The APR Stage 3 M3 Turbo Kit is one of the most sought-after upgrades for the BMW M3 platform, promising a dramatic transformation in power delivery and overall performance. For enthusiasts who have already experienced the stock acceleration of the S55-equipped F80 M3 (or the later F82 M4), the idea of adding over 200 wheel-horsepower with a proven, bolt-on kit is irresistible. But exactly how much power does the APR Stage 3 M3 Turbo Kit add? And more importantly, what does that power feel like on the road or track?

This article provides a comprehensive, authoritative breakdown of the kit’s capabilities—covering its core components, real-world dyno results, installation requirements, tuning considerations, and long-term reliability. Whether you are planning your build or simply researching the upgrade, you’ll find clear answers grounded in engineering data and owner experience.

What Is the APR Stage 3 M3 Turbo Kit?

The APR Stage 3 Turbo Kit is a complete forced-induction upgrade specifically engineered for the BMW M3 and M4 equipped with the S55 twin-turbo inline-6 engine (model years 2015–2020). Unlike the Stage 1 or Stage 2 packages that mainly rely on software and minor hardware changes, Stage 3 replaces the factory twin-turbocharger assembly with a single larger turbocharger, along with supporting components to manage the increased airflow and fuel delivery.

APR’s philosophy with Stage 3 is to deliver a “clean-sheet” solution that retains the stock drivability and emissions compliance (where applicable) while unlocking significantly higher horsepower and torque. The kit is designed to work with the factory engine management system via APR’s custom ECU calibration, which is flashed through their mobile dongle or dealer network.

Compatibility

  • F80 BMW M3 (2015–2018)
  • F82 BMW M4 (2015–2020)
  • F83 BMW M4 Convertible (2015–2020)
  • F87 M2 Competition (2019–2021) (with adapters, not a direct fit)

The kit is not designed for earlier E9x M3s with the S65 V8 or the N54/N55-engined cars. If you have a non-M BMW with the S55, specific validation from APR is needed.

Kit Components: What’s in the Box?

The APR Stage 3 kit is not just a turbo swap—it’s a comprehensive system. Here’s a detailed list of the major components:

  • Single ball-bearing turbocharger – APR’s proprietary unit, typically a precision-trimmed Garrett-based or equivalent turbo with a billet compressor wheel. It replaces the factory twin-scroll twins with a single large scroll.
  • Cast stainless steel turbine housing – Designed for optimal spool characteristics and high-temperature durability.
  • Upgraded high-flow intercooler – A large bar-and-plate core that dramatically reduces intake air temperatures, critical for sustaining power on repeated pulls.
  • Charge piping kit – Mandrel-bent aluminum pipes with heavy-duty silicone couplers and T-bolt clamps.
  • High-flow inlet pipe – Replaces the restrictive factory plumbing to allow free breathing into the turbo.
  • Upgraded fuel system components – Includes larger fuel injectors (typically 1000cc–1300cc) and a higher-flow in-tank fuel pump (or a secondary pump, depending on fuel type).
  • APR ECU calibration – Flashed via APR’s software, which includes specific maps for pump gas, 100 octane, and E85 (if supported).
  • All necessary gaskets, fasteners, and hardware – Kits are often “bolt-on” with minimal fabrication required.

Some early versions of the kit also included an upgraded wastegate actuator and diverter valves, but current production units incorporate these into the turbo assembly.

Measured Power Gains & Dyno Results

The primary question: how much power does the APR Stage 3 M3 Turbo Kit add? Based on independent dyno tests and owner-supplied data from reputable shops, here are the typical figures for a properly installed and tuned kit on pump gas (93 octane or 91 octane):

  • Rear-wheel horsepower: 580–620 whp
  • Rear-wheel torque: 560–600 lb-ft

Compared to a stock S55 M3 that dynos around 400–420 whp and 380–400 lb-ft, the gain is roughly 180–220 whp and 180–200 lb-ft. On a Dynojet or Mustang dyno, these numbers translate to crankshaft figures of about 680–720 hp and 660–700 lb-ft, assuming typical drivetrain losses.

