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S400 Cummins ISX / ISX15 / X15 Complete Turbo Conversion Kit T6
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S400 Turbo Cummins
S400 Turbos for Cummins: ISX15 / X15 Conversions, Compounds, and Pickup Builds
S475, S478, and S480 turbos built on the S400 platform, with T6 conversion kits for the ISX15 / X15 and S400 options for 5.9L and 6.7L Cummins pickups.
Diesel Power Source® S400 turbos are built on the S400 platform, the larger frame above the S300. On the Cummins ISX15 / X15, a DPS S400 replaces the factory VGT as a single turbo through the S400 conversion kit, or runs as both stages of an S400-over-S400 compound kit. On 5.9L and 6.7L Cummins pickups, the S400 is the large atmospheric turbo in DPS compound and Add-A-Turbo kits, and it is available as a single turbo in the Turbonator® VGT line. Every size in the current lineup uses a 96mm turbine inducer; the compressor wheel and housing A/R change with the power goal.
S475, S478, S480
75mm, 78mm, and 80mm compressor wheels on a 96mm turbine
S478 Most Popular
The most popular turbo in DPS ISX15 / X15 conversion kits
T6 for ISX15 / X15
Paired with the DPS T6 exhaust manifold for a complete conversion
Turbonator® VGT Ready
VGT turbine housings available for S400 turbos
Shop S400 Turbos and Kits
- S400 ISX15 / X15 Complete Turbo Conversion Kit: A DPS S400 turbo, T6 exhaust manifold, and conversion hardware that replace the factory VGT on deleted ISX15 / X15 trucks. Available with the S475, S478, or S480.
- S400 Turbo for T6 ISX: The DPS S400 turbo on its own in S475, S478, and S480 sizes, for customers building their own T6 setup.
- S475, S478, and S480 S400 Turbos (T6): T6-flange S400 turbos in S475, S478, and S480 sizes. An ESN is required at order.
- T6 Exhaust Manifold for Cummins ISX15 / X15: The DPS T6 manifold for S400 conversions on deleted trucks. Cast from High Silicon Molybdenum Ductile iron (HSMD), CFD-tested, with a press-fit multi-piece design.
- S400 ISX Conversion Kit: Piping and Hardware: The piping, oil lines, adapters, and hardware for customers who already have an S400 turbo and T6 manifold.
- ISX15 / X15 Compound Turbo Kit: An S400-over-S400 compound system, with S400-platform turbos as both the high-pressure and atmospheric stages.
- Turbonator® VGT S300 and S400 Turbos (T3 and T4): Complete S400 turbos with the Turbonator® VGT turbine housing in T3 and T4 flanges for Cummins pickup builds.
- Turbonator® VGT Housing for S400 T6 Turbos: Adds variable geometry to an existing T6 S400, with or without engine braking.
S400 Sizing for the ISX15 / X15 Conversion
| Turbo | Compressor Wheel | Best For |
|---|---|---|
| S475/96/1.32 | 75mm | Builds below 550 HP; the smallest and quickest-spooling option |
| S478/96/1.32 or 1.15 | 78mm | 550-650 HP; daily hauling plus performance, and the most popular DPS ISX conversion turbo |
| S480/96/1.32 | 80mm | Builds above 650 HP |
HP figures are approximate and vary with tuning, fueling, and supporting modifications. An engine serial number (ESN) is required on every ISX15 / X15 order. Verify your ESN with DPS before ordering.
Where the S400 Fits in a Cummins Build
ISX15 / X15 Single Turbo Conversion
The S400 conversion kit replaces the factory VGT turbo and manifold with a DPS S400 and T6 exhaust manifold. It lowers exhaust drive pressure and EGTs. On an ISX single turbo, DPS targets exhaust pressure 5-10% higher than boost, with 1.09:1 as the ideal ratio. The conversion is for trucks that have already been deleted.
ISX15 / X15 Compound Kits
DPS ISX compound kits use S400-platform turbos for both stages and produce a 20-25% power increase over the stock ISX15 / X15. The compound setup splits heat across two turbines and targets an exhaust-to-boost ratio of about 1:1.
5.9L and 6.7L Compound and Add-A-Turbo Kits
On Cummins pickups, the S475 is the standard atmospheric turbo in most DPS compound and Add-A-Turbo kits, and the S480 is the upgrade for higher power. When the small turbo has a 66mm or larger compressor wheel, DPS recommends the S480.
Single S400 on a Pickup
A single turbo large enough for 600-650+ HP gives up low-end response. For a truck that needs to tow and drive well at that power level, a compound kit is typically the better choice. For moderate power with quick spool, see S300 single turbos.
