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      08-02-2013, 12:13 AM   #1
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For those of us running catless downpipes, I found a neat little trick

For those of us running Catless Downpipes we can hear the turbo whine and turbo spool much more clearly now. If you ever notice that when you are driving at low speeds, say 40-50mph or slower, and you let off of the gas pedal, while the car is decelerating, you can then clearly hear the wastegates. It sounds like a weird whooshing, rattling, tingling sound and when I first heard it after installing my catless downpipes I was wondering if there was something wrong with my M5. That wooshing, rattling, tingling sound is actually wastegate flutter I later found out. When you let off the gas the DME opens and closes the wastegates and you hear the air rushing out of them. With catless downpipes you can really really hear it and in fact it's a little annoying. Again, you can only hear it at slow speeds and only while decelerating.

So I was reading through this outstanding Blog on everything about the F10 M5 today when I came across something very interesting, which I did not know before.

Here:

http://m5carblog.blogspot.com/search...&by-date=false

I came upon this paragraph, which caught my attention:

"To help further reduce turbo lag, when in "Sport" engine mode the wastegate is kept closed longer. This leads to increased fuel consumption as the exhaust is backed up, but increases response as the turbos are kept better spooled up in case they are needed."

So I was thinking hmmm, if the wastegates are kept closed longer then they probably won't make that annoying sound. So tonight I was on my way to a car meet, and I thought that I would test it out. At first I kept the Throttle Response button setting to "Efficient," I accelerated and then let off the gas pedal and sure enough that wooshing from the wastegates was clearly there. I then switched the button to "Sport" mode and accelerated once again and then let off the gas once again, and what do you know, no more wooshing sound from the wastegates. I was like sweet! Now I know how to control the wastegates, and not have that annoying sound anymore.

Well for those of us who are running catless downpipes, you can try this out for yourself and see that it works. It's also good to know for those of you who are thinking about getting catless downpipes.

Cheers and happy driving.
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      08-02-2013, 07:32 AM   #2
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RPiM5 that is an excellent test and observation. Thank you for sharing!
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      08-02-2013, 07:36 AM   #3
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My only question is WHY WERE YOU EVER IN EFFICIENT MODE IN THE FIRST PLACE TO HEAR THE WHOOSHING NOISE?!?!?
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      08-04-2013, 03:07 PM   #4
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Good find D. I might join the cat team next week when I get back in town.

Last edited by boots; 08-05-2013 at 06:10 AM..
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      08-04-2013, 10:09 PM   #5
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Quote:
Originally Posted by boots View Post
Good find D. I might join the cat team next week when I get back in town next week.
You are gonna love it Brian!
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      08-04-2013, 10:50 PM   #6
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Quote:
Originally Posted by Tom C
My only question is WHY WERE YOU EVER IN EFFICIENT MODE IN THE FIRST PLACE TO HEAR THE WHOOSHING NOISE?!?!?
Haha, I though the same thing!

Efficient Dave. Just doesn't sound right.
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      08-05-2013, 01:38 AM   #7
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hmm, so, you discovered "sport" mode? ...what?
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      08-05-2013, 07:03 AM   #8
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What!!?? Dave in efficient mode something is wrong here....good find though
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      08-05-2013, 10:02 PM   #9
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This reads like a bunch of NA engine guys discovering turbos for the first time lol

I love all the burps, farts and sneezes turbo cars make.. Compensates for the weaker exhaust noise... Well that and 200 extra ft/lbs of torque
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      08-07-2013, 01:46 PM   #10
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Quote:
Originally Posted by RPiM5
For those of us running Catless Downpipes we can hear the turbo whine and turbo spool much more clearly now. If you ever notice that when you are driving at low speeds, say 40-50mph or slower, and you let off of the gas pedal, while the car is decelerating, you can then clearly hear the wastegates. It sounds like a weird whooshing sound and when I first heard it after installing my catless downpipes I was wondering if there was something wrong with my M5. That wooshing sound is actually wastegate flutter I later found out. When you let off the gas the DME opens and closes the wastegates and you hear the air rushing out of them. With catless downpipes you can really really hear it and in fact it's a little annoying. Again, you can only hear it at slow speeds and only while decelerating.

So I was reading through this outstanding Blog on everything about the F10 M5 today when I came across something very interesting, which I did not know before.

Here:

http://m5carblog.blogspot.com/search...&by-date=false

I came upon this paragraph, which caught my attention:

"To help further reduce turbo lag, when in "Sport" engine mode the wastegate is kept closed longer. This leads to increased fuel consumption as the exhaust is backed up, but increases response as the turbos are kept better spooled up in case they are needed."

