At AET, we are often entrusted with turbochargers that represent important moments in motorsport engineering. Recently, we were tasked with an especially unique challenge – recreating a BorgWarner (KKK) Eberspächer EB/3K ball bearing turbocharger, originally used on the legendary Porsche 934/935 racing cars.
This particular turbocharger is an early ball bearing turbo design, fitted to a 2.14L petrol racing engine developed in the early turbocharged era of Porsche motorsport. In race trim, these engines were capable of producing around 500 BHP, making them formidable competitors during the mid-1970s.
Given its design and period of development, the EB/3K raises an interesting question:
Could this be one of the oldest ball bearing turbochargers in the world?
AET’s History with the EB/3K
AET has been servicing these turbochargers since 1976, supporting both motorsport teams and historic vehicle owners. However, as with many specialist racing components from this era, replacement parts have not been available for many years.
In 2025, we were approached to support a retro Porsche 934 rally project, which required the recreation of a fully functioning EB/3K turbocharger built to its original specification.
The project presented significant challenges from the outset.
The Starting Point
While many of the major components were present in some form, the turbocharger arrived in extremely poor condition:
- No bearings or seals were available
- The turbine shaft and wheel had severe piston ring groove damage
- The compressor wheel was missing blades
- Several components were effectively beyond serviceable limits
In short, this was not an ideal starting point. But with the right engineering approach, even seemingly unusable components can be recovered.
Engineering Solutions Developed by AET
To bring this historic turbocharger back to life, our engineering team developed several new solutions.
New Ball Bearing System
Since the original bearings are no longer available anywhere, we developed entirely new replacement journal ball bearings, engineered specifically to replicate the original EB/3K design and performance characteristics.
Billet Compressor Wheel
The original compressor wheel had suffered severe damage, including missing blades. To resolve this, we designed and manufactured a new billet compressor wheel, ensuring the aerodynamic performance matched the original specifications.
Turbine Shaft and Wheel Restoration
The turbine shaft and wheel had extensive piston ring groove damage, which would normally render the component scrap.
Our engineers developed new remanufacturing techniques to restore the sealing surfaces and allow the shaft and wheel assembly to be reused – preserving an otherwise irreplaceable component.
Recreating the Turbocharger
Following the development of these replacement components and restoration techniques, AET successfully produced a fully remanufactured turbocharger built to original EB/3K specification.
The result is effectively a new historic turbocharger, capable of supporting a period-correct Porsche 934 rally project while maintaining the integrity of the original design.
The Porsche 934 and 935
In 1976, new CSI motorsport regulations introduced revised Group 4 and Group 5 categories, prompting Porsche to develop a new generation of turbocharged racing cars derived from the 911 Turbo (Type 930).
The Porsche 934 was created as a Group 4 customer racing car, designed to remain closely related to the production 911 Turbo while meeting the homologation requirement of 400 cars produced over two years. Powered by a turbocharged flat-six engine, the 934 quickly became a highly competitive GT car in international racing.
Alongside it, Porsche developed the more extreme Porsche 935 for Group 5 competition, where regulations allowed much greater modification. While the 934 retained much of the standard 911 body and mechanical layout, the 935 evolved into a far more radical machine and became one of the most successful endurance racing cars of the late 1970s.
Both models marked a defining moment in Porsche’s early turbocharged motorsport programme, laying the foundations for decades of turbocharged racing success.
With over 50 years of experience and an ISO 9001 accreditation, AET continues to support customers across motorsport, passenger car, marine, agricultural, machinery and power generation sectors, delivering turbocharger solutions that exemplify the highest standard of quality.
If you own a performance classic or historic vehicle like this one, our specialist technicians are here to help keep it running at its best.
Contact us today.
🌐 www.aet-turbos.co.uk
🛍️ www.aet-turbos-shop.com
📞 01924 894171
📧 [email protected]
