally, if the goal is 700+ horsepower, even a rebuilt stock-frame turbo may hit flow limits; a larger hybrid or completely different turbo system (e.g., single turbo conversion) may be required.

Cost Breakdown for RS5 2.9TT Turbo Rebuilds

The headline figure of $4,000+ for a complete rebuild of both turbos (including removal, disassembly, parts, and reinstallation) is realistic but varies widely. Below is a detailed cost breakdown based on typical market rates and parts:

Parts Direct Costs

  • Rebuild kit (bearings, seals, piston rings, gaskets): $200–$600 per turbo. High-quality kits from brands like Turbo Rebuild Kits, Melett, or genuine BorgWarner components cost more but offer better longevity.
  • Upgraded components: Billet compressor wheel ($150–$400 per turbo), ported housing ($100–$300), ceramic ball bearing cartridge ($800–$1,200 per turbo). Going full ball-bearing can add $1,600–$2,400 to the total parts cost.
  • Exhaust manifolds and gaskets: Since the turbos sit in the hot vee, the manifold gaskets and heat shields should be replaced. Expect $150–$300 for genuine Audi parts.
  • Oil and coolant lines: Hard lines can be cleaned, but rubber supply hoses and banjo bolts with integrated screens should be replaced. Budget $100–$250.

Labor Costs

Labor accounts for the largest portion of the expense. The RS5 2.9TT engine requires significant disassembly to access the turbos: removal of the intake manifold, intercooler, coolant pipes, and sometimes the subframe. A professional shop typically charges 12–18 hours of labor at $100–$200 per hour. Total labor for removal and reinstallation: $1,200–$3,600. If the shop also performs the internal rebuild (disassembly, cleaning, reassembly, balancing), expect an additional 4–6 hours per turbo, adding $400–$1,200.

Additional Costs During Rebuild

  • Turbo balancing: After reassembly, the rotating assembly must be dynamically balanced. This costs $75–$150 per turbo at a specialist. Skipping this leads to premature bearing failure.
  • Pressure testing and cleaning: Ultrasonic cleaning of housings and pressure testing of core castings: $50–$100 per turbo.
  • Miscellaneous: Coolant, oil, and new fasteners (e.g., stretch bolts) can add $100–$200.

Total estimated range for a professional rebuild of both turbos (with standard parts): $3,500–$6,000. Including upgraded billet wheels or ball bearings pushes the total to $5,500–$8,500. Always obtain quotes from several shops, and confirm whether the quote includes removal and reinstallation or just the rebuild service.

Installation Process for RS5 2.9TT Turbo Rebuilds

Rebuilding the turbos themselves is one part of the equation; removing and reinstalling them on the vehicle is equally critical. Below is a detailed walkthrough of the installation process, which should only be attempted by experienced technicians with proper tools (e.g., engine support bar, torque wrenches, specialty sockets).

Preparation

  • Disconnect the battery and drain the engine coolant (to avoid coolant entering the engine valley during turbo removal).
  • Remove the engine undercovers, front bumper, and intercooler (if top-mounted) to access the turbocharger area.
  • Release the high-pressure fuel rail and injectors? Not necessary for turbo access on the EA839; the intake manifold must come off to reach the turbos.

Step 1: Remove Intake Manifold and Throttle Body

The plastic intake manifold sits above the turbos. Unbolt it carefully, disconnect the camshaft adjuster connectors, and set it aside. Cover the intake ports with clean rags to prevent debris from falling into the engine.

Step 2: Disconnect Turbo Inlet and Outlet Pipes

Each turbo has a compressed air outlet (to the intercooler) and an inlet from the air filter box. Remove the charge air cooler pipes and the intake ducting. Also release the wastegate actuator rods from the exhaust manifold linkage.

Step 3: Drain Coolant and Oil Supply

Remove the coolant return lines from each turbo. There are two small rubber hoses connecting to the water pipe bridge. Expect coolant spillage. Then remove the oil feed and return lines. The oil drain is a hard pipe; unbolt it from the block and turbo.

Step 4: Unbolt Exhaust Manifold and Turbo Assembly

The turbos are bolted to the exhaust manifolds via V-band clamps. Many choose to remove the manifolds and turbos as one unit. Unbolt the exhaust manifold from the cylinder heads (8 bolts per bank, access is tight). Nuts are often corroded; use penetrating oil and a breaker bar. Carefully lift the combined manifold-turbo assembly out through the top. Repeat for the other bank.

