The Jeep Cherokee (XJ) is a unibody (monocoque) compact SUV. It shared the name of the original full-size SJ model, but without a body-on-frame chassis. Early versions had the 4.0 L (242 CID) six-cylinder engine only; the 2.5 L (150 CID) engine did not arrive in Europe until 1995.In the middle of the 1999 model year, vehicles with the 4.0 liter (242 CID) engine received a much improved intake manifold. This was done to help counteract smaller exhaust porting on the latest casting of cylinder heads, which was done to meet more stringent emissions control laws. Both the 4- and 6-cylinder engines were offered through the 2000 model year, though only the straight-six was available in 2001. For the 2000 and 2001 model years, all six-cylinder XJs received a distributorless ignition system using coil-on-plug ignition replacing the 'traditional' system previously used; coupled with better exhaust porting and the newer intake manifolds, this gave a minor increase in power over the previous models. Transmission, axle, and transfer case choices were carried over from the previous models.