The BorgWarner EFR supercharger has become a go-to forced induction solution for Challenger owners who demand serious power without compromising everyday drivability. These units combine advanced aerodynamics, integrated wastegates, and lightweight construction to deliver a turbocharger-like response with the linear power delivery of a supercharger. Choosing the right EFR size for your driving style—whether that means a streetable daily driver or a track-focused weekend warrior—determines how much of that potential you unlock.

Understanding BorgWarner EFR Superchargers

BorgWarner’s EFR (Engineered for Racing) family originated in motorsport, but its engineering has trickled down to performance street cars like the Dodge Challenger. Every EFR unit features a forged-machined compressor wheel, a Gamma-Ti turbine wheel (for reduced inertia and faster spool), and a dual ceramic ball bearing cartridge that minimizes friction and tolerates high exhaust temperatures. Many models also integrate a boost control solenoid and a blow-off valve, simplifying installation and reducing the number of aftermarket parts required.

The integrated wastegate is a standout feature: it uses a stainless-steel diaphragm and a ported shroud design that prevents boost creep and provides precise boost control. This is especially valuable on the Challenger’s heavy platform, where consistent pressure under load is critical for traction and tuning reliability.

Why EFR Superchargers Fit the Challenger

The Challenger’s 6.4L Apache and 6.2L Hellcat engines respond exceptionally well to positive-displacement and centrifugal superchargers. EFR units fall into the centrifugal category, meaning they produce boost proportional to engine speed. Unlike twin-screw or roots blowers that deliver peak boost almost instantly, EFR superchargers build boost progressively. This trait makes them ideal for both street and track because:

  • Street manners – Low-rpm boost is less aggressive, improving part-throttle fuel economy and reducing drivetrain shock in daily driving.
  • Track performance – At high rpm, the centrifugal design flows enormous air volume, supporting 800–1,200+ wheel horsepower depending on the size.
  • Heat management – Centrifugal compressors generate less intake air temperature rise than displacement blowers, allowing more consistent power on hot track days.

Choosing the Right Size for Daily Driving

Daily driving demands a supercharger that enhances acceleration without turning the Challenger into a temperamental beast. The ideal streetable EFR strikes a balance between spool speed, peak output, and thermal stability. Here are the top contenders for a dual-purpose street car that also sees occasional spirited driving.

EFR 6258 – The Street-Friendly Performer

The EFR 6258 (58mm inducer / 72mm exducer) is the smallest EFR commonly used on a Challenger. It spools extremely quickly—often reaching 5–7 psi by 2,500 rpm on a 6.4L engine. This size provides a strong, usable torque increase below 4,000 rpm, making stop-and-go traffic and highway merging effortless. Power output typically falls between 550–650 wheel horsepower on pump fuel with a conservative tune. Owners report that drivability remains stock-like; the boost comes on smoothly and the engine never feels overwhelmed.

Ideal for daily drivers who want a noticeable kick without changing the car’s fundamental character. The 6258 also leaves the drivetrain mostly stock, reducing the need for supporting modifications like fuel system upgrades or heavy-duty half-shafts.

EFR 6758 – The All-Arounder

Stepping up to the 6758 (62mm inducer / 76mm exducer) adds roughly 50–70 wheel horsepower over the 6258 while retaining strong low-end response. On a 6.4L Challenger, this supercharger reaches 6–8 psi by 3,000 rpm and can push 680–750 wheel horsepower on 93 octane with a custom tune. The slightly larger turbine wheel shifts the power band upward without sacrificing the responsive feel that makes EFRs pleasant on the street.

Ideal for owners who occasionally take their Challenger to autocross or drag strips but still commute daily. The 6758 requires few supporting upgrades: a good fuel pump, larger injectors, and a quality intercooler are sufficient to support 700 wheel horsepower safely.

EFR 7064 – The Overlooked Middle Child

Though not as common as the 6758, the EFR 7064 offers a unique compromise. With a 64mm inducer and a slightly larger turbine housing, it provides 750–800 wheel horsepower with excellent throttle response above 3,500 rpm. Streetability is still good, but the boost threshold rises to about 3,200 rpm, meaning the car feels more “lazy” below that point. For daily drivers who spend most of their time in the upper rev range, this can be acceptable, but casual drivers may prefer the 6258 or 6758.

Best Sizes for Track Performance

Track driving—whether drag racing, road course lapping, or high-speed open track—demands maximum airflow, minimal lag, and the ability to survive sustained high rpm. For these applications, larger EFR units shine, but they require more aggressive tuning and supporting hardware.

