Understanding the B58 Engine in the A90 Supra

The Toyota Supra A90 is powered by BMW’s B58 engine, a 3.0‑liter inline‑six that has quickly earned a reputation for exceptional strength and tunability. The B58 combines a closed‑deck block, forged steel crankshaft, and a dual‑VANOS valvetrain to handle substantial power increases without immediate failure. Its twin‑scroll turbocharger provides responsive low‑end torque, while the integrated water‑to‑air intercooler keeps intake temperatures in check during sustained pulls.

Key design aspects that make the B58 ideal for high‑horsepower builds include:

  • Closed‑deck block – reduces cylinder wall flex under high boost.
  • Direct injection (DI) and port fuel injection (PFI) – enables superior fuel atomization and addresses carbon buildup concerns.
  • Integrated exhaust manifold – improves spool and reduces weight.
  • High‑strength connecting rods – forged from steel, capable of holding 600+ whp on pump gas.

With these foundations, the B58 can reliably support 650+ horsepower when paired with the right turbocharger and supporting modifications.

Why Upgrade to a BorgWarner EFR Turbo?

BorgWarner’s Engineered For Racing (EFR) series is a staple in high‑performance forced induction. These turbochargers use a gamma‑titanium turbine wheel, a stainless steel turbine housing, and a dual ball‑bearing cartridge to minimize lag while maximizing efficiency. For a 650‑hp Supra build, an EFR turbo delivers several tangible benefits over stock or other aftermarket options.

Performance Advantages

  • Faster spool – titanium turbine wheels reduce rotational inertia, improving transient response.
  • Higher efficiency – the compressor maps are designed for high‑boost applications without excessive heat generation.
  • Lightweight construction – the entire unit is lighter than many cast‑iron alternatives, reducing front‑end mass.
  • Integrated recirculating wastegate – eliminates boost creep and simplifies plumbing.
  • Extreme durability – rated for continuous operation at 100,000 rpm and high exhaust temperatures.

Compared to the factory twin‑scroll unit, an EFR turbo can increase airflow by 30–50% while maintaining excellent drivability. This makes it an ideal choice for owners who want a strong street setup that still performs on track.

Choosing the Right BorgWarner EFR Turbo

Selecting the correct EFR size depends on your power goal, desired response, and fuel type. The two most popular options for the A90 Supra are the EFR 7670 and the EFR 8374, but other variants exist for specific needs.

EFR 7670 (700 hp candidate)

  • Compressor inducer: 58mm / Exducer: 76mm
  • Turbine inducer: 67mm
  • Best suited for 600‑700 whp on E85 or high‑octane fuel.
  • Spools noticeably faster than larger units, often reaching full boost before 4,000 rpm.
  • Excellent for street‑oriented builds that still want to crack into the 9‑second quarter‑mile.

EFR 8374 (750+ hp candidate)

  • Compressor inducer: 62mm / Exducer: 83mm
  • Turbine inducer: 74mm
  • Target for 700‑800 whp with proper supporting mods.
  • Slower spool than the 7670 but capable of higher peak power.
  • Ideal for dedicated track cars or drag‑focused builds.

Both turbos can be used with the B58’s factory engine management after reflashing, but the 8374 will demand stronger fuel system upgrades and careful wastegate control.

Installation Process for the B58 BorgWarner EFR Upgrade

Converting to an EFR turbo on the A90 Supra is a significant job. While many enthusiasts complete it in a home garage, professional installation is recommended to avoid complications. Below is a high‑level outline of the typical steps.

Prepare the Vehicle and Parts

  • Disconnect the battery and drain the coolant and oil.
  • Remove the intake system, charge pipes, and intercooler.
  • Unbolt the exhaust manifold downpipe and the factory turbo assembly.
  • Inspect engine bay for clearance issues – many EFR swaps require a custom downpipe and charge pipe routing.

Install the EFR Turbo

  • Mount the new oil and coolant lines. EFR turbos use a specific feed/return configuration; mismatched lines can cause catastrophic bearing failure.
  • Bolt the turbine housing to a custom or adaptor manifold. Several aftermarket manifolds are available specifically for B58‑EFR swaps.
  • Install the turbo in the engine bay, ensuring alignment with the frame rails and subframe.
  • Connect the wastegate actuator and boost reference lines.
  • Reassemble the exhaust system with a high‑flow downpipe to reduce backpressure.
  • Attach the charge pipes, intake, and intercooler system. A larger front‑mount intercooler is strongly advised.

Final Checks and ECU Programming

  • Refill all fluids and pressurize the cooling system to check for leaks.
  • Install a boost controller and wideband oxygen sensor for monitoring.
  • Flash a custom tune tailored to the EFR turbo. This is the most critical step – the stock ECU cannot compensate for the drastically different airflow and fuel demands.
  • Perform a slow break‑in procedure, gradually increasing boost while verifying air‑fuel ratios and knock levels.

Common pitfalls include insufficient fuel supply (which we address below) and incorrect wastegate spring selection. Most EFR turbos come with an internal gate that works well, but some builders opt for external wastegates for finer control.

