New carbon fibre can exhaust..

[ChrisGB]

Hi to All

Got round to getting a carbon fibre can fitted today. The Blueflame exhaust I had was OK, but it did suffer a resonance when coupled with the PPE manifold, so I thought I would try a large carbon fibre can to see if that cured the problem. At the same time I also ditched the cat and now have a PPE decat pipe fitted.

On the plus side, the carbon can (a 150mm diameter 400mm long item with a 2" inner bore) weighs a bit less than half of fu, er not a lot. A glasspack with thin walled high temperature CF the silencer is rigid and very dry sounding. Also on the plus side, the resonant boom that the PPE creates is not matched to this silencer, so I can now cruise at 70mph without having to put up with a strong resonant drone.

On the minus side, although quieter in the car, outside is it unfeasibly, embarrassingly loud. Best way I can describe it is thus. If you are pottering very gently indeed, it is very civilised, if you have a bit of throttle on at low revs it is conspicuous and if you give it loads, you get a fierce crackle to go with the very loud sound. A good comparison would be a formula Renault open single seater. If I get my clog down, all plod for a mile in all directions will know someone is having too much fun.

So I am going back in the next week or two to get another run of CF can fitted in the space that is left. Meanwhile, I may try refitting the cat to see if that takes the edge off it. Will post some pics of the can and the finished system tomorrow.

Chris

[MR 2ster]

Whats the problem with the noise?

My Celica is 97db at 4500rpm  - under full chat its a lot louder but - but who cares, just turn the stereo up!

[NickNJ]

that's too loud, same db as my other car and it hurts your ears after a while. By the time I pull up at lights my stereo is roaring and i'm none the wiser and my ears are used to the exhaust drone.

[SteveJ]

My Hass twin outlet was measured at 99.8db at it's last outing to Keevil (almost twice as loud as 97db) before being replaced by a more civilised 89db system.

[Wabbitkilla]

What??

Oh yeah, i've started wearing earplugs   s:lol: :lol: s:lol:

[custardavenger]

Nick you girl!!

[NickNJ]

this girl is getting old and conservative ha, this hass exhaust worries me and i'm pretty sure ill want to quieten it down. I want it more stealth.

[ChrisGB]

Several reasons for wanting it quieter. First is that I don't want to attract the wrong sort of attention (the boy racer or blue flashing light variety). Second, it is really loud. Certainly loud enough to get black flagged off most tracks in the UK. Having said that, it is fun for a blast.

Chris

[Star_69]

My Hass twin outlet was measured at 99.8db at it's last outing to Keevil (almost twice as loud as 97db) before being replaced by a more civilised 89db system.

Jesus, thats pretty loud!

[Anonymous]

Mine's 104dB  s8) s8)   s:oops: :oops: s:oops:

[ChrisGB]

Mine's 104dB  s8) s8)   s:oops: :oops: s:oops:

If I don't get mine sorted before the July run, you wont be able to hear yours over the row mine makes  s:oops: :oops: s:oops:  

Chris

[Anonymous]

Awesome   s:lol: :lol: s:lol:    s:lol: :lol: s:lol:    s:lol: :lol: s:lol:  

Got any pics of it yet Chris?

[ChrisGB]

Awesome   s:lol: :lol: s:lol:    s:lol: :lol: s:lol:    s:lol: :lol: s:lol:  

Got any pics of it yet Chris?

I am just about to go out for a "running in" blast. Will do pics when I get back. If you have a window open, you should be able to hear it. I am heading up your way in a minute.

Chris

[ChrisGB]

Some pictures. From the top left, the carbon fibre on its former, the can made up, the connection to the downpipe. I did not get any pictures beyond this because from here in it was mostly fabricated on the car, just taken off for welding. The carbon fibre is thin, around 2mm at the ends and 1.4mm in the middle. The silencer weighs very little, I would estimate less than 1.5Kg.



Tailpipe trim is a little oval CF silencer.

The noise is still too much. In the car with the roof and windows up you can have quiet and comfortable (well relatively) cruising. The 70mph boom that the PPE manifold makes is completely tamed. No more need for earplugs. Outside the car the noise is serious. It is competition car loud and it is only a matter of time before I get pulled. I went through a small tunnel today (Goes under the dual carriageway near Great Lieghs racecourse if anyone wants a tunnel to blast through) and it was physically painful at WOT.

