Audi S3 IS38 Turbo Upgrades: An Overview

The factory EA888 Gen 3 2.0 TFSI engine in the Audi S3 (8V/8Y) is a remarkable piece of engineering, delivering spirited performance right off the showroom floor. However, for driving enthusiasts seeking a more visceral experience, the stock IS20 turbocharger inevitably becomes a bottleneck. The CTS Turbo IS38 upgrade offers a well-established path to substantial power gains by swapping to a larger compressor wheel and turbine housing originally found in the Golf R and Audi S3 8V Performance models. This article provides a thorough, step-by-step breakdown of the installation, a detailed cost analysis, and an honest look at what you can expect from this popular modification.

What the CTS Turbo IS38 Upgrade Delivers

The CTS Turbo IS38 assembly is a direct physical replacement for the stock IS20 unit. While the architecture retains the BorgWarner design, CTS Turbo uses a larger 11-blade billet compressor wheel and a CNC-machined turbine housing to improve flow. The result is a turbocharger capable of flowing roughly 10-15% more air under the same boost pressure, which directly translates to higher horsepower and torque when paired with appropriate supporting modifications.

Key Performance Gains

  • +60–80 whp over stock IS20 with a Stage 2 ECU tune
  • +70–90 lb-ft of torque across the mid-range, peaking around 3,800–4,500 RPM
  • Retains OEM-like spool characteristics; full boost arrives by ~3,200 RPM
  • Sustained power to redline, avoiding the stock turbo’s top-end fall-off

Important note: The CTS IS38 is a bolt-on upgrade for the AWD 8V/8Y S3 and the Golf R 7/7.5. It requires an ECU tune to operate safely; running the turbo without recalibrated fuel and boost maps can cause lean conditions and engine damage. Popular tuning solutions include Unitronic, APR, and Integrated Engineering.

Full Installation Process

This upgrade is considered intermediate-level DIY work. Expect to spend 6–10 hours in a well-equipped garage. Below is a detailed walkthrough with torque specs and critical steps not found in basic guides.

  • 3/8″ and 1/2″ drive socket sets (e.g., 10mm, 13mm, 16mm, 18mm quick-release sockets)
  • Torque wrench (ft-lb and in-lb) – critical for turbo mounting bolts
  • Triple-square (M10 M12) and E-Torx (E14, E18) sockets
  • Long flathead screwdriver for hose clips
  • Pick set for O-ring removal
  • Oil catch can (optional but recommended to avoid PCV oil entering the intake)
  • New gaskets, crush washers, and copper spray (if reusing OE gaskets)
  • V-band clamp tool or large channel-locks
  • WD-40 or anti-seize on fasteners

Step 1: Safety & Battery Disconnect

Disconnecting the negative battery terminal is mandatory to prevent accidental short circuits and to allow the ECU to reset after installation. Wait 10 minutes for the system voltage to drop.

Step 2: Drain Coolant & Oil

Drain the engine coolant from the radiator petcock (approximately 6–8 liters) and remove the oil drain plug for an oil change. The turbocharger is oil- and water-cooled; draining prevents spills when hoses are disconnected.

Step 3: Remove Air Intake & Turbo Inlet Pipe

Unclip the intake air box, MAF sensor connector, and the charge air pipe. Remove the turbo inlet pipe (TIP) by loosening the three T25 Torx screws and pulling it off the compressor housing. This step provides the access needed for the turbo oil feed and drain lines.

Step 4: Disconnect Intercooler Hoses & Charge Pipes

Using a flathead screwdriver, release the spring clamps on the lower intercooler hose and the charge air pipe behind the passenger-side headlight. On some models, you may also need to unbolt the fender liner to reach the intercooler. Take care to not tear the silicone boots.

Step 5: Remove the Downpipe

Unbolt the downpipe from the turbo outlet (three nuts, 13mm) and the exhaust hangers near the front subframe. The oxygen sensor must be unplugged (gray and black connectors). Swivel sockets help with the tight angles. A penetrating oil like Permatex is recommended on the rust-prone nuts.

