Upgrading to a cold air intake is one of the most effective bolt-on modifications for the Audi B8 S4’s 3.0L TFSI supercharged V6. The ACS Tuning Cold Air Intake kit is engineered to reduce intake restriction and deliver cooler, denser air to the supercharger, yielding a verified gain of 15–20 horsepower at the wheels. This guide covers every step of the installation, along with tips to ensure optimal fitment, performance, and long-term reliability.

Why Upgrade the Intake on a B8 S4?

The factory airbox on the B8 S4 is designed for quiet operation and cost efficiency, not peak performance. It uses a restrictive intake path and a paper filter that becomes a bottleneck as engine speeds rise. Replacing it with the ACS Tuning cold air intake opens up the intake tract, reduces inlet air temperatures, and allows the supercharger to breathe more freely. The result is sharper throttle response, a more aggressive intake tone, and a noticeable power increase—especially in the mid-range and upper RPM band.

Because the 3.0T supercharger compresses incoming air, keeping that air as cool as possible before it hits the rotors is critical. The ACS kit uses a heat-shielded airbox and a high-flow dry or oiled filter to pull air from outside the engine bay, away from radiant heat sources. Combined with the larger diameter intake tube and smoother transitions, the system flows significantly more volume than stock.

Tools and Materials Needed

  • ACS Tuning Cold Air Intake Kit (includes airbox, filter, intake tube, clamps, brackets, and hardware)
  • Socket wrench set (10mm, 13mm, and 14mm sockets)
  • Flathead screwdriver (for prying trim clips if necessary)
  • Phillips screwdriver
  • Torque wrench (10–55 N·m range)
  • Allen key set (for set screws on the intake tube)
  • Trim removal tool (optional, for removing plastic fasteners)
  • Shop towels or microfiber cloths
  • Safety glasses and gloves

Note: Some B8 S4 models may require minor relocation of the windshield washer reservoir or a different MAF sensor housing depending on the production year. Confirm fitment with your kit’s instructions before beginning.

Preparation Steps

Park the vehicle on a level surface and allow the engine to cool completely—ideally overnight. A warm engine can burn you, and hot intake components are more brittle. Disconnect the negative battery terminal to prevent any electrical shorts or accidental airbag deployment while working near the battery area (the B8 S4 battery is in the left rear of the engine bay, but disconnecting it is still good practice).

Clear the work area around the engine bay. Remove any debris, leaves, or tools that could fall into the open intake port. Wear safety glasses at all times; the factory airbox clips can snap brittle plastic pieces.

Check the Kit Contents

Lay out all components from the ACS Tuning kit and compare them to the included parts list. Verify you have the correct filter (dry or oiled—many prefer dry for less maintenance), the correct tube diameter, and all necessary gaskets or O-rings. If the kit includes a replacement silicone coupler, ensure the hose clamps are the correct size.

Removing the Factory Air Intake System

The stock system consists of an airbox, a long intake tube, a mass airflow (MAF) sensor, and a resonator tube often attached to the airbox. Removing it requires careful attention to the MAF sensor and its wiring.

  1. Open the hood and locate the airbox. It sits on the driver’s side (left) of the engine bay, secured by two 10mm bolts at the top and one push-clip at the rear.
  2. Disconnect the MAF sensor. Press the red or gray locking tab, then press the release tab and pull the connector straight out. Do not yank on the wires.
  3. Loosen the hose clamps on the intake tube connecting the airbox outlet to the supercharger. Use a 7mm socket or flathead screwdriver, depending on the clamp type.
  4. Remove the intake tube by sliding it off the throttle body (supercharger inlet) and pulling it free from the airbox. If the tube is stuck, gently twist and pull.
  5. Remove the small vacuum line attached to the side of the factory intake tube (if equipped).
  6. Unbolt the airbox. Use a 10mm socket to remove the two top bolts. Then reach underneath to release the bottom clip (push the tab inward). Lift the airbox straight up and out. You may need to disconnect a small secondary air injection hose if it’s connected to the airbox.
  7. Remove the lower airbox support tray if your car has one—this is often clipped in. Pry it out with a trim tool.
  8. Inspect the factory intake path for any debris. Use a shop towel to wipe away any oil or dust from the supercharger inlet.

Keep the factory bolts and clamps in a labeled bag. The MAF sensor will be reused on the new intake tube—handle it with care. The sensor element is fragile.

Installing the ACS Tuning Cold Air Intake

With the stock system removed, the installation of the ACS kit is relatively straightforward. Follow the sequence below for best results.

Step 1: Install the Airbox/Heat Shield

Place the ACS aluminum or composite heat shield into the area where the factory airbox sat. Many kits use the factory mounting points. Insert the new bolts (often M6 or M8) and tighten them hand-tight. Then secure with a torque wrench to 10 N·m (7.4 ft-lb). Do not overtighten—aluminum threads can strip.

If your kit includes a divider panel that isolates the filter from the hot engine bay, install that now. It may require attaching brackets to the chassis rail or existing studs.

Step 2: Attach the Filter

Slide the high-flow cone filter onto the MAF housing or directly onto the intake tube, depending on kit design. Use the provided clamp to secure it. The filter should be positioned inside the heat shield, drawing air from the front of the car through a duct (if included). Ensure the filter is not touching any hot surfaces or moving components.

