S3 Exhaust Boom
S3 Exhaust Boom
Author
Discussion

Griffinr

Original Poster:

1,017 posts

203 months

Friday 23rd October 2009
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My S3 has a none standard twin pipe straight thro' exhaust (of unknown origin)which sounds great pottering around and when accelarating hard but has a horrible resonating boom at around 2500 rpm which is 'A' road cruising speed. At motorway speeds it goes quiet again. Interestingly at tickover it sounds like a V8.
Anyone know of a simple fix. (already thought of ear defenders)
Iv'e seen some american info on pipe inserts to change the exhaust charactoristics but I cant find any UK info.

Jed-S

660 posts

245 months

Friday 23rd October 2009
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There are some systems that are twin pipe upto the rectangular silencer then twin pipe after. Is that what you've got? I don't think you'll find any insert will reduce the resonance - you need a silencer for that.

I had the standard system with a long oval front section and this was empty and as a result caused a bad resonance in the 2500-3000rpm range. I ended up having a custom system made up and it is very quiet now. Details on my website should you be interested. The only thing is that it won't appeal to the majority of TVR drivers because it is too quiet but that suits me fine as it doesn't get so much attention.

Jed

clarenceboddiger

1,398 posts

244 months

Saturday 24th October 2009
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Not sure what you mean by Boom but if it is a resonance problem it may be worth bracing the 2 pipes to change the frequency at which they resonate, maybe a few trials with a ratchet strap would prove the viability? I have the same problem with a gearlever Buzz at exactly 70mph.

Loubaruch

1,445 posts

227 months

Sunday 25th October 2009
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Had a similar problem on an S due to the top blowing off the central box, it required MIG welding back every few months. Made a horrible racket!

Griffinr

Original Poster:

1,017 posts

203 months

Monday 26th October 2009
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Thanks for the replies guy's I think I'll just have to experiment a bit. The system is 2 completely seperate straight through pipes terminating in 53mm bore tailpipes. The tailpipes are very close together which may be the cause of the resonance so I am thinking of cutting through the rear support brace and spreading them apart futher to see if it makes a difference. There should be enough flex in the pipes to do this and I can knock up a new bracket to suit. Will post the results when I've done it.

Rob

Edited by Griffinr on Monday 26th October 10:10

Wildfire

9,948 posts

281 months

Tuesday 27th October 2009
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Just out of interest, is your car Cooper Green, with 2.5" tail pipes, aspposed to 2" ones?

Griffinr

Original Poster:

1,017 posts

203 months

Tuesday 27th October 2009
quotequote all
Wildfire said:
Just out of interest, is your car Cooper Green, with 2.5" tail pipes, aspposed to 2" ones?
Hi, I believe the colour is Brooklands racing green and the tailpipes are 2.25" O/D, why do you ask?

Wildfire

9,948 posts

281 months

Tuesday 27th October 2009
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If it was a Metallic Cooper Green car, I could have helped with id-ing the system. I had a fully besspoke system made up for my S3, by ACT when I owned it.

It was partially sleeved, with the internal pipes made smaller to keep the back pressure the same,as the standard system does have baffles in it, and I had Griff sized tailpipes put on it.

Griffinr

Original Poster:

1,017 posts

203 months

Tuesday 27th October 2009
quotequote all
Wildfire said:
If it was a Metallic Cooper Green car, I could have helped with id-ing the system. I had a fully besspoke system made up for my S3, by ACT when I owned it.

It was partially sleeved, with the internal pipes made smaller to keep the back pressure the same,as the standard system does have baffles in it, and I had Griff sized tailpipes put on it.
Thanks for that, very interesting, as I think my system was by ACT but fitted 2 owners ago and the history is lost. Mine has no internal sleeving but I was considering fitting some to see if I can shift the resonance point. Been reading up a bit on exhaust design and aparently pipe length, diameter and support position can have a significant effect. Might also contact ACT to see if they can help.

Wildfire

9,948 posts

281 months

Tuesday 27th October 2009
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If you bought it off a chap called Jon (on the South Coast), who later bought an Elise, then that will be my old car.

Brooklands Green is like British Racing Green, where as Cooper Green in all 3 of it's shades (year depending) is metallic.

Excellent car by all standards and never let me down. Did just under 20k in it everyday, up and down the country.

Never had a cruising boom though.

Have you tried different mounting rubbers etc?

Edited by Wildfire on Tuesday 27th October 16:55