Tuning for Maximum Performance and Reliability

A proper tune is non‑negotiable when moving to a BorgWarner EFR. The B58’s Bosch ECU can be reflashed through platforms such as Bootmod3, MHD, or custom bench tuning. A skilled tuner will adjust boost targets, fuel pressure, ignition advance, and cam timing to exploit the new turbo’s compressor map.

Fuel Tuning Considerations

  • EFR turbos require more fuel volume than the stock unit. At 650‑700 whp, the factory high‑pressure fuel pump (HPFP) can become a bottleneck. Upgraded HPFPs or a low‑pressure system may be needed.
  • Ethanol blends (E30‑E85) are strongly recommended for their cooling effect and octane rating, but require retuning of injector pulse width.
  • Target lambda values around 0.78–0.82 at peak power to keep cylinder temperatures safe.

Boost Control Strategy

  • Most EFR swaps use a boost‑controlled solenoid (e.g., MAC valve) to manage the wastegate duty cycle.
  • Begin with conservative boost (10–12 psi) and monitor knock. Slowly increase to target (20–25 psi) on the chosen fuel.
  • Use a boost map that ramps up gradually to maintain torque curve and reduce stress on the drivetrain.

Dyno tuning is preferred because it allows real‑time adjustments and provides a clear record of power output. Expect final figures of 630‑680 whp on pump gas with an EFR 7670, or 700‑780 whp on E85 with aggressive timing.

Supporting Modifications for 650+ HP Reliability

No turbo upgrade exists in a vacuum. To consistently achieve and sustain 650+ horsepower, several supporting systems must be upgraded.

Fuel System

  • High‑flow fuel pump – the in‑tank low‑pressure pump may need upgrading to deliver sufficient volume to the HPFP.
  • Upgraded HPFP – several aftermarket options (e.g., Spool Performance, XDI) can push 600+ lph.
  • Larger injectors – the stock direct injectors can run out of capacity around 650 whp. Port injection or upgraded DI injectors may be necessary.

Cooling System

  • Intercooler – a stepped or high‑density core is essential. Look for a unit with bar‑and‑plate construction and at least 30% larger internal volume than stock.
  • Radiator upgrade – the stock radiator is marginal for continuous high‑boost use. A CSF or Mishimoto unit provides better heat rejection.
  • Oil cooler – an auxiliary oil cooler helps maintain viscosity during sustained pulls.

Exhaust System

  • A full 3‑inch or 3.5‑inch catless downpipe and exhaust reduces backpressure and allows the turbo to breathe. Be aware of emissions regulations.
  • High‑flow catalytic converters are available but will slightly restrict top‑end power.

Drivetrain and Chassis

  • Clutch upgrade – the stock clutch (manual transmissions) or torque converter (automatic) will slip at 500+ whp. Switch to a twin‑disc or upgraded converter.
  • Differential mounts – polyurethane or metal bushings prevent wheel hop and improve traction.
  • Wheels and tires – at least 275‑width summer tires are needed to hook up power; wider is better.

Cost and Value Considerations

A full BorgWarner EFR swap for the A90 Supra is a serious investment. The turbocharger itself ranges from $1,800 to $2,500 depending on size and options. When combined with a manifold, downpipe, intercooler, fuel system upgrades, and professional installation, total cost often reaches $8,000–$12,000. Tuning adds another $800–$1,500. However, the result is a reliable 650+‑hp machine that can outperform many supercars in a straight line and on circuits.

For reference, many owners have documented their builds on platforms like SupraMKV Forum or BimmerPost, where they share dyno sheets and long‑term reliability data.

Real‑World Performance Expectations

With a 7670 EFR and proper tuning, expect quarter‑mile times in the low 10‑second range at 135‑140 mph on drag radials. On a road course, the linear power delivery and fast spool make the car easier to drive at the limit than many larger turbo setups. The 8374 variant pushes trap speeds into the 140‑145 mph range when paired with E85 and a built transmission.

Many owners report that the car remains fully streetable, with air conditioning and idle quality virtually unchanged. The BorgWarner EFR’s noise signature is a bit louder than stock – a distinct turbine whistle – but not obnoxious.

Potential Pitfalls and How to Avoid Them

  • Oil supply issues – The EFR bearings require clean oil. Use a quality 5W‑40 synthetic and consider an oil filter restrictor if oil pressure is too high.
  • Boost creep – If the internal wastegate is too small for your power target, install an external wastegate or upgrade the actuator spring.
  • Heat soak – Without adequate intercooling, intake air temperatures climb after repeated pulls, reducing power and risking knock. A water‑meth injection system is a worthwhile addition for track days.
  • Engine management limitations – The stock ECU can be tuned for up to about 750 whp. Beyond that, a standalone ECU (e.g., MoTeC, Syvecs) becomes necessary.

Conclusion

Upgrading the A90 Supra’s B58 engine with a BorgWarner EFR turbocharger is a proven path to 650+ horsepower. The combination of the engine’s robust architecture and the EFR’s efficient, responsive design yields a powerful and reliable street‑legal machine. Success depends on choosing the correct turbo size, investing in supporting mods, and obtaining a professional tune. With proper execution, a Supra equipped with an EFR turbo can deliver supercar‑slaying performance for years of enjoyment.

For further reading, BorgWarner provides detailed technical documentation on its official website, and forums like SupraMKV offer community‑vetted build guides.