The F8X M3/M4 models (2014-2020) didn't just inherit an iconic badge; they turbo-charged it, marking a significant departure from naturally aspirated M-cars of the past. While the S55 engine delivered impressive power out of the box, for many enthusiasts, it was merely a starting point. The quest for more — more horsepower, more torque, more sheer exhilaration — quickly led to pushing the boundaries of what this twin-turbocharged inline-six could achieve, transforming an already potent machine into a true track weapon and street dominator.
This guide dives deep into F8X M3/M4: Turbocharging the Icon (2014-2020), exploring how these vehicles respond to serious power upgrades, specifically focusing on aftermarket turbocharger systems designed to unlock their full potential.
At a Glance: Unlocking Your F8X's Full Potential
- The S55 Engine: A robust, twin-turbo platform highly responsive to upgrades.
- Why Upgrade Turbos? Stock turbos become a bottleneck beyond a certain power level.
- Pure Turbo Stage 2+: A popular, proven upgrade for the S55, offering substantial power gains.
- Key Components: Billet compressor wheels, improved turbine wheels, robust thrust systems.
- Real-World Power: Expect 670+ wheel horsepower (whp) on pump gas, 800+ whp with E85 and proper tuning.
- Installation & Core Charge: Professional installation recommended; a significant core charge applies.
- Legal Considerations: These upgrades are strictly for off-road/competition use and are not street legal in many regions.
- Beyond Turbos: Requires supporting modifications like fueling, cooling, and tuning.
The S55 Legacy: Why It's Ripe for Boost
When BMW introduced the F8X M3 and M4, purists initially balked at the switch from the high-revving, naturally aspirated S65 V8 of the E9X generation to the forced-induction S55. However, the 3.0-liter twin-turbo inline-six quickly proved its mettle. Delivering 425-450 horsepower (depending on the model year and variant like the Competition Package) and a generous 406 lb-ft of torque, the S55 was a torquey beast from the get-go.
What makes the S55 such a fantastic candidate for turbo upgrades isn't just its inherent strength, but its design philosophy. Built from the ground up for forced induction, it features a closed-deck block, a robust forged crankshaft, and sophisticated cooling systems. This solid foundation means the engine itself can handle significant increases in boost pressure and horsepower, provided the supporting modifications are in place. Unlike some other platforms, you're not immediately battling the engine's structural limits when chasing big power. For a deeper dive into the lineage, you might find it fascinating to explore all BMW M3 generations.
The Bottleneck: Why Stock Turbos Limit Your Power Gains
You might be thinking, "My M3/M4 already has turbos, why do I need bigger ones?" The stock S55 turbos are excellent for street use, providing quick spool and strong mid-range torque. However, they are sized for efficiency and responsiveness within a specific power band. As you add bolt-on modifications like improved intakes, downpipes, and exhaust systems, along with custom tuning, you'll eventually reach a point where the factory turbos become the limiting factor.
This limitation manifests in a few ways:
- "Tapering Off" at High RPMs: Stock turbos struggle to maintain boost pressure efficiently as engine RPMs climb, leading to a noticeable drop in power at the top end.
- Heat Generation: Pushing smaller turbos beyond their efficiency range generates excessive heat, which can lead to reduced power (heat soak) and accelerated wear.
- Maximum Airflow: Simply put, they can only move so much air. To make significantly more power, you need to force more air into the engine, and that requires larger, more capable compressor and turbine wheels.
If you're looking to consistently achieve and sustain horsepower figures well into the 600s (at the wheels) and beyond, upgrading your turbos becomes a necessity.
The Gold Standard: Pure Turbo Stage 2+ for the S55
Among the various options for S55 turbo upgrades, Pure Turbos has established itself as a leader, with their Stage 2+ kit being a particularly popular and well-regarded choice. This isn't just a basic re-housed turbo; it's a meticulously engineered enhancement designed specifically for the S55 engine to unlock its full potential.
What Makes the Pure Turbo Stage 2+ Stand Out?
The Pure Turbo Stage 2+ Upgrade Turbos for F8X M2/M3/M4 (S55) are built with performance and reliability in mind. Here's a breakdown of their key features:
- Billet Internals: Unlike cast components, billet compressor wheels are machined from a solid piece of aluminum. This allows for more aggressive designs, thinner blades, and a larger overall diameter, translating directly to increased airflow and efficiency.
- Upgraded Point-Milled Billet High Flow Compressor Wheel: This specific design maximizes airflow volume and pressure while maintaining excellent spool characteristics.
