oldbutnotslow Posted October 21, 2005 Share Posted October 21, 2005 I have been asked to post pictures of the insert that Dave at Powerspeed sent me that has been designed to reduce the noise level See here Seems to have knocked 8 or 9 db from mine  Grant  😬 183 BHP of Black and 'Stone Chip' excitement. 😬 here Link to comment Share on other sites More sharing options...
tom7 Posted October 21, 2005 Share Posted October 21, 2005 Good stuff OBNS, Couple of Q's How much did Dave charge for this? Have you had a chance to measure before and after? Have you ever experienced a 'tizz' on the overrun on yours, I've got one at 4500rpm despite 'rebuilding it twice. cheers Tom Link to comment Share on other sites More sharing options...
Jenson Button Posted October 21, 2005 Share Posted October 21, 2005 ...and what does it do for the power.... 🤔 (does it drive noticeably different?)  Link to comment Share on other sites More sharing options...
oldbutnotslow Posted October 22, 2005 Author Share Posted October 22, 2005 In the end this airfield TD did not go ahead because they found 2 x 1,000lbs WW2 bombs near the runway that they had to blow up . In preparation for the Javelin TD on the 16th I have measured the static noise on Black and Stone Chip  5500 rpm gave 99.9db OOOPS! Pass is 98db so that is quite a bit louder than a pass. I seem to remember that an extra 3 db is twice as loud in noise pressure terms Dave at Powerspeed supplied an insert that goes inside the perforated tube that is visible after removing the end cap, which has the effect of pushing more gas through the wadding. This was inserted and the engine re-measured  89.9DB on 3 readings  OK its bound to have an effect on power but for a quiet day what the heck. Its an interference fit so no rattles at the moment. The trick will be to get it out again afterward  The upshot is I haven’t run mine in anger with the insert in place and as the TD on Monday is at Snetterton I have taken it out. I have the zing as well.... odd because I have looked all over to see what it is. Does not seem detrimental and you cant hear it with a race helmet on! Dave did not charge me as this was the first one and as such he is using me as a Guinea Pig.  Grant  😬 183 BHP of Black and 'Stone Chip' excitement. 😬 here Link to comment Share on other sites More sharing options...
Grubbster Posted October 22, 2005 Share Posted October 22, 2005 I spoke to Dave about this and he is also sending me one. On new exhausts now he will use a narrower perf tube to reduce the noise. He doesn't think this insert will make any noticeable difference in performance unless you are running well in excess of 200 bhp. I'll fit it and if I can't notice a performance loss then it'll stay in for good. Roadsport build photo's here Le Mans 2004 photo's here Link to comment Share on other sites More sharing options...
The Polisher Posted October 22, 2005 Share Posted October 22, 2005  Grant, My first motobike, a Triumph Tiger Sports Cub had a not dissimilar insert at the end of the tailpipe which was the other way round ie. crimped end first. This was held by a pop rivet through a hole in the tailpipe so that it could be removed in seconds. It was made from non perforated steel but the 6 convolutions continued in decreasing depth along the length therefore forcing the gasses through a smaller orrifice.The difference it made to the noise level was incredible! Tom, My Powerspeed has a 'tizz' on the overrun despite having rebuilt it and individualy flared the ends of the primaries to be a snug fit in the collector. Mine eats packing having repacked it three times since I bought it off CT's bulk buy. About to try 'long strand E glass' now.  Dave H. Mad about S77ENS Link to comment Share on other sites More sharing options...
Atinod Posted October 22, 2005 Share Posted October 22, 2005 Hmmmm. Did a forklift run over it 😳 Sugano [sp?] posted a picture of a cone shape insert that he was using which looked a little more, er, how shall I say this, dainty. Same effect I guess. Found it here Edited by - Atinod on 22 Oct 2005 10:58:27 Edited by - Atinod on 22 Oct 2005 11:01:00 Link to comment Share on other sites More sharing options...
oldbutnotslow Posted October 22, 2005 Author Share Posted October 22, 2005 Interesting comments about the packing. Ive no hot spots on the can and I have done upwards of 25 track days in the past 2 years with the original packing which will equate to just short of 5,000 track miles most of which will have been spent at 75 to 90% of max revs + the run to Le Mans this year. Strange how one lasts and others dont. Perhaps the moral is screw the Bo££ocks off it! Grant  😬 183 BHP of Black and 'Stone Chip' excitement. 😬 here Link to comment Share on other sites More sharing options...
Jason Plato Posted October 22, 2005 Share Posted October 22, 2005 regardless of what power you have I would never consider using something like that in the exhaust. The back pressure it will make will be no good for the engine or power . I realy do think this is a poor solution to the problem.  I think you need to ask why is it so noisy in the first place - small silencer size ? , silencer overpacked / underpacked ?   Link to comment Share on other sites More sharing options...
Mr Locust Posted October 22, 2005 Share Posted October 22, 2005 Easiest way to check what it is doing by putting a gauge test point on the lambda fitting of the manifold. Engine suppliers I use at work tend to give a figure in the region of 10KPa max back pressure. Admittedly this is for NA and turbocharged diesels but it is a reference point at least. Ian Green and Silver Roadsport 😬 Link to comment Share on other sites More sharing options...
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