These Wastegate Springs are constructed from 17-7 PH Stainless Steel which is capable of maintaining consistent pressures up to 900°F. The boost pressures are approximations from TiAL based on equal intake and exhaust manifold pressures, results will vary slightly for different applications. Higher pressure settings will require the use of both small and large diameter springs working together. In these dual spring setups the pressure is equal to the sum of the individual springs.