A funny one this- my car goes well, but the exhaust sounds raspy at lower revs! Relevant spec is:

FF36 twin scroll
Spec C equal length headers
H&S 3'' Twin scroll decat downpipe
Revolution 3'' exhaust

All on a 98 Classic.

Full boost at good revs (4k plus) it sounds a bit WRC (those with a similar setup will know what I mean), but at lower revs its a little raspy, albeit not quite the full Peugot.

Any suggestions? Im not up for reducing exhaust bore, so if thats the key issue, I will stick with it.

I just dont know what makes an exhaust raspy!

 

Well, aside from changing out the back box - i..e the section deliberately designed to 'tune' the loudness/timbre (disreagrding the equal length headers' effect) - then you'll need to fit a centre section of your desired bore with a fair sized resonator section in it. This can have the effect of 'smoothing' out the 'raspiness'.

Cobra do a 3" centre with a resonator... but don't know whether it has true 3" flanges at both ends(?). Perhaps get a custom one made? (Cobra can also do this for you...)

 

...That's assuming your Revolution's b.b.'s baffles aren't shot, of course...

 

Not sure I would know how to check for shot baffles in the back box- resonator may be the thing though- its slip jointed so that may be possible.

 

Thickness and the quality of the stainless can affect it's resonance IIRC. Rev system is quiet and revered, but is still a budget system ?

 

Doesnt seem that thin, but you could have a point- compared to the steel that came off it is thinner and lighter.

I was finding a lot of the true 3'' exhausts ended up with a 4 1/2 exit, and this is bad enough at 4''. I did wonder about changing the pipe that comes out of it to a 3'' as the pipe out of the back bax is 3'' and then flares to 4''.

I dont want a cannon out the back of the car- been there done that.

 

The bb's tailpipe POST-muffler won't affect sound hardly (unless a <2.5" 'peashooter' ). It's size/style is for a deliberately designed-in aesthetic, mainly.

I agree, aesthetically, anything over 4" dia. is too big on the Impreza (IMO).

 

Mate of mine took off his 3" Japspeed cat back and replaced it with my Apexi N1 1 piece cat back and the difference was night and day. Deep throb of the Apexi v's cheap rasp of the Japspeed. Both big exits.

 

The Revolution slip joints on my system never hold together and will start leaking, which sounds pretty raspy when they start to open up further.
Reclamping with some hi temp silicon joint sealant added solves it up for a while, but the joints always start moving again after a few weeks/months.