Any exhaust experts out there?

[GRP]

So my sons's Polo has benefited in the last couple of weeks from some a couple of forum buys made over the last 12 to 18 months - all good father and son car mod sessions. SEAT front mount intercooler went in the other week - first time doing it so lots of small cuts. Next time I would be much more adventurous with the initial cuts.

Last weekend we borrowed a friends hoist and fitted the full 3" exhaust from Van (the fit is a work of art). Sensational sound but it is seriously loud - you can hear the Polo a km away if on song. Exhaust is 3" from start to finish with a single large muffler at the rear and a high flow CAT up front. So great exhaust note but seriously obnoxious for an urban environment.

How do I reduce the exhaust noise? My reading suggests that a resonator will only change the tone and reduce drone. Put a small muffler before the rear axle? Larger rear muffler (it looks huge being based on a 3" inlet but could be longer) with offset baffle rather than straight through?

Look forward to any input.

Yes, a stage 2 tune is coming (deal to be done with Gavin).

[h100vw]

3 inch exhausts are really loud with inadequate silencing in them. The way to make them quiet is use boxes that have a lot of volume to them. ie the largest boxes you can get in there.

What are the dimensions of the rear silencer?

I fitted a 14 inch long (iirc) 6 inch diameter one in the straight pipe after the cat and before the axle. Where the std one is.

This is too big and is a very tight fit. A 5 inch diameter one would fit much better. Doing the maths, there's a significant difference in volume between the 5 and 6 inch boxes.

Which would affect the loudness of the exhaust in general.

My system at idle is barely different to a std one. On the road it attracts no attention at all. All my noise comes from under the bonnet.

So my sons's Polo has benefited in the last couple of weeks from some a couple of forum buys made over the last 12 to 18 months - all good father and son car mod sessions. SEAT front mount intercooler went in the other week - first time doing it so lots of small cuts. Next time I would be much more adventurous with the initial cuts.

Last weekend we borrowed a friends hoist and fitted the full 3" exhaust from Van (the fit is a work of art). Sensational sound but it is seriously loud - you can hear the Polo a km away if on song. Exhaust is 3" from start to finish with a single large muffler at the rear and a high flow CAT up front. So great exhaust note but seriously obnoxious for an urban environment.

How do I reduce the exhaust noise? My reading suggests that a resonator will only change the tone and reduce drone. Put a small muffler before the rear axle? Larger rear muffler (it looks huge being based on a 3" inlet but could be longer) with offset baffle rather than straight through?

Look forward to any input.

Yes, a stage 2 tune is coming (deal to be done with Gavin).

[sambb]

there are those varex mufflers that have remote controlled butterflys in them. I'm not sure if they actually alter the path of the flow through the muffler internals or if they just shut down one of the two twin exits out of the muffler, but they basically have a low dB setting with choked flow and a high dB setting where flow is unrestricted. You could look into that? $$$$ though. If you look on mighty car mods under polo gti on you tube you'll see their results from fitting one

[seangti]

Yeah I took off the 3" cannon muffler and put a 2.5" offset muffler on as mine was too loud. I also have 2 resonators in mine and can't fit anymore. The issue is space, and very little of it.

[louis19]

My initial 3" setup was way to loud also. I had a small resanator in the centre and a small muffler in the rear. I now run a 4" x 24" long resanator in the middle and 14x8x5" rear muffler and I think it's a good compromise. Around town it's louder then stock but not by to much. WOT there's a decent amount of noise but I don't mind that as that's generally on track anyways, and even then in comparison to my old setup, it's subtle.

We we all actually run pretty different setups, varying in downpipe, resanator and muffler sizing, so there's no set answer as to which is "the best". Just comes down to what you think is acceptable for daily driving. As Gav said, I'd go the biggest size muffler and resanator that you can, you can always downsize one if you want more noise.