August 2, 200818 yr I have recently purchased a used peco style silencer box in steel, to adapt for my B175 and would like to know how much baffle is required for trials use. The reason I ask, is that the box at present, whilst packed, is straight through. I have located a small removable baffle which is available for quietening 4 stroke pipes on road bikes and wonder if it would fit the bill, or is it necessary to have the tailpipe offset from the inlet on the box on a stroker. I admit to having no real knowledge of silencers on trials machines and would appreciate comments please on the subject. Thanks. Steve
August 5, 200818 yr Hi Steve, Straight through would be best, with a perforated tube packed on the outside with fibreglass silencer packing material. Baffles would be power restrictive and with a Bantam, you can't afford to lose any! From memory, exhaust/silencer volume is optimum at a ration of 12:1 of the swept volume, if you want to work that out. I remember Peco made silencers for the Villiers engined bikes, a year or two back now, were a bit noisey I read. Bye, PeterB.
August 7, 200818 yr Author Hi Peter. Thanks for the pointers. I have stripped out the old fibreglass packing as the end cap is removable and intend to repack with loose fibre. I will do a bit of searching on the net regarding the Villiers that you mentioned as I dont yet understand how the calculations are made. The perforated tube is central in the box and is luckily the same bore as my 1 3/4 ins High level Bantam pipe. The tail pipe is the same diameter too, so think I will slim that down a little to 1 1/4" and extend it, as its a bit too short at present and exits right on a seat frame tube. I dont want to make so much noise as to make a pest of myself. Regards. Steve
August 11, 200818 yr Hi Steve, That silencer tube is a pretty large diameter, I'd have used 20 to 25mm ID perforated tube with as much volume as possible. I read in a technical article somewhere that the exhaust silencer volume has an optimum ratio to the swept volume, that I think was 12:1 - best to look this up, try Google, maybe Tuning for speed by Phil Irving. Bye, PeterB.
August 12, 200818 yr Author Hi Peter. Thanks for the help. I did think that the bore was rather on the large side. The internal tube is made from a steel sheet that has been drilled with holes across its surface and then formed into a tube, and, to my mind, does not have enough perforations to make the packing effective. I will have a hunt around to get something that will better suit. The luxury is that the box is all steel and therefore can be Mig welded and finished with linisher. Not a lot of dimensions out in trails land for exhausts for the ole Bantam. Regards. Steve
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