The B8 Audi S4 (2009–2016) is revered for its supercharged 3.0T V6 engine, a powertrain that responds exceptionally well to bolt-on modifications. Among the most sought-after upgrades is the CTS Turbo Supercharger Kit, a complete replacement for the factory supercharger system. Enthusiasts want a clear answer: how much horsepower can you realistically expect from this kit on a B8 S4? This article provides a detailed breakdown of the power gains, the factors that affect those numbers, real-world dyno results, and everything you need to know before pulling the trigger.

The B8 S4 3.0T Engine and Its Stock Supercharger Limitations

Before diving into the CTS Turbo kit, it's important to understand what you're starting with. The B8 S4’s 3.0-liter V6 (engine code CAKA / CCBA) features a roots-type Eaton TVS1320 supercharger from the factory. In stock form, Audi rated the engine at 333 horsepower and 325 lb-ft of torque in North American markets, though many dynos show closer to 310–320 whp (wheel horsepower) due to drivetrain losses.

The factory supercharger is efficient for its size and delivers a broad torque curve, but it becomes a bottleneck as you push beyond ~400–420 whp. The Eaton TVS1320 reaches its flow limit and generates excessive heat under sustained boost. The intercooler bricks (air-to-water heat exchangers located inside the supercharger bypass) also become a limiting factor, as they struggle to keep intake charge temperatures in check during aggressive driving.

This is where the CTS Turbo Supercharger Kit enters the picture. It replaces the entire supercharger assembly, including the rotors, housing, and bypass valve, and integrates a much larger dual-pass intercooler core. The result is significantly increased airflow capacity and vastly improved thermal management.

CTS Turbo Supercharger Kit: What’s Included?

The kit is marketed as a "stage 2.5" upgrade, bridging the gap between a simple pulley upgrade and a full twin-turbo conversion. Here’s what you get in the box:

  • CTS Turbo billet supercharger housing – a direct replacement for the OEM housing, machined from 6061-T6 aluminum with larger internal passages and a redesigned bypass channel.
  • High-flow 1600 cc rotors – 15% larger than the stock Eaton TVS1320 lobes, providing a substantial increase in air displacement per revolution.
  • Integral dual-pass intercooler core – replaces the factory heat exchangers with a much larger cooling surface area and more efficient water routing.
  • Upgraded bypass valve – a billet dual-port unit to handle higher boost without leakage.
  • Reinforced drive snout – includes a 191 mm (7.52") pulley that increases boost pressure by ~3.5–4 psi over stock when combined with a proper tune.
  • All necessary gaskets, o-rings, and hardware – the kit is intended to be a direct bolt-on, using factory accessory brackets and belt routing.

The kit is designed to work with the factory ECU, but it absolutely requires a custom tune to realize its potential. Without a tune, the engine will run lean and knock, and the supercharger will not achieve its rated power.

Expected Horsepower Gains: Realistic Numbers

Based on extensive dyno data from tuning shops and owner reports on forums such as Audizine and Audisport.net, let’s break down the horsepower expectations in a clear table:

Configuration Approximate Wheel Horsepower (whp) Approximate Crank Horsepower (chp)
Stock B8 S4 (manual/DSG)310–320 whp333 chp (factory)
Pulley upgrade + Stage 2 tune370–390 whp~420–440 chp
CTS Turbo kit + custom tune (pump gas)440–470 whp500–530 chp
CTS Turbo kit + tune + supporting mods (E85, fueling, exhaust)480–510 whp540–580 chp

On a conservative 93-octane tune, most owners report dyno numbers in the 440–470 whp range. That translates to roughly 500–530 crank horsepower when accounting for approximately 12–15% drivetrain loss on the DSG transmission (slightly more for manual). With ethanol blending (E30–E85) and upgraded low-pressure fuel pumps, some have crept past 500 whp, hitting 570+ crank hp.

These gains are significant – you’re looking at a 60–70% increase in wheel horsepower over the stock engine. The torque numbers are equally impressive, often exceeding 450 lb-ft at the wheels, giving the B8 S4 a power-to-weight ratio that rivals many modern supercars.

