Compound Turbos for Cummins: The Complete Guide
Posted by Diesel Power Source® on May 25, 2026
Compound Turbos for Cummins: The Complete Guide
Compound turbo systems are the single biggest upgrade you can make to a Cummins diesel engine. Not because they add the most horsepower — though they do — but because they fundamentally change how efficiently the engine burns fuel. EGTs drop approximately 200–400°F under load. Fuel mileage improves. The truck tows better at every power level. And the engine lasts longer because it’s not fighting itself to make power.
This guide explains how compound turbos work on Cummins engines, why they outperform single turbos, what’s included in a DPS compound kit, how to choose the right size for your build, and what supporting modifications you need at different power levels.
How Compound Turbos Work on a Cummins
A compound turbo system uses two turbochargers working together in series — a smaller high-pressure turbo and a larger atmospheric turbo. The term “compound” refers to the two-stage compression that happens on the intake side, and the sequential energy extraction that happens on the exhaust side.
Exhaust Side (Where the Energy Comes From)
Exhaust gases leave the engine and hit the small turbo first. Because the small turbo has a compact turbine wheel and tight housing, it spools up quickly at low RPM — delivering the instant throttle response that Cummins owners expect. After the exhaust gases pass through the small turbo, they continue to the large turbo, which uses the remaining exhaust energy to spin its larger turbine wheel and add a second stage of compression on the intake side.
Intake Side (Where the Air Goes)
Fresh air enters through the large turbo’s air filter first. The large turbo compresses it (first stage). That pre-compressed air then feeds into the small turbo, which compresses it again to full boost pressure (second stage). The doubly compressed air passes through the intercooler to cool down before entering the engine.
Why This Works So Well
Each turbo operates within its most efficient range. The small turbo handles low-RPM response. The large turbo handles high-end airflow. Together, they cover the full RPM range better than any single turbo can. A single turbo large enough to support high horsepower will always have lag at low RPM. A single turbo small enough to spool fast will always run out of breath at high RPM. Compounds eliminate that compromise.
Why Compounds Outperform Single Turbos
The compound advantage goes deeper than “more air = more power.” Three things happen inside the cylinder that change how the engine operates:
1. More Complete Combustion
Compounds push enough air into the cylinder that combustion becomes significantly more complete. The engine extracts maximum energy from every drop of fuel instead of wasting unburned fuel as heat out the exhaust. This is the primary reason EGTs drop — the energy that used to leave as exhaust heat is now being converted to power inside the cylinder.
2. Excess Air Cools the Cylinder
The extra air molecules that compounds push into the cylinder that are not consumed during combustion actually absorb heat and pull cylinder temperatures down further. EGT reduction comes from two sources: better combustion and cooler cylinders. Most people don’t know this.
3. Balanced Intake-to-Exhaust Pressure Ratio
Compounds bring intake boost pressure up to match or exceed exhaust drive pressure — achieving a 1:1 ratio or better. This means the intake stroke is actually creating power that balances what the exhaust stroke robs from the engine. A single turbo almost always has higher exhaust pressure than boost pressure — you’re always fighting back-pressure. Compounds eliminate that penalty.
The Bottom Line
The compound advantage is: more complete combustion + cooler cylinders + balanced pressure ratio = the engine operating at its true efficiency potential. This is why compound-equipped trucks see approximately 200–400°F lower EGTs, improved fuel mileage, and measurably more power at every RPM — not from any single change, but from all three working together.
Compound Turbo Kit vs. Add-A-Turbo Kit
Diesel Power Source® offers two paths to compound turbo performance on Cummins trucks. Understanding the difference helps you choose the right one for your build.
Full Compound Turbo Kit
A complete twin-turbo system with both turbos, exhaust manifold, all piping, oil lines, and hardware. Both turbos are larger than stock, both are new, and the kit replaces the factory turbo entirely. This delivers the biggest improvement in EGT reduction and power available in the DPS lineup. All compound kits (except the 6.7L add-a-turbo) include a 2G-style exhaust manifold — either 12V (rectangular ports) or 24V (round ports) depending on engine year.
