of the original design's dished type allowed squish from the compression stroke to push the air through the channel around the intake valve to the chamber below the exhaust valve, causing turbulent swirling flow around the spark plug (which had been relocated near the exhaust valve at the top of the chamber). This design created a stratified charge, allowing the engine to run at an unusually high compression ratio for the time (10.5:1 to 12.5:1, depending on market and year) while running a relatively lean fuel mixture. In any given market power levels remained similar to the previous model, but fuel economy was improved by nearly 50%. A new fuel injection system called "Digital P" featuring a digital ECU with integrated manifold air pressure transducer was installed, replacing the older analogue control unit and remote pressure sensor from Bosch's original D-Jetronic design. (However, cars sold in Australia, Sweden and Switzerland continued to use the D-Jetronic system until at least 1985.) The OPUS ignition was replaced by Lucas's Constant Energy Ignition (CEI) in 1982, to deliver a more reliable spark. Series 3 XJ12 and Daimler Double Six cars used the CEI system until the end of their production in 1992, but it was superseded in the XJ-S in mid-1989 by another from Magneti Marelli. The Marelli ignition system was used until the end of XJ-S production, and on the version used in the XJ81 four-door saloons made in 1993 and 1994. The 5.3 HE was used in the following applications: 1981–1992 Jaguar XJ12 (Series 3) 1981–1992 Jaguar XJ-S 1981–1992 Daimler Double-Six (Series 3) 6.0 Litre HE The engine was stroked to in 1992 for a displacement of to make this one of the most powerful Jaguar production engines to date at at 5,400 rpm and at 3,750 rpm. The XJR-S stayed in the line until 1993 with power raised at at 5250 rpm and at 3650 rpm of torque. The engine on X305 used a new Nippondenso distributorless crank-fired ignition system with coil packs very similar to Ford EDIS-6 units. The last Jaguar V12 engine was produced on 17 April 1997. The 6.0 HE was used in the following cars: 1992–1995 Jaguar XJS 1991–1993 Jaguar XJR-S 6.0 1993–1997 Jaguar XJ12 (XJ81 and X300) 1993–1997 Daimler Double-Six (XJ81 and X300) TWR In 1985, Tom Walkinshaw Racing became Jaguar's official team in World Endurance Championship, taking over the project from American team Group