were rated at , while the 1993 W41 was rated at as a result of the first round of exhaust port size reduction to improve emissions and other changes to the Quad 4 architecture to reduce NVH. The additional came from longer duration cams and a different PROM. Part of the W41 drivetrain was a specific version of the HM-282/NVG-T550 with a gear set otherwise unavailable. All W41 five-speed transmissions had a final drive ratio (FDR) of 3.94:1 whereas the 1988–1992.5 LD2 and LG0 transmissions all used a 3.61:1 FDR; the 3.94:1 FDR was used on all 1992.5-1994 LG0 transmissions, but retained the standard HM-282/NVG-T550 gear set. W41 applications: 1991 Oldsmobile Cutlass Calais 1992–1993 Oldsmobile Achieva SCX L40 A SOHC variant of the Quad 4 was intended to replace the Pontiac 2.5 L Tech IV OHV "Iron Duke" engine. Debuting in 1992, this Quad OHC was an eight-valve engine and produced , less than the Quad 4 of the same era. Torque was . Power dropped to in 1993 with an attempt by GM to reduce the NVH of the engine. Although power and fuel economy were better than the Tech IV, the Quad OHC was retired after 1994 when the DOHC version became standard. Applications: 1992–1994 Oldsmobile Achieva 1992–1994 Pontiac Grand Am 1992–1994 Buick Skylark LD9 The LD9 Twin Cam was a Quad 4 variant with balance shafts, and a redesigned cylinder head which debuted in 1996. In the mid-nineties, these engines, like their earlier 2.3L counterparts, were known for timing chain failures, as well as water pump failures, in which the water pumps were often difficult and costly to access and replace. They also had very small oil passages, making for less than adequate lubrication, and costly engine repairs if not maintained properly. Bore was decreased from and stroke increased from for better torque. Power came in at . This engine received a minor update halfway through the 1999 model year that eliminated the exhaust gas recirculation, increased the compression ratio from 9.5:1 to 9.7:1, and switched from low impedance fuel injectors to high impedance. For increased reliability this engine also saw other minor updates in the 2000s towards the end of its use in General Motors vehicles. In 2001, changes included a smaller knock sensor, flat-top pistons instead of dished, new oiling passages, newer stronger timing chain, a newer-designed water pump, a redesigned starter motor and a