Best for: Heavy towing, high-HP builds, and customers wanting maximum performance and EGT reduction.
Add-A-Turbo Kit (Stocker Compound Kit)
This kit keeps the factory turbo in place and adds a larger DPS atmospheric turbo (S475 or S480) in front of it. The new large turbo “turbocharges” the factory turbo, creating a compound system at a lower cost because only one new turbo is needed. Available for 2007.5–2018 6.7L Cummins trucks. The factory turbo serves as the high-pressure (small) turbo: HE351VE on 2007.5–2012 trucks, HE300VG on 2013–2018 trucks.
On 2010–2018 trucks, DPS uses a patented cast hot pipe — a single casting that routes all exhaust from the stock turbo to the atmospheric turbo and back to the factory downpipe. This cast design does not crack like welded pipe designs. No competitor offers this.
Best for: Customers whose factory turbo is in good condition, who want compound benefits at a lower price, or who want a future upgrade path to a full compound kit.
Emissions compatibility: The add-a-turbo kit is designed to work with or without factory emissions equipment. EGR, DPF, and factory exhaust brake can all remain intact. This is a key advantage over full compound kits, which require emissions removal.
Compound Turbo Sizing Guide
5.9L Cummins Compound Kits (1989–2007)
| Small Turbo (HP) | Large Turbo | Max HP (RWHP) | Best For |
|---|---|---|---|
| S362/68/.70 | S475/96/1.32 | 625 | Entry-level compound. Towing, daily driving. |
| S363/68/.70 | S475/96/1.32 | 625 | Daily/towing. Slightly more air than S362. |
| S363/73/.80 | S475/96/1.32 | 650 | Versatile. Towing + moderate performance. |
| S363/73/.80 | S480/96/1.32 | 700 | Performance + towing. More top-end headroom. |
| S366/73/.80 | S480/96/1.32 | 1,000 | Performance builds. Sled pulling, racing. |
| S369/73/.80 | S480/96/1.32 | 1,200 | High-performance. Competition. |
Budget pick for 5.9L: The S362/68/.70 over S475 is the entry-level kit. It spools up very well even on slightly modified 5.9L trucks and tows amazingly despite being the smallest configuration.
6.7L Cummins Compound Kits (2007.5–2018)
The 6.7L is approximately 13.5% larger displacement than the 5.9L. Larger turbos on the 6.7L spool similarly to smaller turbos on the 5.9L, which is why 6.7L compound kits start with larger turbos than 5.9L kits.
| Small Turbo (HP) | Large Turbo | Max HP (RWHP) | Best For |
|---|---|---|---|
| S363/73/.80 | S475/96/1.32 | 650 | Entry-level 6.7L compound. Towing, daily. Spools like S362 on 5.9L. |
| S363/73/.80 | S480/96/1.32 | 700 | Towing + moderate performance. S480 adds top-end flow. |
| S366/73/.80 | S480/96/1.32 | 1,000 | Performance builds. Popular mid-to-high range. |
| S369/73/.80 | S480/96/1.32 | 1,200 | High-performance. Competition. Largest S300 compressor. |
6.7L Add-A-Turbo Kits (2007.5–2018)
| Factory Turbo (Years) | Atmospheric Turbo | Max HP (RWHP) | Best For |
|---|---|---|---|
| HE351VE (2007.5–2012) | S475/96/1.32 | 600 | Towing, daily. Emissions compatible. |
| HE300VG (2013–2018) | S475/96/1.32 | 600 | Towing, daily. Emissions compatible. |
| HE300VG (modified) | S480/96/1.32 | 800 | Extreme power, factory turbo retained. |
How to choose: Estimate your target horsepower at the rear wheels. For most towing and daily driving builds on the 5.9L, the S362 or S363 over S475 covers it. For the 6.7L, start with the S363/73/.80 over S475. If your power goals exceed approximately 650 RWHP, move to the S480 atmospheric turbo for more top-end headroom. Competition and sled-pull trucks typically run S366 or S369 configurations.
What’s Included in a DPS Compound Turbo Kit
DPS compound kits are complete — everything needed for installation comes in one box. No hunting for parts from multiple suppliers.
