Upgrading the intake system on your B9 or B9.5 Audi S4, S5, RS4, or RS5 alters how your turbocharger(s) breathe and how the engine sounds under load. However, intake performance relies on more than simply exposing a filter in the engine bay. Intake geometry, filter surface area, construction, and heat management all play a crucial role in delivering the most air to the turbo with the least pressure drop.
At Can Auto Performance (CAP), we engineer intake systems using our own Audi development vehicles. This guide explains the mechanical differences across the EA839 engine family, how we evaluate factory hardware, and the practical ownership details required to make an informed upgrade decision for your specific build.
Quick Answer: Is a B9 Audi Intake Worth Upgrading?
Yes. On the B9/B9.5s, an intake is one of the first mods worth doing, and it pays off whether you stay stock or tune later.
- Sound: The factory intake is designed to keep the cabin quiet. An open-filter intake dramatically amplifies the sound of the turbo spooling and air pulling into the engine.
- Airflow: An open-filter intake reduces restriction ahead of the turbo, so the engine breathes easier on the stock tune and has more headroom for when you add one.
Understanding the 3.0T and 2.9T Intake Systems
The B9 S4 and S5 use Audi's 3.0T EA839 V6 with a single twin-scroll turbocharger. The RS4 and RS5 use the 2.9T EA839 V6 with two turbochargers, one serving each cylinder bank.
Both engines feature Audi's Hot-V architecture, with the turbos mounted inside the V, but their turbo layouts differ, so turbo inlets are engine-specific. The intake itself is shared.
Factory B9 S4/S5 Intake Design and CAP Development
Audi designed the factory B9 S4/S5 intake to balance filtration, airflow, packaging, durability, and noise. It uses an enclosed airbox with a cylindrical pleated filter (Audi Part No. 8W0133843) and molded plastic tubing.
As airflow demand increases, resistance throughout the intake path becomes an important consideration. Pressure losses depend on the complete system, including the filter, tubing, transitions, and turbo inlet.
CAP developed the V2 Intake using 3D engine-bay scanning and Computational Fluid Dynamics (CFD) analysis to evaluate the factory intake geometry and engine-bay tolerances, and to identify opportunities for improvement.
Shown: CAP V2 Intake, reinforced silicone version with 8-inch filter.
A properly designed intake creates as little total pressure drop as possible. As the turbo pulls air in, the air speeds up and its static pressure drops. That part is unavoidable. A poorly designed intake adds to it through wall friction, sharp inlet entries, abrupt bends and transitions, sudden area changes, and obstructions.
Our CFD analysis shows a smooth, organized airflow path from the filter to the turbo inlet, with no major restrictions along the way.
Thermal Considerations
An upgraded intake exists to get more air to the turbo with less restriction. Air temperature matters too: hotter air is less dense, so the same volume carries less air.
When the car is moving, the fresh-air duct feeds cooler outside air to the filter. Heat becomes a factor when the car is stopped and the intake can heat-soak in a hot engine bay. The CAP V2's heat shield, with integrated weather stripping, separates the filter from that hot engine-bay air.
For the tube, reinforced silicone insulates against engine-bay heat. Titanium's thin wall stores very little heat, so it recovers quickly from heat soak once air starts moving. Add its strength-to-weight ratio, corrosion resistance, and resistance to heat-cycle aging, and it's the premium choice for builds that want the best of everything.
CAP Titanium vs. Reinforced Silicone Specifications
To accommodate different build goals, the CAP V2 is available in two distinct material configurations.
| Specification | Titanium (Phoenix / Ghost) | Reinforced Silicone |
|---|---|---|
| Filter | 7-inch CAPFlowMax | 8-inch CAPFlowMax |
| Airflow Entry | Integrated bellmouth | High-flow velocity stack |
| Construction | Titanium | Reinforced silicone |
| Finish | Phoenix / Ghost | Black silicone |
| Key Distinction | Metal construction, bellmouth, appearance | Flexible reinforced construction, insulating material properties |
| Inlet Compatibility | Factory / CAP V2 Inlet (3.0T) | Factory / CAP V2 Inlet (3.0T) |
Both versions are the same CAP V2 Intake: same fitment, same heat shield, same fresh-air duct feed, and engineered to the same performance target. The titanium version's 7-inch filter pairs with an integrated bellmouth, while the silicone version's 8-inch filter pairs with a separate velocity stack, so each reaches that target through its own geometry.
Understanding Filter Sizing and Geometry
A bigger number on the filter doesn't automatically mean more airflow. What matters is the total filter media area, how smoothly air transitions from the filter into the tube, and the restriction in the rest of the system.