Step 6: Unbolt the Factory IS20 Turbocharger

Remove the oil feed line (banjo bolt at turbo, 17mm) and the coolant feed and return hoses. The water fittings use O-rings; pry them gently with a pick. Remove the turbo support bracket (E14 bolt). Loosen the V-band clamp securing the turbine housing to the exhaust manifold. With the clamp free, the turbo can be lifted out from the engine bay.

Many DIYers find it easier to go from underneath after removing the under-tray.

Step 7: Prepare & Install the CTS Turbo IS38

Transfer the oil drain gasket and install a new one. Apply a thin layer of high-temp anti-seize to the V-band clamp threads. Position the CTS IS38 turbo onto the manifold, ensuring the oil drain aligns perfectly. Tighten the V-band clamp to 18 N·m (13 ft-lb) and the support bracket to 25 N·m (18 ft-lb). Reconnect the coolant lines (using new O-rings) and the oil feed line.

Use a torque wrench: oil feed banjo bolt to 30 N·m (22 ft-lb) – do not over-tighten as it can damage the threads.

Step 8: Reinstall Accessories & Fill Fluids

Reattach the downpipe (use new gasket), charge air pipes, intercooler hose, turbo inlet pipe, and air intake. Fill the coolant with a 50/50 mix of G12++ or G13 coolant. Add new engine oil (Mobil 1 0W-40, 5W-40, or similar). Reconnect the battery.

Step 9: Priming & Leak Check

Before the first start, unplug the ignition coils and crank the engine for 5–10 seconds to prime the turbo’s oil supply. If the turbo has been dry for more than 24 hours, squirt a few milliliters of oil into the oil feed port. After priming, reconnect coils and start the engine. Check for coolant or oil leaks at the turbo, downpipe, and all hose connections. A small wisp of smoke from the downpipe is normal from machining oil; persistent smoke indicates an oil leak.

Step 10: ECU Tune & Calibration

Do not drive the car hard until the ECU tune is loaded. Use a flash tool like the COBB Accessport or Unitronic OBD kit to install a Stage 2 or IS38-specific file. After the tune, perform a short test drive, keeping boost under 15 psi for the first 50 miles to let the piston rings seat and the turbo break in.

Cost Analysis: Parts, Labor, & Supporting Mods

Upgrading the turbo isn’t just the cost of the turbo itself. Real-world budgets must account for necessary supporting hardware and labor.

Core Components

  • CTS Turbo IS38 (with turbine housing, actuator, and gaskets): $1,299 – $1,399
  • ECU Tune (IS38-specific): $599 – $799 (COBB + tune license, or bench flash)
  • DSG/TCU Tune (recommended for automatic): $499 – $699

Ancillary Hardware

  • High-flow downpipe: $350 – $600 (required for Stage 2 IS38 gains)
  • Intercooler upgrade: $500 – $800 (stock intercooler heat-soaks under sustained boost)
  • Turbo inlet pipe: $150 – $250 (optional but helps spool)
  • High-flow intake: $200 – $400
  • Spark plugs (one step colder): $60 – $80 (NGK 7437-7 or equivalent)
  • Oil & coolant change: $100
  • Gaskets, O-rings, crush washers: $80

Labor Costs

  • DIY: $0 (but plan for 8–10 hours of your time)
  • Independent shop: $600 – $1,000 (typically 6–8 hours at $100–$125/hr)
  • Dealership or high-end specialty shop: $1,200 – $1,600 (8 hours at $150+/hr)

Total Budget Range

ComponentLow RangeHigh Range
Turbocharger & Gaskets$1,380$1,480
ECU Tune$600$800
Downpipe$350$600
Intercooler$500$800
Supporting hardware (intake, TIP, sparks, fluids)$400$730
Labor (professional install)$600$1,600
Total (DIY)$3,230$4,410
Total (professional install)$3,830$6,010

Note: These estimates exclude sales tax, shipping, and optional preventive maintenance like a PCV valve replacement (approx $60). If you are tuning for ethanol (E85), add injectors ($700–$1,200) and a low-pressure fuel pump upgrade ($600).

