Audi B9 S5 Build Guide: How We Hit 650HP on a Budget
When I first picked up my Audi B9 S5 Sportback, it was a solid daily driver making around 3543 horsepower from the factory 3.0T V6. Fast forward to today and this thing is pushing over 650 wheel horsepower while still being used as my daily. Here is a breakdown of every mod we did, what it cost, and what we would do differently.
Stage 1: The Tune and Intercooler (350 to 450HP)
The very first thing we did was install the intercooler and flash an ECU tune. The B9 3.0T responds incredibly well to software alone. With just a Stage 1 ECU tune, we picked up roughly 100 horsepower, and the car felt like a completely different machine. The turbo spool came on earlier, the power band was wider, and shifts became noticeably crisper. If you only do one mod to your B9 S5, make it a tune. We went with our partners at Achtuning for the flash, and the experience was seamless.
Stage 2: Downpipes and Intake (450 ish HP)
Next up was the hardware to support Stage 2. We installed catless downpipes and an upgraded cold air intake from Integrated Engineering. The downpipes let the turbo breathe freely on the exhaust side while the intake fed it more air up front. Combined with a Stage 2 ECU recalibration, the car was now making around 500 horsepower. The exhaust note also got noticeably more aggressive which was a nice bonus. Use code ItspronouncedVAGuh2026 at performancebyie.com to save on IE parts.
Stage 3: Turbo Upgrade and Supporting Mods (450 to 650HP)
This is where things got serious. To break past the 500 horsepower ceiling on the stock turbo, we went with a hybrid turbo upgrade. Along with that came upgraded intercooler piping, a larger intercooler, high-flow fuel injectors, and upgraded spark plugs. The supporting mods are crucial at this power level because the stock turbo is maxed out and heat management becomes a real concern. We also added ROWE motor oil to protect the engine under these higher-stress conditions. After the Stage 3 tune was dialed in, we put down 650 wheel horsepower on the dyno. The car still drives like a normal S5 in comfort mode but absolutely rips when you put your foot down.
What We Would Do Differently
If we were starting this build over from scratch, we would have gone straight to Stage 2 hardware from day one instead of running Stage 1 software for months first. The gains from the tune alone are impressive, but you end up paying for labor twice when you go back to install downpipes later. We also wish we had upgraded the intercooler earlier since heat soak was noticeable on hot days even at Stage 2 power levels.
Watch the Full Build Series
We documented every step of this build on our YouTube channel. Head over to youtube.com/vaguh to watch the full S5 build series from stock to 650HP. If you are planning a similar build, drop a comment and let us know what stage you are at. We love hearing from the VAGUH community.
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