- S300 high-pressure turbo (S362, S363, S366, or S369 depending on stage) with wastegate
- S400 atmospheric turbo (S475 or S480 depending on stage)
- 2G-style exhaust manifold (12V or 24V ports, matched to engine year)
- Cast hot pipe (patented DPS design on 2010–2018 trucks — does not crack like welded steel)
- Complete cold-side charge piping (large-turbo-to-small-turbo and small-turbo-to-intercooler)
- Kevlar/Nomex lined silicone low-pressure charge pipe
- Chrome-plated aluminum high-pressure charge pipe
- Exhaust downpipe (connects to factory exhaust)
- Complete intake with high-flow air filter
- Steel braided oil supply lines for both turbos
- Stainless steel oil drain lines (separate drains for each turbo)
- Support bracket for atmospheric turbo
- V-band clamps, T-bolt clamps, and all hose clamps
- Turbo and manifold gaskets
- All mounting bolts, adapters, and hardware
Not included: Intercooler unit (uses your existing stock or aftermarket intercooler — notify DPS if running an aftermarket unit with larger connections), tuning/programmer, and emissions delete components.
Optional Upgrades
Turbonator® VGT Exhaust Housing
The Turbonator® VGT can replace the standard fixed-geometry exhaust housing on the S300 high-pressure turbo. This adds variable geometry capability for approximately 200–300 RPM faster spool-up (depending on turbo size) and optional exhaust braking. The VGT uses patented aerospace-grade stator technology that adjusts the effective A/R ratio from approximately 0.45 to 1.1 — giving you the spool of a small turbo at low RPM and the airflow of a large turbo at high RPM.
- VGT without exhaust brake (+$950) — Adds approximately 200–300 RPM faster spool
- VGT with exhaust brake (+$1,850) — Adds spool improvement plus integrated exhaust braking
Ball Bearing CHRA
The dual ceramic ball bearing center section replaces the standard journal bearing CHRA on the S300 high-pressure turbo. Ball bearings have less rotational friction, which improves spool-up by approximately 200 RPM — a consistent gain independent of turbo size. Cost is approximately $550 more than journal bearing.
Ball bearing and VGT can be combined. Stacking both yields up to approximately 500 RPM faster spool than a comparable journal bearing fixed-A/R turbo — the fastest-spooling compound configuration DPS offers.
Large Turbo Billet Upgrade
Optional billet compressor wheel upgrade available on the S475 or S480 atmospheric turbo with race housing for additional airflow capacity at the top end.
Supporting Modifications by Power Level
Compound turbo kits can support power levels from stock fueling all the way to 1,200+ RWHP. But the engine and drivetrain need supporting modifications at certain thresholds. Here is what to plan for:
| HP Threshold (RWHP) | What Needs Attention | Details |
|---|---|---|
| ~400 | Transmission | Factory transmission typically requires modifications or upgrades. First major component to need attention. |
| ~500–550 | Fuel System | Stock fuel system reaches its limit. Injectors, pump, and supply upgrades needed. |
| 45–55 PSI boost | Head Studs | 1988–2002: 45 PSI. 2003–2007: 55 PSI. 2007.5–2018: 48 PSI. |
| 55–65 PSI boost | Fire Rings / O-Rings | 1988–2002: 55 PSI. 2003–2007: 65 PSI. 2007.5–2018: 55 PSI. |
| ~800+ | Aftermarket Connecting Rods | General rule across all modern Cummins. Below this, stock rods handle the load with proper tuning. |
Many customers run compounds on completely stock fuel with zero other upgrades. EGTs drop approximately 200–300°F, the truck tows better, and fuel mileage improves — all because the engine is finally burning fuel efficiently. Compounds are not exclusively for high-HP builds. When sized correctly, they work at any performance level, even stock fueling.
