All motors are four-cylinder gasoline engines. All have cast iron blocks with aluminum cylinder heads. The 4G63/4G64 engines retain the balance shafts for smoother operation, while the 420a does not use them. The 1995–1999 turbo engines were given an increased compression ratio of 8.5:1, up from 7.8:1, and a smaller turbo, a Garrett T25 set to 12 psi in place of the previous Mitsubishi TD04-13G (automatic cars) and TD05-14B (manual cars). This was done to minimize turbo lag, which was an undesirable trait for mass-market appeal in the U.S. These changes led to increased horsepower and torque vs. the previous 1G turbos. The 2G turbo cars produced at 6000 rpm ( at 6000 rpm w/ AT) and at 3000 rpm ( at 3000 rpm with AT.)