Dyno Results from the Community

I scoured multiple dyno threads on Audizine and posts from reputable tuners like 034Motorsport and EPL. Here are three representative examples:

  1. User "QuattroS4" – 2014 B8 S4 DSG: After installing the CTS kit, a 93-octane tune, and a Milltek cat-back exhaust, his car laid down 461 whp and 478 lb-ft on a Mustang dyno. On the same dyno, a stock car baseline was 314 whp. That’s a gain of 147 whp.
  2. User "BoostedB8" – 2013 S4 with CTS kit + E85: Running a custom E85 tune, he saw 498 whp and 521 lb-ft with an APR CPS kit and a lightweight pulley. Air intake was a CTS cold-air intake with a larger filter.
  3. Tuner shop example – 034Motorsport: They tested a B8 S4 with the CTS kit, their own Stage 2+ tune, and a full 3" catless downpipe. On 94 octane, it made 471 whp. With an ethanol blend, it hit 505 whp.

These numbers confirm that the CTS Turbo Supercharger Kit, when paired with a professional dyno tune, consistently delivers over 460 whp on pump gas and can crest 500 whp with race fuel or E85.

Factors That Influence the Final Horsepower Number

The CTS kit itself is a powerful upgrade, but the outcome depends heavily on supporting systems. Here are the key variables:

1. Tuning: The Brain of the Operation

The stock ECU cannot compensate for the extra airflow and boost. A custom tune by a reputable shop (e.g., 034Motorsport, EPL, Unitronic) is non-negotiable. Tunes differ in aggressiveness, timing advance, and fuel mapping. A conservative tune might leave 10–20 whp on the table but provides a safety margin. An aggressive tune, especially with higher-octane fuel, extracts maximum power.

Most tuners offer remote tuning via a handheld device, which is convenient. However, a dyno tune allows for fine-tuning air-fuel ratios and ignition timing across the entire RPM range, often yielding the best results. Expect to spend $500–$1,000 plus dyno time for a proper calibration.

2. Fuel Quality and Octane

Higher octane fuel (93 or 94 RON, or E85) allows more ignition timing without knock. Some regions only have 91 octane; in that case, you will need to back off timing and power. With 91 octane, you may see 420–440 whp rather than 460+. If you have access to E85, you can run significantly more boost and timing, putting you over 500 whp. However, E85 requires upgraded injectors (at least 850cc) and a higher-capacity low-pressure fuel pump. The stock fuel system is marginal past 480 whp.

3. Exhaust System

The factory exhaust manifolds are cast iron and flow fairly well, but the rest of the exhaust is restrictive – especially the downpipes (cats) and the cat-back system. A set of catless downpipes or high-flow catalytic converters can free up 20–30 hp at the top end. An aftermarket cat-back (e.g., AWE Touring, Milltek, or Remus) adds a few more and reduces backpressure. Many owners report that a 3" catless downpipe combined with the CTS kit is the sweet spot.

4. Heat Management and Cooling

The CTS kit includes a larger intercooler core, but the factory auxiliary coolant pump and reservoir can still be overwhelmed during sustained pulls. Upgrading the secondary intercooler pump (e.g., CWA100 or a Bosch pump) and adding a larger heat exchanger (like the one from PLM or CTS Turbo's own auxiliary cooler) helps maintain consistent intake temperatures. With a proper cooling setup, you can do multiple 3rd–4th gear pulls without pulling timing. Without it, heat soak will reduce power by 20–40 hp after the first pull.

5. Air Intake and Inlet Pipes

The factory intake plumbing is adequate, but a larger cold air intake (e.g., the integrated CTS Turbo intake designed for this kit) reduces restriction and provides a small gain (maybe 5–7 hp). The stock airbox is actually pretty good, so this is a minor factor. However, the inlet hose connecting the MAF to the supercharger is often replaced with a silicone hose to prevent collapsing under high boost.

6. Clutch / Transmission Capability

With over 500 ft-lbs at the crank, the factory clutch on manual transmission cars becomes a weak point. DSG gearboxes can hold the torque with a good tune, but the clutch packs may slip if you’re on track frequently. A stage 2 or 3 clutch (e.g., Southbend or Ringer Racing) is recommended for manual cars. For DSG, a tcu tune (like the one from TCU Tuning or 034) improves clamping pressure and shift strategy.

