It reads ignition advance. There's probably close to 40 items that it will read. It has different display modes, 2/4/8 parameters and a 2 parameter scrolling graph. It's just like the standard Chysler/Dodge gauge they've sold for years, just now has specific Hellcat pids added along with the cool down modes and Hellcat power up screen.What about total timing or is that somewhere in the knock part? Who makes this?