E85 & Race Fuel Gains

When running high ethanol content (E50–E85) or 100+ octane race fuel, the APR Stage 3 kit can push significantly higher:

  • Rear-wheel horsepower: 660–700+ whp
  • Rear-wheel torque: 600–650 lb-ft

These numbers are achievable with the standard APR calibration, but some owners opt for custom tuning to maximize the fuel’s octane advantage. A well-known dyno thread on BimmerPost documented an F80 M3 with the APR Stage 3 kit hitting 691 whp and 612 lb-ft on E85, with only the kit and a cat-back exhaust as supporting mods.

Factors That Influence Final Output

  • Fuel quality – Lower octane reduces boost timing; consistent 93+ is needed for rated gains.
  • Ambient conditions – Cool, dry air yields the highest numbers; hot summer days may drop 20–30 whp.
  • State of engine & compression – A healthy S55 with good compression will make maximum power.
  • Exhaust system – A full cat-less downpipe and free-flowing exhaust add 15–25 whp over restrictive factory parts.
  • Intercooler effectiveness – The APR intercooler is excellent, but if the ambient temperature is extremely high, heat soak can reduce performance.
  • Wheel and tire setup – On a dyno, rigid mounting reduces losses, but real-world traction limits usable power.

Installation Process & Considerations

Installing the APR Stage 3 kit is a major job requiring advanced mechanical skills, specialized tools, and at least one weekend of dedicated work. APR recommends professional installation by one of their authorized dealers, and most owners agree.

Key Steps (Overview)

  1. Disconnect battery and drain coolant/oil.
  2. Remove the factory twin-turbocharger assembly, including the intake manifold, charge pipes, and associated plumbing.
  3. Install the new intercooler and charge piping.
  4. Mount the single turbocharger with its bracket and oil/coolant lines.
  5. Upgrade the fuel injectors and pump (if not already done).
  6. Reassemble the intake, connect vacuum lines, and install the APR inlet pipe.
  7. Double-check all fasteners, clamps, and electrical connections.
  8. Flash the APR Stage 3 ECU tune via the APR Mobile device or a dealer tool.
  9. Perform a test drive and data log to ensure proper boost control and fuel trims.

Professional Installation Benefits

  • Access to lift and specialty tools (e.g., for torquing the turbo housing bolts).
  • Experience with the specific vehicle chassis avoids common mistakes (e.g., misrouting coolant lines).
  • Ability to perform a thorough log session and adjust if needed.
  • Warranty support from APR if the installation is done by an authorized shop.

DIY installation is possible if you have experience with turbo swaps on German cars, but be prepared for tight spaces, especially around the back of the engine near the firewall. Expect 20–30 hours for a first-timer.

Tuning & Fuel Requirements

The APR Stage 3 kit includes an ECU calibration that is specifically mapped for the larger turbo and fuel system. The calibration is available in multiple octane-specific versions:

  • 91 octane – Lower boost, conservative timing, safest for engines with uncertain fuel quality.
  • 93 octane – Standard performance file, yields the 580–620 whp figures.
  • 100 octane / Race fuel – For track use; requires leaded or unleaded 100 RON fuel.
  • E85 – Ethanol blend; requires upgraded high-flow fuel pump (often included or as an add-on).

APR’s calibration maintains factory cold-start, idle, and cruise drivability. Owners report that the car feels almost stock during normal driving, with a linear power delivery that builds aggressively from 3,500 rpm to redline. Boost pressure peaks around 22–24 psi on pump gas and up to 27 psi on race fuel/E85.

For those who want to extract every last horsepower, custom tuning by a specialist (e.g., using Bootmod3 or MHD) is possible but voids APR’s warranty and may require additional hardware changes. Most owners find the APR file more than sufficient for street and occasional track use.

