Help I need a photo of the internals of the standard or CP exhaust

[jim996]

Hi can anyone help?

I'm looking to modify a spare CP exhaust I've bought for my car and I'm trying to understand what is inside the silencer and if it is worth cutting it open to make changes to the interior or not. If anyone has done this already and has a picture it would be most appreciated thanks.

[knightarmor]

Check the intro to the new M3/M4 thread. There are drawings of the complete oe system. I'm about to begin looking for another oe exhaust as i want to also modify the oe can (to reduce weight). I've already removed the secondary cats and the car sounds great (for me anyway).

[knightarmor]

Here's the link BTW http://f80.bimmerpost.com/forums/sho...d.php?t=979417

[jim996]

Originally Posted by knightarmor

Here's the link BTW http://f80.bimmerpost.com/forums/sho...d.php?t=979417

Thanks thats really helpful. I'm speaking to an exhaust fabricator and I'm planning to remove the secondary cats and weld in straight pipes and we might replace the resonator centre box with an x pipe.

The fabricator talked about opening the rear box and replacing any perforated pipes with straight pipes. As I have the exhausts set to open in the exhaust I don't see any advantage of doing this as it seems the gases exit without going through the rear silencer when the flaps are open......am I right or should we be modifying the rear box as well?

[aBMWfan]

I would leave the rear box as is, and do the other changes you mentioned

[jim996]

Originally Posted by BenM4Dominate

I would leave the rear box as is, and do the other changes you mentioned

That's what I thought, no advantage in opening the rear box.......

[jim996]

Originally Posted by BenM4Dominate

I would leave the rear box as is, and do the other changes you mentioned

Thinking out loud and anyone please let me know if this is a stupid idea but as I run with the flaps open all the time could I just get the fabricator to cut the rear box away completely and weld up the pipes that feed into it? Gets rid of the weight and the ugly dustbin rear silencer?

[gatorfast]

Originally Posted by jim996

Thinking out loud and anyone please let me know if this is a stupid idea but as I run with the flaps open all the time could I just get the fabricator to cut the rear box away completely and weld up the pipes that feed into it? Gets rid of the weight and the ugly dustbin rear silencer?

I could be wrong but I think even though that diagram linked previously shows the exhaust gasses going straight out when the flaps are open, in actuality some is still passing through the rear silencer. Thus, if you were to remove the rear muffler and in essence run straight pipes, it would be much louder than simply opening the valves.

[jim996]

Originally Posted by gatorfast

I could be wrong but I think even though that diagram linked previously shows the exhaust gasses going straight out when the flaps are open, in actuality some is still passing through the rear silencer. Thus, if you were to remove the rear muffler and in essence run straight pipes, it would be much louder than simply opening the valves.

Thanks that makes sense, I used to have a straight through pipe on a 911 once and it was insanely loud and actually stopped me flooring the throttle because I was scared of it scaring other drivers....

[knightarmor]

Originally Posted by jim996

Thanks thats really helpful. I'm speaking to an exhaust fabricator and I'm planning to remove the secondary cats and weld in straight pipes and we might replace the resonator centre box with an x pipe.

The fabricator talked about opening the rear box and replacing any perforated pipes with straight pipes. As I have the exhausts set to open in the exhaust I don't see any advantage of doing this as it seems the gases exit without going through the rear silencer when the flaps are open......am I right or should we be modifying the rear box as well?

Hopefully you've been following this thread http://f80.bimmerpost.com/forums/sho....php?t=1401078

I also have removed the secondary cats and am loving it.
My next idea is to cut the OEM muffler and make a "slim" design to reduce weight and improve areo at the rear. If you've seen the mufflers front side you'll know what i'm talking about. This is low on my priority list though.

I also thought making the diameter of the valve cutout section larger. This should help the flow as the volume of gas flow is currently restricted by the ID + the valve shaft even when the valve is open.

I look forward to your review of the secondary cat + mid muffler replacement with X-pipe!

[jim996]

Originally Posted by knightarmor

Hopefully you've been following this thread http://f80.bimmerpost.com/forums/sho....php?t=1401078

I also have removed the secondary cats and am loving it.
My next idea is to cut the OEM muffler and make a "slim" design to reduce weight and improve areo at the rear. If you've seen the mufflers front side you'll know what i'm talking about. This is low on my priority list though.

I also thought making the diameter of the valve cutout section larger. This should help the flow as the volume of gas flow is currently restricted by the ID + the valve shaft even when the valve is open.

I look forward to your review of the secondary cat + mid muffler replacement with X-pipe!

Thanks for that, subscribed. Think I'm just going to decat and modify rear box initially. I'm told it's better to leave the middle section alone