21. Most designs of the time therefore included secondary air injection , which injected air into the exhaust stream. 22. Also for 1999 provisions for a new air injection reaction system was introduced aimed at improving engine emissions. 23. Most newer vehicles have electronic fuel injection systems, and do not require air injection systems in their exhausts. 24. Since 2008, an expanded air injection system has been used alone to control and treat contaminants in groundwater. 25. A pilot groundwater aeration ( air injection ) system was added in 1992 to augment the pumpout system. 26. The early air injection diesels always had a superior combustion without the sharp increase in pressure during combustion. 27. A new catalytic converter was introduced with an air inlet for forced air injection from the air pump. 28. _A ban on the pre-slaughter practice of using air injections to the head intended to stun cattle before slaughter. 29. Additional air injection wells were placed in operation in 1995 to aerate the width of the contaminant plume while pumping continued. 30. All 2ZZ-GE heads from 03 / 03 onwards carry this modification even if the vehicle does not have the air injection system.
