What Are Downpipes?

In turbocharged vehicles, the downpipe is the section of the exhaust system that connects the turbocharger’s turbine outlet to the rest of the exhaust. Its primary job is to channel high-temperature, high-pressure exhaust gases away from the turbo as quickly as possible. The factory downpipe is typically restrictive, designed to meet noise and emissions regulations while keeping costs low. Aftermarket performance downpipes, like those from Borla, open up this critical bottleneck to reduce backpressure, improve turbo spool time, and increase overall engine efficiency.

By reducing the restriction immediately after the turbo, an upgraded downpipe can unlock significant horsepower and torque gains, often without any other modifications. The effect is most noticeable in vehicles where the factory downpipe has a narrow diameter, crushed bends, or a high-cell-count catalytic converter. The Borla Stinger Downpipe replaces these restrictive components with mandrel-bent, smooth-flowing tubing and a high-flow or catless design, ensuring exhaust gases escape with less backpressure.

The Borla Stinger Downpipe Line

Borla’s Stinger downpipes are engineered for owners who want a noticeable increase in power and a more aggressive exhaust note without sacrificing quality or durability. Each Stinger downpipe is constructed from T304 stainless steel, offering excellent corrosion resistance and longevity. Mandrel bending preserves the inner diameter through every curve, maintaining optimal flow velocity and preventing turbulence.

Two main variants are available:

  • High-Flow Catalytic Converter (Catted) Downpipes – Designed for street use, these downpipes incorporate a high-flow, low-restriction catalyst that reduces emissions while still improving flow. They are less likely to trigger a check engine light (CEL) and are legal for use in areas with emissions testing, provided the vehicle retains its original ECU calibration or a tune that supports the catalyst.
  • Catless Downpipes – Removing the catalytic converter entirely provides the maximum possible flow and the loudest, most aggressive sound. Catless downpipes are popular for dedicated track cars or off-road use but will often trip a CEL unless the ECU is tuned to disable the rear O₂ sensor’s catalyst efficiency monitor. They are not legal for on-road use in many regions.

Both options feature a direct-fit design with OEM-style flanges and hangers, allowing for a straightforward installation process. Borla also includes all necessary hardware, gaskets, and instructions. The Stinger name carries through a variety of applications including popular turbo platforms like the Ford Mustang EcoBoost, Ford Focus RS, Ford F-150 (EcoBoost engines), and several European turbo models.

Benefits of Upgrading to Borla Stinger Downpipes

Increased Horsepower and Torque

By reducing the exhaust restriction after the turbo, Borla Stinger downpipes allow the engine to expel spent gases more efficiently. This lowers the pressure ratio across the turbine, enabling the turbo to spool faster and produce more boost with the same wastegate setting. Typical wheel horsepower gains range from 15 to 30 hp and 20 to 40 lb‑ft of torque, depending on the vehicle and supporting modifications. On some platforms, pairing the downpipe with a custom tune can push gains even higher.

Enhanced Sound – The Stinger Signature

The aggressive, deep exhaust note is perhaps the most celebrated feature of Borla Stinger downpipes. Removing or replacing the restrictive factory catalyst dramatically changes the sound profile. The tone becomes deeper and more authoritative, with a distinct rasp under hard acceleration. At idle, the exhaust is noticeably louder, and a crisp burble is common on deceleration. Many owners describe the sound as “race-car like” without being excessively obtrusive during cruising.

The Stinger family includes both resonated and non-resonated options on some applications. A resonated downpipe adds a small resonator to reduce drone while preserving the aggressive character. Non-resonated versions are louder and more raw, preferred by those seeking maximum sound intensity.

Improved Turbo Response

With less backpressure after the turbine, the turbocharger can accelerate faster. This leads to quicker spool times and reduced lag, especially in lower RPM ranges where boost pickup occurs. The result is a more responsive throttle and a more engaging driving experience. Many users report that the car feels livelier through the mid-range, with power building smoothly from just off idle.

