With the 1986 XJ, Jaguar dropped the “Series” designation. This model, codenamed XJ40, began development in the early 1970s; however, the project suffered many delays until Jaguar debuted the new model in 1986. Jaguar improved quality, increased chassis stiffness, reduced cabin noise, and saved weight. The new platform also gave the XJ a significant design change. The fourth-generation XJ was more angular than the model it replaced. A new straight-six engine was offered with the V12 returning in 1993.