Keeping tension on your timing chain is imperative for keeping your cams turning properly. If some slop develops in your chain because of a poor tensioner, the timing set can skip a tooth, causing catastrophic damage and potentially ruining your engine. This replacement can keep everything tight.
The chain runs against this tensioner which keeps your chains tight on the cam gears and crank. It makes sure no teeth are missed and your engine stays in time. Quiets loud chains.