- Upgraded HiFlow Turbine Wheel: On the exhaust side, a larger and more efficient turbine wheel helps evacuate exhaust gases more effectively, reducing back pressure and allowing the engine to breathe easier at higher RPMs.
- Large Diameter Thrust Upgrade: Turbochargers spin at incredibly high speeds (often over 200,000 RPM). The thrust bearing system is crucial for handling the axial loads. An upgraded, larger diameter thrust bearing enhances durability and reliability, especially under increased boost and power levels.
- In-House Manufacturing and Balancing: Each unit is built and balanced in-house at Pure Turbo. This meticulous attention to detail ensures optimal performance, longevity, and reduces the risk of vibration-related failures.
- LHD Models Only: It's crucial to note that this specific turbocharger kit is intended for Left Hand Drive (LHD) models only. Always double-check compatibility with your vehicle.
- Broad Compatibility: These turbos fit a range of S55-powered vehicles including the F87 M2 Competition (2019-2021), F80 M3 Sedan (2015-2018), F82 M4 Coupe (2015-2020), and F83 M4 Convertible (2015-2020).
Performance You Can Expect
The numbers speak for themselves. With supporting modifications (Full Bolt-Ons, or FBO) and 93 octane pump gas, performance testing shows these turbos are capable of delivering an impressive 671whp and 557wtq.
However, the S55 truly comes alive with alternative fuels. With proper E85 fueling and aggressive custom tuning, these turbos are capable of pushing 800+whp. This level of power completely transforms the F8X, making it competitive with supercars. Understanding a comprehensive guide to E85 fueling is essential for reaching these power figures safely.
The Full Picture: Beyond Just Turbos
Upgrading your turbos is a significant step, but it's rarely a standalone modification. To safely and effectively harness the power potential of the Pure Turbo Stage 2+ kit, you'll need a suite of supporting modifications.
Essential Supporting Modifications
- Fueling System Upgrade: At 600+ whp, the stock fuel system will be maxed out. You'll need upgraded fuel pumps (low pressure and/or high pressure), potentially an ethanol sensor for flex-fuel tuning, and possibly larger injectors, especially if running E85.
- Intake System: While many aftermarket intakes offer minor gains on stock turbos, a high-flow intake system is critical for upgraded turbos to ensure they can draw in enough air without restriction.
- Charge Pipes: The stock charge pipes are prone to cracking or bursting under increased boost pressure. Upgraded aluminum charge pipes are a must-have for reliability.
- Cooling System: More power means more heat. An upgraded heat exchanger, intercooler (charge-air cooler), and possibly an auxiliary oil cooler will be crucial to prevent heat soak and maintain consistent power output, especially during track use or aggressive driving.
- Exhaust System & Downpipes: Aftermarket downpipes that remove the restrictive catalytic converters significantly reduce back pressure, allowing the turbos to spool faster and produce more power. Pair this with a free-flowing exhaust system for maximum benefit. For various options, consider exploring aftermarket exhaust upgrades for the F8X.
- Engine Tuning: This is non-negotiable. A custom tune specifically calibrated for your upgraded turbos, fueling, and other modifications is absolutely essential. Off-the-shelf tunes won't cut it. This requires a skilled tuner who understands the S55 platform deeply. You'll want to learn the fundamentals of S55 engine tuning before diving in.
- Engine Health & Maintenance: Before embarking on such an extensive upgrade, ensure your S55 engine is in top condition. Perform all necessary preventative maintenance. Consistent and thorough care, including regular oil changes and spark plug replacements, is critical for highly tuned engines. Refer to essential maintenance for your F8X M3/M4 for guidance.
Installation & Core Charges: What You Need to Know
Installing upgraded turbos is not a DIY job for the faint of heart. It requires specialized tools, significant mechanical expertise, and often involves removing a considerable number of components from the engine bay. Professional installation by a reputable shop experienced with BMW M cars and turbo upgrades is highly recommended.
The Core Charge Explained
When purchasing the Pure Turbo Stage 2+ kit, a $1,500 core charge applies. This is a common practice in the automotive aftermarket for remanufactured or upgraded components. Here's how it works:
- You pay the core charge upfront with the purchase of the new turbos.
- Once you receive and install the new turbos, you'll send your original, "core" turbos back to Pure Turbo.
- Upon receipt, the core will be inspected. It must match the supplied part in terms of fitment, type, application, accessories, and hardware. Crucially, damaged or modified cores will not receive a refund.
- The refund is issued only after the core has been inspected and approved.