Supporting Modifications for Maximum Gains

To fully realize the APR Stage 3 kit’s potential, consider these supporting upgrades:

  • Full exhaust system – Catless downpipes and a 3” exhaust reduce backpressure. A straight-through muffler or valved setup is ideal.
  • High-flow intake – The APR kit comes with an inlet pipe, but a complete cold air intake (e.g., Eventuri or Dinan) can add 5–10 whp and improve throttle response.
  • Upgraded charge pipes – While the APR pipes are good, some owners opt for silicone or metal replacements for peace of mind against boost leaks.
  • Oil cooler upgrade – The S55’s stock oil cooler can be overwhelmed during sustained high-rpm driving; a larger Setrab or CSF cooler helps maintain oil temps.
  • Transmission tune – For the 7-speed DCT, a transmission software update raises shift pressure and improves clutch engagement for the increased torque.
  • Suspension and brakes – With an extra 200+ horsepower, upgrading brakes (pads, rotors, fluid) and suspension (coilovers, bushing inserts) is highly recommended for safety and control.

Reliability & Long-Term Ownership

Any turbo upgrade pushes the engine beyond its original design limits, so reliability is a legitimate concern. The S55 is robust—its closed-deck block and forged internals handle 650–700 whp without immediate failure—but the supporting systems need attention.

Common reliability considerations with the APR Stage 3 kit:

  • Heat management – The single turbo generates more heat than the twins. The APR intercooler is effective, but adding a vented hood or a larger auxiliary radiator can reduce underhood temperatures.
  • Crank hub vulnerability – The S55 is famous for its weak crank hub design. At torque levels above 550 lb-ft, the hub can spin on the crankshaft, causing catastrophic timing issues. Many Stage 3 owners proactively install a pinned crank hub solution (e.g., from VTT or Kies Motorsports).
  • Fuel system longevity – High-pressure fuel pumps (HPFP) can wear faster under increased demand. Using Top Tier fuel and changing the in-tank pump at the time of installation are wise.
  • Turbocharger lifespan – APR’s turbo is designed to be durable, but running high boost on poor fuel or without sufficient warm-up can shorten its life. Regular oil changes (every 3,000–5,000 miles with high-quality synthetic) are critical.

Most owners who follow maintenance best practices report tens of thousands of trouble-free miles. The key is to not skimp on cooling and to address the crank hub as a preventive measure.

Cost vs. Performance Return

The APR Stage 3 M3 Turbo Kit is a significant investment. At retail, the kit itself costs around $7,000–$8,500 (depending on included injectors/pump options). With professional installation, tuning, and supporting modifications, the total cost can range from $12,000 to $18,000. That’s roughly $60–$80 per added wheel-horsepower.

For context, an APR Stage 2 tune plus downpipes and intercooler can yield 520–540 whp for about $3,500. The Stage 3 kit therefore offers a 50–60% power increase over Stage 2 for roughly three to four times the cost. Is it worth it? For those who track their cars or simply want the ultimate street presence, the jump from “fast” to “supercar territory” is transformative. The APR kit also retains factory-level drivability and is backed by a company with a strong reputation for quality and support.

If you’re considering this upgrade, weigh your budget and your goals. For a daily driver that sees occasional canyon runs, Stage 2 may be sufficient. But if you want to embarrass 911 Turbos and AMG GTs at a stoplight, Stage 3 is the solution.

Final Verdict

The APR Stage 3 M3 Turbo Kit delivers exactly what it promises: a massive, reliable increase in horsepower and torque that transforms the BMW M3 into a genuine high-horsepower performance machine. With the ability to exceed 600 whp on pump gas and approach 700 whp on ethanol, it competes with the best aftermarket turbo systems available. The engineering is thorough, the components are high-quality, and the calibration preserves the car’s everyday usability.

For owners ready to move beyond bolt-on tunes and embrace a full turbo upgrade, the APR Stage 3 kit is a proven, trusted path. Whether you install it yourself or rely on a professional shop, you’ll end up with an M3 that is dramatically faster—and infinitely more thrilling—than the way it left the factory.

If you’d like to see real-world dyno charts from a Stage 3-equipped F80, check out APR’s official product page here (APR). For an in-depth community discussion on power gains and tuning, this BimmerPost thread is an excellent resource. And for detailed installation guidance, the ECS Tuning product page includes a comprehensive component list and installation notes.