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Down Pipe Rattle.

Old Jul 31, 2007 | 09:18 PM
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Default Down Pipe Rattle.

Hello all,
I had rattle under the car so I suspected it was the catalytic converter since I had the same problem on a 1992 Pontiac Bonneville ssei that I use to own. However, I changed the converter with a magnaflow on the 2000 Bonneville and still had the rattle..further inspection and found it to be the down pipe...Will the rattling down pipe cause any problems to the engine like poor mpg'*,engine back pressure,lost of horse power or even engine damage?
Thanks.
Rod.
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Old Jul 31, 2007 | 09:51 PM
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It could very well cause false KR, resulting in decreased performance and fuel mileage.
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Old Jul 31, 2007 | 10:12 PM
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Originally Posted by willwren
It could very well cause false KR, resulting in decreased performance and fuel mileage.
Thanks Willwren,
Sorry, I'm still fairly new to club..What is "KR"?
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Old Jul 31, 2007 | 11:49 PM
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KR = Knock Retard

Definition: The engine management computer (PCM) checks for predetonation using a knock sensor. The knock sensor could pick this up (the downpipe rattling) as 'knock', and will retard timing to prevent engine damage. This in turn could reduce gas milage, power etc.

Make sense?
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Old Aug 1, 2007 | 05:50 AM
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Originally Posted by Freddi
KR = Knock Retard

Definition: The engine management computer (PCM) checks for predetonation using a knock sensor. The knock sensor could pick this up (the downpipe rattling) as 'knock', and will retard timing to prevent engine damage. This in turn could reduce gas milage, power etc.

Make sense?
Yes it does make sense make sense, thanks...Now can this downpipe be welded or is that a bad idea?
Rod.
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Old Aug 1, 2007 | 07:51 AM
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Have you been able to determine what is rattling on the downpipe?

Our downpipes are a two layer pipe with welded ends and flanges. Can't say that we've ever heard of one rattling before unless a bolt came loose.
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Old Aug 1, 2007 | 05:10 PM
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Originally Posted by BillBoost37
Have you been able to determine what is rattling on the downpipe?

Our downpipes are a two layer pipe with welded ends and flanges. Can't say that we've ever heard of one rattling before unless a bolt came loose.
When the cat was taken off I could see it was two layers but, I was not concerned with the down pipe thinking it was the cat rattling..As far as where the rattle is coming from not really sure..when put on the lift and banged on the down pipe can hear the noise was coming from there...I see there is a rigged round attachment on top connecting to the exhaust manifold..Is that part of the down pipe? or is it the flex flange? could that possibly make noise?
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