Proper Piston Ring Gap Is Crucial For Best Engine Performance

Piston ring gaps are a small aspect of the internal combustion engine that is often overlooked. Many times, a set of piston rings come with the pistons we are going to use. The piston rings are then checked for proper gap clearance and then the engine is assembled. But do we ever stop and consider that this clearance plays an extreme role in how the engine will perform? Though engine builders understand the importance of piston ring gaps, there have been changes to the ring gap procedures that need to be addressed. Extensive testing, along with changes in piston ring material, has brought about changes in these necessary gaps. To get some solid information about piston ring gaps, we reached out to MAHLE Motorsport because, well, they know piston rings.

Manufacturers of piston rings will often specify ring gaps that are based on the performance use of the engine. This measurement comes from testing and resources that have been found to optimize engine performance based on the application. The optimum gap for the top piston ring should be as tight as possible without the two ends ever touching. During engine operation, the smallest gap would provide the best seal for combustion and have the least amount of blow-by. This will provide maximum performance and help reduce emissions.

Iron vs. Steel

At one time, the standard material for piston rings was ductile iron. More recently, compression ring material was upgraded from ductile iron to steel. The biggest change has been attention to the second compression ring gap. Manufacturers will often give specific details about the second compression ring gaps in the instructions.

“The second ring-gap recommendations have continued to change over the years,” says Zach Jones of MAHLE Motorsport….