The B9 Audi A4 2.0T: A Worthy Platform

The B9 Audi A4 (2017–present) represents a high point in the compact executive sedan segment, blending quattro all-wheel-drive stability with a responsive 2.0-liter turbocharged inline-four. While the factory intake system is adequate for daily driving, it is designed primarily for low noise and cost efficiency, not maximum airflow. Enthusiasts seeking sharper throttle response, a more engaging soundtrack, and a genuine power gain often turn to aftermarket intakes. The Forge intake stands out as a well-engineered solution that delivers a claimed 15 horsepower increase at the wheels, along with a noticeably deeper induction note. This guide covers everything you need to know about selecting, installing, and owning a Forge intake on your B9 A4 2.0T.

Why the Forge Intake Specifically?

Several aftermarket intakes exist for the B9 A4, but the Forge unit offers a unique combination of proven gains, quality construction, and ease of installation. Unlike some open-element intakes that pull hot engine bay air, the Forge system uses an enclosed carbon fiber heat shield that ducts cooler outside air directly to the filter. This design preserves intake air density, which is critical for maintaining power after the initial hit. The included dry synthetic filter provides excellent filtration without the need for oil, reducing the risk of contaminating the MAF (mass airflow) sensor. Forge also retains all factory PCV and evap connections, ensuring no check engine lights or drivability issues.

Key Benefits Over Stock

  • Horsepower and Torque: Independent dyno testing has shown gains of 12–17 hp and 10–14 lb-ft of torque across the mid-range, with peak improvements near the redline.
  • Throttle Response: The larger intake tube and reduced restriction allow the turbo to spool more freely, sharpening tip-in response noticeably.
  • Sound: The intake produces a rich, whooshing flutter under heavy throttle and a distinct blow-off valve like sound on lift-off (even with the stock diverter valve).
  • Heat Management: The carbon shield and sealed ducting keep IATs (intake air temperatures) within 5–10°F of ambient during sustained driving, compared to 20–30°F with the stock airbox in similar conditions.

Tools and Materials Checklist

A successful installation requires only basic hand tools, but having the right items on hand will prevent frustration. The Forge kit comes with all necessary hardware, clamps, and the filter pre-oiled (if you order the oiled version; the dry filter is recommended).

  • Socket set: 8mm, 10mm, 13mm sockets (deep and shallow).
  • Torx drivers: T25 and T30 bits for engine cover and hose clamps.
  • Flathead screwdriver: For prying loose hose connections and rerouting wires.
  • Trim removal tool: To safely pop off plastic push pins and covers.
  • Small allen key set: For set screws on the Forge coupler.
  • Clean microfiber cloths: For wiping the intake bore and surrounding area.
  • Thread lock (optional): For securing the heat shield screws if you drive on rough roads.

Installation Steps: A Detailed Walkthrough

The process takes roughly 45–90 minutes for first-time installers. Work in a well-lit area with the engine cold to avoid burns. Always disconnect the battery negative terminal before starting any work on the intake system to prevent electrical shorts and accidental deployment of the airbag system if you are near the crash sensors.

Step 1 – Disconnect Battery and Remove Engine Cover

Locate the negative battery terminal on the driver side of the engine bay (under a red plastic cover). Loosen the 10mm nut and slide the terminal off, then tuck it away so it cannot contact the post. Remove the engine cover by unscrewing the four Torx bolts (T30) that hold it to the valve cover. Lift the cover straight up and set it aside.

Step 2 – Uninstall the Factory Intake

Start by loosening the two T25 hose clamps that secure the intake hose to the turbo inlet. Gently wiggle the hose free. Next, release the PCV hose from the rear of the intake tube by pressing the retaining clip and pulling. Disconnect the MAF sensor electrical connector by lifting the red tab and pressing the release. Unscrew the MAF sensor from the stock airbox using a T20 driver. Remove the four push pins that hold the airbox lid, then lift out the lid with the filter. Unclip the temperature sensor wire from the airbox housing. Remove the lower airbox by pulling upward; it may require a firm tug. Set all OEM parts aside—many owners keep the stock airbox for resale or emissions inspection.

Step 3 – Prepare the Turbo Inlet and Heat Shield

Inspect the rubber turbo inlet pipe for any debris or oil residue. Clean it with a cloth if needed. Install the supplied silicone adapter onto the turbo inlet; it should slide over the factory plastic tube and be secured with the Forge worm-drive clamp. Do not fully tighten yet. Slide the carbon fiber heat shield into position over the adapter, aligning the three mounting tabs with the existing studs on the chassis. Secure the shield with the provided washers and nuts, torquing to hand tight plus a quarter turn.

