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Cummins ISX15 / X15 Performance

Cummins ISX15 Performance & Replacement Parts

Diesel Power Source engineers high-performance turbos and exhaust manifolds for the Cummins ISX15 engine used in Class 8 semi-trucks and heavy-duty industrial applications. Built for consistent power under load, these upgrades deliver improved airflow, lower EGTs, and extended turbo life—keeping fleets productive and profitable.

Every DPS ISX15 performance part is designed to meet the rigorous demands of commercial trucking. Using high-nickel, thick-wall cast materials and CNC precision machining, our components outperform factory parts in both flow and durability. Whether you're maintaining a single rig or managing a fleet, Diesel Power Source offers solutions that boost efficiency, reliability, and performance without compromising emissions compliance.

Why Upgrade Your Cummins ISX15?

  • Lower Exhaust Gas Temperatures (EGTs): Increased flow reduces backpressure, preventing heat buildup under sustained heavy loads.
  • Improved Fuel Efficiency: Optimized air-to-fuel ratios enhance combustion for measurable MPG gains on long hauls.
  • Extended Engine Life: Cooler operating conditions and balanced airflow help reduce strain on pistons, valves, and turbos.
  • Stronger Materials: High-nickel castings resist cracking and fatigue caused by thermal expansion and vibration.
  • OEM-Compatible Fitment: Bolt-on design for easy installation with factory hardware and turbo configurations.

Applications Supported

  • Cummins ISX15 CM2350 / CM2250: Designed for modern EPA-compliant engines with precision flow characteristics.
  • ISX Dual Cam & Single Cam Variants: DPS manifolds and turbos fit both configurations with minimal modification.
  • Class 8 Trucks: Freightliner, Peterbilt, Kenworth, Volvo, International, and Western Star platforms supported.

Top ISX15 Performance Upgrades

  • ISX15 Exhaust Manifolds: High-flow, crack-resistant designs that stabilize boost pressure and improve turbo spool.
  • ISX15 Turbo Conversion Kits: Increase power and reliability with conversion options engineered for direct fitment.
  • S400 Turbo Systems: Ideal for fleets or performance builds seeking maximum boost control and efficiency.
  • Replacement Turbochargers: Direct-fit replacements with improved bearing life and temperature resilience.

Fitment & Maintenance

  • Fits Cummins ISX15 14.9L engines in Class 8 on-highway trucks and heavy-duty applications.
  • Always replace manifold and turbo gaskets during installation for proper sealing.
  • Use high-temp anti-seize and re-torque fasteners after initial heat cycles.
  • Compatible with both OEM and aftermarket EGR configurations when installed correctly.

Built for Fleet Efficiency & Reliability

Owner-operators and fleet managers rely on DPS for reduced downtime, stronger pulling power, and long-term reliability. Our ISX15 components are proven in both vocational and long-haul environments—supporting sustained boost pressure, stable EGTs, and efficient exhaust flow mile after mile.

Explore related categories: ISX15 Exhaust Manifolds, ISX15 Turbo Conversion Kits, and Commercial & Semi Performance Parts.

For smaller engine platforms, view Dodge Cummins Performance or Add-A-Turbo Kits.

 

Frequently Asked Questions

Diesel Power Source® offers three upgrade paths for the ISX15 and X15. The HE400VG replacement in 67mm or 70mm is a direct-fit option that maintains full emissions compatibility and factory functionality - the right choice for emissions-equipped trucks. The S400 complete turbo conversion kit replaces the factory VGT with a fixed-geometry S400-frame turbo and T6 manifold for deleted trucks targeting meaningful performance improvement. The ISX15 compound turbo kit brings two-stage compound technology to the platform - S472/S488 and S475/S488 configurations supporting 550 to 700 HP with faster spool and cooler operating temperatures than any single turbo setup.

The HE400VG replacement uses the same variable geometry turbine housing as the factory unit with the same mounting pattern and actuator interface - it installs directly in place of the OEM turbo with no manifold changes and maintains full emissions system compatibility. The S400 conversion replaces the factory VGT with a larger fixed-geometry S400-frame turbo using a new T6 exhaust manifold. The S400 flows significantly more air and delivers better EGT reduction under high load, but is designed for deleted trucks and does not maintain the variable geometry spool characteristics of the factory VGT. The correct choice depends on whether the truck is emissions-equipped or deleted, and what power level is the target.

The Diesel Power Source® ISX15 compound turbo kit uses two BorgWarner S400-series turbos in a series configuration. The high-pressure S472 or S475 turbo mounts at the exhaust manifold and spools quickly at low RPM, providing boost early in the power curve. The atmospheric S488 secondary turbo receives the compressed air from the high-pressure turbo and compresses it a second time before it enters the engine. This two-stage compression delivers faster spool than a large single turbo, more total airflow at peak load than a smaller single can provide, and cooler charge air temperatures from the more thermally efficient two-stage compression process. It is the same compound turbo technology Diesel Power Source® has proven on thousands of Cummins 5.9L and 6.7L pickup truck installations, scaled for the 14.9-liter ISX15 engine.

Yes. All Diesel Power Source® ISX15 turbo upgrade options - HE400VG replacement, S400 conversion, and compound kit - are designed to maintain factory Jake brake functionality. Engine braking is essential for safe operation of a loaded semi-truck on grades and descents, and preserving it was a core design requirement across the ISX15 product lineup. If you have specific questions about Jake brake compatibility with your truck's particular configuration, provide your Engine Serial Number when contacting the team for confirmation.

For emissions-equipped fleet trucks the HE400VG replacement in 70mm provides the best combination of reliability improvement and modest performance gain without any emissions system changes - straightforward to install across a fleet with consistent results. For deleted fleet trucks where performance and fuel economy improvement are priorities, the S400 conversion delivers consistent, meaningful results across applications. For owner-operators or performance-focused fleet applications on deleted trucks, the compound kit delivers the best overall result - better spool, better EGT control, and higher power potential - with the same bolt-in installation approach as the single turbo options. Diesel Power Source® offers fleet and dealer programs for volume purchasing.

Yes. Many Diesel Power Source ISX15 components are designed for emissions-equipped engines. Always verify part specifications and follow federal and local emissions guidelines.

In most cases, yes. Smoother airflow and reduced backpressure help the ISX15 engine burn fuel more efficiently, often improving mileage under load.

No tuning is required for direct-replacement parts. However, if additional fueling or airflow modifications are made, calibration can further optimize performance.

Yes. Our manifolds use thick-wall, high-nickel cast iron and precision CNC machining, significantly reducing cracking and warping common with OEM designs.

Absolutely. Diesel Power Source offers dealer and fleet programs with volume pricing and logistics support for ongoing maintenance needs.

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