[Shady67]

Hi guys,

I recently installed a CTS Turbo catted downpipe on my 440i GC w/ MPPS exhaust, and there's a really weird (and annoying) trumpet sound that happens from time to time. It was doing it all weekend, so I took it to my mechanic this morning and of course it stops making the noise. He tightened the clamp and looked around but couldn't find what could be making the noise, but it basically sounded like the video below;

We couldn't replicate it, it seems to come and go. Has anyone dealt with this noise after installing a downpipe? I found a post on the M5 forums, but there was no solution unfortunately.

Any tips would be appreciated.

[J3Vr6]

You sure the cat isn't damaged? The filter inside could be loose or clogging in a way that it makes that sound.

[Shady67]

Originally Posted by J3Vr6

You sure the cat isn't damaged? The filter inside could be loose or clogging in a way that it makes that sound.

Thanks for the response!


The downpipe was brand new and was installed on Friday (4 days ago). It didn't look used when I received it, and a quick look at the filter showed no damage. I went to stage 2 the day after the install, maybe that possibly damaged it? I was able to tighten the clamps and it's not rattling as much, but it's still VERY raspy. Based on videos I've seen on YouTube, it's not meant to sound like that.

Not sure what to do at this point tbh. I don't have a downpipe to compare it with unfortunately. I'll see if I can find a local B58 with a similar setup to compare.

[Exarmy2010]

Being brand new has nothing to do it possibly being bad. I have ordered from the NFL and gotten a shirt that was printed way off center. If a shirt can get thru quality control, a downpipe easily can.

[AMG KLR]

If you have MPPSK its practically straight piped. It might just be rasp from that aspect and not damage

[Shady67]

Originally Posted by AMG KLR

If you have MPPSK its practically straight piped. It might just be rasp from that aspect and not damage

After tightening the clamps, the sound is almost gone, but you're right, it's the rasp from the MPPSK. It sounds like it's coming from the exhaust, and there's not much I can do about that. There's a small window around 1900-2000rpm where it makes that noise, but otherwise it's gone. Thanks for the help guys.

[leew102]

Originally Posted by Shady67

After tightening the clamps, the sound is almost gone, but you're right, it's the rasp from the MPPSK. It sounds like it's coming from the exhaust, and there's not much I can do about that. There's a small window around 1900-2000rpm where it makes that noise, but otherwise it's gone. Thanks for the help guys.

Similar thing happened with mine too. After driving on it more though, it went away. I think also it's just the way the exhaust resonates against the dp/mid pipe.

[_N54]

Sounds like a Civic lol !

[Wires]

You sure the DP/midpipe isn't rubbing the frame under load? When I did my DP and exhaust, the midpipe was rubbing causing nasty noises until I loosened the clamps and made sure there was clearance.

When you load the engine, it does twist on the mounts which will push the exhaust into the frame if there isn't enough clearance.

[Chris@VargasTurboTech]

Yikes! Tighten clamps, make sure nothing is hard up against other metal and consider adding a resonator.

[mgeller]

Did you end up figuring out this issue? I just installed a CTS catted downpipe with the MPPSK and it sounds the same as the video. Sounds horrible

[G.Newt]

Originally Posted by mgeller

Did you end up figuring out this issue? I just installed a CTS catted downpipe with the MPPSK and it sounds the same as the video. Sounds horrible

He explained what he did several posts up. 🙂

[shiftdnb]

[mgeller]

Originally Posted by g.newt

he explained what he did several posts up. 🙂

🤦*♂️

[Shady67]

Originally Posted by mgeller

Did you end up figuring out this issue? I just installed a CTS catted downpipe with the MPPSK and it sounds the same as the video. Sounds horrible

I ended up taking the downpipe off, as I couldn't get the noise to fully go away. There was always this window somewhere around 2000RPM where it would make that noise.

Let me know if you ever find out the solution.

[vektorprime]

I have a 440xi with cts 200 cell DP (not MPPSK) and it sounds great, nothing like that. To me, it sounds like you have some rattling. Something not clamped on tight. Or it's vibrating against something else. Try replacing the DP, and if that fails you'll have to check the components around it.

[mgeller]

Originally Posted by Shady67

I ended up taking the downpipe off, as I couldn't get the noise to fully go away. There was always this window somewhere around 2000RPM where it would make that noise.

Let me know if you ever find out the solution.

I caved and had a shop look reinstall with all new clamps. I'll let you know when I get the car back tomorrow. I'm hoping it was just a bad install on my part. But yeah, anything above 2k in 1st and 2nd sounded like a complete brass section for me. Not exactly the orchestra of sound I was hoping for haha.

[Info@mad-us.com]

Wow. Never heard anything like that before.

[Ciaran2903]

Any update on this? I have the same issue on my 440ix w/MPPSK and VRSF Cattless DP.

I went back to the stock DP and it got way better, so figured it was the cattless DP. I still noticed it slightly with the stock DP so thought it might be the exhaust rattling on the frame somewhere.

I put the VRSP DP back on and installed a spaced on the right cross-member. This helped, but I still get that sound in the same rev-range.

I think it might be rubbing on the rear sub-frame, causing the noise. I haven’t had a chance to look at it yet, but that is my hope.

I still think I want to go catted DP to tame the overall noise down, but want to get rid of this noise first.

[mgeller]

Originally Posted by Ciaran2903

Any update on this? I have the same issue on my 440ix w/MPPSK and VRSF Cattless DP.

I went back to the stock DP and it got way better, so figured it was the cattless DP. I still noticed it slightly with the stock DP so thought it might be the exhaust rattling on the frame somewhere.

I put the VRSP DP back on and installed a spaced on the right cross-member. This helped, but I still get that sound in the same rev-range.

I think it might be rubbing on the rear sub-frame, causing the noise. I haven’t had a chance to look at it yet, but that is my hope.

I still think I want to go catted DP to tame the overall noise down, but want to get rid of this noise first.

Ended up switching downpipes from CTS to AKRA. It sounds great with the MPPSK now.

[BrandEZ]

The problem is the CTS Turbo DP itself. Bad design, sounds pretty terrible on my car, with the dinan midpipe and stock muffler it was fairly embarrassing shifting around the 2k mark under load. I swapped the stock midpipe back on and it’s much better but too quiet now. I can’t bother to swap the downpipe again with another but if I did I’d go for ER.

[PeterWT]

Originally Posted by Brandon435

The problem is the CTS Turbo DP itself. Bad design, sounds pretty terrible on my car, with the dinan midpipe and stock muffler it was fairly embarrassing shifting around the 2k mark under load. I swapped the stock midpipe back on and it’s much better but too quiet now. I can’t bother to swap the downpipe again with another but if I did I’d go for ER.

I had exactly the same experience with the CTS catted DP, Dinan midpipe and OE muffler. It sounded TERRIBLE and I also had the the OE midpipe put back in. That cost couple hundred dollars and yes, it is too quiet now. I am torn as to what to do next.

Have a bullet resonator welded into the Dinan midpipe and have it put back in?
Replace the CTS DP with another brand and have the Dinan midpipe put back in (no resonators)? If so, which DP?

These options would cost another few hundred dollars and there's still no guarantee I'd like the sound.

I regret trying the CTS catted DP.