Cummins ISX15 / X15 Compound Turbo Kit — S472/S488 and S475/S488 Configurations
The Diesel Power Source® Compound Turbo Kit for Cummins ISX15 and X15 engines brings proven compound turbo technology from our pickup truck platform to the Class 8 semi truck market. This complete kit includes a DPS high-flow exhaust manifold, and two S400 series turbos in a compound staged configuration, delivering 500-900 horsepower with reduced turbo lag, cooler operating temperatures, and improved throttle response compared to a single turbo setup.
Two turbo combinations are available. The S472 over S488 configuration uses a 72mm high-pressure compressor for faster spool-up and stronger low-RPM response, making it well suited for towing and daily driving. The S475 over S488 configuration uses a 75mm high-pressure compressor for increased top-end airflow for higher horsepower engines.
Why Compound Turbos on an ISX15?
A compound turbo system uses two turbos working in series — a smaller high-pressure turbo feeds compressed air into a larger atmospheric (low-pressure) turbo. The atmospheric turbo compresses the air a second time before it enters the engine. This two-stage compression delivers several advantages over a single turbo setup on a 15L (14.9-liter) Cummins ISX15.
The high-pressure turbo spools faster because it's sized smaller relative to the engine displacement. This eliminates the lag common on large single turbo conversions, giving the truck immediate throttle response.
The result is a turbo system that acts like a small, responsive turbo at low RPM and a large, high-flow turbo at high RPM — without the compromises of either approach alone providing the sustained airflow needed for heavy-haul and high-HP applications.
Turbo Configuration Options
| Configuration | High-Pressure Turbo | Atmospheric Turbo | Best For |
|---|---|---|---|
| S472 / S488 | S472 — 72mm compressor inducer | S488 — 88mm compressor inducer | Towing, daily driving, faster spool, 500–900 HP |
| S475 / S488 | S475 — 75mm compressor inducer | S488 — 88mm compressor inducer | Higher HP goals, heavy haul, sustained load, 600–900 HP |
Both configurations use DPS S400-series turbochargers, forged milled compressor wheels, and 360-degree thrust bearing assemblies. These are the same proven, reliable turbo platforms used across the diesel performance industry for both pickup and Class 8 applications.
Key Features
- Compound (Twin-Stage) Turbo System — Two turbos working in series for faster spool, broader power band, and cooler intake air temperatures
- 500–900 HP Support — Sized for serious horsepower with proper tuning and supporting modifications
- High-Pressure Turbine Housing — Fast spool and strong low-RPM response on the S472/S475
- Atmospheric Turbine Housing — S488 sized for sustained high-RPM flow on the ISX15
- Maintains Most Jake Brake Functionality — Designed to allow engine braking
- Mounts in Factory Position — Engineered to fit cleanly with minimal cutting or fabrication
- Complete Kit — All components needed for installation are included
- Reduced Turbo Lag — The high-pressure turbo spools faster than any single turbo setup, delivering immediate throttle response
- Cooler Operating Temperatures — Two-stage compression produces cooler charge air than a single turbo working at higher pressure ratios lowering EGT's
- Fuel Mileage Improvements — Many drivers report measurable fuel economy gains due to improved combustion efficiency from cooler, denser charge air
- Proven Compound Technology — Engineered using our proven compound turbo design
Important Installation Note
Although mostly a bolt-on kit, depending on your truck configuration, additional modifications may be required during installation. This is typical for compound turbo systems on Class 8 platforms which have many variants between truck manufacturers.
Fitment
This compound turbo kit fits Cummins ISX15 and X15 engines with CM2250 and CM2350 ECM platforms. This kit is designed for use on previously deleted, non-emissions trucks only. Diesel Power Source® does not provide emissions delete components.
Please provide your Cummins Engine Serial Number (ESN) when ordering so our team can verify compatibility before shipment.
Compatible Truck Platforms: Freightliner, Peterbilt, Kenworth, Volvo, International, and Western Star with Cummins ISX15 or X15 power.
What's Included
- DPS High-Flow Exhaust Manifold — Press-fit 3-piece design, HSMD ductile iron, high temp coated
- S472 or S475 High-Pressure Turbocharger (based on selection) — Forged milled wheel, 360-degree thrust bearing, ported compressor housing
- S488 Atmospheric Turbocharger — 88mm compressor, forged milled wheel, 360-degree thrust bearing
- Compound turbo mounting brackets and hardware
- Inter-stage piping (high-pressure turbo outlet to atmospheric turbo inlet)
- Charge air piping, silicone couplers with Kevlar/Nomex liner
- V-band clamps
- Oil feed and drain lines for both turbos (flexible stainless steel braided)
- Exhaust downpipe
- Universal air intake system
- High-flow air filter
- All mounting hardware, gaskets, and installation components
- Complete installation instructions
- Includes both 5" to 5.5" and 5" to 7.33" intake couplers
Included Exhaust Outlet Configuration
- This kit includes a 90° exhaust outlet connection
- If your setup requires a different configuration, 45° outlets or cast elbows are available as add-on options at checkout.
