The B9/B9.5 S4 and S5 are Audi's first venture back into a turbocharged compact S-platform since the B5 S4, and they did not disappoint. With a 3-litre displacement and a single turbo "hot-v" configuration, Audi modernized their S car while keeping packaging tight and allowing lots of room for improvement.


The EA839 is a replacement for the EA837 Supercharged engine, using a single turbocharger (or twin turbos in the case of the RS4/RS5) and reverse-flow cylinder heads with integrated exhaust manifolds instead of the supercharged configuration of the previous generation. What this means for you is more efficient power, less heat, and much more potential for upgrades!


What follows is our recommendations based on hundreds of in-house builds of all shapes and sizes and years of tuning and development. The upgrades in this guide are used by us on a weekly basis and are recommended/required by almost every tuning company currently providing software for the EA839. RS owners - follow along, as most of these upgrades still apply to you.


For all stages and custom tuning, we recommend Jackal Motorsports - their calibrations are dialed in specifically for these platforms, and we trust them with our own builds. That said, any reputable tune will get the job done.

 


Stage 1 - The Foundation

Expected output: 400-490HP / 460-600TQ

 

 

Stage 1 is the best bang-for-buck move you'll ever make on this platform. A flash alone wakes the 3.0T up dramatically with a broader powerband, more boost, a higher rev limit, and 0-60 times that'll have you grinning. Gains of anywhere from 50 to 150 hp are on the table depending on fuel, with E85 blends delivering the biggest gains for anyone with access to it.

 

What you'll need:

 

Optional:

 

The tune is the only requirement for Stage 1. That said, an intake and turbo inlet are the two upgrades we'd never skip. They're not just for show - the factory airbox is a restriction, and opening it up earns real power and torque while dropping the pressure ratio across the compressor wheel, which takes stress off the turbo. The soundtrack is a bonus: proper spool and that intoxicating blow-off whoosh the B9 hides from the factory.

Who it's for: Every new owner. If you do one thing to your car, do this.

 


Stage 2 - The Sweet Spot

Expected output: 460-510HP / 520-650TQ

 

 

You've lived with Stage 1 for a while, the novelty's worn off, and the car feels tame, maybe even slow. Stage 2 is a straightforward bolt-on step that stacks another 20-60 hp on top of Stage 1 by fixing the two things holding it back: airflow and heat.

 

What you'll need:


Optional: 

 

The downpipe unlocks exhaust flow (and adds a noticeably sportier note), while the intercooler and charge pipes keep intake temps in check so the tune can hold timing and boost when you're leaning on it.

The high-pressure fuel pump upgrade is the one to think hard about here: it's recommended for everyone and effectively required if you're running an ethanol blend, since the stock pump runs out of headroom once you start feeding the motor more air.

To unlock an additional +12HP/+20TQ, our throttle body upgrade is highly recommended.

Who it's for: The daily driver who wants a genuinely quick car and a great sound without opening up the turbo. For a lot of owners, Stage 2 is enough to satisfy their needs.

 


Stage 3 - Hybrid Turbo

Expected output: 560-800HP / 600-750TQ

 

 

This is the biggest jump since going Stage 1. Stage 2 got most of your supporting mods in place; Stage 3 adds the one thing the stock turbo simply can't give you - volume. Bolt in a hybrid turbo and you're looking at gains of 250-400 hp over stock, depending on fueling. This is supercar territory in a car that still drives to work on Monday.

 

What you'll need:

 

Optional:

 

Fueling is no longer optional at this stage. The HPFP upgrade and RS injectors are both required. Hybrid turbos move more air than the stock fuel system can keep up with, even on pump gas, and running lean at these power levels is how motors die. Our 4-bar MAP sensors give the tune the range it needs to read the higher boost pressures accurately.

Who it's for: The owner chasing a number, a trap speed, or bragging rights. If you've got the itch and a fuel budget for E85, this is the payoff.

 


Stage 4 - Full Frame/Built Motor

Expected output: 800+hp / 800+tq



This Stage is what separates the boys from the men. Going with a full-frame turbo is a tough choice (especially with the various hybrid turbo options), but one that can easily slot you in the top of your class. We recommend a built engine for this stage, as chasing high power levels and removing the limits and constraints of a typical hybrid turbo setup can quickly stress your bottom end if not kept in check.

Due to the open-ended nature of going Stage 4/Full Frame, you may find the limits of certain components such as the stock plastic EA839 intake plenums (which can crack at higher boost pressures) and the low-pressure fuel pump (LPFP), which can become overwhelmed when running additional port injectors and high ethanol contents.

It's important to note at this stage that the AL552 transmission can show weakness, requiring a trans build if you're prone to launching the car or racing from a dig. We are Pure Drivetrains dealers and offer an 8HP upgrade service for those in need.


What you'll need:
  • GAS Full Frame Turbo Kit (Coming Soon)
  • All Stage 3 upgrades

 

Optional:



Ready to get started?

 

Browse the full B9 S4/S5/RS catalog, or reach out and we'll help you map a build to your budget and goals.

 

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