Add-A-Turbo Kits
Add-A-Turbo Kits for Cummins
Add a Large Second Turbo to Your Existing Setup
Add-a-turbo kits provide everything you need to add a large second turbo to your current Cummins turbo—instantly creating a compound twin-turbo system.
Your existing turbo becomes the small "primary" turbo, and our kit adds the large "secondary" turbo downstream. Keep your current turbo and manifold, add our large turbo kit, and unlock compound performance: 200-300°F cooler EGTs, eliminated turbo lag, massive airflow capacity, and lower drive pressure.
Keep Your Current Turbo
Works with your existing small turbo and manifold
Large Turbo Included
Big turbo, mounting, piping - everything but small turbo
200-300°F Cooler EGTs
Compound thermal management without replacing primary
Complete Add-On System
Large turbo, bracket, piping, all hardware to complete compounds
What's Included: Large turbo, mounting bracket, intercooler piping, oil lines, all hardware. What You Supply: Your existing turbo (becomes the small primary turbo in compound setup).
Best For: Owners with existing upgraded turbos (S300, S400, VGT) who want compound performance without replacing everything.
Add-A-Turbo Kit FAQs
An Add-A-Turbo kit adds a second turbocharger to an existing single-turbo diesel setup, creating a compound turbo system without replacing the primary turbo. The factory or upgraded turbo provides quick spool and low-RPM response, while the added turbo supports higher airflow and boost under load. This results in improved throttle response, lower exhaust gas temperatures, and increased horsepower compared to a single turbo.
Add-a-turbo kits work with most aftermarket single turbo setups.
Compatible existing turbos (your small primary turbo):
- S300 singles: S362, S366, S369 → We provide S472 or S475 large turbo
- S400 singles: S472, S475 → We provide S480 or S483 large turbo
- VGT turbos: HE300VG, HE400VG, Turbonator → We provide appropriately sized large turbo
- Most aftermarket singles: If you have a quality aftermarket turbo, we can likely match it
Sizing the large turbo:
- The large turbo must be bigger than your current turbo
- Example: You have S366 → We provide S475 large turbo (perfect match)
- Example: You have S475 → We provide S483 large turbo (great for high power)
What won't work:
- Stock turbos: Too small to drive a large turbo efficiently (upgrade to S300 or better first)
- Worn turbos: If your existing turbo is worn/damaged, replace it before adding second turbo
- Very small turbos: Undersized primaries don't have enough exhaust energy
Not sure if compatible? Tell us what turbo you currently have (model/size), your engine, and power goals. We'll recommend the right large turbo size for your add-a-turbo kit.
Two turbos working together outperform any single turbo—especially for towing and street use.
Advantages of add-a-turbo (compounds) over single large turbo:
- Keep your current spool: Your existing turbo already spools well. Adding large turbo doesn't slow that down—it just adds top-end flow.
- No lag penalty: Your small turbo handles spool, large turbo adds airflow capacity. You get quick response AND massive flow.
- 200-300°F cooler EGTs: Two turbos sharing the work run way cooler than one big turbo working hard
- Lower drive pressure: Less backpressure = less cylinder stress, less head gasket risk
- Better for towing: Instant response when you need it (pulling grades, passing), not laggy like big singles
- Upgradeable: Start with add-a-turbo now, upgrade small turbo later if needed
Compare the approaches:
Upgrading to single large turbo (e.g., S366 → S480):
- ✗ Significant lag at low RPM (frustrating in traffic, towing from stops)
- ✗ Smoky until boost comes in
- ✗ High drive pressure under sustained load
- ✗ EGTs still spike waiting for boost
- ✓ Lower cost
- ✓ Simpler install
Adding large turbo (compounds with your current small turbo):
- ✓ Keeps your current quick spool
- ✓ Adds massive airflow capacity
- ✓ 200-300°F cooler EGTs
- ✓ Much lower drive pressure
- ✓ Best daily drivability at high power
- ✗ Higher cost than single upgrade
- ✗ More complex installation
Bottom line: If you're happy with your current turbo's response but need more airflow, cooler EGTs, or want 600+ HP, adding a large turbo is the smart move.
Power depends on the size of both the existing small turbo and the large secondary turbo added by the kit, along with supporting fuel system modifications and tuning. A typical Add-a-Turbo setup using a quality single S300 or VGT as the small turbo with an appropriate large secondary supports 600 to 700 HP with compound-specific tuning and supporting fuel work. The more consistent benefit — regardless of power target — is the 200 to 300 degree EGT reduction under load, which is the primary reason most working truck owners choose the compound path even when power is not the primary goal.