Available Platforms
DPS builds compound turbo kits for every Cummins platform:
- 12V Cummins Compound Kit (1989–1998)
- 24V Cummins Compound Kit (1998.5–2002)
- 3rd Gen 5.9L Compound Kit (2003–2007)
- 6.7L Cummins Compound Kit (2007.5–2018)
- Add-A-Turbo Kit for 5.9L & 6.7L Cummins
- Fummins Compound Kit (Ford Cummins Swap)
- Chummins Compound Kit (Chevy Cummins Swap)
DPS is the only manufacturer that builds compound kits specifically engineered for Fummins (Ford Cummins swap) and Chummins (Chevy Cummins swap) conversion vehicles. No other manufacturer produces a compound kit designed to fit these conversion chassis.
Frequently Asked Questions
Do I need a compound turbo kit, or is a single turbo enough?
DPS makes excellent single turbos, and for many builds a single turbo is the right choice. But if you want mild street manners and want to tow over approximately 600–650 HP, compounds are typically the only way to get both at the same time. At those power levels, a single turbo large enough to make the power gives up low-end response. Compounds solve that by splitting the load between two turbos.
Can I run a compound kit on stock fuel with no other modifications?
Yes. Many DPS customers run compound kits on completely stock fuel with zero other upgrades. The entry-level compound kits (S362 over S475 on 5.9L, S363/73/.80 over S475 on 6.7L) work well even at stock power levels. EGTs still drop approximately 200–300°F, the truck still tows better, and fuel mileage still improves.
How much do EGTs drop with a compound turbo kit?
Compound turbo kits typically drop EGTs by approximately 200–400°F under load, depending on the configuration, fueling, and driving conditions. This is the biggest EGT reduction available from any single upgrade in the DPS lineup.
What is the difference between S475 and S480 atmospheric turbos?
The S475 is the standard atmospheric turbo, designed for stock HP up to approximately 600–650 RWHP. The S480 is the upgrade option for builds exceeding approximately 650 RWHP — it provides more top-end airflow headroom for higher fueling levels. Both use the same 96mm turbine wheel and 1.32 A/R housing.
Do compounds require emissions deletion?
Full compound kits require emissions removal. The add-a-turbo kit (which keeps the factory turbo) is emissions compatible — EGR, DPF, and factory exhaust brake can all remain intact. DPS does not sell emissions delete components.
What does the Turbonator® VGT add to a compound kit?
The Turbonator® VGT replaces the fixed-geometry exhaust housing on the S300 high-pressure turbo with a variable geometry housing. This adds approximately 200–300 RPM faster spool-up and optional exhaust braking capability. It is available on any 5.9L or 6.7L Cummins compound kit from 1988–2018.
Is the ball bearing upgrade worth it on a compound kit?
The ball bearing CHRA costs approximately $550 more and improves spool-up by approximately 200 RPM. For a customer already spending $4,000+ on a compound kit, $550 for measurable spool improvement is a smart investment. Ball bearing is especially valuable if you’re choosing a larger turbo configuration for more top-end power — it closes the spool gap without sacrificing airflow.
What comes in the kit? Do I need to buy anything else?
DPS compound kits include both turbos, exhaust manifold, all charge piping, oil lines, intake, air filter, downpipe, gaskets, clamps, and all hardware. The kit bolts directly to the stock intercooler, intake, and exhaust connections. You do not need to buy intercooler piping, intake piping, or exhaust piping separately. Tuning (programmer) is your responsibility and not included.
Why Diesel Power Source for Compound Turbo Kits
Diesel Power Source® built its reputation on compound turbo kits for Cummins diesel trucks. DPS compound kits are designed using CAD/CAM software and CFD (Computational Fluid Dynamics) testing to deliver factory-like fit with performance-level results. Every kit is a complete, bolt-on system — no hunting for parts, no fabrication, and no compatibility guesswork.
- Complete kits — Everything in one box, nothing else needed
- 13+ stage options on 5.9L alone — From 625 HP towing builds to 1,200 HP competition
- CFD-tested airflow — Optimized piping and manifold geometry
- Bolt-on fit — No cutting, welding, or fabrication
- Patented cast hot pipe — Does not crack like welded steel (2010–2018)
- Thousands of kits sold — Proven across every Cummins platform
- Designed and built in the USA
Ready to upgrade? Browse DPS Compound Turbo Kits to find the right configuration for your Cummins. Need help choosing? Call 801-930-8404.
