This BorgWarner Schwitzer Turbocharger Guide exists because decades of mergers, rebrands, and cross-referenced part numbers have left even seasoned mechanics guessing which turbo actually bolts to their engine. Schwitzer, KKK, and 3K all live under the BorgWarner umbrella now, and the naming conventions overlap in ways that cause ordering mistakes and downtime. At PT Turbo, we have been sorting out these part numbers since 1978, and this guide lays out the S-Series, K-Series, and KKK families in plain language.
Whether you run a fleet of on-highway trucks or maintain heavy equipment, knowing how these turbo families relate saves money and prevents mismatched installs. Let’s break down the lineage, the frame sizes, and the parts you actually need to keep these units running.
How Schwitzer, KKK, and 3K Became BorgWarner
Schwitzer was an American turbocharger manufacturer with roots going back to the early 20th century. It built a reputation for rugged diesel turbos used in trucks, construction equipment, and industrial engines.
KKK (Kühnle, Kopp & Kausch) and 3K were German turbocharger brands. Through a series of acquisitions in the late 1990s and 2000s, BorgWarner consolidated all three under its BorgWarner Turbo Systems division.
The practical result: an old Schwitzer casting number, a KKK part number, and a current BorgWarner reference can all point to the same physical turbocharger. That is why cross-referencing matters so much on these units.
If you want the fundamentals of how these machines move air, this turbocharger overview covers the basics. Everything below assumes you already know a compressor wheel from a turbine wheel.
The S-Series: Schwitzer’s Diesel Workhorses
The S-Series is the backbone of BorgWarner’s medium and heavy-duty diesel lineup. These are the turbos you find on Cummins, Caterpillar, Detroit Diesel, and countless industrial engines. The “S” stands for Schwitzer, and the number that follows indicates the frame size.
Frame size climbs with airflow capacity. An S200 handles smaller displacement engines, while an S400 moves enough air for large-bore diesels making serious horsepower.
S-Series Frame Reference
| Frame | Typical Engine Range | Common Applications |
|---|---|---|
| S200 | 4.5L to 9L | CAT C9, mid-range trucks, ag equipment |
| S300 | 5.9L to 12L | Cummins ISB/ISC, Detroit Series 60, CAT |
| S400 | 10L to 16L | Cummins ISX, Detroit DD15, large industrial |
| S500 | 15L and up | Mining, marine, power generation |
The S200 is a favorite in machine and truck applications alike. We cover it in detail in our Caterpillar C9 Turbocharger Guide, which walks through the exact fitments and rebuild considerations for that platform.
The S300 is arguably the most versatile turbo BorgWarner ever built. Its huge selection of compressor and turbine wheel combinations makes it a go-to for both OEM fitment and performance builds. Our full BorgWarner S300 Application Guide breaks down which variant fits Cummins, CAT, and Detroit engines.
For Detroit Diesel operators specifically, the Series 60 Turbocharger Guide covers S300 replacement and real-world cost figures.
The K-Series and KKK: German Engineering Under BorgWarner
The K-Series carries the KKK heritage. You see these on European diesels, most notably Volvo, Mercedes, MAN, and various passenger and light commercial applications. The “K” frames run K03, K04, K16, K24, K27, K29, K31, and up.
Smaller K frames like K03 and K04 dominate light-duty gasoline and small diesel applications. Larger frames like K27, K29, and K31 handle heavy truck diesels.
Common K-Series Frame Sizes
| Frame | Class | Typical Use |
|---|---|---|
| K03 / K04 | Light-duty | Passenger cars, small commercial diesels |
| K16 | Medium | Vans, mid-range engines |
| K27 / K29 | Heavy | MAN, Mercedes, marine diesels |
| K31 | Heavy truck | Volvo D12 and similar big-bore diesels |
The K31 is the one most North American heavy-duty operators encounter, thanks to Volvo. If you run a D12, our Volvo D12 Turbocharger Guide covers the K31 fitment, symptoms of failure, and replacement pricing.
KKK numbers typically start with a 5-digit code followed by dash suffixes (for example, 53xxx or 51xxx series). These map directly to BorgWarner references today, so if you have an old KKK number, we can cross it for you.
Actuators: The Part That Fails Before the Turbo Does
On modern S-Series and K-Series turbos, the wastegate or variable geometry mechanism is controlled by a pneumatic actuator. When boost control goes haywire, the actuator is often the culprit, not the turbo itself.
A sticking or leaking actuator throws boost codes, causes limp mode, and kills fuel economy. Replacing the actuator instead of the whole turbo saves real money when the cartridge is still healthy.
Many of these engines use Garrett and Mitsubishi actuators that interchange across platforms. We stock the units that cover the most common heavy and light-duty fitments.
- The Garrett Pneumatic Actuator 757979-5102 is a heavy-duty unit for VNT-style turbos, available from PT Turbo for $240.94.
- The Garrett Pneumatic Actuator 445963-0040 covers larger commercial fitments and is available for $465.52.
- For Mitsubishi TD03 applications, the Mitsubishi TD03 Pneumatic Actuator 49S3118761 runs $104.33.
- The Mitsubishi Pneumatic Actuator 4918918935 is a budget-friendly replacement at $83.99.
Before you condemn a turbo on a variable geometry unit, verify the actuator and the vane mechanism. If you are unfamiliar with how these systems modulate boost, this variable-geometry turbocharger reference is a solid primer.
New vs Remanufactured: What Makes Sense
Nearly every S-Series, K-Series, and KKK turbo we handle is available both new and remanufactured. For fleet operators watching cost per mile, a properly rebuilt turbo is often the smarter buy.
A quality reman uses new bearings, seals, and a balanced center cartridge. When it is done right, it performs to the same spec as new. The key phrase is “done right,” which is where our 45-plus years of experience matters.
| Factor | New | Remanufactured |
|---|---|---|
| Cost | Highest | 30 to 50 percent less |
| Lead time | Varies by OEM stock | Often same-day if in stock |
| Performance | OEM spec | OEM spec when properly balanced |
| Warranty | Full manufacturer | Backed by rebuilder |
Browse our remanufactured turbochargers to see what is in stock for your frame size. If you would rather send us your core, our turbocharger rebuild service restores your existing unit to spec.
Reading and Cross-Referencing Your Part Number
Every BorgWarner Schwitzer Turbocharger Guide comes down to one thing: getting the right number off the unit. There are usually two or three tags or stamps to check.
- The compressor cover stamp often shows the frame size, such as S300 or K31.
- The center housing tag carries the full BorgWarner or Schwitzer assembly number.
Cross-Reference & Superseded Part Numbers
The turbochargers covered in this article match or supersede the following OEM and manufacturer part numbers. If you are searching by part number, these are the units stocked by PT Turbo for this application:
479514-RMN • 53047109901-BILLET • 53047109904-BILLET • A4720901480-RMN • NEW-FTR-TWN-TRB • RMN-BRG-V2S-TWN • RMN-BRG-V2S-TWN-GR-TO • RMN-BRG-V2S-TWN-NO
Can’t find your number above? Contact PT Turbo — our team has been matching part numbers since 1978.
Need This Turbo Rebuilt?Need a Turbocharger?
PT Turbo has rebuilt and sold turbochargers since 1978. We stock remanufactured units for Cummins, Duramax, Power Stroke, Detroit Diesel, and more — backed by a 12-month unlimited mileage warranty and same-week shipping from San Bernardino, CA.
📞 (909) 824-1020 · 346 S I St. #3, San Bernardino, CA 92410 · [email protected]
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