This core charge serves two purposes: it encourages the return of usable components for future upgrades and ensures the quality of returned parts. Be sure to carefully package your old turbos for shipment to avoid any damage during transit.
Legal & Environmental Considerations: Drive Responsibly
This is perhaps the most important caveat for any high-performance modification. The ground truth states:
"This product is intended only for vehicles that may never be used, registered, or licensed for use upon a public highway. It is illegal to remove, disable, or alter emissions equipment on pollution-controlled road vehicles, or to install devices/software that trick, disable, or modify emissions controls. This product is sold solely for racing, competition, track, hobby, or other off-road use. It is not legal for installation or use in California or any state, province, or jurisdiction governed by CARB or EPA regulations on any pollution-controlled motor vehicle."
This isn't just legal jargon; it's a serious warning. In many jurisdictions, installing components that alter or bypass emissions controls (like catalytic converters or specific tunes) makes your vehicle illegal for street use. The F8X M3/M4, when modified to this extent, is essentially becoming a dedicated track or competition machine.
- Emissions Compliance: Your vehicle will almost certainly not pass emissions testing if equipped with these turbos and associated supporting mods (like catless downpipes) and tunes designed for maximum power.
- Public Highway Use: Driving such a vehicle on public roads can lead to fines, vehicle impoundment, and potential legal issues.
- Insurance: Modifying your vehicle extensively, especially concerning power and emissions, can impact your insurance coverage. Always check with your provider.
It's critical to understand understanding BMW emissions regulations before committing to these types of modifications. Respecting these regulations and using your high-powered F8X responsibly is paramount.
Common Questions & Misconceptions
"Will this make my car unreliable?"
Any significant power increase puts more stress on engine components. However, with proper installation, quality supporting modifications, expert tuning, and diligent maintenance, the S55 with upgraded turbos can be remarkably reliable. Reliability issues typically arise from cutting corners on supporting mods, using aggressive or poorly designed tunes, or neglecting maintenance.
"Can I run these turbos on stock fueling?"
No, absolutely not. The stock fueling system (pumps, injectors) cannot deliver enough fuel to support the kind of power these turbos are capable of. Running them without adequate fueling will lean out your engine, leading to catastrophic failure. Fueling upgrades are a prerequisite.
"Do I need a new clutch/transmission for an 800whp S55?"
If you have a manual transmission (F80/F82/F83 M3/M4), the stock clutch will almost certainly slip at high torque levels. An upgraded performance clutch is necessary. If you have the DCT (Dual-Clutch Transmission), it is generally quite robust, but for 800+ whp, a DCT clutch upgrade and tune are highly recommended to ensure it can handle the increased torque without slipping or causing premature wear.
"What about turbo lag?"
While larger turbos inherently introduce some degree of lag compared to smaller units, modern billet wheel technology and proper tuning mitigate this significantly. The Pure Turbo Stage 2+ is designed for strong mid-range pull and excellent top-end power, meaning it spools up effectively for most driving scenarios. It won't feel like a sluggish, old-school turbo setup.
The First Start: Priming Your New Turbos
A crucial step often overlooked during installation is properly priming your new turbos with engine oil before the first engine start. Turbos rely on a constant supply of oil for lubrication and cooling. If they run dry for even a few seconds on the initial startup, severe damage can occur.
How to prime your turbos:
- After installation, disconnect the spark plugs (or fuel injectors) and crank the engine for several seconds without letting it start. This allows the oil pump to circulate oil throughout the engine and fill the turbo oil passages.
- Repeat this process a few times.
- You can also manually fill the turbo's oil feed line with clean engine oil before connecting it, if accessible.
- Once primed, reconnect everything and start the engine, allowing it to idle for a few minutes while you check for any leaks.
This simple step ensures your new, expensive turbos have lubrication from the very first rotation.
Turbocharging Your Icon: A Journey, Not Just an Upgrade
Transforming your F8X M3/M4 into an 800+whp beast with upgraded turbos like the Pure Turbo Stage 2+ isn't just about bolting on parts; it's a commitment to a new level of performance. It's about understanding the intricate dance between airflow, fuel, cooling, and tuning. The S55 engine provides an incredible canvas, but realizing its full potential requires careful planning, significant investment, and a dedication to proper maintenance and responsible use.
When done correctly, the result is an F8X M3/M4 that pushes the boundaries of performance, delivering an exhilarating driving experience that few other cars can match. It truly solidifies its place as an icon, not just for its heritage, but for its utterly brutal, turbocharged power.