Add-a-Turbo Kit for 12V Cummins 1989–1998 | 1st Gen & 2nd Gen Compound Turbo
The Diesel Power Source® Add-a-Turbo Kit for 1989–1998 Dodge Ram 1st gen and 2nd gen trucks adds an S475 atmospheric turbo to your existing factory 12-valve turbocharger, creating a compound twin turbo system that delivers 300–500°F lower EGTs and significantly more horsepower and torque across the entire RPM range. Your stock turbo stays in place. The S475 spools identical to your stock turbo while raising airflow dramatically.
This kit includes everything for a complete 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. Direct factory-like fit with no cutting or fabrication.
How This Kit Works on a 12V Cummins
Your factory 12-valve 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.
On the 12V platform, this compound effect is especially dramatic because the mechanical injection system responds immediately to the improved airflow and lower drive pressures. Throttle response feels stock or faster, with the S475 adding massive airflow capacity as RPM and load increase. The result is a 12V that tows cooler, pulls harder, and smokes less 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.
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 line (single drain — 12V engines have one oil drain port)
- 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 12-valve turbocharger (stays in place as the high-pressure turbo).
Key Features
- Uses Your Stock 12V Turbo — No turbo replacement needed
- 300–500°F Lower EGTs — Dramatic EGT reduction under load and while towing
- Spools Identical to Stock — Factory turbo handles low-RPM spool, no added lag
- Supports Stock to 600 HP — S475 sized for the full 12V 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
- Kevlar/Nomex Silicone Piping — Easier to install than steel, better flow
- 3-Piece Manifold — Pre-tapped for pyrometer, expansion joint design
Performance Specs
| Specification | Value |
|---|---|
| Horsepower Range | Stock to 600 HP |
| EGT Reduction | 300–500°F |
| Boost Capability | 55+ PSI (adjustable) |
| Intake Air Temp | Over 100°F cooler than single turbo at same boost |
| Spool Behavior | Identical to stock |
1st Gen vs 2nd Gen Installation Notes
This kit fits both 1st gen (1989–1993) and 2nd gen (1994–1998) 12-valve trucks. There are a few generation-specific installation considerations:
- 1st gen trucks (1989–1993): Intercooler hose modifications may be necessary depending on your specific truck configuration.
- 2nd gen trucks with automatic transmissions (1994–1998): Some trucks 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.
- All 12V engines: 12V engines have a single oil drain port, so the kit includes one oil drain line (newer platforms include two).
Add-a-Turbo vs Complete Compound Kit (12V Cummins)
| Feature | Add-a-Turbo Kit (This Product) | Complete Compound Kit |
|---|---|---|
| Stock Turbo | Keeps factory 12V turbo | 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 12V, 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 12V compound kit gives you more headroom and includes both turbos.
Head Studs and Fire Rings
On 1988–2002 12V and 24V Cummins engines, head studs are highly recommended for boost pressures over 48 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 1989–1998 Dodge Ram trucks with the 5.9L 12-valve Cummins engine. Covers both 1st gen (1989–1993) and 2nd gen (1994–1998) trucks.
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 24V Cummins 1998.5–2002
Related 12V Cummins Products
Frequently Asked Questions- 12V Add a Turbo Kits
Yes. Your factory 12-valve 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.
Yes. This kit fits 1989–1993 1st gen and 1994–1998 2nd gen 12-valve Dodge Ram trucks. 1st gen trucks may require intercooler hose modifications. Some 2nd gen trucks with automatic transmissions may require trans cooler relocation (DPS sells a $149 relocation kit). 12V engines have a single oil drain port, which the kit is designed for.
EGTs typically drop 300–500°F with the add-a-turbo kit installed. The 12V platform sees especially dramatic EGT improvements because the mechanical injection system responds immediately to the improved airflow and lower drive pressures from the compound setup.
Head studs are highly recommended for boost pressures over 48 PSI, and fire rings for pressures over 55 PSI. This system is capable of well over 55 PSI. If you plan to increase fueling or tow at sustained boost, head studs are a smart investment.
Yes. All 2002 and older add-a-turbo kits include a 4" exhaust downpipe. Everything you need for a complete installation is in the box.
5 Reviews
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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
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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!
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Stocker
Great compounds,makes towing a breeze with 50# of boost & egt about 300 less now
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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.
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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.
