The exhaust system was fully titanium with single muffler. A cross-flow muffler gives a "factory" dual exhaust appearance. In addition, the cylindrical muffler was replaced by two flame-suppressing mufflers. The standard engine includes a muffler exhaust system with an extra after-muffler as optional. They are used for collector, tubing, muffler, catalytic converter, tailpipe. In the UK, a silencer is the equivalent to the US muffler. It is basically a Baby Bee with a clunk tank and a muffler throttle. The injected engine received a new muffler and in California a catalytic converter. The last version came with both pipes welded to the slip-on muffler. Cox also sold the muffler, cylinder and high comp. Options include a sports muffler and HKS suspension. Emissions controls are a catalyzed muffler, AIR Injection system, and an evaporative fuel canister. This engine, quieted by a Trabant muffler, turned long fan blades to inflate the balloon. During the 1970s, UOP worked on pioneering a combined muffler catalytic converter. Most models feature a spark screen which is integrated into the muffler.