Wastegate rattle 2 days after MHD stage 1

Arbi

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Mar 2, 2020
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Hi guys,

Let me start off by saying thank you for accepting me at this forum. I hope I can learn a lot from you guys and (eventually) give some advice in return :).

I've read a lot about wastegate rattling and the fixes. However I have a question for the brainiacs ;).

My '07 BMW N54 has 208k km. on it and I've owned it for about 3 months now. After purchasing the car, which had a dealership history, I had the oil changed immediately and again after 1000 km. (as a kind of flush), a regular service (spark plugs, etc.), the transmission and diff serviced by ZF and a wallnut blasting. The mechanic, specialized in BMW's, said it drives like a charm. After 3 months I finally felt confident to flash it with MHD to stage 1.

Last Thursday I did the flash. All went well. Drove the car back home, but because it was raining I didn't do any WOT's. Friday the same. On Saturday I had a long trip and after a proper warming up (45 min+) I decided to gently work up to a couple of WOT's. After arriving at the destination I noticed the car started rattling when I'm decelerating or when I'm in P or N and tap the throttle and when releasing it, you will hear a rattling. Same goes for when I shut the engine down. Clear case: wastegate rattle!

Today I went to a garage specialized in BMW's and had a mechanic look at the problem. Told the mechanic my story and we went for a drive. He did a couple of WOT's (I was hurting since my oil was only at 200 degrees -_-), he said my car pulls strong (not faulty) and there are no codes. Back in the shop he had me rev the engine while he was looking etc. He pulled a vacuum line from the vacuum cannister and the ticking stopped. So we're 100% certain it's the wastegate(s).

However his only fix is replacing the turbo's. I told him that it started 2 days after the flash. If it started right away, I could imagine my previous software (I'm guessing BMW, since the last visit to the dealership was in 2017) had suppressed the WG rattle. But now that it started only after 2 days, I made the suggestion a vacuum line could have a (small) crack and maybe if all the vacuum lines that are involved with the turbo's were to be changed, the WG rattle would be fixed.

Although, after a visual inspection, he said that a couple of lines could use replacing, he also said he doubted it strongly that replacing the vacuum lines would solve the problem, since vacuum lines are only there for vacuum. But isn't it vacuum that keeps the WG closed on decelartion? So to sum it up:

  1. Wastegate starts rattling, but 2 days after the flash to MHD stage 1. If it happened right after the flash, I'd blame the flash (or better yet, the lack of a suppressant in the flash). Now, after 2 days, I can imagine the extra boost wore the vacuum hoses out.
  2. The wastegate is kept closed by vacuum, right? So couldn't one or more faulty vacuum hoses cause my wastegate rattle? Keep in mind that the car pulls strong according to the mechanic (and as far as I can tell, never driven another 335i before), I have 0 codes and the rattle only occurs during deceleration not during acceleration or idle. So could a loss of vacuum (hose or whatever) so small, cause wastegate rattling only at deceleration and not throw any codes?
I haven't tried flashing back to stock or chose for the 'anti-wastegate rattle option' in MHD. I prefer to figure this out without creating lag :). I have this feeling in my gut I can fix this without replacing the turbo's or the regular "fixes" like 'anti-rattle options' and tightening the wastegate.

Any help would be much appreciated!

Thanks a lot!

Otto
 
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Milan

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Dec 24, 2016
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Welcome to the forum and the wonderful world of owning a TT N54. The short answer is you are always going to have rattle until you decide to do the reliability mod aka single turbo

There is a reason twins (stock and aftermarket) are for sale constantly. My advice is either deal with the rattle or do what most of us on here have done and throw all that stuff in the trash and go to single turbo, it's not even expensive anymore
 
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Arbi

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Mar 2, 2020
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Thanks for the welcome and the reply :)! And when it's necessary I will definitely look up my options for a single turbo!

I know that almost every n54 with the OEM turbo's has the rattling. However, until 2 days ago at 208k km. I had zero rattling. And then 2 days after flashing MHD stage 1 (not even right after the flash), it starts rattling. It's all too much of a coincidence if you ask me.

Before replacing my turbo's, I want to make sure it's not a simple fix (like vacuum). Not only because I'll save a heck of money, but also because fixing this, if it actually is a vacuum leak, will give me a 'f* yeah'-moment :). And that's why I posted this question.

Thanks again :).
 

Milan

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Even if you replace the turbos they are going to rattle. If you look at the WG design and what's being asked of them there is no way for them not to rattle.

