The B58 M240i is an outstanding platform for enthusiasts who crave serious power. With the right combination of bolt-on parts and tuning, this inline-six powerhouse can easily eclipse 550 wheel horsepower while retaining daily-driver manners. This guide walks through the essential modifications—especially the upgraded turbocharger and intercooler—needed to hit that benchmark, along with supporting upgrades and real-world considerations.

The B58 Engine: Built for Boost

BMW’s B58 engine debuted in 2015 and quickly earned a reputation for being one of the most robust six-cylinder engines on the market. It’s a 3.0-liter, twin-scroll turbocharged unit that shares DNA with the larger S58 but uses an open-deck block and a cast-iron crank for durability. In the M240i (F22/F23), stock output is roughly 335 horsepower and 369 lb-ft of torque, though many dyno tests show it under-rates to around 340–350 whp from the factory.

  • Displacement: 3.0 liters
  • Configuration: Inline-six
  • Forced Induction: Twin-scroll turbocharger (TD03-style)
  • Fuel System: Direct injection (up to 3,000 psi)
  • Block Material: Closed-deck with iron main bearing caps

The B58’s strengths are its robust bottom end, clever water-to-air intercooler, and an ECU that responds well to tuning. Stock internals have been proven to handle over 600 wheel horsepower without failure, provided the engine is not detonating and fuel supply is adequate.

Why Upgrade the Turbocharger?

The factory turbocharger is efficient and spools quickly, but it runs out of breath around the 480–500 whp mark. To push past 550 whp you need more air volume—a larger compressor wheel, a bigger turbine housing, or a completely different turbo. Upgrading the turbo delivers:

  • Increased airflow – More pounds per minute (lb/min) translates directly to higher power.
  • Better high-rpm power – The stock turbo chokes above 6,200 RPM; a larger unit holds boost to redline.
  • Room to grow – If you later add port injection or ethanol, the turbo won’t be the limiting factor.

Top Turbo Upgrades for B58 M240i

Several manufacturers offer bolt-on turbo upgrades that require minimal modification to the engine bay. Here are the three most proven options:

  • Pure Turbos Stage 2 (P800) – One of the most popular choices for the 500–600 whp range. It uses a billet compressor wheel and a ported shroud, allowing up to 580 whp on pump gas and 620 whp with ethanol. Spool is similar to stock, with full boost by 3,100 RPM.
  • BMS (Burger Motorsports) Stage 2 Turbo – A more budget-friendly upgrade that reuses your factory core but adds a larger wheel and housing. It reliably produces 520–560 whp on 93 octane and has a strong track record for daily reliability.
  • VRSF Race Turbo – Designed for those who want maximum top-end power. It flows enough air for 600+ whp, but spool is slightly slower than Pure. Many owners pair it with upgraded intakes and charge pipes for best results.

For 550 whp target, any of these three will work well. Choose based on your budget, desired spool characteristics, and future power goals.

Intercooler: The Cooling Foundation

Heat is the enemy of high-boost engines. The B58 uses a factory water-to-air intercooler (sometimes called a “heat exchanger”) that is decent for stock power but quickly heat-soaks during back-to-back pulls. Once the intercooler temp rises, intake air temperatures (IATs) climb, and the ECU pulls timing to protect the engine. Power drops significantly.

Upgrading to a larger intercooler—either a bigger water-to-air unit or a front-mount air-to-air conversion—dramatically stabilizes IATs. The benefits are clear:

  • Lower intake temps (often 20–40°F cooler than stock)
  • Consistent power – Even after multiple gear pulls, horsepower stays flat.
  • Supports higher boost – Denser air allows the engine to make more power without knock.
  • VRSF Intercooler (Race or Street) – The Race version is a direct-fit bar-and-plate unit that flows 35% more than stock and drops IATs by around 30°F. It’s a popular choice for 500–600 whp builds.
  • Mishimoto Intercooler – Known for excellent heat rejection and a robust core. Mishimoto includes a lifetime warranty and all required silicone hoses, making installation straightforward.
  • CSF Intercooler – A high-end water-to-air unit that uses a thicker heat exchanger and larger water capacity. It’s ideal for cars that see track time or frequent high-speed pulls because it recovers quickly between sessions.
Pro tip: No matter which intercooler you choose, consider adding an auxiliary radiator or an upgraded coolant pump if you plan to track the car. Heat management becomes critical above 550 whp.

Supporting Modifications for 550+ Horsepower

Bolting on a bigger turbo and intercooler will get you closer to your goal, but you can’t stop there. The stock fuel system, intake, and exhaust become bottlenecks. Here’s what else you’ll need:

Fuel System Upgrades

The B58’s HPFP (high-pressure fuel pump) maxes out at around 480 whp on pump gas and slightly higher on ethanol. For 550+ whp, you have two paths:

  • Dorrch Stage 2 HPFP – A drop-in replacement with an upgraded piston that flows enough for 600+ whp on E40 mixes.
  • Port injection – Adds secondary injectors in the intake manifold. This is more complex but allows full flex-fuel capability and much higher power ceilings.

