It raises exhaust gas temperature David. Hot gas molecules move faster hence increased flow. This provides exhaust scavenging which allows cylinders to pump with less resistance hence some power gain. Similar effect to wrapping exhaust down pipes.


Richard

2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone