Audi S3 8V tuning: Stage 1 to Stage 4 explained

Power by stage

Peak engine horsepower claimed by the tuners, on the best fuel each file supports (up to E85 where offered). Real results depend on fuel, weather and the individual car.

Stock292 hp

Stage 1357–381 hp Stage 2372–397 hp Stage 3470–536 hp Stage 4550+ hp

Software only

+65 to +89 hp

A new calibration flashed to the factory ECU through the OBD port, with no parts needed. The S3 shares its tune files with the Golf R Mk7 and the TTS, so you get the same big first step.

Stage 1 tunes compared

Brand	Fuel	Claimed power	Claimed torque	Notes
APR Stage 1	91–100 US / 95–104 RON	357–381 hp	349–392 lb-ft	Low-torque files for the stock 6-speed S tronic or stock clutch
APR Plus	91 US / 95 RON	357 hp	349 lb-ft	Stage 1 with APR's limited powertrain warranty
Unitronic Stage 1 / 1+	Multiple	See brand page		Can be flashed at home with UniCONNECT+
Integrated Engineering	Multiple	See brand page		Octane-specific files
034Motorsport	Multiple	See brand page		Software plus a full hardware range from the same company
EQT	Multiple	See brand page		Custom tunes, popular for bigger turbo builds later on

Recommended with Stage 1

Gearbox (TCU) tune recommended APR Unitronic IE
APR notes its full-torque file may need an upgraded clutch or its TCU upgrade to avoid clutch slip. A gearbox tune raises clutch clamping and sharpens shifts.
Colder spark plugs recommended APR
Tuners recommend a colder heat range with a tighter gap to prevent misfires at higher boost.

Before you buyCheck which S tronic gearbox your car has, 6-speed or 7-speed, before choosing a file. The 6-speed is the one that needs a low-torque file or a gearbox tune.

Software plus breathing parts

+80 to +105 hp

Stage 2 opens up the exhaust after the turbo with a downpipe and runs a file written for it. The S3 uses the same all-wheel-drive downpipe as the Golf R, and there are cat-back and turbo-back systems made specifically for the S3.

Stage 2 tunes compared

Brand	Fuel	Claimed power	Claimed torque	Required hardware
APR Stage 2	Multiple	372–387 hp	367–409 lb-ft	Downpipe (see APR)
Unitronic Stage 2	93 US / 98 RON	397 hp	368 lb-ft	AWD downpipe; Stage 2 DSG software on S tronic cars

Parts list

Downpipe with high-flow catalytic converter required APR Unitronic IE CTS Turbo 034Motorsport AWE Tuning Milltek Sport
Buy the AWD version, the same one the Golf R uses. Choose one with a catalytic converter to stay road legal.
Gearbox (TCU) tune required Unitronic APR IE
Unitronic's Stage 2 file requires its Stage 2 DSG software on S tronic cars.
Intake system recommended APR Unitronic IE RacingLine 034Motorsport Eventuri Neuspeed
Most intakes are shared across the MQB family, so the Golf R and S3 use the same parts.
Intercooler upgrade recommended Wagner Tuning APR Unitronic CTS Turbo Mishimoto Forge Motorsport
The IS38 makes more heat than the smaller turbos, so the stock intercooler heat-soaks sooner.
Charge pipe and turbo inlet recommended Unitronic IE CTS Turbo Mishimoto Forge Motorsport
The factory plastic charge pipe is a known weak point at higher boost.
S3 cat-back or turbo-back exhaust optional Unitronic AWE Tuning Milltek Sport
Mostly sound. Make sure the system is made for your body style, Sportback, saloon or cabriolet.

Before you buyOnly buy catalysed downpipes. Catless ("race") downpipes break emissions laws in most countries and fail inspection.

Bigger turbo and fuel system

up to +244 hp

The S3 already has the IS38, so Stage 3 means a hybrid or big turbo plus more fuel. APR's Stage 3+ file claims 470–536 hp and 425–474 lb-ft with its EFR7163 turbo and fuel upgrade. This is where you start to reach the limits of the stock connecting rods.

Stage 3 tunes compared

Brand	Claimed power	Claimed torque	Required hardware
APR Stage 3+	470–536 hp	425–474 lb-ft	APR EFR7163 turbo, plus port injection and low-pressure pump (US) or low- and high-pressure pumps (rest of world)
Integrated Engineering Stage 3	up to 490 hp	up to 493 lb-ft	Turbo and supporting hardware per IE

Parts list

Hybrid or big turbo required APR EFR7163 TTE Pure Turbos IE
IS38-frame hybrids keep the factory look and fit; big-frame kits make more power at the top end.
Fuel system upgrade required APR BAR-TEK IE CTS Turbo Autotech
Port injection and/or upgraded fuel pumps. The stock direct-injection system can't supply enough fuel at this power, especially on ethanol.
Turbo-specific tune required APR IE EQT
The file must match your exact turbo and fuel setup.
DSG clutch packs or upgraded clutch required APR (TCU tune)IE (TCU tune)Dodson (DSG clutch packs)South Bend Clutch
Stock clutches can't hold this torque, even with a gearbox tune.
Intake, downpipe, intercooler required From Stage 2
All Stage 2 breathing parts carry over.

Before you buyAt the top of this range you are close to what the stock rods are known to survive. If you think you'll want more later, do the Stage 4 bottom end now, while the engine is already being worked on.

Forged engine, big turbo

550+ hp

The EA888 Gen 3's stock rods are often cited as surviving around 500 wheel horsepower, but one lean spike can break them much sooner. With quattro all-wheel drive the S3 can put this power down, so this is where serious S3 builds go: forged bottom end, big turbo, full fuel system and a custom tune. A bottom-end build costs roughly $2,000–3,000; a rod through the block is a $5,000–8,000 repair.

Parts list

Forged pistons and steel connecting rods required IE JE Pistons Wiseco BAR-TEK kit
The same parts as the GTI, since both use the EA888 Gen 3. Choose compression ratio with your tuner.
Rod bolts and head studs required BAR-TEK IE
Keeps the head sealed and the rods together under high cylinder pressure.
Big-frame turbo required TTE Pure Turbos CTS Turbo
For a 2.0 litre engine, compressors in the 58–66 mm range are the usual sweet spot.
Full fuel system for E85 required BAR-TEK IE CTS Turbo Autotech
Port injection, upgraded pumps and injectors. Running lean is how built engines break.
Custom dyno tune required EQT IE Unitronic
The factory ECU can be flash-tuned to around 600–650 wheel horsepower; beyond that, builders move to a standalone ECU.
Gearbox, cooling and driveline required BAR-TEK Wagner Tuning Dodson (DSG clutch packs)Mishimoto
DSG clutch packs, oil cooler and a bigger intercooler. Check the rear driveline and brakes too.

Before you buyStage 4 is an engine build, not a bolt-on. Choose one shop to build, tune and stand behind the whole package.

Questions to ask the shop

Which exact file will you flash, and for which fuel octane?
Is my car on the 6-speed or 7-speed S tronic, and does it need a TCU tune at this power?
Is it an off-the-shelf file or a custom tune on your dyno?
Will you log the car after tuning and show me the results?
Can the tune be returned to stock, and what does that cost?
Are all exhaust parts catalysed and road legal where I live?