OZ951

After hollowing out my catalytic converter recently I noted that I can now hear a resonance from the cat under hard acceleration. I also note that I get a KLR fail/excessive knock error code but this also only occurs after a run at wide open throttle. This has led me to wonder about the possibility of the cat resonance being the cause of the excessive knock signal.
Does anyone else have any thoughts on this ?

Next step will be to pull the cat off and insert a section of pipe through its center. I suspect that will eliminate the turbulent flow in the existing cat and eliminate most of the resonance.

Wayne.

dan b

My 85.5 951 or my wifes87 n/a both have hade the cat's removed and a straight pipe installed and i never had a trouble code yet. mabe this lnfo could help you on yours. dan b

David J. Harrington

Wayne, as you know, I "cleaned" my cat as well. I haven't had any errors. If I run the car very rich, I will shoot a couple foot flame out the end while shifting near redline at WOT. It makes an awesome sound at WOT anywhere above 3000. Try the pipe to reduce resonance. Sounds like your on the right track. Just be careful and check other things that might lead to knocking. Definately something you don't want to misdiagnose. However, I believe our knock sensors are acoustic, so your theory holds some weight.

Dave