Audi · C8 · Mod guide

Audi RS6 C8 Mod Guide

In the US, the C8 RS6 is sold only as an Avant, with Audi's 4.0T twin-turbo V8, an 8-speed Tiptronic automatic and quattro. That V8 responds to software in a big way, so the real work is protecting the car, keeping the gearbox happy and getting the chassis to match. This guide covers the order we recommend, what each step does, and what to check before you start.

Covers: Audi RS6 (C8)

Chassis
C8
Years
2021 to 2026
Engine
4.0L twin-turbocharged V8 (EA825)
Transmission
8-speed Tiptronic automatic
Drivetrain
quattro all-wheel drive
Stock power
591-621 hp / 590-627 lb-ft

Before you buy

  • Check which suspension your car has

    Every US RS6 comes standard with RS adaptive air suspension. Dynamic Ride Control (DRC) with steel springs was an option, and the 2025 RS6 Avant GT has its own adjustable coilovers. The coilovers and spring kits we carry for the C8 are built for DRC cars only, so check your window sticker or build sheet, or send us your VIN, before choosing suspension.

  • Know your model year and output

    2021 to 2023 US cars are the 591 hp RS6 Avant. 2024 and later cars are the 621 hp RS6 Avant performance, and the limited 2025 GT is also rated at 621 hp. Some parts change by year, for example the Unitronic intake needs a PCV adapter on 2023 and later cars, so check the fitment notes on every product page.

  • Plan for the transmission

    The 8-speed Tiptronic handles a Stage 1 tune well, but tuners such as Unitronic report torque limits in the transmission software at higher power levels. Bigger builds need a transmission (TCU) tune, and 034Motorsport notes that 2022 and later cars need an extra harness to flash the TCU. Budget for it before you chase big numbers.

  • Sort out maintenance and recalls first

    A tune makes existing problems worse. Get any open recalls done, catch up on oil changes and spark plugs, and fix any warning lights before adding power. You can check your VIN for open recalls at nhtsa.gov.

  • Check emissions status for your state

    Many intake and exhaust parts for this car are not CARB legal, and downpipes are sold for off-road use only. If you live in California or a state that follows CARB rules, or your inspection checks for modified parts, check each product's emissions status before you order.

Start here

  1. Step 1

    Protect the RS6's oil cooler from road debris with a guard

    The RS6 sits low and wide, and the openings in the lower front bumper leave the coolers behind them exposed to stones and road debris. A guard puts a sturdy mesh in front of the oil cooler so a highway rock chip doesn't turn into a leak. It's cheap insurance, and it comes first because everything else on this list adds heat and load.

    Fitment can vary with bumper and grille styles, so check the fitment notes for your model year and trim before you order.

  2. Step 2

    Free up the RS6's V8 sound with a midpipe

    A midpipe replaces the factory resonators between the downpipes and the cat-back, so the 4.0T V8 gets louder and rawer, especially on a cold start and at full throttle. Expect more volume everywhere and some drone at highway speed. It's mostly a sound upgrade, with any power gain coming once the car is tuned.

    European RS6s carry a particulate filter (OPF/GPF), but tuners such as APR and CTS Turbo list North American cars as non-OPF, so US cars don't need an OPF delete and should use US or non-OPF versions of exhaust parts. A midpipe keeps the factory catalytic converters, but many aren't CARB legal, so check your state's inspection rules. The Akrapovic link pipe set is designed to pair with the Akrapovic Evolution Line cat-back.

  3. Step 3

    Take control of the RS6's exhaust valves

    The RS6's exhaust uses electronically controlled valves, and the car decides when they open based on drive mode and load. A valve controller lets you open or close them on demand: quiet for an early start in the neighborhood, open for a back road. It pairs well with a midpipe or cat-back, since it lets you pick when you hear the extra volume.

    Choose a controller that is listed for the C8 RS6 and your model year, and keep the factory parts in case you need to return the car to stock for service.

  4. Step 4

    Add a carbon intake and turbo inlets to the 4.0T

    The factory airbox and inlets on the 4.0T are built for quiet running. A carbon intake with larger turbo inlets lets the engine breathe easier and makes the turbos much easier to hear. On a stock car the gain is modest. Unitronic claims up to 58 hp and 54 lb-ft for its intake and inlets on its Stage 2 93 octane software, so the real payoff comes with a tune.

    Unitronic says 2023 and later cars need its PCV adapter to fit its intake, so check the fitment notes for your year. Most intakes for this car aren't CARB legal, so check the emissions status if you live in California or a state that follows CARB rules.

  5. Step 5

    Match RS6 coilovers or springs to your air or DRC setup

    Lowering the RS6 tightens up body control and closes the wheel gap, but the right part depends on which suspension your car has. Every US RS6 comes standard with RS adaptive air suspension. Dynamic Ride Control (DRC), with steel springs and linked dampers, was an option, and the 2025 GT has its own adjustable coilovers.

