2007 Re: I gutted Re: muffler bypass - pointless!

From : midlant

Q: emissions regulations vary considerably from jurisdiction to jurisdiction as do what engines are regulated. in north america any spark ignition engine of over 19 kw 25 hp power output built later than january 1 2004 probably has a three-way catalytic converter installed. diesel engine regulations are similarly varied with some jurisdictions focusing on nox nitric oxide and nitrogen dioxide emissions and others focusing on particulate soot emissions. diesel engines for compression ignition i.e. diesel engines the most commonly used catalytic converter is the diesel oxidation catalyst. the catalyst uses excess o2 oxygen in the exhaust gas stream to oxidize co carbon monoxide to co2 carbon dioxide and hc hydrocarbons to h2o water and co2. these converters often reach 90% effectiveness virtually eliminating diesel odor and helping to reduce visible particulates soot however they are incapable of reducing nox as chemical reactions always occur in the simplest possible way and the existing o2 in the exhaust gas stream would react first. to reduce nox on a compression ignition engine it is necessary to change the exhaust gas - two main technologies are used for this - selective catalytic reduction scr and nox nox traps or nox adsorbers. another issue for diesel engines is particulate soot. this can be controlled by a soot trap or diesel particulate filter dpf as catalytic converters are unable to affect elemental carbon however they will remove up to 90% of the soluble organic fraction. a clogging soot filter creates a lot of back pressure decreasing engine performance. however once clogged the filter goes through a regeneration cycle where diesel fuel is injected directly into the exhaust stream and the soot is burned off. after the soot has been burned off the regeneration cycle stops and injection of diesel fuel stops. this regeneration cycle will not affect performance of the engine. all major diesel engine manufacturers in the usa ford caterpillar cummins volvo mmc starting january 1 2007 are required to have a catalytic converter and a soot filter inline as per a new dot legislation.citation needed .