So I was thinking hmmm, if the wastegates are kept closed longer then they probably won't make that annoying sound. So tonight I was on my way to a car meet, and I thought that I would test it out. At first I kept the Throttle Response button setting to "Efficient," I accelerated and then let off the gas pedal and sure enough that wooshing from the wastegates was clearly there. I then switched the button to "Sport" mode and accelerated once again and then let off the gas once again, and what do you know, no more wooshing sound from the wastegates. I was like sweet! Now I know how to control the wastegates, and not have that annoying sound anymore.

Well for those of us who are running catless downpipes, you can try this out for yourself and see that it works. It's also good to know for those of you who are thinking about getting catless downpipes.

Cheers and happy driving.
Dave I gotta say, I am SHOCKED that YOU of all people would EVER have his car in "efficient" anything!-lol
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      08-07-2013, 01:48 PM   #11
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Too funny! I posted my comment above about Dave in efficient mode without reading anyone else's comments first. Looks like we ALL were thing the same thing!

I think this may be his mother's M5 after all. He's been putting us on!
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      08-10-2013, 07:58 AM   #12
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Hi guys,

i m drew n after spending "some longer" time reading thru diff. posts n all the excellant inputs n valuable experiences shared by you guys, i feel very lucky to hav found this site!

Having said that, me and my few m5 friends are in the beginning stage of modding our cars and considering the followings:

Dp -
1) Ams catless w microcat or
2) supersprint catless w microcat
(But then i heard even w microcat, CEL will still appears n thats a concern if need to bring in for bmw service)

Ecu tune -
Personally, my major objective is to delimit. Then if it comes w some gains of power also, then its fine. But then i read some posts where it says there are no real ecu tune at the moment. Its all bmw beta files now even w AC schnitzer, hartge or Eurocharged?? If it can provide delimit, some power gain and cancellation of CEL (w catless dp),then whats the difference??

Exhausts -
I already hav disappointment after installing a set of E sport + center exhaust which is way too queit (personal preference). So i hope adding a set of either ams or SS catless dp (if i can eliminate CEL w Eurocharged tune) or catted dp would increase the level of sounds, but hav no idea by how much and is stuck w choosing catted or catless...

I was once considering buying coldlist beautiful E race (hi coldlist, i wish i had spent more time in browsing this forum so i can get to know the experts n big boys here) after my disappointment w the E sport, but thought to myself lets try adding dp 1st n see...

Anyway, just wanna say hi to every elite members here and wanna say thank you for sharing all cool inputs & valuable experiences.

will post some photos of my ride. my initial modd. are mostly cosmetic:
- duke dynamic CF vented hood
- CF rear trunk spoiler
- matt wrapp in suntech film at impressivewrap
- E sport + center
- advan racing GT 20" wheels (weight: front 21lb, rear 23lb)
- CF front grill
- CF side mirror covers
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      08-10-2013, 08:03 AM   #13
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happened to see a white matt.
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      08-10-2013, 07:31 PM   #14
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Quote:
Originally Posted by slowcarsonfastlane View Post
(hi coldlist, i wish i had spent more time in browsing this forum so i can get to know the experts n big boys here) after my disappointment w the E sport, but thought to myself lets try adding dp 1st n see...
Hey, I'm no expert on exhausts other than I've gone through 4 on my M5 in 6 months only to now be trading it!-lol!

Congrats on the M5! Looks awesome.
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      08-21-2013, 03:41 PM   #15
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Car looks great, those wheels are well out whats the ET (off-set).
My winters are 20" with ET 15 fronts ET 20 rears.
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      09-08-2013, 07:27 AM   #16
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Unless the engine has a dump valve, what is suggested here is not safe to do. Closed WG causes unwanted positive pressure and in long term may cause problems in your charge pipe route and damage your turbos.

Last edited by Soorena; 09-08-2013 at 07:37 AM..
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      09-09-2013, 01:40 PM   #17
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Quote:
Originally Posted by Niko1414 View Post
What!!?? Dave in efficient mode something is wrong here....good find though
+1
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      09-15-2013, 11:30 AM   #18
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Quote:
Originally Posted by Tom C
My only question is WHY WERE YOU EVER IN EFFICIENT MODE IN THE FIRST PLACE TO HEAR THE WHOOSHING NOISE?!?!?
Exactly

I set my MDM in all my m cars to sport mode and never ever turn it off
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