This is an engine simulation app that helps you estimate horsepower using data about an engine. Crankshaft Stroke, Piston bore, and cylinder head flow data are required, without those details the app wont work for your vehicle. You can usually find the data in your cars repair manual, measuring directly or from the internet or an auto parts store. Using that data along with a "tune" meaning the fuel consumption, air fuel ratio and boost or vacuum level you can estimate horsepower. Typically accurate to within 10hp if you compare to engine dyno output. As with any app reliant on a large number of calculations "garbage in, garage out" if you dont have these details the app wont be as accurate. Use the weather parameters you set to estimate horsepower or use SAE standard "corrected" weather. Use the app to estimate 1/4 mile times and changes in your 1/4 mile time based on the weather. See calculated part sizes for things like exhaust, carb or throttle body, fuel injectors and more.