Doesn't MHD have a rattle fix slider? Just move it over to keep them open more
 

Arbi

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Mar 2, 2020
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Yes, MHD has that option. Was going to try it later on, if I don't fix it. Problem is that you're opening the wastegate and thus creating lag. Ah well, better than that ticking, I guess...
 

tisdrew

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Welcome to the forum and the wonderful world of owning a TT N54. The short answer is you are always going to have rattle until you decide to do the reliability mod aka single turbo

Neither my stock twins (23psi) nor upgraded aftermarket twins (30psi) had any rattle. There are many many people who have wastegate rattle and many many who don't. Wastegates can be made to withstand nearly-stock flash tuning as the OP is using.
 

Arbi

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Mar 2, 2020
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Neither my stock twins (23psi) nor upgraded aftermarket twins (30psi) had any rattle. There are many many people who have wastegate rattle and many many who don't. Wastegates can be made to withstand nearly-stock flash tuning as the OP is using.
Thanks for the reply! What do you mean with "can be made to withstand"? You have to be lucky?

But the fact that there are many people who don't have the rattle, is exactly the reason why I'm guessing it has to be a vacuum leak. The car had 208.000 kms before tuning and no rattle whatsoever. Right after the flash, there was no rattle, so we can rule a software-fix in my previous OEM-flash out. The fact that it only started after 2 days and after a couple of WOT's (didn't do a WOT the first 2 days due to the rain), has me guessing the extra boost caused a (small) tear in one of the hoses.

Can you guys confirm that the vacuum keeps the WG closed when decelerating? And therefore a vacuum leak could cause the WG rattle when decelerating? Again, during acceleration (soft or hard) or during idle you don't hear it. Only during deceleration and when turning the engine off.
 

Milan

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Neither my stock twins (23psi) nor upgraded aftermarket twins (30psi) had any rattle. There are many many people who have wastegate rattle and many many who don't. Wastegates can be made to withstand nearly-stock flash tuning as the OP is using.

No they rattled you just tuned them out at the cost of lag
 

Torgus

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The problem is inherent with the stock waste gate design. My stock turbos were shot at 80k probably long before but I tried everything over 10k miles and nothing fixed it, new vac lines, new solenoids, custom tune, etc. you name it and I wasted time and money on trying to fix the worn wastegates. Waste gate rattle makes your BMW sounds like Piece of Shit. Everyone stares, it's loud and annoying, especially when they stop you for hitting your boost target and you get that nice 30FF code every pull.

New vac lines are cheap try it. As long as you hit your boost targets and are ok with the rattle and no codes just keep driving it. As said above try the WG rattle fix in MHD and play around with that. @ 125k it is not surprising you need new turbos, it seems like they all do around that mileage.

The solution is a single turbo or twins with upgraded wastegates...
 

limitdown

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Your turbos were already on their last legs. Working them a bit harder just pushed them over the edge. If you move up to Stg2, more things will break.
 
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Wastegate rattle is usually one of two things: the first is just the flapper being held off the turbine housing and rattling. This is normal and is adjustable in all modern tunes (wastegate rattle fix). The second is when the actual wastegate pieces are rattling in the housing -this means they're worn out and need to be replaced. It's best to look up close, but when the motor is COLD you can reach down and grab the rear turbo wastegate assy and gently pull it side to side, see if there is slop where the flapper pivot pin is.

Most likely since you didn't experience it before, you just need to adjust in tune.

Chris
 
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seb.apprenti

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Hi. I allow to revive the subject. I explain to you. I am in stage 3, Turbos Hydra performance hp650, complete exhaust line vrsf street. when starting my car, as soon as I shift into reverse or first gear, a loud metallic noise appears...it is also present when accelerating up to 2000 rpm. I was convinced it was my vrsf exhaust. this morning I did some tests...and. finally it is the wastegate rod that makes this noise. I put the rattle fix at 20%... and it's magic... no more noise. I don't have the impression that it's the wastegates that make noise but the adjustment rod. Is it wise to touch it or do I let mhd do its job?
 

SLOWESTN54

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Hi. I allow to revive the subject. I explain to you. I am in stage 3, Turbos Hydra performance hp650, complete exhaust line vrsf street. when starting my car, as soon as I shift into reverse or first gear, a loud metallic noise appears...it is also present when accelerating up to 2000 rpm. I was convinced it was my vrsf exhaust. this morning I did some tests...and. finally it is the wastegate rod that makes this noise. I put the rattle fix at 20%... and it's magic... no more noise. I don't have the impression that it's the wastegates that make noise but the adjustment rod. Is it wise to touch it or do I let mhd do its job?
My RB's did this too, @carabuser had to work some magic into the tune. Never heard it again, Spool was unaffected.
 
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