On Wed, 10 Mar 2004, content22207 wrote: > Other than the DeLorean, I've never seen a turn of the decade > catalytic converter equipped vehicle without a smog pump from the Almost every car has a smog pump. The purpose of the smog pump on a catalytic converter equipped vehicle is to provide additional air for the catalytic converter. They call it a smog pump, but it doesn't pump smog, it pumps ordinary air. A catalytic converter needs oxygen in order to convert unburned hydrocarbons into H2O + CO2. Without a smog pump, it has to rely on the oxygen in the exhaust. There's some, but there's not enough. Without it, the carbon builds up inside the catalytic converter. This reduces its effectiveness until eventually it stops working. There are catalytic converters in existence that are designed to work without this additional air. They are almost all in aftermarket applications and typically do not last for more than a couple of years. The primary factors determining the success of a catalytic converter without a smog pump are the design of the cat, and the richness of the mixture. A too-rich mixture will eventually damage any cat, whether there is an air pump or not. The reason cars with air pumps installed typically have a valve to control it is that too much air can cause the cat to overheat and can actually make it harder to convert nitrogen oxides. Do not remove the smog pump on any vehicle. They use less than 1 HP of power and without it you will have to replace your catalytic converter (unless you removed that too, but then you have no chance of passing emissions). (Following quotes are from previous emails by other authors in the thread). > fact is the Delorean runs so clean that it doesn't even need an > exhaust gas recirculation system. Of course it does need to be The primary purpose of exhaust gas recirculation is actually to lower combustion temperatures. On a low compression car like the DeLorean, you don't need it. > The great "catalytic converter stops up because mixture is too rich" > vs "catalytic converter stops up because mixture is too lean" debate. Both can damage the converter. They are fairly robust devices, but they can still both plug up and overheat. To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/