The camshaft plays a crucial role in the performance of a PD (Pumpe Düse – Unit Injector) engine. While Volkswagen’s PD engines are renowned for their efficiency and power, the design of the camshaft has been a point of contention among engine builders. This article delves into the intricacies of the Pd Camshaft, exploring its design limitations, the shift to billet manufacturing, and common modifications for improved performance.
Questioning the Original PD Camshaft Design
Multiple camshaft engineers have expressed confusion over Volkswagen’s original PD camshaft design. The consensus is that the profile resembles that of a solid lifter camshaft, yet it was implemented in a hydraulic lifter system. This design choice raises questions about its effectiveness and overall performance potential.
Billet Steel: The Modern Standard for Camshaft Production
The question of whether billet steel is the superior material for camshaft construction is frequently debated. While longevity might not significantly differ between billet and cast steel cams, the economics of production have shifted in favor of billet.
A comparison of several popular camshafts revealed a surprising truth: many seemingly different brands were virtually identical, likely originating from the same billet source. Modern CNC machining allows for rapid and precise production of camshafts from billet stock. A multi-million dollar CNC cam cutting machine can produce a finished camshaft blank, ready for hard surfacing, in mere minutes.
The Economics of Billet vs. Cast Steel
The transition to billet camshaft manufacturing is primarily driven by cost efficiency and the “just-in-time” manufacturing model. Traditional casting involves a labor-intensive process requiring significant energy consumption and large production runs. Billet machining, on the other hand, allows for on-demand production with minimal waste and reduced inventory costs. The scrap metal is easily recycled, further contributing to the cost-effectiveness of this method. Ultimately, billet manufacturing offers a more adaptable and economical solution without compromising quality.
Practical Modifications for Improved Performance
Beyond the material itself, specific modifications can enhance the performance of the PD camshaft system. One such modification involves swapping the BRM (1.9L TDI PD) engine’s sprocket, chain, and tensioner onto ALH (1.9L TDI) and BEW (1.9L TDI PD) engines. This alteration allows for utilizing the smaller BRM sprocket for potentially optimized timing.
Another cost-effective modification targets the oil pump. By using the ALH oil pump body (identical to the BRM pump body) and replacing the ALH sprocket with the BRM sprocket, oiling, especially at low RPM, can be improved.
Optimizing Camshaft Bearings for Enhanced Oiling
Finally, addressing the camshaft bearings can further enhance performance and longevity. While Glyco bearings offer a cost-effective alternative to OEM parts, occasional quality control issues necessitate careful inspection. A crucial modification, developed to combat lifter overheating, involves modifying the bearings to increase oil flow to the cam followers. This modification directly addresses a known weakness in the PD engine’s lubrication system.
