96 replies to this topic

[CHILL Gone DUTCH]

1. Chill 3" please

[Arno]

And as you can see from the location of the end pipes (that indeed point down on the 111R and then make a 90 degree) the silencer is offset in the Elise to 1 side and a new designed one could actually be made quite a bit longer (on the intake side) and the body even a little wider/deeper if needed.

 

Of course a key point is also that this silencer is not round, but more of a square/trapezoidal shape so it makes more use of the available room under the car than a plain round silencer. (and I suspect the angles in the casing also help sound waves bounce around in such a way that their maximum power areas 'miss' the exit pipes in the two chambers a lot of the time helping to cut the noise out the ends)

 

The OEM VX220 one is internally more complex, by might also provide some inspiration and key points.

 

The disadvantge? These are not really light...

 

But at some point a reality check is needed.. Either you get enough silencing and take a weight hit or you want the lightest out there, but don't expect too much noise attenuation

 

Bye, Arno.

[Exmantaa]

 

Quote from 2bular on the lotus exhaust:

Here's the inside of a stock 111R silencer. You can see it's a basic Z-flow box but the final transfer section is restrictive with a small chamber and relying on the perforated baffle to allow gas flow to the two tailpipes. With such a large chamber for the entry pipe to discharge into, it's only at the top-end that this box will lose out. The large entry-tube at the bottom is perforated at the first chamber (on the right) where the Acoustafil packing is used. At the other end is the important absorbtion section to stop any resonance (also the silencer is double-skinned to help with that).
It's good and simple and comparatively light - given the regs they have to meet, I think CLF did a good job.

 

[Nev]

If it is of any use to people, I have accurately measured the void on my VX220 and the max size box that you can fit in there from underneath with the clam still in situe is 280mm * 160mm * 780mm with 1.5" radius curves on the corners. This assumes the void still retains the silver heat insulating stuff.

 

 

 

Edited by Nev, 20 November 2016 - 02:48 PM.

[Jetpilot]

 

whilst manifolds are nice to admire, ideally I wanted this thread to focus on the packaging of the rear silencer in to the space available and the noise levels / repacking issues.

 

personally I do not run a main cat, but I know many do and have problems with the options versus cost for longevity.

 

I would want a 3" U section on the left , but retaining the boot heatshield could be replaced with nimbus and have a clam cutout

 

 I feel those are fairly arbitrary requirements that have been created without studying the constraints of the current system. 

 

For example, consider the tailpipe position. A central tail pipe requires that the pipe has to turn 180 degrees on exiting the silencer to return to the central point. This adds weight, cost, and limits the size of the silencer as the maximum volume occupied by the silencer is now a function of silencer diameter + separation between silencer and tailpipe return + tailpipe diameter.

 

This would direct me to asking the following questions:

 

1. is the current pipe routing within the engine bay the best solution. What are the compromises of changing the routing?

2. Is the current tailpipe routing the optimal solution, what are the compromises of changing it (for example, cutting an exit into the rear diffuser).

 

If both of the above answers are that there is too much compromise, I direct you towards the Posche 911 silencer approach, which essentially uses a silencer in each bumper corner to maintain a central tail pipe. Would using two small silencers enable more optimisation of available space?

 

 

This is exactly what i am in the process of trying.

 

I am getting a silencer made up the same size as the std oval as its pretty much the biggest i figure you can get in, there is nothing available that size of the shelf so had the oval made up by a sheet metal worker.

 

The silencer will be straight through absorption, the problem i see is as you mention, getting a 3" exit 180 degrees and twin tailpipes out the centre due to room, so mine will have a 90 degree exit and fire out through the diffuser, its a mmg so not that fussed about cutting an exit hole. If i am really that bothered i will weld on some fake tailpipes.

 

Also there seems to be a fair bit of room to run a decent size round silencer in place of the cat pipe, worst case, a further small slip on silencer could be attached with a 90 degree at the exit in the diffuser, if you struggle with all but the worst db limits, bedford/goodwood etc

 

I will keep up to date but i doubt many will want it as it means cutting the diffuser. 

 

I think the problem with most after market creations is no one wants to actually fabricate anything (probably due to cost) i.e use of pre formed bends and whats available off the shelf with regards to silencer size, or just simple round sleeves.

Edited by Jetpilot, 20 November 2016 - 02:56 PM.

[siztenboots]

Follow up call with Jim this morning, really to discuss Z flow designs, versus the older straight through resonator.

 

The worst usage case is for SC setups, for myself VXT I could probably get my noise target with the lightest possible simple option.

 

[Nev]

The prima facie sound levels on my new exhaust design are good, down to 98 dB (C filter) at idle, which is a minor miracle as the old exhaust was 105 dB on C filter.

 

My designs and flow arrangement are completely new for a VX220, but seem to work well, even though I am using 3.5" pipe everywhere and have an outrageously noisy engine. I think any normal VX220 using 3" pipe with this arrangement would be nigh on "stealth mode" if they were to copy my approach.

 

I haven't measured back pressure yet, but according to my calcs it should be low as my perforated x-sectional area is 7 times the 3.5" pipe x-sectional area. The only major restriction is the wave reflection inlet pipe really.

 

You could point Jim at my design and see what he says (I suspect "too complicated" or "too expensive" will be the answer!), it's certainly taken me bloody ages and a lot of head scratching.

 

 

Edited by Nev, 06 December 2016 - 09:32 PM.

[Mangham54]

Do you have any pictures?

[Nev]

Do you have any pictures?

 

https://sites.google...gn/05-build-log

[Mangham54]

[Ratouf]

What do you think about a 2"5 2bular back box on a turbo regarding noise? I'm afraid it would not be enouth

[Nev]

What do you think about a 2"5 2bular back box on a turbo regarding noise? I'm afraid it would not be enouth

 

Are you sure your info is correct, as far as I know he never made a VX200 system with just 2.5" pipework...  

[Ratouf]

 

What do you think about a 2"5 2bular back box on a turbo regarding noise? I'm afraid it would not be enouth

 

Are you sure your info is correct, as far as I know he never made a VX200 system with just 2.5" pipework...  

 

 

Can't be sure it's info from seller

[TheHood]

What do you think about a 2"5 2bular back box on a turbo regarding noise? I'm afraid it would not be enouth

  Are you sure your info is correct, as far as I know he never made a VX200 system with just 2.5" pipework...  

He did for the 2.2 - I have one on my car 👍

[Ratouf]

Ok but it feets the turbo.

[Ratouf]

On the 2.2 the sound is good ? Enough noisy ? Because on the turbo it will be less

[TheHood]

It's not super loud and easily looses the sound battle with the independent throttle bodies on my car😁 (As far as I can remember - hasn't run in a while 😕)