Installation: What to Expect

The CTS Turbo Supercharger Kit is a significant install, requiring removal of the entire stock supercharger assembly. Expect a solid weekend of work if you’re handy, or about 8–12 hours of shop labor. Here is a high-level step-by-step:

  1. Disconnect battery, drain coolant, and remove the air intake, throttle body, and intake manifold.
  2. Remove the serpentine belt and accessory belts.
  3. Unbolt the supercharger from the valley. This requires unbolting four long bolts and lifting the unit out (the factory intercooler bricks come out with it).
  4. Transfer the throttle body and injectors to the new CTS supercharger housing.
  5. Install the new supercharger, torquing the bolts to spec, and reconnect coolant hoses to the intercooler core.
  6. Reassemble intake, belts, and recheck all connections.
  7. Fill coolant, bleed the system, and prime the supercharger by cranking with the fuel pump relay pulled before first start.
  8. Flash the tune and monitor initial idle and boost pressure.

Most importantly, follow the CTS Turbo installation guide precisely. The kit includes high-quality hardware, but you must use a torque wrench – the supercharger is aluminum and delicate. Many owners recommend having a professional install it to avoid gasket leaks or stripped threads. Labor cost is typically $800–$1,500.

Comparison to Other Supercharger Upgrades

How does the CTS kit stack up against other popular upgrades? Let’s compare:

  • Pulley-only upgrade (Stage 2): Adds 50–60 whp for about $500 for a pulley and tune. The CTS kit costs closer to $4,000 (without tune) but provides 130–170 whp. The pulley upgrade is fine if you’re on a budget, but it will still heat-soak quickly. The CTS kit is a better long-term solution for high power.
  • Larger supercharger (e.g., Mercracing 1900 TVS): A 1900cc blower (like the one from Merc Racing) can make 550+ whp with supporting mods, but it costs $6,000+. The CTS kit is a cost-effective middle ground.
  • Twin-turbo conversion: For extreme power (600+ whp), a twin-turbo kit is the ultimate, but it costs $10,000+ and involves far more complexity. The CTS kit is a simpler bolt-on.
  • EPL Ultracharger: This replaces the supercharger with a single turbo mounted in the same location. It’s more expensive ($7,000+), but offers higher top-end power. The CTS kit retains the supercharger character (instant response) rather than the lag of a turbo.

In summary, the CTS Turbo Supercharger Kit is the best price-to-performance upgrade in the B8 S4 community, providing a massive torque curve with minimal compromise in drivability.

Reliability and Longevity Considerations

Pushing a stock engine to nearly double its factory power raises reliability concerns. However, the 3.0T block is robust (closed-deck) and forged rods in most years. The CTS kit does not dramatically increase cylinder pressures if tuned conservatively – 500 whp is within the engine’s physical limits. The weak point is the cooling system and the transmission/clutch. Ensure you upgrade the coolant pump and consider a larger heat exchanger. Also, pay attention to the PCV system – the increased boost can force oil into the intake. Many owners install a catch can.

With professional tuning and proper maintenance (oil changes every 3,000–5,000 miles, spark plugs every 20,000 miles), this kit can be daily-driven reliably. Expect to replace the supercharger oil every 30,000 miles, as CTS recommends. Also, check the belt tension regularly – the larger pulley increases side-load on bearings.

External Resources and Further Reading

Conclusion: Is the CTS Turbo Supercharger Kit Worth It?

If you want a substantial, reliable horsepower increase without going to extremes, the CTS Turbo Supercharger Kit is an excellent investment. On a properly tuned B8 S4 with supporting mods (exhaust, fuel system, cooling), you can expect 450–500 wheel horsepower – a massive step up from the stock 310–320 whp. The kit retains the supercharger’s instant throttle response and works beautifully with the factory DSG or manual transmission (with the appropriate clutch upgrade).

However, be prepared to spend extra on a custom tune, cooling upgrades, and possibly transmission components. No supercharger kit is a standalone solution – the whole car needs to be balanced. With that caveat, the CTS Turbo kit transforms the B8 S4 into a serious performance machine, capable of surprising cars costing twice as much.