Date: Tue, 1 Dec 1998 01:06:03 -0000 From: "chris Baillies" <christiannopsamlies.freeserve.co.uk> Subject: Re: 99 strange noise
Hi John, Yes I have considered resonance, as it only occurs at this critical rev range. Works out as 3600 rpm, (no rev counter). I'll try tightening the exhaust, its a genuine Saab stainless steel, but hasn't been touched for 8 years. I try and avoid thrashing it; the previous owner only did 2500 miles per year, the sudden usage may stress out the car! Johan LAUWERS wrote in message <73r7fo$a8v$1nopsam3.Belgium.EU.net>... >Hi chris, > >I had the same with my '83 900 GLi. The problem in my case was rather >simple. If you know anything about Fysics you know that every single object >is vibrating. Well at a certain RPM the vibration of the car became the >same as the one of my exhaust. In that case the exhaust starts to vibrate a >lot because the car's frequency is fortifieing the exhaust' s and that was >the sound. In fysics this effect is called resonance. >You can check if it is not possible to tighten it a bit more in order to >make the self-resonance of the exhaust higher then the vibrations in your >car (e.g. at 8000 RPM, an RPM you'll never reach). >
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