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**macdonald.dm** · 06-08-07, 05:25 PM

Re: Side exhaust - hello Dane!.

Thanks Sue!

This is a job I'll be tackling pretty soon - yes, that means I haven't done it yet...

I do have the silencer box - a Polycarbonate and SS 'Poyzhaust' unit - and my local metalworks has supplied me with the correct length of 2" SS pipe with a slight bend (to match contour of Berli chassis) and a sleeve for £20 cash.

The old system already has a new-looking length of flexi pipe on it which I'll use to connect from the manifold to the pipe just outside the bodywork, so all I need now is time...

I even have a couple of chrome angle trims to fit on the dual outlets from the box

**str11ker** · 07-08-07, 01:03 PM

Re: Side exhaust - hello Dane!.

Donnie, where did you get the Polyzhaust bsilencer from, the web site i found only says it is being developed!
any info most welcome...as i fancy a different exhaust /silencer on my roadster

**macdonald.dm** · 07-08-07, 01:45 PM

Re: Side exhaust - hello Dane!.

Hi Keith.

See item 200138620978 on Ebay - that's who I got mine from; around £30 all in.

It's certainly much lighter than a full steel box, and the manufacturer's website claims it's a lot more efficient at sound muffling too - I've still to see (er, hear).

I went for the largest box, and it has a twin outlet.

Really, it's meant to be used as a rear box of a two box system, so I don't know how good it'll be on its own - I'm prepared to slip a decibel reducer into the pipe in front of it if necessary.

Also, the reason it's meant for rear use only is that it might get too hot in the front position - again, I'm not sure if enough heat will be lost from the delivery pipe before it gets to the box! So, it's all experimental, but I'll certainly keep peeps posted. (There is a ptfe seal between the pipe and the plastic (polycarbonate) box, so I hope it'll handle the temp...)

**macdonald.dm** · 04-09-07, 01:39 PM

Re: Side exhaust - hello Dane!.

Hmm. Well, it's done!

Putting it all together was a surprisingly straight-forward and satisfying task, aided by the relative light weight of the 'box. The running board itself is easily up to the job of supporting the unit, with 'penny' washers helping to spread the load and protect the fibreglass. A galvanised 'building' strap (yet to be painted!) was persuaded to follow the profile of the 'box, and this was then bolted to the underside of the running board via rubber washers. A further bracket - again working through a rubber bung - adds additional support to the front of the unit and the end of the pipe.

Exhaust wrap was wrapped around any electrical cables within potential scorching distance, instead of being applied to the exhaust pipe itself. This was because I wanted the pipe to be able to lose as much heat as possible to protect the plastic (really!) silencer box.

So, what does it sound like? I knew even before the engine burst into life that it wasn't going to be as quiet as I hoped - a very distinctive 'whooop - whooop' sound came pulsing out of the twin pipes as the engine cranked over.

And then... BRUUUMMMMM, THRUMM, THRUMM, THRUMM!

It's not that it's loud exactly - it isn't particularly. But, the low tone of the note has the misfortune of matching the resonant frequency of my skull and every other hollow object within a 2-mile radius.

It's like being struck repeatedly by a soft mallet - and that isn't as nice as it sounds. It even makes the car itself resonate - the vibrations are very noticeable as tho' the body is acting like a guitar sound-box.

A quick look at the 'needforspeed' website had a decibel reducer winging its way towards me. This made bugger all difference (pardon my French...).

THRUMMM, THRUMMM, THRUMMM... Resonate, resonate, resonate...

So, I guess I'll have to try and find a better sounding 'box, because this one is doin' ma heed in, literally and metaphorically.

Any ideas?

Attached Files

**macdonald.dm** · 04-09-07, 02:37 PM

Re: Side exhaust - hello Dane!.

My two thoughts at the moment are:

1) A large car 'box which has the pipes separated inside - ie: NOT a through-flow design like the one currently fitted. Surely this would be a lot more effective, or

2) (I think I read about this on the MOC forum somewhere) using a can from a ~1000cc motorbike. As was said by the original poster, a 1000cc bike engine revving at 10k rpm should have about the same gas throughput as a 2.0L pinto at 5k rpm!

Thoughts?

**macdonald.dm** · 05-09-07, 05:36 PM

Re: Side exhaust - hello Dane!.

Ok, I placed the decibel reducer in the correct place - up the tail pipe - and it seems to have helped matters.

So, 'where on Earth did you put it in the first place - and keep the answer clean' I hear you ask.

Since the 'box I chose has a single inlet and twin outs, I thought I'd position it before the actual silencer. Hey, I couldn't see why it shouldn't do something - but it clearly didn't.

Putting another one into the second outlet will obviously help, but I'm dead curious to know how a 'bike 'box would compare.

Incidentally, the 'decibel reducer' is just a foot-long length of pipe which is internal-pipe-diameter sized for about 3 inches, and then drops to a slimmer bore for the rest. It is plain tube - no perforations or nufink. How does it work?!

**jon_cox** · 07-09-07, 04:23 AM

Re: Side exhaust - hello Dane!.

Donnie,
See my reply in the new post.
But to answer your new question.....
A decibel reducer should be placed in the straight piece of pipe that runs inside the silencer box. The pipe in the box has holes in it for the noise to be absorbed by the wadding. What the tapered pipe of the db reducer does is force more of the airflow into the wadding. Simple as that!!!