    The coilovers and springs in this step are for DRC cars only. The KW V4 coilovers are listed for cars with DRC, the H&R RSS+ coilovers and H&R Sport Springs for RS Sport Suspension plus with DRC, and the KW H.A.S. kit for cars without air suspension. Retailers list the H&R height-adjustable (VTF) springs for RS Sport Suspension plus with DRC as well. None of these fit an air suspension car, so if yours has air, talk to us before ordering. Get an alignment after any ride height change.

  6. Step 6

    Tune the RS6 4.0T and respect the 8-speed's torque limits

    Software is the biggest single upgrade on the 4.0T, and we put it last so it can be matched to the parts you've already fitted. The NEUSPEED Power Module EVO plugs in alongside the factory ECU with no flashing, and NEUSPEED claims +70 hp on the RS6 C8. A full ECU flash goes further and lets the tuner calibrate for your intake, exhaust and fuel.

    The 8-speed Tiptronic is the limit to watch. Unitronic reports transmission software torque limits at higher outputs and requires its TCU software for Stage 3, and 034Motorsport notes 2022 and later cars need an extra harness to flash the TCU. Run the octane your tune is built for, keep up with spark plugs and oil changes, and check emissions status, since NEUSPEED lists the module as CARB EO pending.

Known issues

  • Rearview camera recall (NHTSA 25V900)

    Audi recalled 2021 to 2026 RS6 Avants because the rearview camera image may not display. The fix is a free software update at the dealer. Check your VIN at nhtsa.gov and get it done before your next service.

  • Gateway module and reduced power mode (NHTSA 22V861)

    On 2021 and 2022 cars, the gateway module sits under the rear seat, and a spilled drink can short it and put the car into reduced power mode. Audi's fix is a protective cover. If your car falls in this range, make sure the recall has been done.

  • Big wheels and curb damage

    The RS6's huge brakes mean 21 inches is the smallest wheel that clears, and the optional 22s are easy to curb. That also limits winter tire choices, so plan your wheel and tire setup around it.

  • PCV changes on 2023 and later cars

    Unitronic notes that 2023 and later RS6s need its PCV adapter to fit its intake system. If you're shopping for intake parts, check that they're listed for your exact model year.

Supporting mods

  • Intercooler upgrade

    A tuned 4.0T makes a lot more heat, and when intake temperatures climb the engine pulls timing to protect itself. Upgraded intercoolers from CSF and Wagner Tuning help keep power consistent on hot days and back-to-back pulls.

  • Downpipes (off-road use only)

    Downpipes pair with Stage 2 software and bigger turbos, and they make the car much louder. They replace the factory catalytic converters, so they're sold for off-road use only and won't pass an emissions inspection.

  • Spark plugs and ignition coils

    Fresh, correctly gapped plugs and strong coils keep the spark clean at higher boost. APR's plugs and coils for the EA825 are a cheap way to keep a tuned car running smoothly.

  • Brakes

    More power needs more stopping. Performance pads, stainless lines and fresh high-temperature fluid are the first upgrade for spirited driving or track days. Check whether your car has the steel or carbon ceramic brakes before ordering pads.

  • Gauges and monitoring

    A digital display such as the Wagner Tuning MFD28 shows boost, temperatures and other live data in real time. It's the easiest way to spot a problem early on a modified car.

  • Bigger turbos

    Once the factory turbos run out of headroom, upgraded turbos such as the PURE900 take the 4.0T further. They need the intake, intercooler and downpipe upgrades above, plus matching engine and transmission software.

FAQ

Do I need a transmission (TCU) tune?

Not for a mild Stage 1. APR says its engine software makes full torque without a TCU upgrade. At higher outputs, Unitronic reports torque limits in the transmission software and requires its TCU tune for Stage 3. A TCU tune also sharpens shifts and launch control.

Does my US RS6 have a particulate filter?

European RS6s use a gasoline particulate filter (OPF/GPF). Tuners such as APR and CTS Turbo list North American cars as non-OPF, so US owners should buy the US or non-OPF version of exhaust parts and don't need an OPF delete.

Will a tune void my warranty?

In the US, a manufacturer can't void your whole warranty just because you installed aftermarket parts, but it can deny a claim if it shows a part caused the failure. Expect engine and transmission claims on a tuned car to get a closer look.

Which suspension parts fit my car?

It depends on whether your RS6 has the standard air suspension or the optional DRC setup. The coilovers and springs in this guide are for DRC cars only. Check your build sheet, or send us your VIN and we'll confirm.

Which fuel should I run?

Most tunes come in 91 and 93 octane versions, and 93 makes more power. Ethanol blends can make more still, but they need software built for them, so stick to what your tune calls for.

Do RS7 parts fit the RS6?

The C8 RS7 shares the 4.0T, transmission and much of the chassis, so a lot of engine and drivetrain parts are listed for both. Body, exhaust and suspension parts can differ, so always check the fitment on the product page.

What order should I do mods in?

Protect the oil cooler first, then add a midpipe and valve controller for sound, an intake, and suspension. Tune last, so the software can be matched to the parts you've fitted, and add a TCU tune before you push past Stage 1.

Shop all Audi RS6 (C8) parts

Last reviewed October 31, 2026