[M3to335]

I'd pretty much bet this has been discussed before, but honestly I cant find it. So, here we go...

Last week I had a shop replace the piping from the downpipes to nearly the mufflers with 2.5" mandrel bent stainless. The idea was to rid the cats as well as all the nasty crushed piping that is under the car.

I made two observations;

1) Most of the crushed or "smooched" piping occurs in tight interference prone areas. I can understand that. But, some of the crushed piping (namely the passanger side pre-muffler area, is deformed without apparent layout related issues. In other words, someone went out of their way to pay a supplier more money to make extra deformations for no apparent reason. Just something to ponder, but I wonder if its done for killing the sound.

2) I've never owned a car that has a 3Hz vibration isolator on the exhaust pipe (at least that is what I am assuming this is). Is this customary ? Does the stock exhaust have some resonance frequency where if it didnt have the vibration isolator all hell would break loose



For those of you with aftermarket systems, is this isolator added back in? I doubt it, but just wondering.

Lastly, the exhaust sounds pretty darn good now being fully catless from 3" tapered to 2.5" back. I did notice one funny thing though. It does have a raspity metalic sound when going medium throttle off the line or cruising in 6th at very low rpm and blipping the throttle. Wonder if thats related to what was mentioned above, or if its just the nature of the catless beast. My understanding of what people thought was RASPY is not this sound.

[scalbert]

I know what you mean about the rasp. And IMO, after nearly a week I am not sure I will live with it. Meaning, I may go back to the stock midpipes.

[enrita]

thats exactly why i kept my stock midpipes and the CAT in the middle. Important is to free it right after the turbos and at the end.

[M3to335]

Nah its not that bad. For my particular case its only under very specific conditions. Hell, if my wife doesnt mind driving around with me, it must be OK

So what about my other questions/observations?

[M3to335]

NE one?

[Sniz]

I was wondering the same thing. fully catless britalman exhaust setup causes drone in the mid 2000rpm range. I was looking at that vibration dampener on the stock system and looking how to replicate it on the britalman exhaust.

I found idead for noise cancelation add on pipes that ran parallel w/ the actual exhaust and piped in at a 90 degree angle.

see here: http://forums.corral.net/forums/showthread.php?t=496793

I'll probably never get to do this as I think my car is totalled, but maybe someone else can give it a shot?

[RBP AW]

I've noticed the same thing with my Britalman, though I still retain the stock downpipes and thus 2 cats. That being said, I have a unique set up - I have the original VRS rear diffuser (e92) which, as some may recall, actually shrouds the exhaust tips. After heat expansion, it vibrates against the diffuser at low RPMs where you would usually encounter drone. To get to the point, if you are interested in fixing your drone issues, its very easy for me to pinpoint the exact RPM that corresponds with particular exhaust frequencies. If you need to calculate pipe section lengths etc. just let me know

[cn555ic]

Originally Posted by Sniz

I was wondering the same thing. fully catless britalman exhaust setup causes drone in the mid 2000rpm range. I was looking at that vibration dampener on the stock system and looking how to replicate it on the britalman exhaust.

I found idead for noise cancelation add on pipes that ran parallel w/ the actual exhaust and piped in at a 90 degree angle.

see here: http://forums.corral.net/forums/showthread.php?t=496793

I'll probably never get to do this as I think my car is totalled, but maybe someone else can give it a shot?

What the F..k happen to your car? Totalled...holy shit man that really sucks...What are you planning to get afterwards...You had one of the nicest rides on this forum!!