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.
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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.
75mm, 78mm, and 80mm compressor wheels on a 96mm turbine
The most popular turbo in DPS ISX15 / X15 conversion kits
Paired with the DPS T6 exhaust manifold for a complete conversion
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.
Helpful Guides
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.
Frequently Asked Questions
What's the difference between the S475, S478, and S480 turbos?
The number after "S4" is the compressor wheel size in millimeters. All three use a 96mm turbine inducer.
- S475 (75mm): The smallest and quickest-spooling option. On the ISX15 / X15, best for builds below 550 HP. On 5.9L and 6.7L pickups, it is the standard atmospheric turbo in most DPS compound and Add-A-Turbo kits.
- S478 (78mm): For 550-650 HP on the ISX15 / X15, covering daily hauling plus performance. It is the most popular turbo in DPS ISX conversion kits.
- S480 (80mm): For ISX15 / X15 builds above 650 HP. On pickups, it is the atmospheric upgrade for higher power, and DPS recommends it when the small turbo has a 66mm or larger compressor wheel.
HP figures are approximate and vary with tuning, fueling, and supporting modifications. An ESN is required on every ISX15 / X15 order.
Can I daily drive a truck with an S400 single turbo?
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 Kits
S400 singles are best for dedicated competition trucks, weekend racers, or builds where performance matters more than daily comfort.
How much horsepower can I make with an S400 turbo?
On the ISX15 / X15 conversion, DPS sizes the S400 by power goal:
- S475: Builds below 550 HP
- S478: 550-650 HP
- S480: Builds above 650 HP
On 5.9L and 6.7L pickups, a single turbo large enough for 600-650+ HP gives up low-end response, so a compound kit is typically the better choice at that power level.
Supporting mods to plan for at high power on a pickup:
- Larger injectors
- Dual CP3 pumps or modded CP3 (6.7L)
- Built transmission
- Custom tuning
- Upgraded fuel system (lift pump, lines, filters)
- Upgraded intercooler and cooling system
- Forged internals recommended beyond 800 HP
HP figures are approximate and vary with tuning, fueling, and supporting modifications.
Will an S400 turbo work for towing heavy loads?
As a single turbo on a pickup, it is not recommended. Here's why:
- Poor 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 recommend:
- Compound Turbo Kits: best low-end response, cooler EGTs, drive pressure control
- Large-frame S300 (S369): usable for moderate towing if you keep power under 600 HP
On the ISX15 / X15, the S400 is the right frame for a single turbo conversion, sized to the power goal with the S475, S478, or S480.
S400 single turbo vs. compound turbos for high horsepower, which is better?
For competition/dyno/drag racing (peak power): S400 single
- Simpler to tune for max power
- Less complexity = fewer failure points
- Lower cost than a compound system
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, an S400 single works. If you want high power that's also usable for towing or street driving, compounds are the better choice.