Step 5: Disassemble and Inspect

Once on the bench, separate the turbo from the manifold by unbolting the V-band. Inspect the turbine wheel for cracks, the compressor wheel for blade damage, and the housing for scoring. Measure shaft play. If the turbo is rebuildable, proceed to disassemble the center housing and replace bearings, seals, and piston rings.

Power Potential After Rebuild and Tuning

The RS5 2.9TT responds exceptionally well to optimized turbocharger performance. Rebuilding with upgraded components unlocks significant power gains beyond factory levels. The key variables are the rebuild quality, fuel type, and engine management tuning.

Stock Level Gains

Even a simple stock-spec rebuild—using OEM-quality bearings and seals—restores lost boost pressure and spool speed. This alone can regain 20–30 horsepower if the turbos were previously worn. The primary benefit here is reliability and responsiveness, not maximum power.

Upgraded Billet Compressor Wheels

Installing billet aluminum compressor wheels with higher flow capacity allows the turbos to move more air at the same boost pressure or hold boost higher in the RPM range. Combined with a tune, these upgrades typically yield 550–600 wheel horsepower (whp) on 93 octane pump gas, and 600–650 whp on ethanol blends (E50/E85) with upgraded fuel pumps and injectors. The torque curve shifts upward and holds longer, delivering a linear, aggressive pull.

Hybrid Turbos or Larger Frames

Some rebuild shops offer hybrid turbos that fit within the stock housing but use larger compressor and turbine wheels. These can flow enough for 650–700 whp on ethanol. At this level, supporting mods become mandatory: larger intercooler, upgraded high-pressure fuel pump (HPFP), port injection, and a turbo-back exhaust with downpipes. Clutch/flywheel upgrades are needed for manual transmission cars; for DSG, a TCU tune and possibly clutch packs are required.

Beyond 700 Wheel Horsepower

To exceed 700 whp reliably, the stock turbos, even when heavily rebuilt, become the bottleneck. Owners typically move to larger single-turbo kits (e.g., Full-Race, Pure Turbos) or twin-scroll setups. These systems require custom downpipes, wastegate placement, and extensive tuning. A 900+ whp RS5 is possible but demands a fully built engine, upgraded transmissions, and a race fuel strategy.

Reliability and Maintenance After Rebuild

Proper break-in and maintenance are critical after a turbo rebuild. Follow these guidelines to maximize lifespan:

  • Oil priming: Before starting the engine, disable the ignition and crank the engine (with fuel pump fuse removed) for 10–15 seconds to get oil to the turbo bearings. This prevents dry start damage.
  • Break-in procedure: Avoid sustained high boost for the first 500 miles. Vary engine speeds and allow full warm-up before any spirited driving.
  • Oil change interval: Change the oil and filter at 500 miles after rebuild, then return to normal intervals (every 5,000 miles with high-quality full-synthetic 5W-40).
  • Inspect oil feed lines: Ensure the banjo bolt filters (if present) are clean. Clogged oil screens are a common cause of turbo failure.
  • Catch can system: A PCV (positive crankcase ventilation) catch can reduces oil vapor contamination in the intake system, keeping compressor wheels and intercooler cleaner.

Most failures after a rebuild stem from contaminants in the oil or improper balancing. Using a reputable shop with a dynamic balancer and full assembly documentation vastly improves outcomes.

External Resources for Further Reading

Conclusion

Rebuilding the turbochargers on an Audi RS5 2.9TT is a high-value performance investment for anyone looking to restore lost power or push the platform to its limits. Costs can range from $4,000 for a basic stock rebuild to over $8,000 for a fully upgraded ball-bearing setup with billet wheels—but the payoff in responsiveness and peak output is substantial. The installation demands professional-level skill, but the results speak for themselves: a properly rebuilt RS5 can deliver 550–650 whp on pump fuel and remain daily drivable when supported by suitable engine management and maintenance. For those chasing extreme numbers, the rebuild serves as a stepping stone to even larger systems. Always vet your rebuild shop, insist on dynamic balancing, and budget for supporting mods to ensure your upgraded turbos live a long, trouble-free life.