pewe
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| posted on 29/1/08 at 04:07 PM |
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Exhaust pipe restrictor
Thinking ahead to SVA (times when I never thought I'd be saying that!) can anyone tell me where to buy or show me a pattern for an exhaust pipe
restrictor as I'm sure it will fail the noise test.
Is it a simply like a big washer with a hole in it or a spiral that fits in the tailpipe?
Any suggestions gratefully received.
Cheers, Pewe 
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Guinness
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| posted on 29/1/08 at 04:11 PM |
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Have a look at the reply I gave a while back. The ebay link still works.
http://www.locostbuilders.co.uk/viewthread.php?tid=75776
I still have mine in the trackday tool box. Could lend it to you at the appropriate time, but by the time we both pay the postie, you'd be
better off buying one!
Mike
[Edited on 29/1/08 by Guinness]
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pewe
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| posted on 29/1/08 at 04:49 PM |
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Mike, thanks for that.
Had a look on fleabay and it's similar to the one I just bought from Merlin M/sport.
Problem is removing the silencer every time to shove the pipe into the exhaust pipe forwards of the silencer.
I recall someone on here buying/borrowing one from Stuart Taylor on his SVA day which simply shoved up the tail pipe but can't find it.
Cheers, Pewe
PS shoot up to Forest Hall to see my old Auntie a couple of times a year - next trip will be trailering the Jota up for a wellie across the moors late
Spring.
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v8kid
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| posted on 29/1/08 at 05:39 PM |
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I got one from DT which shoves up the exhaust pipe just for SVA.
Fitted it and could not tell the difference.
Bought a sound level meter and tested it with and without.
Result? 1 measly bd reduction.
Experimented pointing exhaust down to the ground - no difference.
Experimented stuffing wire wool up exhaust - wire wool caught fire? (yup its a hot exhaust)
Solution turned out to be welding 4 washers 0.5 times the exhaust pipe diameter every 90 degrees up the last 4" of exhaust pipe. Reduced db by
5.
Strangled engine power though and it ran even hotter.
Search google on Exhaust Science demystified by vizard for a proper solution. Dunno if it works I'm in the middle of building a new system on
these principles
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pewe
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| posted on 30/1/08 at 05:20 PM |
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Thanks guys. The silencer was purchased from CBS and they reckoned it was SVA acceptable. It just seems fecking loud and I know it can't be
judged by ear as it's a logarithmic measurement. Maybe I'll worry about it after it's passed or failed then do something about it
foe re-test and track-days.
Cheers, Pewe
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NS Dev
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| posted on 30/1/08 at 07:03 PM |
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I made one which dropped it 7db.
I used some exhaust pipe that was a tightish slip fit inside the main pipe, slit it alternately from each side 2/3 of the way through the pipe, then
tack welded in 2/3 circles of 0.9mm thick steel sheet, meaning that the gases have to zigzag up and down to get though. 4 or 5 plates will do the
trick, spaced abotu an inch apart. the 0.9 sheet slips perfectly down hacksaw cuts.
I then drilled a 2.5mm hole in the underside main pipe before the silencer, after slipping the restrictor inside, so a self tapper went through both,
holding the restrictor in place and blocking the small hole at the same time. Put the silencer back on an bob's your uncle. no restrictor
evident up the tailpipe, but really quiet engine (but strangely down on power, can't think why lol!! )
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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