Real-World Performance Gains

Numerous independent dyno runs from Audizine and the MK7 Golf R platform show the CTS IS38 with a Stage 2+ tune producing 370–400 whp and 370–400 lb-ft of torque on 93-octane fuel. That is roughly a 70–100 whp increase over a stock IS20 Stage 2 car. At the drag strip, a properly equipped S3 can run sub-11.5-second quarter-miles with good tires and a DSG tune.

The power is not just peak numbers: the CTS IS38 holds boost to redline and provides a much flatter torque curve than the IS20, which drops off after 5,500 RPM. This makes the car feel strong at any RPM above 3,000.

Supporting Modifications You Should Not Skip

While the IS38 can physically bolt on to a stock engine, its true potential is unlocked only with a few essential upgrades.

Intercooler: The Single Most Important Supporting Mod

The stock S3 intercooler is marginal even at stock power. With the IS38, charge air temperatures can exceed 60°C (140°F) after a few pulls, pulling timing and robbing power. A quality front-mount or direct-fit charge air cooler (e.g., Wagner, IE, or CTS Turbo) will lower IATs by 15–25°C, allowing consistent performance. Budget $500–$800 for a good unit.

Downpipe & Exhaust

A high-flow downpipe (catted or catless) is essentially required for any Stage 2 IS38 tune. The factory downpipe has a restrictive catalytic converter that chokes exhaust flow. With a 3-inch downpipe, the turbo spools faster and makes 15–25 whp more than with the stock pipe. Ensure the tuner supports the downpipe option; most Stage 2 files are designed for it.

Fueling System Considerations

On 93-octane, the factory fuel system (HPFP + direct injectors) is adequate up to about 400 whp. If you plan to run ethanol blends (E30 to E85), you must upgrade the injectors to the RS3 or a Bosch 420/450 HPFP and possibly an LPFP controller. The 034 Motorsport or Autotech HPFP upgrade kits are popular choices.

DSG Tune

If your S3 has the 7-speed DSG (DQ381), the factory shift timing and clamping pressure are not calibrated for high torque. A DSG tune raises line pressure, shortens shift times, and increases torque limits. Without it, the transmission may slip or enter limp mode under heavy load.

Reliability & Maintenance

The CTS IS38 has proven to be a durable unit for daily-driven cars, provided maintenance is respected. Key reliability points:

  • Oil changes every 5,000 miles – the turbo’s cartridge bearing is sensitive to oil degradation.
  • Let the car idle for 30–60 seconds after a hard run – prevents coking in the turbo oil passages.
  • Check the PCV valve annually – a failed PCV can cause excessive crankcase pressure and oil blowing past the turbo seals.
  • Use high-quality coolant – the water jacket around the turbine housing helps manage heat; maintain proper mixture.

Most failures are linked to improper tuning (overboosting, knock) or neglected oil changes. A conservative tune with a responsible driver will see 50,000+ miles of trouble-free use.

Conclusion

The CTS Turbo IS38 upgrade remains one of the most cost-effective ways to significantly increase the performance of your Audi S3 without moving to a hybrid or full-frame turbo. The installation is challenging but achievable for a skilled DIYer, and the total cost, including supporting mods, typically falls between $3,800 and $6,000. That investment returns a car that feels both quicker and more responsive—both at the track and on the street.

If you are ready to push your S3 beyond the factory limits, this turbo, paired with a reputable tune and proper cooling, will deliver an exhilarating experience. Just remember: no upgrade is complete without addressing the supporting systems, and after the install, careful break-in and maintenance will keep your car running strong for many miles to come.