If you plan to run E85 blends (E40 or higher), a HPFP upgrade is essential. Even on 93 octane, the stock pump can run out of headroom at the boost levels required for 550 whp, so budget for this upgrade.

Intake and Charge Pipes

The factory intake is restrictive once the turbo flows more air. A cold-air intake (like those from Eventuri, Injen, or BMS) adds 5–10 whp and improves throttle response. Upgraded charge pipes—silicone or aluminum—prevent boost leaks and improve flow. Look for options from VRSF or MST that retain the factory connections.

Exhaust System

A high-flow downpipe (catted or catless) is mandatory for any turbo upgrade. The factory catalyst is restrictive; a VRSF catless downpipe or MST downpipe can free up 15–20 whp on its own. Pair it with a 3-inch midpipe and an axle-back exhaust for a free-flowing system that supports high horsepower without excessive backpressure.

ECU Tuning

All the parts in the world won’t help without a proper tune. For the B58, you have two main options:

  • Bootmod3 (BM3) – The most common platform, with custom tuning from experts like Halim Performance or ProTuningFreaks. A custom tune specifically for your turbo upgrade is recommended over off-the-shelf maps.
  • MHD Tuning – Another popular option with a growing base of custom tuners. MHD offers flex-fuel support and built-in data logging.

Don’t skimp on the tune. A poorly calibrated map can melt pistons or crack the cylinder head. Invest in a reputable tuner who has proven results on similar builds.

Installation Considerations

While some enthusiasts can tackle turbo and intercooler swaps in a home garage, B58 engine bay space is tight. Here are critical points to keep in mind:

  • Professional installation is recommended for the turbo, as it requires removing the coolant lines, exhaust manifold, and heat shields. A shop experienced with BMW can do it in 8–12 hours.
  • Compatibility check – Some intercoolers are model-year specific. 2016–2018 models use one water-to-air setup; 2019+ LCI models use a revised bumper and intercooler mounting. Always verify fitment before ordering.
  • Maintenance intervals – After modifications, shorten your oil change interval to 3,000–4,000 miles. Use a high-quality oil like Liqui Moly 5W-30 or Motul 8100.
  • Boost leaks – Check all charge pipe connections after installation. A leak can cause rough idle and lost power.

If you’re not comfortable doing the work yourself, expect to pay $1,500–$2,500 for labor on a full turbo, intercooler, and supporting mods install at an independent shop.

Estimated Cost Breakdown for 550+ whp

Achieving the goal isn’t cheap, but the B58 rewards investment. Here’s a sample budget:

  • Turbo upgrade (Pure Stage 2): $2,400–$2,800
  • Intercooler (VRSF Race): $700–$900
  • HPFP upgrade (Dorrch Stage 2): $1,200–$1,500
  • Downpipe (VRSF catless): $400–$600
  • Intake and charge pipes: $500–$800
  • Custom tune (BM3 plus e-tune): $850–$1,200
  • Labor (estimated): $1,500–$2,500
  • Total: $7,550–$10,300

Prices vary by region and brand, but this range gives a realistic picture of what it takes to safely hit 550 whp.

Reliability and Daily Driveability

A properly built 550+ whp M240i can still be a daily driver if you take the necessary precautions. The B58 engine is famously robust, but the drivetrain needs attention:

  • Transmission – The ZF 8HP50 (8-speed automatic) is strong, but at torque levels above 550 lb-ft, consider upgrading the torque converter or cooler. The 8HP70 from S58 cars is a direct swap for more margin.
  • Differential mounts – Stock mounts can stress under hard launches. Replace with Powerflex or Rogue Engineering inserts.
  • Catch can – High-boost engines produce more blow-by. A Mishimoto or VRSF oil catch can helps keep the intake valves clean.

With careful tuning and routine fluid changes, many B58 owners report tens of thousands of problem-free miles at 550–600 whp.

External Resources & Further Reading

Before you start buying parts, spend time on community forums. These sites contain build logs, dyno graphs, and real-world advice:

Conclusion

Reaching over 550 horsepower in a B58 M240i is not only possible but repeatable with the right approach. Start with an upgraded turbocharger (Pure Stage 2 or VRSF Race), pair it with a high-capacity intercooler, and address the fuel system and exhaust. A custom tune ties everything together, delivering reliable, thrilling performance that can keep up with much more expensive machinery. Choose quality parts, invest in professional installation if needed, and maintain the car diligently. The result is a street machine that punches far above its weight class—a true enthusiast’s benchmark.