If you're looking to install an older style oxidation catalyst, then yes, it can be done but you will need to add some way of injecting air into the exhaust system before the converter. Also you will need to keep the car in good tune so you don't end up with excess fuel in the exhaust and end up overheating the converter. You'll need to inject air because normally a carbureted car runs on the rich side of the ideal air-fuel ratio. That is because slight variations in air/fuel ratio on the rich side of ideal have a much smaller effect on engine performance versus the same variation on the lean side. When an engine is running rich, there is an excess of fuel and very little oxygen in the exhaust. Without enough oxygen, the converter can't do its job (oxidize), so it'll be necessary to inject air, or else you might as well leave the converter off as it won't do much at all. That's why the older cars had an air pump. Three-way catalysts will require the use of a closed-loop fuel system (O2 sensor).


Newer cars with three-way catalysts get away without the air pump because of two reasons: One is the air/fuel ratio goes either side of ideal, which allows some oxygen into the exhaust, also the reduction converter strips the oxygen out of the NOx emissions before the oxidation converter.

No matter how well you tune an engine, there will be unburnt fuel if for no other reason than the combustion process generates CO2 which acts as a fire extinguisher in the cylinder. So there will be exhaust odor no matter what on a non-catalyst car.

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Erich Loepke
2010 Ford Focus
Currently Benz-less