Fitment
- Cummins ISX15 / X15 (CM871, CM2250, CM2350, CM2450), ESN required
- 5.9L and 6.7L Cummins pickups through DPS compound, Add-A-Turbo, and Turbonator® VGT products
- Flanges: T6 for ISX15 / X15 and compound atmospheric turbos; T3, T4, or T4i for pickup single S400 turbos
Notes
- ISX15 / X15 S400 conversions are for trucks that have already been deleted. Diesel Power Source® does not sell emissions delete components.
- Warranty under the Diesel Power Source® PMA: S300 and S400 turbos are covered for 1 year / 15,000 miles, whichever comes first. Registration within 14 days of purchase is required.
- Not sure which size fits your build? Call 801-930-8404 or email sales@dieselpowersource.com.
Related categories: ISX15 Conversion Kits | ISX15 / X15 Performance | Compound Turbo Kits | Add-A-Turbo Kits | S300 Single Turbos. Free shipping on orders over $350.
Cummins is a registered trademark of Cummins Inc. Diesel Power Source® is not affiliated with Cummins Inc.
S400 Single Turbo Systems - FAQs
The numbers indicate compressor wheel inducer size (millimeters) and frame capacity:
- S472 (72mm): Smallest S400, best low-end spool for the class. Good for 600-700 HP builds wanting some street manners. Still laggy below 1,800 RPM.
- S475 (75mm): Most popular S400 for 650-800 HP street/strip trucks. Balanced spool vs. airflow. Common in mild competition use.
- S480 (80mm): Serious competition turbo. 750-900+ HP capability. Expect significant lag—this is for dedicated builds, not daily drivers.
- S483 (83mm): Maximum airflow for 900-1000+ HP. Sled pulling, pro drag racing, dyno competition. Professional-level builds only.
Larger turbos need more supporting mods (injectors, pumps, built transmission, aggressive tuning) to make power worth the lag trade-off.
Technically yes, but we don't recommend it. Here's why:
- Significant turbo lag: Below 2,000 RPM, you'll have minimal boost. City driving, stop-and-go traffic, and parking lots feel sluggish.
- Smoke: Without boost, the truck will smoke heavily until the turbo spools. Not great for daily use or emissions areas.
- Drivability: You'll constantly be downshifting or waiting for boost. Frustrating in normal driving.
Better options for street/daily use:
- 400-550 HP goals: S300 Single Turbos (S362, S366, S369)
- 600-700 HP with street manners: Compound Turbo Systems
S400 singles are best for dedicated competition trucks, weekend racers, or builds where performance matters more than daily comfort.
S400 turbos support serious horsepower with proper fueling and tuning:
- S472: 600-725 HP
- S475: 650-825 HP
- S480: 750-900+ HP
- S483: 900-1000+ HP
⚠️ Critical supporting mods required for these power levels:
- Large injectors (150-200% over stock or larger)
- Dual CP3 pumps or modded CP3 (6.7L)
- Built transmission (rated for 700+ HP)
- Aggressive custom tuning
- Upgraded fuel system (lift pump, lines, filters)
- Upgraded intercooler and cooling system
- Forged internals recommended beyond 800 HP
These are professional-level builds, not bolt-on upgrades. Budget $15k-30k+ for a complete S400-based high-HP system.
Not recommended. Here's why:
- Terrible low-RPM response: When pulling a grade from lower speeds (1,200-1,800 RPM), the turbo won't spool. You'll smoke and lose speed.
- Constant downshifting: You'll need to keep RPMs above 2,000-2,500 to maintain boost, meaning constant gear hunting.
- Frustrating experience: What should be confident towing becomes a struggle to keep the turbo lit.
For towing with high power (600-700+ HP), we strongly recommend:
- Compound Turbo Systems — Best low-end response, cooler EGTs, drive pressure control
- Large-frame S300 (S369) — Usable for moderate towing if you keep power under 600 HP
S400 singles shine in competition where you're in the high RPM range constantly. For real-world towing, they're the wrong tool.
For competition/dyno/drag racing (peak power): S400 single
- Simpler to tune for max power
- Less complexity = fewer failure points
- Lower cost ($3,500-5,000 vs. $5,500-7,500 for compounds)
- Proven in competition at 800-1000+ HP
For street/strip, heavy towing at high power, or sustained performance: Compound system
- Much better low-end response and drivability
- Cooler EGTs under sustained load
- Lower drive pressure = less engine stress
- Can tow heavy loads safely at 700+ HP
Bottom line: If you're ONLY racing and don't care about street manners, S400 singles are king. If you want high power that's also usable for towing or street driving, compounds are the better choice despite higher cost.