On my way home, I gave it some beans in third up a local bit of road and the missus could hear it in the house from over half a mile away  s:twisted: :twisted: s:twisted:  . I don't know if it is partly due to removal of the CAT, but it is taking the piss loud and I need to get it tamed.

Chris

[markiii]

beautiful

mind if i ask how much

and is it just the case that is carbon? or are the baffles and internal pipe carbon as well?

[MR 2ster]

What about making a bung for it?

[ChrisGB]

beautiful

mind if i ask how much

and is it just the case that is carbon? or are the baffles and internal pipe carbon as well?

Was £310 all in but was a bit of a faff, so might be more for the next one. I will ask when I speak to the guy on Monday. Cost is going to go up by at least £60 and possibly more as I am having a second can rigged below the first one (there is room). Hopefully that will allow me to run catless with acceptable noise.

Construction wise, the connecting pipework is 304, 57 x 2mm, the perforated pipework is 304 54 x 2mm, the end caps are spun 304 and the bands laser cut 304 sheet, looks like 1mm thick. Flange is lasered from a P&O mild steel 3mm thick. Packing is long strand E-Glass. Bends are just ordinary forming. To get the second can in, we are going to have to do a 180 deg mandrel bend of around 6.5" between centres which is quite tough in 57 x 2. The can case is the only carbon bit 150mm diameter with nominal 1.4mm wall thickness. High temperature resin gives the can wall a continuous service temperature of 350 deg C (662F? for you SC- ers). The system is made up of two parts so easy to pop in and out, even with the downpipe in place and the silencers have to be re packed when the glass wears out to avoid scorching the can wall. Riveted construction makes this a quick job. I expect the can to last 5 - 10,000 miles at least between packings.

I am mostly happy with the construction except that I wanted 2" tubing all the way through, which is what we originally agreed. The 2.25" tube used gives more open area which may be part of the noise problem. May also be giving a less than optimum scavenge, but need to get it on the rolling road to tell. Midrange seems stronger, not sure about the top end though.

On the plus side, and it is a really noticeable thing, the reduced weight makes a tangible difference to the handling in a good way.

Chris

[ChrisGB]

What about making a bung for it?

Not great for performance. Have contemplated an electronically operated restrictor. Have to see if the Unichip Q has a spare channel.

Chris

[Anonymous]

Apexi do a butterfly valve you bolt in position between two joints. Not sure if they even do anything that would fit (or could be made to fit), but they do work as I was considering one for my setup.

[ChrisGB]

Apexi do a butterfly valve you bolt in position between two joints. Not sure if they even do anything that would fit (or could be made to fit), but they do work as I was considering one for my setup.

Is it electrically operated?

Have just been out and measured up and I can get another 6" can in there at a push. Failing that a 4" would drop in comfortably.

Chris

[Anonymous]

There's definitely some kind of remote operation, let me go look for it.


*EDIT*
Right, the link for it is here, but it appears that the control for it is a mechanical cable. According to the same site, they used to do an electronically operated version of it, but it seems that's now been discontinued.

[custardavenger]

There are lots on the market.
 m http://www.superstang.com/powered_exhaust.htm m

[AllanE]

Have you considered using two silencers in parallel?
Just a suggestion, but that would mean only half the (sound) energy is going through each silencer, without such a (180°) bend being required.

I would also think that the diameter isn't too big if the midrange has improved.

[ChrisGB]

Have you considered using two silencers in parallel?
Just a suggestion, but that would mean only half the (sound) energy is going through each silencer, without such a (180°) bend being required.

I would also think that the diameter isn't too big if the midrange has improved.

I have considered that, but if I did go that route, I would need two smaller diameter boxes to keep the gas velocity up. Because these silencers weigh so little, I am not worried about having two of them in the system. It will still be lighter out the back than any system I have had previously.

Thinking about power, the system builder has used a 9" diameter bend where I specified a 6" one and other pipe routing that leads to a long run. I think this may be the cause of my doubt on the top end power as I need to get a minimum of 12" off the total length of the system to have it tuned to the manifold properly. The engine sounds properly on tune in the upper mid and off the pipe slightly in the top end.

I am getting it sorted week after next, then on the rollers for vvti tuning. It feels like it could live with more valve overlap up the top end now.

Chris

[AllanE]

Do you need high gas speeeds in the silencer? -  A lower speed may reduce the noise level without increasing back pressure.
It could be that the section/area changes will bounce stronger pulses than the end of the exhaust so the total length may not make much difference.

Of course I could be completely wrong!