it lets you adjust at what rpm you want vtec to engage and at what rpm you want vtec to stay on at once it has been engaged. on mine I have it hit at 5100 rpm and it stays on from 4900 rpm and up once it has been engaged. but heres a little info for you guys; vtec on gs-r's is set to engage at 4500 rpm stock. but in a way you dont get " full" vtec until 5600 rpm when the second runner opens on the stock manifold which allows more air to flow. so in other words, dont raise vtec passed 4500 rpm on the vtec controller. if you get a skunk2 manifold like I have, it doesnt have a second runner but it flows a lot of air all the time because the ports on the runners are so big.