I'm going to be adjusting the air/fuel ratio in my car's computer soon. For normal driving, I'm going to maintain a 14.7:1 air/fuel ratio with the car's computer. At WOT, the mixture might go as rich as 12.5:1, and at cruise it might be as lean as 15.5:1. I have an annual emissions test, so a catalytic converter is necessary for me. Are those ratios too extreme for a cat? What will happen if they are?

 

IIRC...
If you run too rich, your exhaust can heat up, and/or you'll have unburnt fuel burning in the exhaust. High temperatures in the Cat will melt the catalyst. Higher temperatures also produce NOX...

 

Does a melted catalyst cause a restriction in exhaust flow?

 

definetely and can also cause chunks of it to get inside your muffler and cause blockage there too.

 

I see... so would those air/fuel ratios I mentioned be too much for a cat?

 

the leaner the mixture the hotter the exhaust.....the richer the cooler it is..

that being said, running too rich, will plug your cat with deposits...and running too lean could burn it right out as well as other things

 

Right. What I'm asking is are those *specific* ratios overkill for a catalytic converter? Is there a way to tell (without destroying a few cats)?

 

youd have to be waaaay off in either direction to really hurt the cat in a short amount of time.....

youd be so far off though that your engine would run like sh*t....if it was that lean youd be in danger of burning a piston, it would ping and run hot as hell......

if it was rich enough to plug the cat it would make horrible black smoke, foul plugs, have awful throttle response etc.

as far as ratios, its tough to say, but very very far from 14:1

 

Thanks 383, that's what I wanted to hear .

 

no problem