Note: This compound turbo kit is for use on previously deleted, non-emissions trucks only. Diesel Power Source® does not sell or support emissions delete components. Please verify that your ESN matches the supported engine platforms before ordering.
How Compound Turbos Work
In a compound turbo system, exhaust gas flows from the engine into the high-pressure turbo first. This smaller turbo spools quickly and begins compressing air at lower RPM. The compressed air from the high-pressure turbo is then fed into the atmospheric (low-pressure) turbo, which compresses it a second time before it enters the engine's intake.
This two-stage compression is more thermally efficient than a single turbo compressing air to the same total pressure ratio in one step. The result is cooler charge air (which is denser and supports more complete combustion), faster boost onset, cooler EGT's, more power and a wider effective operating range.
For a detailed explanation of compound turbo systems, see our blog post: How Do Compound Turbos Work? | Compound Turbochargers Explained
Tuning Considerations
Like any compound turbo system, tuning is recommended to take full advantage of the increased airflow and to optimize fueling, boost targets, and shift strategy for your specific application. Running the compound kit without proper calibration may leave performance on the table and can affect drivability.
DPS recommends working with an experienced Cummins tuner who can adjust fueling and turbo parameters to match the compound turbo configuration. When tuning your truck for these compounds, it is important to note that this is a non-VGT setup.
Why Choose Diesel Power Source?
Diesel Power Source® has built its reputation on compound turbo kits. Our pickup truck compound systems for 5.9L and 6.7L Cummins engines are among the most trusted in the diesel industry, and this ISX15 compound kit brings the same engineering approach to the Class 8 platform. See our proven pickup compound kits here: 6.7L Cummins Compound Turbo Kits (2007.5–2018)
- Proven Compound Technology — Thousands of compound kits sold for Cummins pickup platforms, now engineered for ISX15 / X15
- DPS S400-Series Turbos — Industry-standard reliability with forged milled wheels and 360-degree thrust bearings
- Complete Kit — Everything you need in one box, no hunting for parts
- Factory Position Fitment — Minimal cutting or fabrication required
- Maintains most Jake Brake Compatibility — Designed to work with engine brakes
- ESN-Verified Fitment — We confirm compatibility before shipment
- Made in the USA
Warranty
This Diesel Power Source® Compound Turbo Kit includes a 1-year limited manufacturer warranty and is backed by our technical support team for fitment, installation, and tuning guidance.
Related ISX15 / X15 Products
- 6.7L Cummins Compound Turbo Kits (2007.5–2018) — The proven pickup platform this ISX15 compound kit is based on
- S400 Cummins ISX / ISX15 / X15 Complete Single Turbo Conversion Kit
- S400 Cummins ISX Turbo Conversion Kit (Without Turbo or Manifold)
- ISX15 T6 Exhaust Manifold for S400 Turbo
- HE400VG Turbo Replacement for Cummins ISX15 / X15 (Stock VGT)
- Turbonator® VGT for Cummins ISX Turbo
- Cummins ISX15 / X15 Non-EGR Exhaust Manifold
- ISX15 / X15 Exhaust Manifold Hardware Kit
Not sure whether a compound kit, single S400 conversion, or stock VGT replacement is right for your build? Contact us with your Engine Serial Number (ESN) and your horsepower goals, and we'll help you choose the best path.
- S472/88/1.15 over S488/88/1.58
- S475/88/1.15 over S488/88/1.58
Frequently Asked Questions
Both configurations use the same atmospheric S488 turbo (88mm compressor, 1.58 A/R housing) and the same mounting system. The difference is the high-pressure (primary) turbo, which uses a 1.15 A/R housing in both cases. The S472 uses a 72mm compressor that spools faster and delivers boost earlier in the RPM range, making it the better choice for towing and daily driving at 550–650 HP. The S475 uses a 75mm compressor that moves more air at higher RPM, supporting 600–700 HP for trucks targeting more aggressive horsepower.
Yes. This kit is designed to preserve factory engine brake functionality on Cummins ISX15 and X15 engines. Maintaining engine brake operation was a core requirement during the design and development of this kit.
Tuning is recommended to take full advantage of the increased airflow from the compound turbo system. Proper calibration of fueling, boost targets, and shift strategy will optimize performance, drivability, and fuel efficiency. DPS recommends working with an experienced Cummins tuner and monitoring boost, drive pressure, and EGTs during initial loaded runs.
This kit fits Cummins ISX15 and X15 engines with CM2250 and CM2350 ECM platforms. It is designed for use on previously deleted, non-emissions trucks only. Diesel Power Source does not sell or support emissions delete components. Please provide your Engine Serial Number (ESN) when ordering so we can verify compatibility before shipment.
A single S400 conversion replaces the factory turbo with one larger turbocharger, which improves top-end flow but can introduce turbo lag at lower RPM. A compound turbo system uses two turbos in series — the smaller high-pressure turbo spools quickly for immediate throttle response, while the larger atmospheric S488 handles the sustained airflow at higher RPM and load. The result is faster spool, broader power band, cooler intake temperatures, and higher horsepower potential compared to a single turbo setup. If you want the comparison, see our S400 Complete Single Turbo Conversion Kit.