Durable Construction

Borla backs its downpipes with a limited lifetime warranty, a testament to the confidence in their T304 stainless steel construction and precision welding. The material resists cracking and corrosion even under extreme heat cycles, ensuring the downpipe retains its appearance and performance over many years. The flanges are laser-cut and thick enough to prevent warping, and all welds are contoured to maintain smooth exhaust flow.

Sound Characteristics: A Closer Look

The sound change from a Borla Stinger downpipe is not subtle. With the factory downpipe, the exhaust note is often muffled and tame, especially in modern turbocharged engines that are tuned for refinement. After installing the Stinger, the tone becomes more raw and aggressive, with a pronounced low-frequency rumble at idle.

  • Cold Start – The exhaust is significantly louder during cold start, with a quick rev‑up sequence that transmits a deep bark through the tailpipes. Some owners appreciate this as an audible performance upgrade, but it may be noticeable to neighbors.
  • Cruising – At highway speeds under light throttle, the noise level is manageable, especially with a resonated design. Drone is minimal in most applications, but catless versions can produce a slight resonance between 2000-2500 RPM.
  • Wide‑Open Throttle (WOT) – This is where the Stinger downpipe truly shines. The exhaust note opens into a full, aggressive roar that builds with RPM. The turbo whistle is more present, and gear shifts are punctuated by sharp burbles or pops on overrun, particularly with an aftermarket cat‑back system.

For drivers who want maximum aggression, pairing the Stinger downpipe with a Borla S‑Type or ATAK cat‑back exhaust creates one of the loudest and most distinctive exhaust notes on the market. For a more balanced approach, a touring cat‑back will add deeper tone without excessive volume.

Installation Process

Installing a Borla Stinger downpipe is a moderately challenging job best performed with a lift or jack stands and basic hand tools. The complexity varies by vehicle, but general steps include:

  1. Preparation – Disconnect the battery (to avoid electrical issues) and allow the exhaust to cool completely. Apply penetrating oil to the turbo-to-downpipe bolts and O₂ sensor threads a day before to ease removal.
  2. Removal of Factory Downpipe – Unbolt the turbo outlet connection, disconnect the exhaust from the mid-pipe, and remove the O₂ sensors from the factory catalyst. On many vehicles, the downpipe is tight against the firewall or suspension, requiring the removal of heat shields or steering column braces for access.
  3. Installation of Borla Downpipe – Slide the new downpipe into position, using new gaskets supplied in the kit. Torque the turbo outlet bolts to factory specifications. Reinstall the O₂ sensors – a copper anti‑seize compound on the threads is recommended.
  4. Reconnection – Attach the downpipe to the exhaust mid‑pipe, ensuring all clamps and springs are properly aligned. Torque all fasteners to spec and double‑check clearance from the frame, firewall, and steering shaft.
  5. Final Checks – Reconnect the battery, start the engine, and inspect for exhaust leaks. Let the vehicle idle for a few minutes, then test drive to listen for rattles and ensure no CEL appears immediately.

Professional installation is recommended if you lack experience with exhaust work or the tools required. Many shops charge 2-3 hours of labor. The process is often easier on vehicles with simpler exhaust routing (e.g., the Ford Mustang EcoBoost) than on transverse engine layouts.

Compatibility and Vehicle Fitment

Borla develops Stinger downpipes for a wide range of turbocharged platforms. Some of the most popular applications include:

  • Ford Mustang EcoBoost (2015–current) – The 2.3L four‑cylinder engine sees significant gains, with many owners reporting 20–25 hp and 25–30 lb‑ft at the wheels.
  • Ford Focus RS (2016–2018) – The 2.3L in the RS benefits from reduced restriction, helping the twin‑scroll turbo spool faster.
  • Ford F‑150 (2.7L, 3.5L EcoBoost) – These trucks gain audible turbo spool and a deeper tone without excessive drone.
  • Some Ford Transit and Explorer ST models – Also supported in certain years.

Before purchasing, always confirm that Borla offers a downpipe specific to your engine code and model year. Borla’s online fitment tool or a call to their support team can verify compatibility. Some vehicles may require additional adapters or modifications if an aftermarket intercooler or charge pipe is installed.

