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number9ine

Raspy exhaust on cold start

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Hi all,

I've had my '05 C2S for all of a week now and it's wonderful. However, when starting it up in 45-50 degree weather there's a sharp rasp that appears to come from the driver-side exhaust at idle and on throttle, which subsides after about 20 seconds of driving. I don't have PSE. I've searched around and see that the heat shield may be the culprit, but it really sounds as if it's inside the exhaust.

I had to replace the tensioning bolt on the driver exhaust tip because it was loose, rusty and torqued into a bend. The tip has an '06 date on it, suggesting it's been replaced under the recall for the loose welds. Nothing on it was loose so I assume it's not the problem.

Anything in particular to look for? I've gone underneath and given the system a good tug and nothing appears to be loose. Maybe they all do it? Every C2S I test-drove was started mid-day in sunny 60-70 degree weather so I guess I have no benchmark. I can certainly live with it, just want to make sure it's not a symptom of a larger issue.

Thanks!

Mark

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Hi,

I have a 997 4s gen1.

I have exactly the same problem, but i also can't find a leak.

I think it's one of the chambers inside the left damper.

After 1 min. the temp. rises and the noise is gone.

If sombody knows the failure i like to know.

Greetings,

A. Hoogstraate

Holland

Edited by arjanh

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It is your catalitic converter. Once these things get warmed up,

the metal inside expands. The sound will go away once the cats get dirty

with soot.

Paul

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Guest longene.leonard@yahoo.com

My 2008 C2S is very raspy when it first starts with the fast idle. I runs rough and shakes a bit as well for 10 to 20 seconds. The car had 4 miles on it when I picked it up from the dealer. Its done this from new, so no worries. B)

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Ya, I have the same sound and it troubled me a bit. I had a full PPI done at the Porsche dealer before I purchased my 2005 C2 and no issues were found. I've also read another thread and people say this is normal on the 997. I figure since it disappears after warm-up, it's fine. Just my $0.02...

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Whoops, forgot all about this thread. I brought it to the dealer and they say what most of you do, that it's perfectly normal. Even in the warmer weather it does the same. Free sport exhaust option for a minute or two, I guess. :)

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Whoops, forgot all about this thread. I brought it to the dealer and they say what most of you do, that it's perfectly normal. Even in the warmer weather it does the same. Free sport exhaust option for a minute or two, I guess. :)

My 2008 C2S has done this from the very beginning regardless of outside air temp.....In fact I have listened to several of the C2S and C4S and they all do the same......

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Same here, my C2 was at OPC for 2 days so that they could hear this on a cold start. All fine and normal. Apparently there are quite a few things it could be, not just the cat as definitively stated, but right now i cant remember exactly what the two other things were.

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Ours does the same thing...I've been told that its a normal function something about polution requirement on start up

06 Cab/tip 24,000 miles

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Same on my 2006 C4S with 80KMiles, I asked the question at my Porsche center, thinking I had a loose part in the exhaust or cat cells, they told me that the noise comes from the secondary air injection, not the pump but the effect of excess air, after some investigation (I think I have see it on the workshop manual) I found that it turns on on cold start between 30 sec to 2 min depending on the temperature it fits exactly what I state on my car, above an engine temp of 40°C the secondary air injection does not turn on, which match well the noise on cold start only

If you look up "997 cold start" you will hear this sound on all the cars

I found it horrible at the beginning and start to like it, thinking this is "the 997 gen1 start up noise"

By the way if you have the PSE like me, plug off the orange connection on the top right of the engine, you car will make a killing sound, my neighbors and wife already complained but it is fantastic especially above 3000Rpm when the PSE flaps start to shut down to comply with noise regulations

Enjoy

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Same on my 2006 C4S with 80KMiles, I asked the question at my Porsche center, thinking I had a loose part in the exhaust or cat cells, they told me that the noise comes from the secondary air injection, not the pump but the effect of excess air, after some investigation (I think I have see it on the workshop manual) I found that it turns on on cold start between 30 sec to 2 min depending on the temperature it fits exactly what I state on my car, above an engine temp of 40°C the secondary air injection does not turn on, which match well the noise on cold start only

If you look up "997 cold start" you will hear this sound on all the cars

I found it horrible at the beginning and start to like it, thinking this is "the 997 gen1 start up noise"

By the way if you have the PSE like me, plug off the orange connection on the top right of the engine, you car will make a killing sound, my neighbors and wife already complained but it is fantastic especially above 3000Rpm when the PSE flaps start to shut down to comply with noise regulations

Enjoy

Haha I had the same experience. On a cold start, my 997 gets this rattle sound and when I went to Youtube other 997 startups they all sound the same. After months of listening to it, it really does grow on you. I have the Fabspeed Cold air Intake kit on mine so the engine gets more air and I disable the the flapper valve completely. Everywhere I go I want her to sound beastly!

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Here the extract of the document I referred too, the document is called "997 S technik " it is 7.5 mb so I cannot load it but it is very interesting info for 997 S or 4S owners

The injection of secondary air leads to a reduction of the CO and HC pollutants

that are increasingly created by operating with Lambda < 1 when running cold.

Additionally, the catalytic converters achieve their activation temperature of

approx. 350 °C more quickly due to the waste heat created during the

afterburning.

Activation conditions are achieved during the first cold start process if the

coolant temperature is between -10 °C and +42 °C. When running close to idle

speed, secondary air injection is active for approx. 60 seconds, for a partial

load up to 80 seconds.

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