Just a short note on these for information.
Two-way Cats were fitted to cars up to the year 2000 when three way cats were introduced as providing a higher degree of "cleaning" of the exhaust gases.
Two-way converters combined carbon monoxide (CO) and unburned hydrocarbons (HC) to produce carbon dioxide (CO2) and water (H2O) and having been generally replaced by “three-way” converters since 2000, which also reduce oxides of nitrogen (NOx).
As I understand it, at present it is acceptable to fit a 2-way cat on to vehicles first registered prior to 2000 and these can come in two "types" one of which is a ceramic catalyst (and the second the more recent honeycomb structure of more modern 3-way types).
Ceramic catalysts are significantly cheaper than their more modern equivalents but are more liable to damage to the ceramic structure, resulting in the cat "rattling" slightly when checked by an MOT inspection engineer and can therefore result in the car being failed, if they make the assumption that the cat is "loose" inside.
A cat in this condition will generally pass the MOT test, IF they carry out a proper exhaust gas test on the car.
As there are still a fairly large number of pre 2000 Omegas about, I would recommend that anyone buying a replacement cat should check whether or not it is a ceramic type or the more modern honeycomb tree way type(if its unusually cheap it may well be a ceramic type). The ceramic type will work OK (as I understand it, the MOT tester uses a slightly different test routine on pre-2000 cars), but its as well that you identify to the garage carrying out your MOT that a slightly rattling cat will normally test OK and should not be summarilly failed without carrying out the exhaust emission test.
It has recently been brought to my notice that a small number of MOT failures have been thus attributed and as we all know, its expensive to formally complain about an MOT "failure".
Trust this will be helpful.
Author
Topic: Catalytic Converters (Read 567 times)