Real‑World Performance and Dyno Results

While exact gains depend on the vehicle and whether a tune is used, independent dyno tests on a 2018 Ford Mustang EcoBoost show a 22 hp increase at the wheels with a Borla Stinger catted downpipe and a stock tune. When paired with a quality aftermarket tune, the same car gained 32 hp and 40 lb‑ft over the baseline. Similar results are reported for the Focus RS, where a catless Stinger downpipe combined with a custom calibration produced a 35 hp gain at the wheels.

These figures highlight the importance of tuning. The stock ECU calibration may not fully exploit the extra flow, especially on catless downpipes where the engine’s air‑fuel ratio can be adjusted for maximum power. Many users also note improved throttle feel and quicker turbo spool, which translate to a more fun everyday driving experience.

Considerations Before Purchase

Catless downpipes are not legal for highway use in many jurisdictions (including most US states) because they remove the primary catalytic converter. Catted Stinger downpipes are a better choice for street‑driven vehicles subject to emissions testing. Always check local laws before making a purchase.

Check Engine Light (CEL)

Catless downpipes often trigger a P0420 code (catalyst efficiency below threshold) because the rear O₂ sensor sees the same gas composition as the front. A tune can disable this monitor. Catted downpipes with high‑flow catalysts are less likely to cause a CEL but can still trigger it on some vehicles. An O₂ spacer or mini‑cat may be required for stock ECU cars.

Need for a Custom Tune

While a downpipe can be installed without a tune, optimizing performance and avoiding potential issues (like fueling errors with catless pipes) makes a tune highly recommended. Many tuners offer “downpipe tunes” that adjust boost targets, fueling, and O₂ sensor thresholds.

Warranty Impact

Installing aftermarket parts can void factory warranty coverage for related components, particularly if a failure is traced back to the modification. The Magnuson-Moss Warranty Act protects consumers in the US, but the burden of proof may still require you to demonstrate that the downpipe did not cause the issue. Check with your dealer before modifying a new car under warranty.

Professional Installation

Due to the tight spaces and high torque specs on turbo bolts, professional installation is strongly recommended for inexperienced owners. A mistake at the turbo outlet can cause an exhaust leak that affects boost and spool.

Tuning and ECU Calibration

To fully realize the benefits of a Borla Stinger downpipe, a custom tune or off‑the‑shelf calibration is advised. Tuning allows you to:

  • Adjust boost targets to take advantage of the reduced backpressure.
  • Optimize air‑fuel ratios for maximum power without lean conditions.
  • Disable catalyst efficiency monitors to prevent CELs.
  • Fine‑tune throttle mapping and transmission shift schedules (if applicable).

Many reputable tuners offer remote tuning via email or online platforms. Popular options for Ford and other turbo platforms include Cobb Accessport Tuner vehicles with off‑the‑shelf stage 2 maps designed for downpipe upgrades. For maximum gains, a dyno tune by a professional tuner is best.

It’s worth noting that installing a downpipe without a tune can still provide noticeable gains, but the engine may not run optimally, and some power is left on the table. Always research whether your specific vehicle requires a tune for the downpipe variant you choose.

Conclusion

Borla Stinger downpipes represent a proven upgrade for turbocharged vehicles seeking more power, faster spool, and an unmistakably aggressive exhaust note. With high‑quality T304 stainless construction, options for catted or catless configurations, and a focused design that prioritizes flow, they deliver tangible performance improvements and a thrilling driving experience. However, the choice between catted and catless, the need for a tune, and compliance with local emissions laws should all be carefully considered. For enthusiasts willing to invest in installation and calibration, the Borla Stinger downpipe transforms the character of the car and unlocks its performance potential.

Explore the complete Borla Stinger downpipe lineup at Borla’s official website and check vehicle fitment using their search tool. For pricing and user reviews, trusted retailers such as AmericanMuscle offer application‑specific listings. And if you’re planning a full exhaust system upgrade, Summit Racing carries Borla Stinger downpipes as well as matching cat‑back and axle‑back systems for a coordinated performance build.