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Old 05-05-2003, 07:45 PM
Duke2.6 Duke2.6 is offline
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Join Date: Mar 2003
Location: Southern California
Posts: 2,007
Like I said, since the exhaust O2 content was only 0.1% the catalyst can't be condemned. Once the available O2 is consumed the catalyst can do no more.

Understand that EGR only affects native NOx out the cylinder, but EGR as installed on '89 models would reduce the amount of NOx in the native exhaust, making less O2 available from disassociation in the catalyst.

I had a theory that the '88 valve timing may have had excess overlap to create a greater exhaust residual as this is a strategy that has been used for NOx reduction, but the manifold vacuum is high enough to indicate normal overlap and a check of part numbers yielded the same camshaft for '88 and '89.

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