Overview of ATS Diesel Exhaust Upgrades

Diesel engine performance hinges on efficient air exchange, and the exhaust system plays a critical role in freeing up horsepower and torque while managing heat and backpressure. Among the aftermarket options, ATS Diesel Exhaust upgrades have carved out a strong reputation for reliability, material integrity, and a distinctive acoustic character. This review dives deep into the material quality, sound signature, installation process, and broader performance benefits of ATS exhaust systems, providing both seasoned tuners and first-time upgraders with actionable insights.

Material Quality: Beyond Stainless Steel

Alloy Selection and Corrosion Resistance

ATS Diesel Exhaust systems are predominantly fabricated from T-304 stainless steel, an austenitic alloy containing 18% chromium and 8% nickel. This composition offers superior resistance to oxidation and pitting compared to lower-grade 409 stainless steel commonly found in budget exhausts. The T-304 material withstands exhaust gas temperatures exceeding 1600°F without scaling, crucial for diesel engines that produce sustained high thermal loads under towing or hauling conditions.

For applications where weight is a concern, ATS offers aluminized steel options in certain configurations. While not as corrosion-resistant as T-304, aluminized steel provides a cost-effective alternative for vehicles operating in drier climates and still outperforms standard mild steel by a factor of three to five in rust resistance.

Mandrel-Bent Tubing and Flow Dynamics

The use of mandrel-bent tubing distinguishes ATS from brands that rely on press-bending. Press bends create crimps that restrict exhaust flow by 15–25% in the bend radius. Mandrel bending preserves the full inner diameter through every curve, ensuring that the cross-sectional area remains constant. This is especially important for diesel engines that depend on high-volume exhaust flow to spool turbochargers efficiently. ATS utilizes CNC mandrel benders with precise tooling to achieve consistent, radius-optimized bends that minimize turbulence and backpressure.

Precision Weld Quality

ATS employs automated TIG (tungsten inert gas) welding on all critical joints. TIG welding produces a clean, contamination-free bead with deep penetration, reducing the risk of stress cracks and exhaust leaks at high vibration frequencies. Each weld is visually inspected and pressure-tested for leaks before shipping. The result is a system that maintains structural integrity even under the pulsating loads of a modified diesel engine.

Flange and Hardware Specifications

Flanges are laser-cut from 3/8-inch thick steel and feature a machined sealing surface to accommodate high-quality gaskets. ATS includes grade 8 stainless steel bolts and locking nuts with the system to prevent corrosion seizure, a common issue in exhaust hardware exposed to road salt and moisture. Slip-fit joints, where used, incorporate heavy-duty stainless steel clamps with a 360-degree wrap to ensure even clamping force and eliminate leak paths.

Sound Profile: Balancing Aggression with Civility

Acoustic Characteristics by Configuration

ATS exhaust systems are designed to deliver a deep, commanding tone without the high-frequency rasp associated with some aftermarket systems. The sound output varies by system type:

  • Straight-through (non-muffler) systems: Produce an aggressive, pronounced diesel rumble under heavy throttle, with a moderate cab drone at specific RPM ranges (typically 1800–2200 RPM in automatic transmissions).
  • Muffled systems (ATS performance silencers): Reduce overall decibel output by 4–6 dB while retaining the low-frequency growl. These systems use a packed, perforated core design that attenuates high-frequency noise without creating excessive backpressure.
  • Dual-exit systems: Introduce a broader, more immersive soundstage due to separate resonator paths, though driver perception of volume is similar to single-exit configurations.

Drone Mitigation Engineering

One of the most common complaints with diesel exhaust modifications is the presence of drone – a sustained low-frequency resonance at highway speeds. ATS addresses this through tuned helmholtz resonators integrated into specific applications. These resonators cancel out targeted frequencies around 90–120 Hz, the primary drone band for four- and six-cylinder diesel engines. The result is a cabin experience that remains comfortable during long-distance cruising, with measurable reductions in interior noise by 3–5 dB at 70 mph compared to non-resonated systems.

