Exhaust options

[Brickboy]

To update this post rather than start a new one...

I have downpipes in black, great condition and only some de-blacking. My silencers look good but are super loud straight through devices.

I'm thinking of replacing silencers or the whole system to one colour. Armours seem to be the only stainless supplier of full systems I suspect my black-ish downpipes are stainless. Can they be cleaned back and polished to bare metal, and how?

Or, if it ends up being the whole system is Armours the only choice? At the price of standard, Mdina type , options I think stainless has to be the way ahead. I don't want to shell out twice!

Cheers,

Simon

[hendre]

you mean Silentium silencers? They are indeed not silent...

[Steve Brown]

Sorry? What was that?!

Hollow cans with a perforated plate half way up. Surely there's a way of making them less offensive to anyone within half a mile, or do I have to buy replacement silencers?!!

Cheers,

Simon

I've seen 'silencers' like that too, I don't know how they get away with it either!
What I've done with a few different makes of 'silencer' or bike is to gut the can (that's all it is) and add a baffle to the down pipe that extends as far as you want into the 'can'. I cap the end of this baffle pipe and then either;

a)drill a series of holes at 90 degrees to the pipe and make an effective baffle that way. The more holes the less back pressure obvs.

Or b) hacksaw a few slits across the pipe and then indent one side of the slit. I make the indents on the engine side of the pipe.

The theory (not mine but I like it) is the sound wave hits the capped end of the pipe and then rebounds back up it. Each time the sound wave is stopped and reversed it loses a little energy and a bit of noise. A more effective silencer might have a number of these 'reversals' inside it.
I got the basic idea from an old tuning book by Alexander Graham Bell, who must be very old as he also invented the telephone, didn't he?
The holes type baffle is good but I think the slit and indent type is better. A basic rule of thumb is that the surface area of the holes or slits should add up to more than the surface area of the end of the pipe. I can't detect any performance loss using these home made baffles but they are certainly good at making the exhaust a lot more respectable.
On one single that had a very sharp bark I tried it with the pepper pot idea on the end of the pipe but it was still a bit fruity. So then I added another similar baffle in at the tail end. That made it sound like a Honda single (apart from the tappet noises etc) and still no power loss-it's easy to prove this on the road as these bikes can be held WFO for miles on a main road without getting you into too much trouble. I've yet to do it on a Morini but it may happen soon. I have done it on various British singles and twins, a couple of classic and vintage two strokes and a few high revving Honda twins and fours. They all go very well and get no complaints from MoT testers or the neighbours.

[Ming]

You can find lots of dB killers on the Bay. They appear to use the same principle on indented flaps as advocated by Steve.

BTW, Brevattata is the Italian for Patented.

[Brickboy]

Thanks all,

I have some stainless wool and silencer wadding on its way.

Should that not work it's new silencer time.

It looks like there are two stainless options: Armours and Feked. There seem to be divided opinions on Armours although my own experience of their Jota pipes on my old Laverda was great. I'd be grateful to hear about the Feked ones or any other options.

Cheers Simon