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I've been assured the the extra bends will make a world of difference by someone who has put several cars through IVA, the bends slow the exhaust velocity which is key in keeping noise levels down. My levels at idle are ok, (lower velocity & less 'bangs' in the cylinders) it's at higher revs it's the issue.
Thanks Phil - duly noted!
I'll try the bends first & measure the levels - I can add the Db inserts after if required as they guarantee a 4-5 Db reduction.
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sonus
Europe
Posts: 1,392
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If you know the frequency it peaks at you could fit a helmolz resonator to the exhaust aswell to dampen just the offending frequncies
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Current
1968 TVR VIXEN S1 V8 Prototype
2004 TVR T350C
2017 BMW 340i
Previous
BMW 325d E91LCI - sold
Alfa Romeo GTV - sold
Citroen AX GT - at the breakers
Ford Puma 1.7 - sold
Volvo V50 2.0d - sold
MGB GT - wrecked by fire
MG ZT 1.8T - sold
VW E-golf Electric - sold
Mini Countryman 1.6D -sold
Land Rover Discovery TD5 - sold
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12dB is a lot to lose with just an extra bend, Where is the lost energy/noise going? As the decibel scale is logarithmic a 10dB increase equates to a 10 fold increase in noise so a 10dB reduction would result in reducing the noise by approx 90%! If my understanding of decibels is correct :-) Roughly, an increase of 3dB is double the power, 10dB is double the perceived loudness... |
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Bends ordered today - not cheap so I hope they work! Did some Cad work now I know the specs - not as tight as I thought but they do still fit, if a little near the rear tyres. I can cut the flange off the silencer & shorten it about 30mm if its too tight as it is. Both types of cad employed here  nothing like a cardboard mockup to check it all fits. It's something to do with the sound waves being bounced back up the pipes from the bends that quietens it down - sort of cancelling it out?  |
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Blimey - they are expensive!! But they are also exactly what I had designed to fit inside my silencer which I can make at work. I was also thinking of these - less expensive & saves me making them - approx 5-6Db reduction apparently link |
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And we now have IVA friendly door handles.   |
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Now, they are impressive! Are they actually chromed?
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Nope - just black paint  |
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And we now have IVA friendly door handles. D'you know, I reckon the IVA guys are going to do away with little polystyrene spheres and it'll be, "Nope, doesn't come close to BPR's standard. Fail!" They should give you a pass just for the bloody door handles! |
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Nope - just black paint :-) Now that you mention it.......No, still looks like chrome :-) Nevertheless, a very neat modification. |
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fer4l
Posted a lot
Testing
Posts: 1,497
Club RR Member Number: 73
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Nope - just black paint :-) Now that you mention it.......No, still looks like chrome :-) Nevertheless, a very neat modification. Amazing how the eye sometimes sees what it expects to see - they definitely look chrome to me! |
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Nov 12, 2016 19:27:44 GMT
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Been doing lots of 'honey do' jobs recently so car has taken a back seat. However the exhaust bends (I wont say how expensive these were) and flanges have arrived and a quick mock up shows they will fit under the car ok. Evolution blade got the stainless swarf red hot so might be a bit much for it! I hope it all actually works for the price of the bends. Where flange is is where it will bolt the the silencer and it's laid over the pipe where it will be cut.  |
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Nov 13, 2016 19:09:48 GMT
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Well, stainless pipe 1 Evo blade nil, lol. Back to using 1mm discs in grinder & might need a new Evo blade  Got to this stage - but need to lose at least 30mm off the measurement from flange to back of the 180 degree bend as it fouls the chassis. Not a huge issue but it will take some of the bend out of it near the flange. Old tip next to it for comparison.  |
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Nov 14, 2016 13:31:48 GMT
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There is part of me that loves this project and a past of me that despairs that it is happening.
The fact that you keep ramming this project through a bureaucratic quack-mire that was designed to stop this kind of project in the first place, makes you my hero. This car is an internal combustion powered middle finger to the IVA.
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Nov 14, 2016 19:57:14 GMT
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Thanks bjornagn, ooooh, I'm a hero Been playing with the big boys toys at work - I forget how lucky I am to own such cool machinery. Stainless steel .8mm sheet punched out for an exhaust noise reduction kit  A bit of tin bashing got it to this shape;  and how it will fit inside the exhaust;  Once I've done both I'll fit one at a time and measure the sound difference so people will have an idea of how effective either mod is. I'll check outputs on the lambda sensor with either fitted - this will indicate if its restrictive or not hopefully. |
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Nov 14, 2016 20:20:29 GMT
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In my 2 stroke bike days the expansion chambers had end cans with perforated metal inner sleeve which was wrapped with fibre glass wool packing between it and the outer skin. It used to 'fall out' a lot but did show the difference in sound deadening effect just achieved by wrapping the sleeve. What you have there and DB killers in the end pipe (which are allegedly removable........) should get the noise down. |
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Needs a bigger hammer mate.......
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Nov 14, 2016 20:40:07 GMT
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I hope so duggers - I love the loud exhaust but for longer journeys it would be nice if it were quieter so if it's not restrictive I may leave it in. As you say I can pack it with wire wool as well if required for the test.
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nothing like a cardboard mockup to check it all fits.
