[BQTuning]

After installing the CP-e higflow downpipes, without doubt, low and behold the exhaust and spooling got louder.

However, no drone, no rasp, or the dreadful egg smell was inherited where many people with catless DPs would report.

I have one delima that is bothering the hell out of me when I hear it. I have seen some people hearing something similar with slightly different discription of an anoying sound that may question the installation or manufacture design of the DP.

There is a sputtering or birdy / wistling sound coming directly fron the DP location. It almost sounds like an exhaust leak. However, I get no codes, and no problems with boost or performance. I only hear it when barely pressing on the gas.

I took it in to have it checked and it was said no leaks were found and thats just how those DPs are ? Everything was checked, secured, and some readjustments made, but still got the sputtering / birdy/ wistling sound.

Is this normal for DPs ? Its very fustrating to hear when windows are down

[Randomaccess335]

Mine are cattless and no whistle, I would guess its the high flow cats
How long have u had them on?
Maybe it will go away after they break in

[BQTuning]

Originally Posted by Randomaccess335

Mine are cattless and no whistle, I would guess its the high flow cats
How long have u had them on?
Maybe it will go away after they break in

Less than a month now, about 500 miles break in so far. Hard, medium acceleration the sound doesnt exist, its when applying acceleration lightly, gradual and slowly, when trying not to spool the turbos to save on gas, I will hear it.

[cgeorge]

mine do that. it's fine

[BQTuning]

I was saving these pics for a review on the CP-e highflow catted downpipes. Consider this a prelude

[nitehawk]

I hear that too; I think it's normal. Probably has to do with the way the exhaust gases flow over the lambda sensors.

[Crazylegs]

I heard it after my AA DP were installed, figured it was the turbos spooling under ambient pressure takes nothing for these tiny things to spool. Probably just echoing through the catless downpipes my turbos are pretty much brand new 1700 mile.

[emre]

Originally Posted by BuraQ

Less than a month now, about 500 miles break in so far. Hard, medium acceleration the sound doesnt exist, its when applying acceleration lightly, gradual and slowly, when trying not to spool the turbos to save on gas, I will hear it.

Exactly what I am experiencing.
AR Design Catted N55 here , I too searched for leaks and everything was fine but still bothered me. Glad I came across this thread.

[doraemon]

Are you sure you are not just hearing the turbo spooling sound?

[Crazylegs]

Originally Posted by doraemon

Are you sure you are not just hearing the turbo spooling sound?

Im pretty sure thats what he's describing.

[Randomaccess335]

His car is pretty fast, the noise is probably the other cars crying as he passes them

[BQTuning]

Originally Posted by Crazylegs

Im pretty sure thats what he's describing.

It is concurrent with the turbo spooling sound. The turbo spooling is very distinct, the other sound in question has a sputtering birdy distort wistling sound that will make you think there is an exhaust leak.

I only hear it on slight acceleration from zero throttle, but not when the turbos are in boost

Didnt realize this was a norm when installing DPs. Will get a video posted later.

[Icysheet]

I remember hearing on my previous car (STi) a sound similar to what you're describing and it was the wastegate on the turbo. Sounds like the actuators are moving in response to part throttle inputs preventing too much boost from building and then you hear nothing under full throttle because the actuators are just keeping the gates closed and not moving. This is entirely speculative, but it might be correct. I'm sure someone with more 335i knowledge can speak up on this issue.

[Crazylegs]

Originally Posted by Icysheet

I remember hearing on my previous car (STi) a sound similar to what you're describing and it was the wastegate on the turbo. Sounds like the actuators are moving in response to part throttle inputs preventing too much boost from building and then you hear nothing under full throttle because the actuators are just keeping the gates closed and not moving. This is entirely speculative, but it might be correct. I'm sure someone with more 335i knowledge can speak up on this issue.

Hmm maby a vband is interfering a bit with the actuator arm causing it to open slower? or maby it's squeaking w/g now more noticable?

[dicostal]

Hi All just for the record, I have a 6 Speed Manual and a AA down pipe and I never heard this noise.

[bigdaddycane]

funny you should bring this up, because mine has started doing it recently but not consistantly.

I installed the CP-e c@tless DPs a few months ago and the sound was NOT there.

Now occasionally it's doing it. I was beginning to think it was the dreaded siren sound associated with the accuators. It only does it at about 4K under part throttle and seems to hold boost ok, but yes, it is very annoying.

BuraQ, is yours doing it ALL the time or just sometimes?

[BQTuning]

Originally Posted by bigdaddycane

funny you should bring this up, because mine has started doing it recently but not consistantly.

I installed the CP-e c@tless DPs a few months ago and the sound was NOT there.

Now occasionally it's doing it. I was beginning to think it was the dreaded siren sound associated with the accuators. It only does it at about 4K under part throttle and seems to hold boost ok, but yes, it is very annoying.

Burq, is yours doing it ALL the time or just sometimes?

It seems not ....lol..... when I had the damn thing cornered the twitty sound disapeared when I decided to capture it on the GoPro. However you can still hear the sputtering when the car is slightly idle

After going over the video the sputtering sound seems to be caused by how the exhaust is passing through the catts. I am starting to think the sound will come and go due to temps.

The whistling sound I know are the turbos

[cn555ic]

That sounds normal to me...Catless

[bigdaddycane]

I am starting to think the sound will come and go due to temps.

+1 This is what I'm experiencing and it's NOT turbo spool.....very loud and at 4K when it's hot and humid.

BTW, nice video, especially the part where the cop passed you.

[e92ben]

Is it like a slight siren or turbo whine? What's your mileage. Does it only happen when its cold? Maybe you had slight turbo whine and never knew it until that catless dps were installed.. Slight when cold isn't a problem. But If it starts getting louder and louder ( like a cops behind you lol) then that's a big problem. Also I had a whiney whistley noise on cold starts when Id start driving, turned out to be exhaust leak, it would go away when it would heat up and the metal would expand. Good luck I'm sure it's nothing serious lol

**edit***
Watched the video lol. Sounds like a leak to me.

[BQTuning]

After much its seems CP-e and RENNtech found the problem I was having.

The DP flangs were leaking. Couple of other members with the "335iS" have ran into a similar issue that I have.

I got word back from member TRES that CP-e found it was indeed the flangs that were leaking as they were too thin and not flat enough.

It has been said the wheel base on the 335iS is a tad longer.

Problem resolved for botth TRES and myself, the cars now sound like a BMW

[BmwECY]

Originally Posted by doraemon

Are you sure you are not just hearing the turbo spooling sound?

that's exactly what the sound is.

OP- if you didn't want the turbo swoosh, suck, squish, etc. sounds, go back to stock downpipes. otherwise, enjoy the music from teh turbo's