Saturn S series Twin Cam cylinder head had now featured a new roller-rocker setup with hydraulic tappets and roller cams replacing the conventional bucket lifter setup of the previous engine in the S series. Also introduced for the 1999 model year S-series vehicles that were sold in California was a different type of an exhaust manifold that housed an upstream catalytic converter (this converter had heated up much faster than the conventional unit, and it had also decreased exhaust emissions faster as well), and it also had provisions for an air-injection reaction system (This had injected fresh air into the exhaust to reduce
Steam car steam engine conversions for existing production cars. When air pollution became a significant issue for California in the mid-1960s the state encouraged investigation into the use of steam-powered cars. The fuel crises of the early 1970s prompted further work. None of this resulted in renewed steam car manufacturing. Steam cars remain the domain of enthusiasts, occasional experimentation by manufacturers, and those wishing to establish steam-powered land speed records. In 1967, California established the California Air Resources Board and began to implement legislation to dramatically reduce exhaust emissions. This prompted renewed interest in alternative fuels for motor vehicles and a resurgence