Attached Files

**macdonald.dm** · 07-09-07, 07:06 AM

Re: Side exhaust - hello Dane!.

Wow! Superb info, Jon.

Kind of explains why placing it in FRONT of the 'box had no effect... (Blimey - am I sorry told people about that!)

Thanks again.

**amalgamated users from prior forum** · 07-09-07, 06:08 PM

Re: Side exhaust - hello Dane!.

Message originally posted by: Sue Roedel (MOC Editor)
Do you mind if I use this thread for the mag sometime? It's going well. I will spare any embarrassing comments!

**macdonald.dm** · 08-09-07, 01:49 AM

Re: Side exhaust - hello Dane!.

Usual fees apply, of course....

(Obviously no objections - warts an' all...)

**macdonald.dm** · 13-09-07, 03:14 PM

Re: Side exhaust - hello Dane!.

Hi KEITH DAVIDSON.

With ref to your post above, what system do you have at the moment? Chust curious! Obviously, based on my experience, I cannot recommend a Polyzhaust because of the awful head-banging tone.

I have just this minute bought a cheap Honda 900cc Fireblade silencer of Ebay.

I'll keep you posted...

**macdonald.dm** · 16-10-07, 05:07 AM

Re: Side exhaust - hello Dane!.

Update: A relatively civilised noise level…

Just changed my unbearable ‘Polyzhuast’ for a bike can. Yes, thanks to Mr Honda, my Berli now sports an aluminium alloy exhaust from a 900cc ’95 Fireblade. Not only is the noise level significantly reduced, but my Berli now revs smoothly to 14,000 rpm, banks into corners, and pulls wheelies.

For me the side-exit exhaust conversion was a hugely worthwhile modification - it has effectively increased ground clearance and has seen the end of the embarrassing scrapes and scrunches that greeted me whenever I passed over even very low-lying sleeping policemen. It’s also much easier - and cheaper - to work on and replace.

The bike can is surprisingly light, no doubt due to it being mainly constructed from aluminium alloy. This has the added advantage of it being effectively rust-proof, although I suspect the internals are still made from steel so won’t last forever.

It was also a very cost-effective conversion. I already had a short length of 2” flexi pipe (which is the easiest way to get from the manifold to outside the engine bay), but a 500mm length of this in S/S shouldn’t cost more than about £20. Add to this 1m of straight 2” S/S pipe which, again, comes in at around £20 (I got mine from a local metal-fabricators for this price, and they also put a slight bend in it to match the chassis profile - I took a simple card template along.) The Honda exhaust cost a whopping 99 pence on EBay, or just under £9 when postage was added. Total cost of a side exit system should be as little as £60-70. Ok, the first few inches of the original downpipe - the part with the flared end which joins to the manifold - has to be retained with this cheap setup, but this is usually the longest-lasting part of a system in any event, as it gets hot but doesn’t get wet!

So, what does it sound like?! Well, it has a tasty but nicely subdued ‘rorp’ which provides the badly-needed illusion of power, but it’s quite acceptable at normal road speeds and isn’t in the least bit anti-social around town. It’s a pretty nifty sound when zipping around country lanes but it does get a bit loud when revving hard and is also still a tad too intrusive for my liking when cruising at 60mph+. I can imagine it getting quite tiresome on a longish trip. The situation isn’t helped by my Berli having just a 4 speed box - I’m sure a lower revving engine would fare better. Also, there’s no doubt that having the exhaust outlet exiting almost level with your ear is pretty much the worst place to have it!

Recommended then, as it has lots of ‘pros’ and only one real ‘con’. The noise level is a little too strong for my personal liking although I can live with it until an alternative comes along. I’m sure many of you would find it quite acceptable! I’d love to know how a bigger-engined bike exhaust would compare, such as the one from the 1300 Suzuki!

For anyone considering this job:

A quick look on EBay should present you with a good selection of cans to choose from. You’ll need an exhaust from a 900cc bike upwards (there are plenty even going up to 1300cc!) to ensure your engine can breath as well as before. Also check that the bike it came from used a SINGLE can, as some have twin exhausts and this would mean that each can is only designed to handle half the exhaust gases.

Also make sure you get the associated ‘link pipe’ with the can as this will make it much easier to connect to your pipe - mine came without so I had to cobble together a 60mm diameter coupling to mate it to my 2” pipe. Oh, and check that the link pipe DOESN’T join the can at an angle as most do - look for a straight fitting (unless you want a squint exhaust.).

Looking at pics on EBay, I think - but check before proceeding - that suitable cans can (always wanted to say can-can…) be obtained from the Kawasaki ZX9R, Honda Fireblade CBR900 (certainly the ’95 model!), the Suzuki GSX1300, and I’m sure many others. Oh, oh, and also make sure it’s a ‘standard’ can as supplied with the original bike and not an after-market ‘race’ exhaust which will be tooo loud!!

PS. I thought, since the can was originally painted black, that it would be well enough thermally insulated to tolerate a paint job. So’s I gets out my aerosol of metallic Graphite paint… Mmmm, tasty! At least until my first drive. It’s now a kind of ‘crackle’ finish…

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Side exhaust - hello Dane!.

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