Tip: Dry filters require no oil and are easier to clean. Oiled filters can improve airflow slightly but risk over-oiling the MAF sensor—use sparingly if you choose oiled.

Step 3: Reinstall the MAF Sensor

Insert the MAF sensor into the dedicated bung on the new intake tube. The sensor should sit flush with the tube. Tighten the two small screws (usually T20 Torx) to 2–3 N·m (just snug). Do not overtighten—the plastic housing can crack.

Reconnect the MAF harness. The connector should click into place. Fold any excess wire neatly and secure it with zip ties (not included) to prevent it from contacting the belt or pulleys.

Step 4: Connect the Intake Tube

Slide the silicone coupler onto the supercharger inlet. Some kits use a metal coupling—apply a thin layer of silicone lubricant or dish soap to help it slide. Position the tube so that it clears the engine cover, coolant lines, and strut bar. The ACS tube is designed to fit factory clearances, but you may need to rotate the coupler for best alignment.

Slip the other end over the MAF housing or filter flange, depending on your kit’s design. Tighten all hose clamps to 4–5 N·m (35–44 in-lb). Ensure the clamps are oriented so you can reach them later if needed.

Step 5: Secure Brackets and Final Connections

Some ACS kits include a support bracket that bolts to the intake tube and attaches to the strut tower or a nearby bolt. Install this to prevent vibration. Tighten bracket bolts to 10 N·m.

Reattach any vacuum lines that were disconnected (e.g., the crankcase ventilation line). Check that all clamps are tight, the filter is secure, and nothing is rubbing against belts or the supercharger pulley.

Final Checks and Testing

Before restarting the engine, perform a thorough inspection:

  • Double-check all hose clamps—two are better than one if the kit provided a step.
  • Ensure the MAF sensor connector is fully locked and the wiring is routed away from sharp edges.
  • Confirm the heat shield is not touching the hood liner when closed. Close the hood and check clearance; adjust if necessary.
  • Reconnect the negative battery terminal.
  • Turn the ignition key to ON (not start) for 10 seconds to allow the MAF sensor to relearn idle parameters.

Start the engine. Let it idle for 2–3 minutes. Listen for any vacuum leaks (hissing sounds), rattling, or abnormal whistling. A mild induction noise is normal. Rev the engine gently to 2000–3000 RPM a few times to ensure the intake system seals properly.

Take a short test drive. Verify that the car accelerates smoothly, without hesitation. You may notice a slight increase in intake roar under heavy throttle. If the check engine light comes on, scan for codes—most often a MAF or a lean code indicates an air leak. Re-check all connections.

Performance Expectations and Tuning

The ACS Tuning cold air intake alone adds 15–20 wheel horsepower on a stock B8 S4. This gain is most noticeable above 3500 RPM. The intake also reduces the pressure drop across the filter, which can slightly improve supercharger efficiency and spool. However, to fully exploit the extra airflow, a stage 1 ECU tune is highly recommended. Tunes from APR or 034Motorsport typically increase gains to 40–50 combined horsepower when paired with a cold air intake.

For those who track their car, the ACS intake performs well even at high ambient temperatures, thanks to the heat shield. Combine it with a high-flow supercharger pulley upgrade for even greater results—though that requires a separate tune and installation.

Note that a cold air intake may require a re-tune of the MAF sensor scaling if the tube diameter differs from stock. Many ACS kits are engineered to match the OEM MAF housing diameter, so no tuning is needed for the intake alone. Check the product documentation: ACS Tuning official website provides specific fitment notes.

Sound Improvement

One of the most enjoyable side effects is the enhanced supercharger whine. The B8 S4’s Eaton TVS supercharger has a distinctive gear whine that the factory intake muffles. The ACS intake amplifies this at partial throttle, giving the car a much more aggressive, mechanical soundtrack. Under full acceleration, the induction roar is deep and responsive.

Maintenance and Filter Cleaning

Cold air filters require periodic cleaning to maintain performance. For oiled filters, clean every 15,000 miles using a dedicated kit. For dry filters, tap out loose dirt and vacuum the surface; replace every 30,000 miles or as needed. The ACS heat shield and tube should be wiped down with a damp cloth when you clean the filter. Avoid using harsh chemicals that could degrade silicone couplers.

Inspect the MAF sensor annually. A small amount of oil or dirt can skew readings. Use a specific MAF sensor cleaner spray—never alcohol or abrasive materials.

Potential Pitfalls and Tips

  • Don’t forget the MAF sensor grounding. Some aftermarket tubes require a ground strap if the factory grounding point was on the airbox. The ACS kit generally addresses this, but check your instructions.
  • Watch out for the secondary air injection pump line. It can be brittle; replace if cracked.
  • Use threadlocker on metal-to-metal bracket bolts to prevent vibration loosening.
  • If you live in a region with high water crossings, consider a filter sock to prevent water ingestion.

For further discussion and owner experiences, the Audizine B8 S4 forums are an excellent resource for installation tips and dyno results.

Conclusion

Installing the ACS Tuning cold air intake on your B8 S4 is one of the most satisfying and cost-effective ways to gain real horsepower. The complete job takes about 45 minutes for an experienced DIYer and requires only basic hand tools. With the 15–20 hp boost, improved throttle response, and that glorious supercharger whine, the ACS kit transforms the driving experience. When combined with a quality tune and supporting modifications, it becomes a cornerstone of any serious B8 S4 performance build.