Sound Level Testing Data

Independent noise tests on ATS 4-inch exhaust systems on 6.7L Cummins engines show idle measurements around 72 dB (compared to stock 65 dB) and full-throttle readings of 98 dB at 15 feet. These numbers place ATS systems in the “moderate to loud” category – capable of turning heads without drawing noise complaints from neighbors. By comparison, open-pipe exhausts often exceed 105 dB under the same conditions.

Installation Tips for ATS Diesel Exhaust Upgrades

Pre-Installation Preparation

Before lifting the vehicle, consult the ATS official installation instructions for your specific model, as downpipe routing, sensor locations, and hanger positions differ between 2nd-gen, 3rd-gen, and 4th-gen trucks. Clear the work area of clutter and allow at least four hours of dedicated labor time for a complete system swap.

  • Safety equipment: Wear gloves, eye protection, and hearing protection (especially if the old exhaust must be cut). Use jack stands rated for the vehicle's weight – never rely on a hydraulic jack alone.
  • Penetrating lubricant: Spray all exhaust manifold bolts and oxygen sensor threads with a penetrating oil (e.g., WD-40 Specialist or Kroil) 24 hours before work to ease removal.
  • Torque wrench calibration: Ensure your torque wrench is calibrated for the low range (typically 35–55 ft-lb for exhaust components) to avoid overtightening flanges and stripping bolts.

Removing the Factory System

Diesel exhaust systems often rust-seize at slip joints and clamp connections. Use an oxy-acetylene torch or a cutoff wheel to remove corroded sections if they refuse to separate. Be cautious with oxygen sensors – unplug them from the harness before removing the pipe to prevent wire damage. If sensors are seized, apply heat with a torch and use a dedicated sensor socket to break them free without rounding the hex.

System Alignment and Fitment

ATS exhaust components are pre-formed to factory routing, but hanger positioning may require adjustment on lifted or modified chassis. Start the installation loosely at the downpipe flange, then work rearward, aligning each section to ensure adequate clearance from driveshafts, brake lines, and suspension components. Leave slip joints finger-tight until the entire system is hung, then tighten to the specified torque in sequence.

Leak Testing Post-Installation

After final torque, apply a soap-and-water solution to all joints with the engine idling. Look for bubbles that indicate escaping gases. A common leak point is the V-band clamp on the downpipe – verify it is fully seated and torqued to the manufacturer’s specification (often 50–60 ft-lb). If a leak persists, loosen the clamp, realign the flanges, and re-tighten.

Turbo Backpressure Considerations

Installing a free-flowing exhaust reduces backpressure, which can alter the turbocharger's wastegate response. On modern common-rail diesels, the ECM may need recalibration to prevent over-boost or surge. ATS recommends pairing their exhaust with a quality tuner (like the ATS Dakota Tuner) to optimize fueling and boost maps for the reduced restriction. Failure to address boost control can result in turbo overspeed and long-term damage.

Performance Gains: Measurable Results

Dyno-Tested Improvements

ATS publishes dyno data for their 4-inch turbo-back exhaust system on the 6.7L Power Stroke:

  • Gain of 25–35 horsepower at the rear wheels (peak)
  • Gain of 50–70 ft-lb of torque between 2000–2800 RPM
  • Reduction in exhaust gas temperature (EGT) by 150–200°F under load, allowing safer sustained towing

Results vary by truck model, tuning state, and intake configuration. Stock-tuned trucks typically see the lower end of the range, while those with lifted turbocharger housings or upgraded injectors realize the full potential.

Fuel Economy Considerations

Because the engine expends less energy expelling exhaust gases, fuel economy often improves by 0.5 to 1.5 mpg under mixed driving conditions. However, the aggressive sound can tempt heavier right-foot inputs, negating the efficiency gain. Drivers who maintain consistent cruising speeds report the best results.

