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.
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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.
Works with your existing small turbo and manifold
Big turbo, mounting, piping - everything but small turbo
Compound thermal management without replacing primary
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.
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):
Sizing the large turbo:
What won't work:
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:
Compare the approaches:
Upgrading to single large turbo (e.g., S366 → S480):
Adding large turbo (compounds with your current small turbo):
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 your existing small turbo size and supporting mods:
S300 (small) + S400 (large) - Example: Your S366 + Our S475:
S400 (small) + S400 (large) - Example: Your S475 + Our S483:
VGT (small) + S400 (large) - Example: Your HE400VG + Our S475:
Real improvement examples:
The real benefit isn't just peak HP—it's USABLE power: Compounds make high horsepower that you can actually drive daily and tow with safely.
Add-a-turbo kits include everything EXCEPT the small primary turbo—you use your existing turbo for that.
What's included in the kit:
What you supply (already have):
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:
Why it's easier than full compound kit:
Installation steps:
Skills needed:
Our kits include detailed instructions. We provide phone/email support during installation.
