luke2152
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| posted on 5/2/15 at 05:12 PM |
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Dropping decibels
Need to drop a couple of db after my iva fail and thinking of a few ways to do it (101db should be 99 and less). Some kind of DB baffle would be the
obvious choice. Can't put it in the tailpipe as it has a 45 degree exit as most of ours do. My exhaust from turbo back is one piece tig welded
and not by me so altering that means calling friends for favours (and rightly waiting til they're not busy). That being said the last bit after
the silencer is tacked only with this in mind.
I had an idea of making a copper 'gasket' on the turbo downpipe flange that restricts the flow from 3" to much smaller. Do you
think it would deaden the sound much and still flow well enough at fast idle for the emissions test.
Any other ideas would be appreciated. I've heard of use of wire wool in the silencer but I have no idea how that's done and doesn't
sound very effective to me anyway.
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gremlin1234
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| posted on 5/2/15 at 07:17 PM |
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You should check the rpm for maximum power, noise check is at 75% of that.
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luke2152
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| posted on 5/2/15 at 07:39 PM |
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quote:
Originally posted by gremlin1234
You should check the rpm for maximum power, noise check is at 75% of that.
Good point. Perhaps do a run on a dyno with a very bad map loaded to make max power at about 4000rpm?
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dave_424
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| posted on 5/2/15 at 07:48 PM |
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Get the dyno operator to slowly come off the throttle after your desired max power RPM, no need for a bad map
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gremlin1234
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| posted on 5/2/15 at 08:26 PM |
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or a rev limit /limiter
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Acc8braman
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| posted on 6/2/15 at 09:57 AM |
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I put baffles in the exhaust joint, simple piece of ally with a load of wholes in it.
Did have to trailer the car though.
When I was starting the rev the car, the examiner told me to stop and said that was ok this time, but still have 1000 rpm to go 
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russbost
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| posted on 6/2/15 at 01:17 PM |
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Any restriction will work far better at the tailpipe end than anywhere else. Reducing exhaust noise is all about slowing gases down by the time they
have reached the end of exhaust & having space within the system to allow gases to expand before effectively hearing the original explosion by the
time it reaches the tailpipe. I have cut & bent our standard Db killers before to fit within 90 degree tailpipe, adding wadding further up inside
the exhaust held in place by the Db killer used as a baffle at the end of the exhaust will definitely work - to what extent will vary from system to
system, but it's fairly easy to reduce noise without strangling the system.
We have Db killers & wadding on the website, if you want to ring for advice no. is on there
If the car has already been tested & failed going back with a different map saying max power is 2000 revs lower than you've stated on the
form is hardly likely to impress them - they aren't stupid!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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SteveWallace
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| posted on 6/2/15 at 01:18 PM |
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I had the same problem at my IVA test. The tester did mention that other people have tried the wire wool trick. He said that it did work but that he
had seen a couple of examples of where it was not put in securely enough and a glowing ball of it had shot out during the test (he called it a burning
rat!).
I solved mine with a DB killer. Like you, I couldn't put it in the end because of the bend in the pipe, so I just took the end off, placed it
direct in the end of the silencer and then put the end back on again.
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The Black Flash
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| posted on 6/2/15 at 02:00 PM |
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I had a major problem with this. As said above, the nearer to the tailpipe you put the restriction, the better.
I tried all manor of things to find this out! Ended up with some simple homemeade baffles, which take 2 or 3 db off
Pointing the exhaust exits towards the ground a bit can help as well, if you can rotate them at all.
And to be sure, to be sure, I may have wedged some wire wool up there just outside the test centre, the baffle ensures it can't come out. That
took about 5 db off so is definately the most effective way.
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russbost
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| posted on 6/2/15 at 02:03 PM |
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The wadding is a lot better than wire wool as, one, it won't burn!, Two, it expands with heat & it stays in one piece so as long as you have
a baffle of some sort between it & the end of the pipe it won't escape as wire wool is inclined to!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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johnemms
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| posted on 9/2/15 at 02:06 PM |
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Just found this while clearing the garage ..
Passed IVA with a very quiet exhaust ...
 
Knock the lip of tip insert.. knock lip back on ..
 
Side Exhaust
Bit of Stainless wool round it.. 
[Edited on 9/2/15 by johnemms]
Own chassis & Build - First time pass!!
"7's" aren't really "cars", they are 'experiences"
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