Drop in engine power due to piston ring gap positioning
Whilst carrying out some investigations into oil leaks on a Waukesha engine last week, our engineer, Charlie, came across a separate issue which was causing a loss in power and effectiveness to the engine performance.
As part of the investigations, he removed the pistons and found a common problem:
Those with a keen eye (like Charlie) will notice that the gaps in the piston rings are near each other, almost in line with each other in some cases.
The reason the OEM advises against this is, with around 400psi created during the “bang” part of the cycle, the force will be looking for the easiest route, rather than what you want it to do, which is to be pushing the piston down.
With the ring gaps near each other, it gives this route for the gases, resulting in a loss of compression through blow-by. This is why there is a loss in engine power.
Our advice to avoid this issue: Just prior to piston insertion in the ring compressor locate the piston ring gaps.
You can see in the picture below how the gaps are spaced evenly around the piston while avoiding the piston thrust faces and the area next to the gudgeon pin. This lessens the chance of any two gaps lining up during the running in period, when rings have not fully seated.