A ground-boosted turbocharger is more akin to the conventional turbo setup you find in cars. The turbo is used mainly to increase power output, while the benefit of flying at higher altitudes is a side effect of the compressed air the engine receives.  Ground-boosted turbochargers can increase the manifold pressure to a maximum of 45 inches. The compression ratio of the pistons is usually lower than their naturally aspirated counterparts. In the SR22T, the compression ratio is 7.5 to 1.