Exhausts, The Difference Between Resonators And Silencers...

[Fox 3]

Not a 205 question I'm afraid, but any help would be appreciated.

 

Mrs Fox has a 1.8 2006 Vectra SRi

 

I bought (very cheap) an almost new twin exit exhaust system as removed from a 2008 V6 Vectra, with the two back boxes compared to the cars current one. Her car has all the hangers to fit the additional box.

 

Now the 1.8 system had a front resonator box, and the rear (back box) silencer

 

The V6 system just has twin back boxes, no problem I thought. Now I've fitted it, the exhaust is far more raspier and boomy that it used to be, so I'd imagine its due to the lack of resonator box.

 

I'm looking at buying something like THIS to weld into position, how do I know if it’s a resonator or just (as advertised) a normal silencer?

[JoshGti 8]

That type will just be a silencer type box with a perforated tube through the middle of it, resonators open up in the middle I.e. the bore increases in the box and then back down again for the exit. Would you not be better off just taking a middle box from another system and welding that in?

[Cameron 16]

That type will just be a silencer type box with a perforated tube through the middle of it, resonators open up in the middle I.e. the bore increases in the box and then back down again for the exit. Would you not be better off just taking a middle box from another system and welding that in?

 

Nnnnnnnnot true!

 

Having worked as an exhaust engineer at Ford in a previous life (ok until 2 months ago) I can tell you a resonator is a box designed to tackle one specific frequency, whereas a silencer is a broadband (i.e. covers a wide range) attenuator (i.e. makes things quieter). I have seen resonators with perf pipe all the way through, some with expansions and some with a gap between the inlet and outlet pipes. All were designed to attenuate one frequency so all were resonators.

 

That resonator would have a specific volume and internal geometry to tackle one specific frequency, most likely a low frequency boom noise which fits pretty well with your description of the problem! If you're hoping to fit a cheap aftermarket bottle in there then you'd have to make sure you bought one the right size and with perfs / baffles / whatever in the right places - near impossible! If it were me I'd take the incorrect one off and exchange it for the right one.

Edited November 10, 2011 by Cameron