Universal Exhaust Silencers (duplex)

[wardy18 33 1 Cars]

Hi,

 

Because of the new diffuser i am looking at making a dual side exit exhaust (has to be dual to get enough silencer volume in the space i have). Ideally i need a DUPLEX silencer where the centre pipe exits the tunnel straight into the side of the silencer which will be hung where the std fuel tank used to sit then at either end of the silencer will be an exit pipe to either side of the car. This will enable me to leave the diffuser as a complete flat surface and not have to cut into it to make a tunnel to bring the pipe to the back of the car.

 

HOWEVER, the only Duplex silencer i can find is by Jetex which is 140x220x500mm now the length 500mm is perfect however the silencer is just too fat at 140x220mm. I cannot find a slimmer model, it can be longer and must be slimmer?!

 

My only other option if i cannot find one is to run a "Y" pipe from the centre pipe as its exits the tunnel then run 2x small oval silencers one to each side of the car with a short tail pipe running of each silencer under the sill and out the side of the car.

 

Let me know what you may already know of or if anyone has done this before?

 

Regards

 

Simon

[Tom Fenton 1,542]

I would find a decent exhaust fabricator, they will be able to make a box to your drawing to fit in the space you have with the pipe positions you need.

[tomcolinjones 26]

I would find a decent exhaust fabricator, they will be able to make a box to your drawing to fit in the space you have with the pipe positions you need.

 

what about a car that has twin exhausts already? rx8 mgtf e.t.c

[Henry Yorke 269 3 Cars]

I think XU engines tend to respond to a longer exhaust better than a short one. I've always seen Mi engines pull higher BHP figures in 405s than 205s when on rolling roads (though this could also be down to manifold modifications). An exhaust is a tuned length and the standard system is pretty good. You may lose low down torque by shortening it. I know I lost 50bhp on an Alfa 155 due to a badly designed "custom" exhaust. When they rectified it, it was like it was turbo'd!

[wardy18 33 1 Cars]

I've had a chat with the engine builder and he doesn't have any problem with this set up plus if I were to measure the length of the system I don't think it would be much shorter as it needs to protrude out from my sideskirts which do step out a bit. I'll have a proper measure and compare system lengths.

 

Oh and being such a small island we don't have any sort of exhaust fabricators

[Cameron 16]

Are you talking about a transverse silencer when you say Duplex?

 

It's going to be tricky to get a single entrance, dual exit silencer due to the complex internals needed to make it work properly. You'll need to have something like a Y-splitter from the inlet to divert the gas 90 degrees and also into 2 runs, that or have a chambered design, either way it's going to be expensive! If I were you I'd think about having a single entrance, single exit box and just have the exhaust come out one side of the car; that way you only need 1 90 degree turn in the box, then you can have a simple dual chamber box that will be much cheaper to make. I'll draw you a picture of what I mean..

 

 

Don't be put off by the chamber turn-around at the end, they actually don't add as much back pressure as you'd think. The alternative is to have a 180 bend in there but that's going to be more expensive. The yellow region will be packed and the blue region an open chamber and the good thing is you get decent attenuation of both high and low frequencies, the grey part is where you'd have your perforations.

 

Whichever way you go, you're going to need to have it custom fabricated as something like what you need won't be available off the shelf. If I had my TIG unit up here I'd offer to make something for you but unfortunately I don't have it or any gas!

 

Ps, it isn't the overall length of the system that has an affect on the torque, it's the lengths of the primaries and expansion ratio in the collectors. The length of the system will only have an affect on the acoustic properties.

Edited February 13, 2011 by Cameron

[wardy18 33 1 Cars]

Great info thanks Cameron, a single side exit would be preferable and that design is the best way I could do it to get a big enough silencer in the space I have to bring the db's down. I just want to get the best system for the engine and to suit my situation, really don't want to compromise power!

[Cameron 16]

I wouldn't worry about a power compromise with a design like that, it'll be a slight back pressure increase over a straight-through but sometimes you have to make a compromise - specially if space is tight! If you're really worried about power you can add a 180-bend rather than a chamber, although then you may loose out on boom performance. Having 2 exits means you need to have pretty complex internals to make the gas routing work.

Edited February 13, 2011 by Cameron

[wardy18 33 1 Cars]

I thought the design of a Duplex or transverse silencer would be like you said early, a "Y" pipe within the silencer box which to me sounds quite simple, please correct me if im wrong

 

Is this design not easier than the one you have above, the entrance pipe doesnt have to be in the centre, just offset enough to give a little extra length of the box, let me know what you think:

 

[Cameron 16]

Oh ok, I was thinking you had to have the inlet in the centre!

 

Yes that would be better if you could get the inlet over to the side, just makes things a bit less complex. The thing is you'll still need a baffle plate in there to support the pipe just after the 90deg bend, otherwise you may get cracks around the inlet.

[wardy18 33 1 Cars]

Oh right that makes sense, I have emailed a few companies to see if they can make me something to that design, dimensions I'm looking at are approx 180x120 (oval) x 500, this should give me enough silencing capacity and still fit in the space I have, will need to fix up some heat plate thou as things may get a little hot under there, will slice a few airing holes to let air in and heat out down the length of the system.

[wardy18 33 1 Cars]

Ok emailed loads of companies now and getting rejection, have tried some more.

 

This is the latest demensions, you dont fancy the challenge do you Cameron, would be doing me a massive favour ?