Has anyone had their exhaust coated in glass fibre wrap?
Discussion
I recently bought a VXR8 with a Walkinshaw Performance exhaust. When driving between 1500 and 2000 rpm, there is a really nasty headache inducing resonance which doesn't exist at higher or lower parts of the rev range. Someone has suggested I try the above and I just wondered if anyone else had any experience of this? The other thing I will also do is get someone to have a good look at how the system has been fitted and make sure it isn't touching the car somewhere it shouldn't be. I don't want to add another box if I can help it, as it sounds fantastic the rest of the time, but I am doing 600 miles a week and can't leave it how it is! Thanks. 
i'd work out where the resonance is coming from before putting any money into it. Is there anyway of getting it up on some ramps and getting someone to hold the revs at the bpoint it resonates, to get an idea of where its coming from?
On one of my old cars I had a similar resonance at about the same rpm, once I'd had a stainless system fitted. It was coming from just after the downpipe, where the cat should have been. Put cat back in, resonance was gone. So I had a silenced decat section made up- it was straight through on the inside, but had silencer stuff around it. It took down the exhaust note by a few db, which was a good thing in my book, but removed the horrible buzzing sound at 2000-3000 rpm and made it much more pleasant to drive.
By similar logic, some exhaust wrap might have a similar deadening on the resonance perhaps? If resonance is just metal vibrating at a certain frequency, then some wrap should soften it or stop it all together? like a hand touching a wine glass will stop if resonating?
On one of my old cars I had a similar resonance at about the same rpm, once I'd had a stainless system fitted. It was coming from just after the downpipe, where the cat should have been. Put cat back in, resonance was gone. So I had a silenced decat section made up- it was straight through on the inside, but had silencer stuff around it. It took down the exhaust note by a few db, which was a good thing in my book, but removed the horrible buzzing sound at 2000-3000 rpm and made it much more pleasant to drive.
By similar logic, some exhaust wrap might have a similar deadening on the resonance perhaps? If resonance is just metal vibrating at a certain frequency, then some wrap should soften it or stop it all together? like a hand touching a wine glass will stop if resonating?
Edited by Fordo on Sunday 6th February 13:01
slippery said:
I've tried avoiding that part of the rev range, but between 70 and 85 in top I'm right in the middle of it, which is a pain in the head! 
Drop a cog and don't change into top until you're at 90. If there are peasants stopping you from doing so, the PIT maneuver is preferable.geeteeaye said:
slippery said:
I've tried avoiding that part of the rev range, but between 70 and 85 in top I'm right in the middle of it, which is a pain in the head!
Drop a cog and don't change into top until you're at 90. If there are peasants stopping you from doing so, the PIT maneuver is preferable.
All good fun, but I do really want a solution as opposed to just having to drive around it, If I drop a cog it gets very loud again (but not in the same way) at 3000 rpm, so not always ideal if I don't want to draw unwanted attention.Personly i'd loosen off ll the clamps on the exhaust and give whole system a good shake then re-tighten, the exhaust may well be just pulling on a eubber mount more than the others, a stressed mount wont absorb the vibrations as well, or it could just be the anoying spot a lot of free flow exhaust have, they usually tune em to not drone at cruising speed but ewhat thier isdea of cruising speed is who knows ? i doubt a system designed for a rally or race car would be tuned to not drone at motorway speeds ?
Wrap 'might' help but I think if others have the resonance then it is prolly an issue with the design of the rear section. I would contact someone like Chris Tullet, you would be surprised what you can do to shut them up without reducing the character.
Edited by anonymous-user on Monday 7th February 11:56
slippery said:
Thank you sir! 
What's the make-up of your exhaust mate? From the back of the cats, do you have a balance pipe (X or H), then a central silencer for each side then your two rear boxes? Resonance is usually down to exhaust design.Does the car have tubular headers? They reduced the boominess on my Monaro quite a bit. The overall volume is louder though
Until I get it up on a ramp I'm not totally sure what the set up is, but I'm putting it into Monkfish for a full service in a month or so and it sounds like it's worth getting them to have a really good look at how it's been fitted. If that throws up nothing, I'm going to add another box, but with a electronic bypass valve so I can have full volume when required! The fibre glass wrap sounds like it would be more a case of treating the symptoms than curing the problem. Thanks for your feedback everyone.
The fibre glass wrap sounds like it would be more a case of treating the symptoms than curing the problem. Thanks for your feedback everyone.Gassing Station | General Gassing | Top of Page | What's New | My Stuff