montezumola Posted July 2, 2006 Share Posted July 2, 2006 I've provisionally booked a trackday this month, which has a noise limit of 100dB ... In my quest to get my Supe checked I found a garage over the weekend who tested my car @ 4500rpm with a result of 102/103dB ... I've got a Greddy Racing Ti exhaust & double-decat ... now, the supplied Greddy bung would probably bring the noise down by 7dB's, but I fear that the EGT & turbo temps will rocket with this baffle on a full trackday Any ideas to bring the noise down 3dB's and not suffer in performance a la baffle? Quote Link to comment Share on other sites More sharing options...
Homer Posted July 2, 2006 Share Posted July 2, 2006 The baffle will make a little difference to boost pressure (usually about 0.05 bar), can't see how it would have any real effect on egt's with it being so far from the manifold. Quote Link to comment Share on other sites More sharing options...
Alex Posted July 2, 2006 Share Posted July 2, 2006 I had an additional 3" Silencer welded into my Nur Spec to reduce droning/noise. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 2, 2006 Share Posted July 2, 2006 You need a much more efficient exhaust system, preferably with at least 3 decent sized silencer boxes in it, like the stock one, but with a bit less restriction. AFAIK the only way to get this is to have something custom made. 90% of the MKIV's I get through here would fail track day noise tests woefully. Adding a "bung" is a BAD idea for track usage, it may cause det. Quote Link to comment Share on other sites More sharing options...
Ark Posted July 2, 2006 Share Posted July 2, 2006 100db is still pretty generous - my last track day was limited to 97, others to 92 or less...lucky, 'cos my car tested at 92db with a 2nd decat and a dragger (with a hole in it...thanks for the mild steel HKS!) Quote Link to comment Share on other sites More sharing options...
Gazboy Posted July 2, 2006 Share Posted July 2, 2006 I passed bruntingthorpes 97db static & 87db driveby today with a double decat and stock cat-back system. Quote Link to comment Share on other sites More sharing options...
montezumola Posted July 3, 2006 Author Share Posted July 3, 2006 ... Hmmm, looks like I will have to find a track that has more generous dB limits, like 105! Trouble is, they're all at least 120 miles away! Don't fancy risking the bung after Chris W mentioned the possibility of detonation. Has anybody used exhaust wadding or something 'DIY' to take the note off the exhaust? Quote Link to comment Share on other sites More sharing options...
Alex Posted July 3, 2006 Share Posted July 3, 2006 You need extra silencers or resonators... Quote Link to comment Share on other sites More sharing options...
Pete Posted July 3, 2006 Share Posted July 3, 2006 90% of the MKIV's I get through here would fail track day noise tests woefully. Adding a "bung" is a BAD idea for track usage, it may cause det. Well that probably rules mine out then! Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 3, 2006 Share Posted July 3, 2006 Stock cat back is fine for track days, the Skyline world are finding it a PITA to get a Jap aftermarket cat free system to pass noise tests, same as us. I tried 3 popular afrermarket Jap systems on my car, and even with a turbo with a tiny turbine housing and tame cams it didn't get even CLOSE to the limits. Quote Link to comment Share on other sites More sharing options...
Clarkey Posted July 3, 2006 Share Posted July 3, 2006 Adding a "bung" is a BAD idea for track usage, it may cause det. Chris, can you explain abit more on this ? Quote Link to comment Share on other sites More sharing options...
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