Add-a-turbo kits include everything EXCEPT the small primary turbo—you use your existing turbo for that.
What's included in the kit:
- Large turbocharger: The big second turbo (sized to work with your existing turbo)
- Mounting bracket: Secures large turbo to chassis/frame
- Intercooler piping: Connects your existing turbo → large turbo → intercooler
- Oil feed line: Supplies oil to large turbo
- Oil drain line: Returns oil from large turbo to pan
- All clamps and couplers: For piping connections
- Air filter adapter: Connects to large turbo inlet
- Hardware kit: All bolts, fittings, gaskets needed
- Installation instructions: Detailed guide with photos
What you supply (already have):
- Your existing turbo: This becomes the small "primary" turbo (stays in place on manifold)
- Your manifold: No changes needed
- Upgraded intercooler: Compounds need large intercooler (if you don't have one, you'll need to add)
- Exhaust system: From your existing turbo outlet (may need minor modification)
The concept: Your current turbo does the "small turbo job" (quick spool, low-end response). The large turbo we provide does the "big turbo job" (massive top-end airflow). Together = compound system!
Moderate to advanced installation—easier than full compound replacement but more than single turbo swap.
Installation time:
- Experienced DIY: 8-14 hours
- First-time compound installer: 14-20 hours (full weekend project)
- Professional shop: 6-10 hours ($900-1,500 labor)
Why it's easier than full compound kit:
- ✓ Don't remove your existing turbo (it stays on manifold)
- ✓ Don't touch manifold or primary turbo oil lines
- ✓ Don't have to route new downpipe from manifold
- ✓ One less turbo to mount and plumb
Installation steps:
- Fabricate or bolt large turbo mounting bracket to frame
- Mount large turbo on bracket
- Route oil feed and drain lines to large turbo
- Install intercooler piping (existing turbo → large turbo → intercooler)
- Connect air filter to large turbo inlet
- Modify exhaust from your existing turbo (connect to large turbo inlet)
- Check all connections, boost leaks, proper oil flow
Skills needed:
- Comfortable with hand tools and basic fabrication
- Ability to route piping and check clearances
- Jack/stands or lift for access
- Possibly cutting/welding for exhaust modifications
Our kits include detailed instructions. We provide phone/email support during installation.
An Add-a-Turbo kit converts an existing single-turbo setup to a compound system by adding a large secondary low-pressure turbo. Your current turbo — whether stock, an upgraded S300, S400, or VGT - becomes the high-pressure stage in the compound arrangement. The kit supplies the large secondary turbo plus all piping, oil lines, and mounting hardware needed to integrate it. A complete compound kit, by contrast, includes both turbos and is the right choice for trucks still on a stock turbo. The Add-a-Turbo kit is the right choice when you have already invested in a quality upgraded single turbo and want to build on it rather than replace it.
Yes, and this is one of the kit's primary advantages for 6.7L owners. The Add-a-Turbo kit for the 6.7 Cummins uses the factory VGT as the high-pressure turbo and adds a large secondary turbo upstream - without removing or modifying any emissions equipment. EGR, DPF, and SCR all remain intact. The truck retains exhaust brake function through the factory VGT. This is the only compound path for 6.7 Cummins trucks that must remain emissions-compliant for street use or work in regulated states.
The Add-a-Turbo kit is available with several large turbo options to match different power goals and existing small turbo configurations. The large secondary turbo selection matters - it needs to be sized appropriately for the small turbo it will work with to avoid backpressure mismatches and boost instability. The Diesel Power Source® team can help identify the right large turbo size for your existing setup, power target, and use case. Use the Turbo Selector or contact the team directly with your current turbo and power goals.
In most cases yes, but this depends on the manifold and the specific generation. The Add-a-Turbo kit is designed around factory-position small turbo placement, and the secondary turbo mounts on a bracket independent of the manifold. If you have an upgraded manifold that changes the small turbo's orientation or outlet position, confirm compatibility with the Diesel Power Source® team before ordering. Providing your current manifold make and model along with your truck year allows the team to verify fitment quickly.
Yes. The DPS Add-a-Turbo kit is designed for both the 5.9L and 6.7L Cummins. The 5.9 application works with trucks that have an existing upgraded single turbo as the high-pressure stage. The 6.7 application has the additional benefit of emissions compatibility when using the factory VGT as the small turbo. Piping and mounting are specific to each generation, so confirm your model year when ordering to ensure the correct application-specific components are included.