Step 4 – Install the Forge Intake Tube and Filter

Attach the forged aluminum intake tube to the silicone adapter and heat shield. The tube has an angled section that directs airflow toward the wheel well. Secure it with the supplied clamp, again only snug for now. Install the MAF sensor into the designated bung on the intake tube (using the supplied rubber grommet), and reconnect the electrical connector. Slide the dry filter onto the end of the tube and tighten the integrated clamp. Position the filter so it sits comfortably inside the heat shield enclosure without rubbing against the inner fender liner.

Step 5 – Connect Hoses and Final Tightening

Reattach the PCV hose to the barb on the intake tube; it should click firmly. Reconnect any additional ventilation lines that were disconnected (some model years have a small breather hose near the rear of the tube). Now, tighten all clamps in sequence: the turbo inlet adapter, the heat shield retaining nuts, the intake tube clamp at the adapter, and the filter clamp. Verify that no hoses are pinched and that the MAF wire is routed away from moving parts. Replace the engine cover (it bolts directly over the Forge heat shield without interference). Reconnect the negative battery terminal. Start the engine and let it idle for 30 seconds while checking for air leaks (listen for hissing or whistling). Rev the engine gently—it should respond cleanly without hesitation.

Post-Installation Performance Expectations

Immediately after installation, you will notice a slightly louder intake noise at idle and a pronounced suction sound when accelerating. The sound continues to mellow as the filter loads with dust over the first 200 miles. Expect the 15 hp gain to be most noticeable in the 3500–5500 rpm range, where the turbo is working hardest. Combined with a stage 1 ECU tune, the Forge intake can support up to 280-300 whp on the B9 2.0T, making it a solid foundation for future upgrades. For dyno-verified results, consult Forge Motorsport’s official data and independent testing from Audizine forums.

Sound Improvement: Before and After

The stock intake is nearly silent, producing only a faint whistle under load. With the Forge intake, the tone shifts to a deep growl that is more pronounced with the windows down. The turbo spool becomes clearly audible, and the characteristic “whoosh” as you lift off the throttle mimics a blow-off valve without any mechanical modification. Many owners report that the sound is aggressive enough to enjoy without being intrusive during highway cruising. If you prefer a stealthier look, the carbon heat shield blends well with the engine bay and does not attract excess attention from law enforcement.

Long‑Term Maintenance and Filter Care

The Forge dry filter can be cleaned with compressed air from the inside out every 10,000 miles. For heavier use (dusty roads, track days), clean it every 5,000 miles. Avoid using oil on the dry filter, as it is pre-treated with a static charge that traps particles. The heat shield itself may accumulate road film; a simple wipe with a damp cloth keeps it looking fresh. Inspect the silicone adapters and clamps annually for loosening—a very rare occurrence, but worth checking. Replace the filter every 30,000 miles or sooner if it appears dirty.

Combining with Other Modifications

To maximize the Forge intake’s potential, consider pairing it with a high-flow downpipe and a performance intercooler. The intake removes a restriction on the air side, while the downpipe and intercooler improve exhaust flow and charge air cooling respectively. A corresponding ECU tune (e.g., APR, Unitronic, or IE) will then recalibrate boost and fueling to fully exploit the increased airflow, often yielding 280–300 hp at the crank. Many tuners offer bundled discounts for intake and tune combinations; check with APR or Unitronic for compatible packages.

Common Issues and Troubleshooting

While the Forge intake is known for trouble-free operation, a few minor issues can arise during installation or early use:

  • MAF reading errors: If you see a CEL (check engine light) with a MAF-related code, verify the MAF sensor is seated fully in the rubber bung and that the electrical connector is clicked down. A loose MAF can cause incorrect airflow readings.
  • Whistling at idle: A high-pitched whistle often indicates a small vacuum leak where the silicone adapter meets the turbo inlet. Double-check the clamp tightness and the adapter seal.
  • Filter contacting inner fender: If you hear a rubbing noise, loosen the filter clamp, rotate the filter slightly (usually toward the wheel well), and re-tighten. Ensure the heat shield is centered so the filter has clearance.
  • Increased intake noise at highway speeds: This is normal and expected, especially with the windows down. It is not an indication of any performance issue.

Final Verdict

Installing a Forge intake on your B9 Audi A4 2.0T is one of the most effective and rewarding entry-level modifications available. It delivers a genuine 15 HP increase, transforms the engine’s acoustic character, and lays a solid foundation for future power upgrades. With straightforward installation and minimal ongoing maintenance, it is an excellent choice for both daily drivers and weekend canyon carvers. Whether you are chasing lap times or simply want a more visceral connection to your car, the Forge intake delivers measurable results without sacrificing reliability or daily livability. For DIY installation support, be sure to read the official Forge installation PDF and join enthusiast communities on Audi forums for real‑world tips.