Add-a-Turbo Kit for 24V Cummins 1998.5–2002 | 2nd Gen HX35/HY35 Compound Turbo
The Diesel Power Source® Add-a-Turbo Kit for 1998.5–2002 Dodge Ram 2nd gen trucks adds an S475 atmospheric turbo to your existing factory HX35 or HY35 turbocharger, creating a compound twin turbo system that delivers 250–350°F lower EGTs, approximately 20% more horsepower and torque, and dramatically improved towing performance. Your stock turbo stays in place and the S475 spools faster than your stock turbo does by itself.
This kit includes everything for a complete bolt-on installation: DPS 3-piece exhaust manifold (pre-tapped for pyro), S475 turbo, cast hot pipe, 4" downpipe, all piping, oil lines, wastegate, hardware, and installation instructions. The included exhaust manifold is CARB exempt and EO numbered. Direct factory-like fit with no cutting or fabrication.
How This Kit Works on a 24V Cummins
Your factory HX35 or HY35 turbocharger becomes the high-pressure (primary) turbo in a compound system. The S475 atmospheric turbo compresses intake air first, then feeds that pre-compressed air to your stock turbo for a second stage of compression. This two-stage process delivers intake air that is typically over 100°F cooler than a single turbo at the same boost level, with boost-to-drive pressure ratios approaching 1:1.
Because your factory turbo handles initial spool, throttle response is the same as stock or faster. There is no added turbo lag. As RPM and load increase, the S475 picks up the airflow load and the compound effect delivers dramatically more air volume, lower EGTs, and stronger pulling power. The result is a truck that tows cooler, pulls harder, and drives better at every RPM.
There are a few minor modifications you make to your stock turbo to work with this kit. These modifications are reversible and the turbo can still be used as a standalone unit if you ever remove the add-a-turbo system.
CARB Exempt
The DPS 3-piece exhaust manifold included with this kit is CARB exempt and carries an Executive Order (EO) number.
What's Included
- S475 Atmospheric Turbo (75mm compressor, 96mm turbine, 1.32 A/R housing)
- DPS 3-piece exhaust manifold (pre-tapped for pyrometer ports)
- Cast exhaust hot pipe (routes exhaust from stock turbo to S475)
- Support bracket for S475 turbo
- High-flow air filter
- 4" exhaust downpipe included
- Kevlar/Nomex lined silicone low-pressure charge pipe
- Polished aluminum high-pressure charge pipe
- New wastegate actuator and bracket
- Steel braided oil supply lines
- Stainless steel oil drain lines (two separate drains)
- Turbo and manifold gaskets, oil line adapters, mounting bolts
- V-band clamps, T-bolt clamps, all hardware
- Complete installation instructions
You supply: Your existing factory HX35 or HY35 turbocharger (stays in place as the high-pressure turbo).
Key Features
- Uses Your Stock HX35/HY35 Turbo — No turbo replacement needed
- 250–350°F Lower EGTs — Two-stage compression runs dramatically cooler under load
- 20% HP and Torque Increase — Gains across the entire RPM range
- Spools Faster Than Stock — The compound effect actually improves spool response
- CARB Exempt Manifold — EO numbered 3-piece manifold included
- Supports Stock to 600 HP — S475 sized for the full 24V power range
- 4" Downpipe Included — Complete exhaust routing in the box
- Direct Bolt-On — No cutting or fabrication required
- Cast Hot Pipe — Will not crack like welded pipes
- Dual Oil Drains — Two separate oil drain lines for proper lubrication
Performance Specs
| Specification | Value |
|---|---|
| Horsepower Range | Stock to 600 HP |
| HP/Torque Increase | ~20% |
| EGT Reduction | 250–350°F |
| Mileage Impact | Same to +1 MPG |
| Smoke Reduction | Significant |
| Boost Capability | 55+ PSI (adjustable) |
| Intake Air Temp | Over 100°F cooler than single turbo at same boost |
Add-a-Turbo vs Complete Compound Kit (24V Cummins 1998.5–2002)
| Feature | Add-a-Turbo Kit (This Product) | Complete Compound Kit |
|---|---|---|
| Stock Turbo | Keeps factory HX35/HY35 | Replaces with DPS S300 |
| Manifold | Includes 3-piece manifold | Includes 3-piece manifold |
| Max HP | ~600 HP | Up to 1,100 HP |
| Install Complexity | Moderate (stock turbo stays) | More involved (full turbo swap) |
| Best For | Towing, daily driving, stock-to-moderate builds | High HP builds, competition, full overhaul |
If you plan to stay under 600 HP and want the simplest compound turbo installation for your 24V, the add-a-turbo kit is the right choice. If you want to build beyond 600 HP or already plan to replace your stock turbo, the complete 24V compound kit gives you more headroom.
