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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > catless DPs hissing noise with rattlefix?



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      03-31-2013, 10:40 AM   #1
Lux3m35i
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catless DPs hissing noise with rattlefix?

Hey,

Since I have installed catless DPs, I hear a metallic hissing/raspy noise on light/normal acceleration (the noise is hard to describe with words). I really hate that noise. The car sounds like shit, like a crappy rice-burner or french car. That's definitely not how a proper, expensive car should sound like.

My first set of DPs had a really poor fitment, so I bought a new ones and send the first set back. The new DPs did fit perfectly, but the noise persists.

Then I found a thread where someone explained the same noise. He made some vids which sound exactly like mine!!

http://www.e90post.com/forums/showthread.php?t=622021 best ones are video 2 and 3

They mentioned that it may be the V-clamps causing the rattle. But mine are definitely fine. So I started to figure out when exactly the noise appear.

First at all, I do have wastegate rattle, but I set the WG-position on my procede to 30%. The hissing noise on acceleration sound definitely different as the wastegate rattle we know from decelerating or if the revs drop. Wastegate rattle is a more clear and metallic sound.

My first thought was "Ok, if the wastegates causes this noise, then if you put your procede to map3 (natural aspirated), the wastegates will be fully opened and the noise disappears"
Nada.. the noise remains on map0, map1 and map3 the same.
Since many people in the thread I found claim that the noise is normal I was thinking that this will be the normal acoustics which comes with catless DPs which made me afraid..

The first mod I bought was a FMIC and procede. From the beginning I running my car with WG position set to 30%. Yesterday night I wanted to know how crappy it sound like when I set WG position to 90% with catless downpipes.
Well.. you hear the wastegates ticking on idle and the car sounds like a kid's rattle on decelerating. Also the deep exhaust sound disappears. I really do like the backfire while shifting.
But when I kicked down the paddle, the car pushes immediately forwards and surprisingly i didn't hear any crappy hissing noise!!! First time where I heard proper turbo spool and exhaust sound!!!
And there is one picture on the web which describes that feeling. I simply was like:


But the magic disappears then you let off the throttle and hear the wastegate rattle again.. I got rid of the crappy hissing noise on accelerating while changing it against no turbo lag and wastegate rattle.

So.. with WG position set to 90% i do have NO hissing noise on map1. On map0 (stock mapping) I do hear the hissing noise. On map3.. I didn't remember anymore, but I remember that I had a big smile on the face hearing a proper deap sound, so no hissing sound either.

My explanation would be: Since the flaps do have some kind of scope where they are mounted, at a certain WG position, if you accelerate the streaming exhaust gas cause the flap to rattle/vibrate very fast which sound like a kind of hissing noise. Does this sound plausible?

I tried to find a WG-position where the wastegate rattle stops. Which seems to be at 45% for me. On this value the wastegate rattle AND the hissing noise disappear. But didn't do an extensive test drive yet.
One thing that remains is that you hear short wastegate rattle then you start accelerating and the wastegates are closing. This also appears at 30% but didn't notice at 90%.

My preferred solution would be to fix the rattle so that I can drive with 90%. I love the immediate response of the car! When I installed my DPs I checked the closing position of the wastegates by producing a vacuum on the actuator and the flap doesn't close the wastegate properly. There are about 2mm missing to close the wastegate properly. But I didn't managed to shorten the rod (Mr.5 mod) with a wrench and a plier.. the rod always moved back to position.

Here a few question:
What is the wastegate position from stock? because it produce the hissing noise on that position.

For those who do have the same noise. Would be nice to know your wastegate positions from procede or which tune you are using or which firmware you do have on your car. Try to change the WG position and report if it make the noise disappear or not.

Does someone else do have a explanation why the WG position seems to cause the hissing noise? Maybe shiv has a nice explanation?


I will be happy about every statement, question or suggestion. Help me to get a proper sounding 335!
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      03-31-2013, 11:06 AM   #2
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My wastegates rattle like a son of a b***...Drives me crazy! I'm upgrading to a single turbo setup sometime this summer most likely just to get rid of the rattling tin cans. I wish Vargas had done his big twin setup with external wastegates, cuz then that would be an option on the table too. I hope you get some good info here. Good luck!

oh, and first! :P
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      03-31-2013, 11:18 AM   #3
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Hissing noise? Are you sure it's not the sound of air rushing through the turbo on boost? That's normal
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      03-31-2013, 11:26 AM   #4
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It is definitely not the air which get sucked in by the turbos. Turbo spool/conducted air sounds pretty sweet.


Seems to be that I have to steal the vids from the other thread.

cable96 did a thread once about the same noise I try do describe here.
This vids are from here: http://www.e90post.com/forums/showthread.php?t=622021






Last edited by Lux3m35i; 03-31-2013 at 11:29 AM. Reason: embedded vid didnt show correctly
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      03-31-2013, 12:02 PM   #5
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It could be an exhaust leak at the gaskets
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      03-31-2013, 12:10 PM   #6
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Quote:
Originally Posted by E90Company View Post
It could be an exhaust leak at the gaskets
had been checked after installing DPs.

And why should the noise disappear when changing WG position..
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      04-01-2013, 01:57 AM   #7
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I believe to have the same sound but then I've installed remus exhaust same time with the DP. But I believe it's normal . Having said that, Sorry to hijack but i've got a JB4 and ever since my AR dp is installed my car keeps throwing Engine power Reduced aka limp mode. Is this normal? Because I do not feel any misfiring or and start-up problem.
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      04-01-2013, 07:12 AM   #8
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definity not normal. but should trough error codes? possible issues are o2 sensors/o2 fix or the v-clamps are not installed correctly and the rod is stucking at the v-clamp.
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      04-01-2013, 03:03 PM   #9
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Quote:
Originally Posted by Lux3m35i View Post
It is definitely not the air which get sucked in by the turbos. Turbo spool/conducted air sounds pretty sweet.]
These questions are by no means to mess with you just to clarify...
Is this the first turbo car that you upgraded?
do you have experience with turbos+exhaust sounds?

Cuz honestly every newcomer to turbos, or modified cars always gets the "weird noise paranoia" it's completely normal...

honestly the videos sound is not good enough to hear the sound you describe...
and there are 2 different sounds that turbos on aftermarket exhausts and intakes make...
besides the bov sound ....
one is the sucking of air...but the weird one most people arent used to is the buzzing metallic hissing sound that comes from gutted or catless exhausts...mostly from my experience smaller turbos with 3" gutted pipes tend to make that sound..
you can even hear it at a stand still just lightly revving it up....
I am not pretending to know that this is exactly your problem, but ...just saying weird noises dont exactly mean it is a "problem" and
taking the car to an actual tuner or shop that does a lot of turbo upgrades would be your best bet if you want some peace of mind......definitely the dealer wouldnt know crap...
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      04-01-2013, 03:05 PM   #10
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oh and if it was an exhaust leak, you would definitely notice a big loss of power.
btw just remembered, there is another sound that leaky exhausts make when the dp connnects to the turbo flange, if the bolts are loose but it sounds like a very fast metalic flapping sound...only under boost.and it gets worse as time goes by...
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      04-01-2013, 05:01 PM   #11
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So why does that noise disappear when setting the wastgate position higher?

There is no noise when rev up in neutral. Only under load conditions.

No, there is nothing leaking, the DPs are installed correctly.

And there is NO ONE in this region which do have experience with tuned N54 or other turbo car. They are just flashing the cars with some maps they bought somewhere and that's it. The guys around here are vendors, no impassioned tuner.
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