On 2/20/05 12:10 PM, "Richard A Jones" <jones@COLORADO.EDU> wrote:

>>  No exhaust leaks
>> either. Sorry, but I had a van come in for this procedure and he had a
>> major leak at the two into one collector.  As a result the O2 input was
>> usless.
> 
> Someone explain this to a dense guy.  Wouldn't the exhaust leak
> OUT, rather than air leaking IN to confuse the O2 sensor?
> Or does the "pulsing" of the exhaust gas cause it to switch
> back and forth?  I don't understand....
> 
> Thanks,
>                       Richard A Jones
>                       Boulder, Colorado
> 
> 
Depending on the angle of the pipes at the leaking area it can pull in air
mixing with the exhaust on the way through.  However that would depend on
the condition of the cat and muffler because they normally create a small
amount of back pressure.  At speeds above idle you probably would be venting
rather than pulling air in.

Tuned holes in the exhaust system is an old trick to cheat enviro testers.
Prior to dyno testing.  Those holes become very obvious at higher rpm.  Also
used on some street rods for power boost by dropping exhaust pressure at
higher rpm.
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jimt
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