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Post by cezeta on Feb 3, 2009 10:27:52 GMT
funny enough, just looking through this again vintagescooters.free.fr/tuning/px200_exhaust/px200_exhaust.htmthe three top performers are made by jl, the sip performer is stainless again by jl and was in the top runners. i wonder what the real differance is between stainless and mild. it would be good to have them dynoed back to back as the theory is nothing more than an old wifes tail without some backup evidance
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Post by me on Feb 3, 2009 13:45:20 GMT
I can't see any reason why not to use stainless, apart from the brittleness of it but if welded correctly then its fine. Its the shape of the pipe that effects all its caricatoristics. (spelling)not the type of metal if you read that bit in last months "bible" god himself is makeing hydraplane pipes from ally.
Bible * God..... its just a book and a name, it could be scootering and Lauro as another option
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Post by breezer on Feb 3, 2009 15:44:58 GMT
Won't be laughing when you get struck down, will yer?
;D
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Post by shrew on Feb 4, 2009 1:43:34 GMT
Sorry me.. a bit wrong mate. Look into pipe technology. The material type and thickness is very relevant and critical to pipe design. An expansion pipe is an amplifier.. Now if that amplifier can 'pulse' then the amplified pressure wave will be greater, hence more draw and return. The thinner the metal, the more flexible it is then the more it can resonate. Cezeta. Take into account that the pipes tested are not necessarily a 'good' design to begin with and are generic in that design.They are not engine specific but designed as an off the shelf product for all. And sure the stainless 'scorpion' or 'sip' may be better than a mild 'jl' or another type but this may be just down to the better cone angles working well with that engine. However if you had two identical systems one in stainless and the other in .9 mild you'd ceratinly see the difference. I tried to find some stuff on the web to show how the resonance works and this is the best I found-right at the bottom of the page. Here is a working diagram and a mention of the importance of resonance. You used to see exhausts 'wrapped' with a heat tape. The idea was to raise ex gas temps which were thought to help. Well it does but only by raising temps/shortening the pipe..what happens though is that the pipe cannot resonate and so becomes less effective in its drawing action and so heat wrapping on the main section of two stroke pipes has mainly been dropped and redesign favoured instead. www.southernskies.net/page_info/runningtwostrokeengine.html
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Post by shrew on Feb 4, 2009 1:55:13 GMT
And yes ME Lauro Caforio is making the pipe in ally. On that type of boat the pipes are watercooled and this cools the pipe/gases and effects the resonance, therefore performance. Ally pipes are standard in this from of motorsport. Ally has a fairly low melting point, is fairly fragile in thin wall thickness and hence not good for our application. So here we have proof again that material type is very important.
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Post by me on Feb 4, 2009 22:27:21 GMT
I've been told.... but like you say for our application material doesn't really matter, it's all down to design.
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Post by cezeta on Feb 4, 2009 22:42:10 GMT
i spoke to two people today, one bloke who used to race 2 stroke tripples. he said he has tried everything and not much ever REALLY had a noticeable effect so although agreeing in principle reckons wearing a snugger fitting jacket would have more effect
the other bloke has run stainless on a vespa, a dragster and a ts1 and said never again as each one broke within a few hendread miles.
tbh i only wanted stainless so it stays maint free and my last jl burned all the paint off in a moment.
maybe a proper coating is the answer then
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Post by cezeta on Feb 8, 2009 15:24:48 GMT
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