Knock Suppression in a Turbocharged SI Engine by Using Cooled EGR

The work presented in this paper addresses the effects on combustion of recycling cooled exhaust gas (EGR) to the inlet charge of a standard production, four cylinder 2.3 l turbocharged, SI engine. The effect of various amounts of EGR at different temperatures and ignition timings were investigated. Considerable knock suppression at power output comparable with what was achieved with fuel enrichment, could be achieved by adding cooled EGR.

Due to inherent high thermal loads, turbocharged engines have been operated at rich air/fuel-ratios during high load conditions, with subsequent high tailpipe emissions of CO in particular, but also HC. By substituting fuel enrichment with cooled EGR, a stoichiometric charge can be used, thus enabling the use of a three way catalytic converter at all operating conditions.