Highcost builder
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| posted on 27/10/02 at 08:39 PM |
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exhuast is bl##dy loud, help.
my exhaust sounds loud and ive read that some of you have silenced it a bit for the sva, how did you do that running a x flow with lolo manifold, see
photos.
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Dunc
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| posted on 27/10/02 at 08:45 PM |
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Build an anti-noise tailpipe. A special mic picks up the noise of the pressure wave as it passes though a straight through exhaust, times it, inverts
the signal and exits the sound through a loud speaker. The two waves cancel each other out. Changing the phase can allow for you to have a bigger
sounding engine than you really have. Works similar to the antinoise headphones used in industry.
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Highcost builder
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| posted on 27/10/02 at 08:50 PM |
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kind of hoping someone woulg say shove a bit of metal in it, your suggesting a degree course in electronics, i dont have the time for college again iv
got to finish this bloody car.
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CairB
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| posted on 27/10/02 at 09:47 PM |
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I failed SVA with 102.6dbA at 4000 RPM using a 2.0i Pinto through std manifold, fabbed 2 into 1 into a Lolocost silencer. I fitted a sleeve into the
inlet of the silencer made out of 50mm exhaust tube, slit to reduce dia, fitted a collar to stop it getting lost, then a plate on the end with a 25mm
hole. This reduced the noise to 98.8dbA. On retest it was measured at 99 at 4250 - so theres some scope for opening it up
Hope this helps
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Highcost builder
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| posted on 27/10/02 at 10:08 PM |
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thank you!
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locodude
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| posted on 27/10/02 at 11:14 PM |
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You can get a Jetex 'decibel insert' from Burtons. I have one in front of my Lolo' end can and it flew through SVA. Bit louder now though, not
much wadding left I think! All it is, is a pipe swaged down to a smaller diameter (30-35mm) about 300mm long. I rekon a washer the right size would
also work although the gas flow would be a bit naff.
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Dunc
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| posted on 28/10/02 at 10:39 AM |
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You can experiment like locodude says by getting a length of pipe and putting restrictions in. Gas flow will be pish but the old dBA's will be down.
There are various ways of doing it, even making up an SVA compliant exhaust that you could unbolt easily made from 1 or more of the expansion chambers
of the donor.
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stephen_gusterson
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| posted on 28/10/02 at 08:07 PM |
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on my car (which has 2 exhausts) I just used the back box from a granada 87 e reg, 2.4/2.9 litre car.
Cost about 35 quid from an exhaust factor. Is straight through, and of the 'glass pack' type. It has a round body with the exhaust thro the middle,
and perforations in the tube that 'bounce' sound waves into the glass wadding around it.
No restrictions, not too loud, is in the locost style, and not to expensive.
atb
steve
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david walker
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| posted on 28/10/02 at 08:42 PM |
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CairB - Your noise test should have been carried out at 3500 rev/min not 4000. If they had done it at that you may have sqeezed in the 101 dba
limit.
I failed my SVA first time on noise (104 dba) and upon the advice of the SVA inspector made up a short tube stuffed it with wire wool and pushed it
down the tailpipe locating it with a splitpin. The engine nearly choked to death during the few seconds the test took. As soon as the test was
completed I removed it and drove off!
Dave Walker, Race Engine Services - 07957 454659 or 01636 671277
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CairB
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| posted on 28/10/02 at 09:38 PM |
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It might have just passed at 3.5k but the SVA manual states either 3/4 of maximum power speed - 5.5k which gives 4125 or 2/3 of maximum desgin speed -
6050 which gives 4033. Either way its less than 4250 but I wasn't arguing as I knew it would still be under. (RPM Figures from Haynes for 2.0i
Pinto)
Is anyone using a straight through exhaust that meets the limits without extra baffles?
With hindsight I think that the Lolo.. one is a bit short to be effective.
Removing the baffle completely is tempting but I'm deaf enough as it is and I don't particularly want to annoy the neighbours.
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Peteff
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| posted on 29/10/02 at 06:34 PM |
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yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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Peteff
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| posted on 29/10/02 at 06:38 PM |
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exhaust noise
When I took sva the tester said the test was run at 2/3 maximum revs, which for the pinto was 4000 revs. I recorded 98 db with a homemade silencer. If
you want to quieten it the easiest way is to put a bend on the end and point it at the floor.
yours, Pete.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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david walker
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| posted on 29/10/02 at 10:12 PM |
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I'm sorry to be picky but the SVA Manual states:
a. 3500 rpm or
b. if the engine maximum power speed is less than 4500rpm at 3/4 of that speed.
It goes on to contradict itself with the 2/3 engine maximum design speed, - "Where the engine maximum power speed is not available". By definition
if it is available (as it is with our type of commercially manufactured engines) then the rule is 3500 rpm.
Again, sorry to be picky!
Dave Walker, Race Engine Services - 07957 454659 or 01636 671277
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kamikaze
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| posted on 31/10/02 at 06:10 AM |
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When i "sva-inspect" my motorcycle i have a flue brush placed in to my exhaust.
Just cut it down so it´s a little bit larger than the exhaust an press it in about 100mm.
The handle is ofcause cutted to about 60mm with a loop in the end so you can pull it out easy after the inspection..
[Edited on 31/10/02 by kamikaze]
"Bones heal and chicks dig scars. Pain is temporary,but glory is forever."
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CairB
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| posted on 5/11/02 at 10:47 PM |
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Regarding my previous post. The figures quoted are relevant for the SVA manual that I recived Mar 2002.
Thanks Locodude for the info re Jetex insert, I've just fitted one, direct from Jetex, with 80 extra 5mm holes and a welded collar at the loose end.
The noise level with just the insert was right foot prohibitive but alls well now with the equivilent of a brillo pad wrapped around it, don't know
how long it will last tho.
Cheers,
Colin
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