EFR 7670 – The Track-Ready Standard

The EFR 7670 (66mm inducer / 80mm exducer) is the most popular choice for Challengers that regularly see drag strips or road courses. It flows enough air to support 850–950 wheel horsepower on pump ethanol blends (E85) and spools adequately for a 6.4L engine: full boost around 3,800 rpm. This size pairs well with upgraded valvetrains and billet connecting rods because the torque comes on smoothly at higher engine speeds, reducing the risk of breaking transmissions or axles.

Ideal for dedicated track cars that can tolerate a bit of low-rpm lag in exchange for top-end domination. On a road course, the 7670’s broad power band above 4,000 rpm allows drivers to stay in gear longer, reducing shift points and improving lap consistency.

EFR 8374 – The Extreme Option

For Challenger owners chasing 1,000+ wheel horsepower, the EFR 8374 (72mm inducer / 85mm exducer) is the ultimate choice. This supercharger requires extensive supporting modifications: a built bottom end, dedicated fuel system, upgraded cooling, and usually a boost controller to manage the massive airflow. On race gas or E85, the 8374 can produce over 1,100 wheel horsepower with boost levels above 20 psi.

Ideal for serious competition vehicles that are trailered to events. The 8374 has a pronounced lag below 4,200 rpm; daily driving is not recommended unless the owner has a high-stall torque converter and drag-radial tires to keep the engine on boost. However, once the revs climb, the acceleration is brutal and relentless.

EFR 9180 – The Uncommon Overachiever

Though rarely seen on street-driven Challengers, the EFR 9180 (80mm inducer / 92mm exducer) is available for the most extreme builds. It is designed for 1,500+ wheel horsepower and is best suited for dedicated race cars with massive intercoolers, methanol injection, and sequential fuel systems. The lag is significant—boost often doesn't come on until 4,500+ rpm—but the power potential is nearly limitless.

Factors to Consider When Upgrading

Selecting the right EFR size is only part of the equation. The following factors determine whether your Challenger will run reliably and safely on the street or track.

  • Engine Compatibility – Stock 6.4L Apache engines can handle up to approximately 700 wheel horsepower with proper tuning. Beyond that, forged pistons and rods are essential. Hellcat engines with factory forged internals can tolerate 850+ horsepower, but the cylinder walls and ring pack still have limits.
  • Boost Levels and Fuel – EFR superchargers are most efficient at pressure ratios between 1.5 and 2.5 (roughly 7–22 psi of boost). Running a 7670 at 12 psi produces very different results than running it at 20 psi. E85 fuel allows higher boost without detonation, making it the preferred fuel for track builds.
  • Drivetrain Capacity – The 8HP70 and 8HP90 transmissions are strong, but above 800 wheel horsepower they require upgraded torque converters, valve bodies, and transmission coolers. The differential should also be addressed—truss kits and upgraded half-shafts prevent catastrophic failure.
  • Intercooling System – Centrifugal superchargers heat the compressed air significantly. A properly sized air-to-air intercooler (or a water-to-air setup for heat soak resistance) is vital for maintaining consistent power on track.
  • Tuning Platform – HPTuners or SCT tuning is mandatory. The knock control on modern Challengers is aggressive; a competent tuner who understands EFR boost curves and laminar airflow is worth more than any single hardware upgrade.

Installation Considerations

Installing an EFR supercharger requires moderate mechanical skill and a well-equipped shop. The process involves mounting the unit, routing charge air piping, integrating the wastegate and blow-off valve, and running oil feed/drain lines. Below are key considerations.

Professional Installation vs. DIY

While a competent DIY enthusiast can install an EFR kit, professional installation is strongly recommended for first-time supercharger builders. Mistakes in oil line routing, boost referencing, or wastegate adjustment can lead to engine damage. A shop specializing in forced-induction Dodges will also have the equipment to weld intercooler piping and position the supercharger for optimal belt fitment.

Tuning Requirements

After installation, a custom tune is non-negotiable. EFR superchargers change the volumetric efficiency of the engine significantly; stock fuel tables, spark timing, and boost control maps will not work. A dyno tune ensures the air/fuel ratio stays safe (typically 11.5:1 on pump gas, 7.0:1 on methanol) and that the boost curve matches the supercharger’s compressor map. Most shops charge $500–$1,200 for a complete EFR tune, including idle, part-throttle, and wide open throttle calibration.

Supporting Modifications

Depending on the EFR size chosen, the following upgrades are often necessary:

  • Fuel System – EFR 6258/6758: 1000cc injectors and a 525-lph fuel pump. EFR 7670: 1300cc injectors, dual pumps, and a fuel pressure regulator. EFR 8374+: 1600cc injectors or mechanical fuel injection.
  • Cooling – Oversized radiator, transmission cooler, and a heat exchanger for the supercharger intercooler (if using a water-to-air setup).
  • Exhaust – A larger downpipe and minimal backpressure exhaust (3-inch or larger) allows the centrifugal supercharger to breathe.
  • Driveline – Upgraded U-joints, a stronger driveshaft (carbon fiber or aluminum), and half-shafts for any build exceeding 750 wheel horsepower.