Head Studs and Fire Rings
On 1998.5–2002 24V Cummins engines, head studs are highly recommended for boost pressures over 47 PSI. Fire rings are recommended for boost pressures over 55 PSI. This compound system is capable of well over 55 PSI but is adjustable depending on your truck and tune.
Fitment
This add-a-turbo kit fits 1998.5, 1999, 2000, 2001, and 2002 Dodge Ram 2500 and 3500 trucks with the 5.9L 24-valve Cummins engine and factory HX35 or HY35 turbocharger.
Automatic transmission note: Some 2nd gen trucks with automatic transmissions require relocation of the transmission oil cooler on the side of the engine block (not all automatics require this). DPS sells a trans cooler relocation kit for $149. Check the product options at checkout.
Have a different Cummins platform? DPS makes generation-specific add-a-turbo kits:
- Add-a-Turbo Kit for 6.7 Cummins 2007.5–2018 (Emissions Compatible)
- Add-a-Turbo Kit for 5.9 Cummins 2003–2007 (3rd Gen)
- Add-a-Turbo Kit for 12V Cummins 1989–1998
Related 24V Cummins Products
Frequently Asked Questions
Yes. Your factory HX35 or HY35 turbocharger stays in place and becomes the high-pressure turbo in a compound system. The kit adds an S475 atmospheric turbo. You will make a few minor modifications to your stock turbo, but these are reversible.
Some 2nd gen trucks with automatic transmissions require relocation of the trans oil cooler on the side of the engine block, but not all automatics need this. DPS sells a trans cooler relocation kit for $149 that can be added at checkout. Manual transmission trucks do not require this.
On 1998.5–2002 24V Cummins engines, head studs are highly recommended for boost pressures over 47 PSI, and fire rings for pressures over 55 PSI. This system is capable of well over 55 PSI. The lower thresholds compared to the 3rd gen engines are due to the 24V bottom end design.
Yes. All 2002 and older add-a-turbo kits include a 4" exhaust downpipe. The 2003–2007 kits bolt directly to the factory exhaust and do not need a separate downpipe.
Typical gains are approximately 20% more horsepower and 20% more torque across the RPM range. EGTs drop 250–350°F. Mileage stays the same or improves up to 1 MPG. Smoke is significantly reduced. The S475 supports power from stock all the way to 600 HP.
5 Reviews
-
Compound Kit is Sweet
Not that Larry Bird. Your Add A Turbo Kit for my 2012 made a huge improvement on towing with my truck. Great power and helped with my EGT temps. Once the stock turbo goes out I plan to upgrade with the Turbonator. Thanks for making a great fitting kit
-
Gday
Great choice for an aftermarket turbo, or even compounds! My DPS add on turbo kit is amazing, completely changed the truck, from EGTs, to spool and psi. Completely recommend yall!
-
Stocker
Great compounds,makes towing a breeze with 50# of boost & egt about 300 less now
-
Stocker
I bought this add a turbo kit for my 2005 Cummins and what a difference it made towing. I live in the west and travel some good mountain passes with a travel trailer. No issues with the EGTs and no down shifting. I already want to replace my stock turbo for their Turbonator turbo. Great kit! and everything came in it to install.
-
Stocker Kit for Ram
I don't normally comment on my truck part purchases, but I felt the quality of your kit was worth taking the time for. I recently purchased one of your stocker / S475 kits for my 06 ram. I have to say I am very impressed with the quality and packaging you guys do. This is my first compound turbo set up. I looked at many kits before purchasing yours. I looked at cheaper and more expensive. I had nearly talked myself into buying a cheaper kit. After receiving your kit I was immediately satisfied with spending the extra money on it. I opened the kit and was very impressed with the packaging alone. I thought to myself, if it performs half as well as it's packaged, I was going to be very happy. I had one issue after installation, but it turned out to be my fault for assuming. I assumed the tube from the output of the S475 to the input of my stock turbo was molded to the connector that uses V band clamp onto the S475. I had one extra clamp once installed and I thought it was odd, however I took the truck for it's test ride and was very impressed with the faster spool up but the system got very loud and not as much boost as I had anticipated. I found out very quickly where the extra clamp went. After that mistake was remedied The system is performing flawlessly. I am very satisfied with this kit. I look forward to putting it to the test towing in the Colorado mountains. I will be purchasing your intake for this same truck as well as probably upgrading my stock turbo to one of your new ball bearing turbos in the near future. I will not hesitate to recommend you guys to anyone who asks.
