What Does an Accumulator Groove Do?

Piston ring grooves serve a larger purpose than simply supporting the rings. They impact combustion sealing, oil control, friction, and many more engine attributes. 

Wiseco is a world leader in piston technology because it focuses on the minute details of cylinder sealing science. Among those details, the type of piston rings used in racing and high performance engines is always a hot topic. But the ring grooves in pistons also play a major role in sealing combustion pressure and controlling oil and blow by.

That’s one area where Wiseco extends the extra engineering effort to ensure maximum performance from its pistons. While various types of piston rings are more suitable to specific applications, the ring grooves themselves are often overlooked in the pursuit of optimum cylinder sealing.

The strongest piston in the world is rendered useless when the rings fail to seal against the cylinder wall. 


The accumulator groove provides additional volume below the top ring so pressure doesn’t build up and attempt to unseat the top ring.

The accumulator groove is machined into the piston between the top compression ring and the second (scraper) ring. Its purpose is to provide additional relief space for pressure escaping past the top ring to build up before it attempts to pass the second ring. It supports top ring sealing by relieving pressure and it helps reduce ring flutter due to pressure changes. Accumulator grooves have proved most effective and they are a common feature on many, if not most, high performance and racing pistons.

The quality and placement of the ring grooves on your pistons is just as important as your cam specs. Proper ring groove placement and ultimate sealing quality are the keys to more power and durability under any severe duty applications. Hence it is important that you use the rings specified by your piston manufacturer or be prepared to share your ring pack information if you are providing your own rings.




Contact Reduction Grooves

Contact reduction grooves reduce friction by minimizing piston material in contact with the cylinder wall above the top ring. They also disrupt pressure spikes caused by detonation.

These grooves are machined into the top ring land above the top ring to minimize contact drag when the piston rocks over upon reversal. They add minimal volume to the crevice volume and they also help resist detonation by disrupting flame travel into the crevice volume where pressure spikes might unseat the ring.

Accumulator Groove