Auto Manifesto

April 6, 2008

The Difference A Catalytic Converter Makes

You may remember I recently bought an MR2 off of Craigslist for a project car. Just because I’ve always wanted one like it and plan to restore it to original condition. The engine and gearbox are in decent shape and the body is straight, no rust or accidents. But it’s a little rough around the edges.

So the first thing that had to be done was an inspection. It passed the safety inspection without issues. But then it failed the emissions inspection. All the readings were high, even the passing ones. But the car failed the CO% test. I’ve never had a car fail inspection before. Take a look at the chart below.

On the rolling dyno it failed at 15 mph for emitting too much CO. I gave it a minor tune up, came back a week later and it failed again. Same problem (there are two failed reports but I only posted one since they were nearly identical). So I had the catalytic converter changed and re-inspected the following week. It passed.

Not only that lo and behold the emissions were much lower across the board. HC was reduced by about 80%, CO by about 98%, and NO by about 87%.

Catalytic converters make a huge difference in emissions. In this case driving around with a bad one pollutes as much as five or more cars. It wouldn’t be a bad idea to inspect emissions in more areas.

The next emissions inspection on the MR2 is due in two years. I’ll see at that time how the cat holds up, and if the engine has been doing anything unusual (seems to be fine).

Here’s more info on catalytic converters:

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