The choice comes down to your build: titanium for a more durable construction, low weight, and premium looks, or reinforced silicone for its insulating properties against engine-bay heat.
Performance: Stock, Tuned, and Hybrid Turbos
How much an intake does for you depends on your hardware and where your build is headed.
- Stock ECU: The most noticeable change is the sound: more turbo spool and induction noise. The factory ECU controls boost to a target, so with less restriction ahead of it, the turbo doesn't have to work as hard to hit that target. Measurable horsepower gains on a stock tune depend on the car and conditions.
- Stage 1 and Stage 2: A tune raises how much air the engine demands, and all of it has to pass through the intake first. Pressure drop climbs faster than airflow, so the restriction the stock tune barely notices starts to matter once the car is tuned.
- Upgraded Turbos: The CAP V2 Intake is designed for factory-sized turbo inlet connections, and pairs with the CAP V2 Turbo Inlet on 3.0T cars. Many hybrid turbos and aftermarket inlets change the inlet size. If you're running or planning one, confirm the inlet connection matches before ordering, or check with us first.
Installation Process and Tools
Installation is completely bolt-on and utilizes the factory lower airbox mounting points. The process typically takes 45 to 60 minutes. You will generally need standard metric sockets, Torx bits, and a ratchet.
Reconnect any hoses disconnected during installation, and verify all intake connections are properly seated and secured before starting the engine.
Real-World Sound Expectations
Swapping the enclosed factory airbox for the CAP V2 brings out more turbo spool and induction sound under load. When you lift off the throttle quickly, you'll also hear the diverter valve working. Audi's system routes pressurized air back into the intake instead of venting it, so don't expect the loud, atmospheric hiss of a traditional blow-off valve. Instead, you get a softer whoosh, and depending on when you lift off, a light turbo flutter.
Frequently Asked Questions (FAQ)
Does an aftermarket intake void my Audi warranty?
In the U.S., no. Under the Magnuson-Moss Warranty Act, a dealer may not deny warranty coverage unless it can show the aftermarket part caused the need for repairs. Even then, the rest of your warranty stays in effect.
Will the CAP V2 Intake cause a Check Engine Light?
No. The B9 measures engine load with pressure sensors after the turbo, not an airflow sensor in the intake, so swapping the intake doesn't affect the ECU's air calculation. Make sure every connection is fully seated and clamped.
Do I need an ECU tune to run the CAP V2?
No. It's plug-and-play on the factory ECU. Its benefit grows as you tune, because higher airflow makes intake restriction matter more.
Does the CAP V2 Intake fit the B9 S4/S5 and RS4/RS5?
Yes. The same intake fits the B9 and B9.5 S4, S5, RS4, and RS5. Only the turbo inlets differ between the 3.0T and the 2.9T.
Should I get titanium or reinforced silicone?
Titanium for its welded pie-cut construction, integrated bellmouth, low weight, and premium Phoenix or Ghost finish. Reinforced silicone for its insulation against engine-bay heat, and it doubles as its own coupler. Both fit the same cars.
Why does the titanium version use a smaller filter?
Filter size alone doesn't set airflow. Total media area and how smoothly air enters the tube matter more. The titanium version's 7-inch filter is designed around its integrated bellmouth.
Will an open filter pull in hot engine-bay air?
The CAP V2 is fed by the factory fresh-air duct, and its heat shield, with integrated weather stripping, separates the filter from hot engine-bay air. Like any intake, factory airbox included, it can heat-soak when the car sits.
Will the CAP V2 Intake lower my logged IATs?
Not by much. The IAT sensor your logs read is after the intercooler. If lower logged IATs are the goal, upgrade the intercooler.
What does the CAP V2 Intake sound like? Will it flutter?
Expect more turbo spool and induction sound, plus a softer whoosh from the diverter valve when you lift off. Depending on when you lift off, you may also hear a light turbo flutter. It won't sound like a blow-off valve, because Audi's system recirculates the air instead of venting it.
Does it work with the CAP V2 Turbo Inlet or a hybrid turbo?
It pairs with the CAP V2 Turbo Inlet on 3.0T cars. It's designed for factory-sized turbo inlet connections, so if a hybrid turbo or aftermarket inlet changes the size, confirm the fit before ordering.
Select Your Intake
Choosing the right intake comes down to matching your aesthetic preferences and build goals with the correct hardware. Explore the configurations and upgrade your EA839 engine today:
Shop the CAP V2 Performance Intake for B9/B9.5 Audi S4, S5, RS4, and RS5
