Anyone ever seen the inside of a stock XKR rear silencer (4.2 if it makes any difference)? Some E9x M3 owners have had theirs opened up and found parts of the pipes inside are perforated, they've then had those wrapped and welded the box back up again and found they get a bit more volume from the exhaust at a fraction of the cost of aftermarket silencers.

Anyone done anything like this on an XKR or know much about what lies within the box?

 

If you want louder, just pull Fuse 19 - the vacuum valves on the outer pipes will stay open, and most of the exhaust will bypass the silencer anyway. That's how the active exhaust works - it forces the exhaust through the silencer at intermediate RPM, but opens the bypass valves at low & high RPM.

 

That is a lot of trouble to go through when replacing it with a straight pipe would achieve the same thing with a lot less effort.

 

Ngarara, I've already pulled 19, I did that the day after I picked up the car I also have the Spires stage 1, the similar thing to the performance active exhaust on the 5.0 cars.

axr6, you're probably right but I'd like the exhaust to look pretty much standard and even places selling basically straight through pipes charge way more than I've seen used stock back boxes for on ebay. Additionally a straight through pipe would be even louder wouldn't it?

 

In that case, most of your exhaust is bypassing the silencer, so I doubt you'd notice any difference if you spend the time, effort and/or money to mod the silencer. Basically, you already have (mostly) straight-through pipes from the cats back.

 

When you wrap the perforations in a straight-through type silencer muffler you basically make a straight pipe. There should not be any difference in the sound quality between the two at that point. If I wanted to nit-pick, I would prefer the straight pipe because it would result in a smoother exhaust gas flow as opposed to the wrapped up original silencer that still has the perforations on the inside (assuming that the wrap is on the outside of the perforated pipe section) that disturb the flow somewhat. But, that is super minor difference, really.

I just figured that by the time you get a silencer, tear it apart, have someone bend and weld a wrap around it, weld it back together.... it would be a lot more work than making a straight pipe.

 

Thanks guys, that all makes sense. Nothing to see here