Alta Exhaust 2.5" V2, 2006 MINI Cooper S (part 2)

December 13, 2009
Introduction
Part 1 on this write up can be found here.  After living with the exhaust for a while, here are my thoughts and a few things that happened along the way..

Sound (part 1)
I am really enjoying the sound.  It is not that I didn't at first, but it took some time to grow on me.  My only complaints are that there is sometime a bit of drone on the highway (obviously depending on speed, load and gear), and at mid RPM it sometimes sounds too airy or woofy.  More Fffffff than clear definition.  Bottom line is that the good sounds are better than the bad, so I like it.  

I also noticed that with the windows up, the bubbling and popping (when you leave off of the gas) is easier to hear.  This may be due to the resonator being right underneath you, I don't know. Either way, I am glad to know I will be enjoying the sound of this system even during the "windows up" seasons.

Here is an mp3 recording of 2 hard acceleration runs.  This is in car with the windows up (to avoid wind noise) -link to recording.

Fit
I had to play around with getting the exhaust to fit well and to stay were I put it.  That was a bit frustrating but there is enough adjustment available that  you can get it to fit correctly.

One issue I had was that the rear hanger set screws would loosen and let the rear of the exhaust fall.  In the first part of this article, I mentioned how I had to replace the original set screws because I couldn't get them tight enough without the Allen wrench slipping out.  Although I can get my  replacement set screws very tight, they too are loosening up.  Maybe it is because they are made of a different material and are effected more/less by the heating and cooling of the exhaust.  I don't know.  Since I had bought them longer than I needed (to make sure all the threads were making contact,) I was able to put nuts on top of them effectively jamming them together and locking them in place.  So far they have held nicely.

I was still a little concerned about those 2 small set screws holding up the rear of the exhaust, so while I was in the hardware store, I found a collar that I could use to give additional support to the existing collars.  I had to file off part of it so it was flush with the bottom of the collar above it,  but at least it was there now offering additional support.
The nuts (on the right) are on the longer set screws locking the set screws so they don't loosen up. The top 2 collars are the stock ones welded to the exhaust. I added the bottom one (not welded.) You can see the set screw on the left. It doesn't have a locking nut as I felt it wasn't necessary.
Note that I filled down the side (on right) of the bottom collar so it wouldn't touch the exhaust and so it would be flush horizontally with the bottom of the 2nd collar.


Resonator Replacement
After time I did develop a rattle that slowly got worse. After working with the folks at Alta, it was decided I should replace the resonator.  When I got the new resonator, it was obvious that it was smaller.  I was told that this was their new design that they came up with just before deciding to stop selling the exhaust.

The old resonator is on the left, the new on the right.  A very big difference.
The old resonator weighed about 9 lbs, the new one about 6 lbs.
There is a whole lot more available space in the tunnel with the new resonator.  
Good for mounting and compensating for any movement.
Being smaller, it also doesn't hang down very low.


Sound (part 2)
The sound with this smaller resonator is even better than the old one.  There is the same drown around 2800-3100 or so RPM.  The "whooshing" sound at higher RPM is still there, but it is not as obvious until much higher RPM.  The one thing I am concerned about is that the exhaust is now significantly louder across the entire RPM range.

Here is a sound clip (with windows up) link to recording. I tried to make it close to the sound clip above for comparison purposes. Since the unit I recorded this with automatically sets the sound level, this clip doesn't sound louder than the one above.  However, the exhaust with the smaller resonator is definitely louder than with the original resonator. Keep that in mind as you listen.  Also, there is a lot less air noise (the jet sound).  I don't know if it is because other sounds are louder or because it it is just not there.  

Conclusion
With the new resonator, the rattle is gone. The sound is great, but I'll have to see what it is like to live with. I think it will be OK.  I am hoping the exhaust settles in and need no more of my attention. Now that it is winter here, I wouldn't be able to do anything with it anyway.  Hopefully it survives all the road salt that comes with winter.  I'm just looking forward to enjoying it now.

 
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