Product Line Overview

ATS offers several exhaust system tiers to suit different budgets and performance goals:

  • Nutty Stage 1 (4-inch aluminumized steel): Entry-level, gains 15–20 hp, moderate corrosion resistance.
  • Stage 2 (4-inch T-304 stainless, with muffler): Best balance of durability and sound control, most popular option.
  • Stage 3 (5-inch T-304, straight-through): Maximum flow for heavily modified engines (500+ hp), loud under load.
  • Downpipe-back kits: Designed for trucks with aftermarket downpipes already installed, replacing mid-pipe and tailpipe sections only.

Complete systems include all required gaskets, clamps, and hardware. Downpipes are sold separately for vehicles without an existing upgrade.

Compatibility and Vehicle-Specific Notes

Dodge Ram with 6.7L Cummins (2007.5–2023)

These trucks benefit significantly from an ATS exhaust due to the restrictive factory diesel particulate filter (DPF) and selective catalytic reduction (SCR) system on later models. ATS offers delete-compatible exhausts that eliminate the DPF and SCR – note that deleting emissions equipment is illegal for on-road use in most jurisdictions. The sound profile on Cummins engines is particularly deep and throaty, with a distinctive turbo whistle enhancement.

Ford Power Stroke (2017–2024 6.7L)

ATS 4-inch systems for the 6.7L Power Stroke address the complex routing around the def tank and SCR. Installation is more involved due to the number of connections, but the acoustic gains are dramatic – the 6.7L engine produces a controlled rumble that avoids the drone of competitor systems.

Ram with 5.9L 24V (1998.5–2007)

These pre-2007 models lack complex emissions, making ATS exhaust a straightforward performance upgrade. Expect 30+ hp gains with a 4-inch system, and a raw, aggressive tone typical of earlier Cummins trucks.

Maintenance and Longevity

ATS T-304 stainless systems, if properly installed, should outlast the vehicle. Periodic inspection of clamp tightness (especially after the first heat cycle) and removal of road salt accumulations with a hose can prevent corrosion at fittings. Aluminized steel systems require more diligence – touch up any scratches with high-temp paint and replace corroded clamps annually.

Diesel exhaust soot deposits inside the pipe are normal and do not degrade flow meaningfully. However, if the engine produces excessive soot (indicated by black smoke), check for fueling malfunctions that could clog the exhaust over time.

Warranty and Support

ATS backs their exhaust systems with a limited lifetime warranty on construction defects for the original purchaser. The warranty covers weld failures, flange cracking, and premature corrosion on T-304 stainless systems. Aluminized products carry a one-year warranty. Exchanges require proof of purchase and inspection by ATS; installation damage or modifications are not covered. Customer support is available via phone and email, with typical response times under 24 hours on business days.

Competitive Comparison

When compared to aftermarket brands like MBRP, Flowmaster, or Magnaflow, ATS generally commands a 10–20% premium in pricing. The value proposition lies in the mandrel-bent T-304 construction, precision welding, and drone-canceling design that many budget systems lack. Users frequently cite the perfect balance of sound and comfort as the deciding factor. For those seeking the loudest possible setup, a straight-through 5-inch from ATS will outperform most competitors in flow volume.

Final Recommendations

ATS Diesel Exhaust upgrades represent a well-engineered choice for anyone serious about improving their truck's performance and auditory feedback. The materials deliver longevity in salt-belt climates, the sound is refined yet authoritative, and the installation process, while requiring patience and basic mechanical skill, is well-supported by documentation and customer service. For daily drivers, the Stage 2 4-inch T-304 system with muffler provides the best mix of gains, durability, and cabin comfort. For weekend track trucks or show rigs, the Stage 3 5-inch straight exhaust offers uncompromising flow and an unmistakable presence.

Whether you are upgrading to support a turbo swap or simply want to wake up the silence of a stock exhaust, ATS delivers a product that meets the expectations of the diesel community. For the latest application guides and pricing, visit the ATS Diesel Performance website and consult forums like Cummins Forum and Power Stroke Nation for real-world owner reviews and installation photos.