Real-World Performance Expectations

To ground the discussion, here are typical dyno results for Challengers equipped with EFR superchargers (all numbers corrected to SAE, tested on 93 octane unless noted):

  • EFR 6258 – 580 wheel horsepower / 520 ft-lb at 8 psi (6.4L, stock headers, 3-inch exhaust)
  • EFR 6758 – 690 wheel horsepower / 580 ft-lb at 10 psi (6.4L, long-tube headers, E85)
  • EFR 7670 – 880 wheel horsepower / 700 ft-lb at 15 psi (6.2L Hellcat, forged pistons, E85)
  • EFR 8374 – 1,020 wheel horsepower / 820 ft-lb at 22 psi (6.2L built block, race gas)

These numbers are achievable with proper tuning and supportive cooling. In real-world conditions, the 7670-equipped Challenger can run 9-second quarter-mile times with drag radials and a good suspension setup.

Comparison with Other Supercharger Options

EFR superchargers compete with traditional centrifugal units (Vortech, ProCharger) and positive-displacement blowers (Whipple, Maggie). How do they stack up?

  • EFR vs. ProCharger – ProCharger kits are easier to install and come pre-assembled, but EFR superchargers offer better mid-range response and lower weight. The integrated wastegate on EFR units is also simpler than ProCharger’s separate spring-type setup.
  • EFR vs. Whipple – Whipple twin-screw blowers make incredible low-end torque (often 650+ ft-lb at 2,000 rpm), but they heat soak quickly on track and consume significant horsepower to spin. EFR units are more efficient at high rpm and produce less parasitic loss.
  • EFR vs. Turbocharging – Turbos offer superior top-end power, but require complex exhaust plumbing and suffer from lag on heavy Challengers. EFR superchargers retain the simplicity of a belt-driven system and produce a more linear power curve that many drivers prefer for both street and road course duty.

Common Pitfalls and How to Avoid Them

Experienced Challenger builders point to a few frequent issues with EFR supercharger installations:

  • Underestimating heat rejection – Many owners install an EFR 7670 but keep the stock intercooler. The result is IATs over 140°F after a single pull, triggering knock retard. Solution: upgrade to a bar-and-plate intercooler with at least 800–1,000 HP rating.
  • Ignoring oil drainage – EFR units require a gravity-fed oil return. If the drain line is too small or has sharp bends, oil pressure can force past the turbine seal, causing smoke. Use -10 AN lines and ensure the drain point in the oil pan is at least 1.5 inches above the supercharger centerline.
  • Boost creep with small wastegate – The integrated wastegate on EFR units is sized for the compressor wheel; however, in high-boost applications (over 20 psi), a secondary external wastegate may be needed for precise control.
  • Belt slip – Centrifugal superchargers place high load on the drive belt. Use a dedicated belt tensioner and consider a 8-rib or 10-rib belt system for builds exceeding 900 horsepower.

Cost Breakdown for a Full EFR Upgrade

Budgeting for an EFR supercharger installation should account for more than the unit itself. Here is a realistic cost breakdown for a Challenger:

  • EFR supercharger (new): $2,500–$4,000 depending on size
  • Bracketry and mounting kit: $400–$1,200
  • Intercooler and piping: $600–$2,000
  • Fuel system upgrades (pump, injectors, regulator): $800–$2,500
  • Professional installation: $1,500–$3,500
  • Tuning and dyno time: $500–$1,200
  • Miscellaneous (oil lines, fittings, fluids, gaskets): $300–$700

Total estimated range: $6,700 to $14,000+ for a turnkey installation. Higher track-focused builds with the 8374 or 9180 will push costs toward $20,000 due to required engine and driveline upgrades.

Additional Resources

For more technical data on compressor maps, installation guides, and real-world dyno results, refer to BorgWarner’s official EFR page. Challenger-specific build threads on Hellcat Forum and Challenger Talk also contain owner experiences with each EFR size. Finally, consider consulting a major performance retailer for bundled kit pricing that includes the supercharger, brackets, and fuel system components.

Conclusion

Upgrading to a BorgWarner EFR supercharger transforms a Challenger from a potent street machine into a serious performer capable of competing with cars costing twice as much. The key is selecting the size that matches your driving environment: a 6258 or 6758 for a balanced daily driver, a 7670 for a track car that still sees the occasional commute, and an 8374 or larger for all-out competition. Pair your chosen EFR with proper tuning, adequate cooling, and a robust fuel system, and you will have a build that delivers reliable power and an unforgettable driving experience.