Air-to-liquid intercoolers, also known as "charge air coolers", are heat exchangers that transfer intake charge heat to an intermediate liquid, usually water, which finally rejects heat to the air. These systems use radiators in other locations, usually due to space constraints, to reject unwanted heat, similar to an automotive radiator cooling system. Air-to-liquid intercoolers are usually heavier than their air-to-air counterparts due to additional components making up the system (water circulation pump, radiator, fluid, and plumbing). The Toyota Celica GT-Four had this system from 1988 to 1989, 1994 to 1999, also in the Carlos Sainz Rally Championship Version from 1990 to 1993. The 1989-1993 Subaru Legacy with the 2.0 L DOHC flat-4 engine also used a top installed air-to-water intercooler on the GT and RS models sold in Japan, Europe, and Australia.