Porsche designed Volkswagen air-cooled flat-fours for VW Beetles and most early VW and Porsche cars such as the Volkswagen Type 2 (T1), Porsche 356, 550, and the 912. The Porsche 914 that replaced the 912 used an enlarged version of a VW engine originally designed for Volkswagen Type 4. Many kit aircraft use a modified air-cooled VW flat-four.