The 90 240 I bought had a defective CAT and failed the emission test. So I told the garage to empty the CAT. I wanted to see what kind of number you get without a CAT. I then had a brand new CAT installed, drove ~ 100K miles and then took the test again. Below are the numbers I got:
With an empty CAT:
At 40km/h (24mph) Curb idle test
HC ppm 134 107 CO % 0.86 0.85 NO ppm 2753 N/A
With a brand new CAT:
HC ppm 46 24 CO% 0.09 0.00 NO ppm 94 N/A
SMALL TYPO: it is ~100 mile and NOT ~100K miles... duh...
I thought the data was interesting. Of course it pollutes less, but it's interesting to see some quantities. The difference on that car is much smaller than I've seen on some cars, the 240 would still pass the emissions inspection here without a cat, many cars wouldn't. With one it's very clean.
Thanks for taking the trouble to do the comparison. It's interesting to see the actual numbers.
Andy I.
I get where a cat helps unburnt hydrocarbons. Interesting it has such affect on carbon monoxide and nitrogen oxides. My old 240 is always right on the edge for NO (better though, with the knock generator vacuum line plugged.) May be time for a new cat.
CO is just partially burned hydrocarbons, so it's no surprise there. 3 way converters are specifically designed to reduce nitrogen oxides as well.
I put a cat on it six or eight years ago. I'll bet those bastids put a single speed one on it instead of the 3 way...
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