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Discussion summary
YOUR RESEARCHExhaust going quiet at 3500rpm on my 996 with PSE
Leading reported evidence
Check vacuum pressure at idle
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Suggestion · Original poster
I have also had a small go at checking vacuum pressure at idle on both sides of the Y piece in the engine bay but both hold good pressure.
Leading evidence: 'Check vacuum pressure at idle' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check vacuum pressure at idle' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
You can disable it by disconnecting the speed signal wire to the exhaust relay in the passenger footwell.
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Suggestion · Original poster
I have the PSE system and when I press the button you can audibly hear the exhaust note change - quieter when on and louder when off.
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To all 996 owners with PSE, especially those with a 4S.
I think my 996 C4S exhaust behaves oddly. I think it's a fault but you might tell me it's normal behaviour. The problem is that I've always had this 'fault' on my car so I don't know if it's a fault or intentional behaviour. If you have the same car, perhaps you can shed some light on this.
When I start it, it's noisy and sounds great. It quiets down as it runs for the first 5 mins.
I have the PSE system and when I press the button you can audibly hear the exhaust note change - quieter when on and louder when off. Default is off so loud.
Here's the rub. Up to around 1500rpm it's got a good noise then it fades out to the point where it's so quiet it's like driving my partners Yaris. If I keep accelerating, when I get to around 3500rpm the exhaust suddenly gets loud again. I mean it's immediate - like someones flipping a switched marked loud. It sounds great.
It happens in 2nd and 3rd gears most noticeably and the PSE is in the 'off' position. If I have the PSE button on, then it's just quiet all the time and that works fine.
So why the silent spot?
I did read somewhere that German market cars might have had a system that turns on and off the PSE at certain speeds to prevent people driving round residential streets with a loud exhaust but information is thin and I don't think I was ever on UK cars.
I have also had a small go at checking vacuum pressure at idle on both sides of the Y piece in the engine bay but both hold good pressure. One side has only a microscopic leak but not enough to cause this kind of issue.
It's supposed to do that. You can disable it by disconnecting the speed signal wire to the exhaust relay in the passenger footwell. Most people take the relay our, take off the cover, and snip the wire. I can't recall the pin number, but the wire leading up to the relay socket is grey/pink.
Awesome thanks @Richard_Hamilton.
At least that finally puts that to bed.... will get that sorted later.
Any idea if it will throw an error or warning light after doing that?
