Why are “cold start” emissions so important?
The catalyst requires heat to reach the temperature ( >300-350C ) where it functions most efficiently, and the delay until it reaches operating temperature can produce more hydrocarbons than would be produced during the remainder of many typical urban short trips. It has been estimated that 70-80% of the non-methane HCs that escape conversion by the catalysts are emitted during the first two minutes after a cold start. As exhaust emissions have been reduced, the significance of the evaporative emissions increases. Several engineering techniques are being developed, including the Ford Exhaust Gas Igniter ( uses a flame to heat the catalyst – lots of potential problems ), zeolite hydrocarbon traps, and relocation of the catalyst closer to the engine [47]. Reduced gasoline volatility and composition changes, along with cleanliness additives and engine management systems, can help minimise cold start emissions, but currently the most effective technique appears to be rapid, deliberate heat
