My boost leak saga

RNM

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Jun 3, 2019
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I have been having this issue ever since I put in bigger turbos on my car December of last year. Originally, I bought a set of used rb next gens to replace my perfectly working stock turbos. I took logs and noticed that I never held boost at higher rpms. I did smoke tests, pressure tests (by several different indy bmw shops), changed out my bov spring, boost solenoids, new vacuum lines, and even took it back to the guy who I had bought the turbos from to double check the installation as he went from rb next gens 15t to single turbo on his N54. Everything came back as if there was no leaks despite what my logs said.

One day, we (guy who sold and installed the turbos) were logging on the highway and the rear turbo shaft had snapped and there was lots of smoke coming out of the tail pipe. So maybe it was bad turbos that needed to be rebuilt you would think? I sent them back to Rob (excellent communication) for analysis and had them upgraded to next gen plus 17t. This took several months and again, had the guy put in the turbos in for me as he felt partially responsible for what had happened.

Fast forward to this day and I am still having the same issue on brand new, rebuilt turbos. Sorry for the long rant, but I felt like I needed to explain what I have been going through the past 10 months as it has not been easy (financially and mentally dealing with this). I am still not ready to throw in the towel as I want to tackle this issue and stick with my N54 for the next few years.

I also want to mention that I had an indy shop perform a compression test on the motor when I got my turbos rebuilt and all cylinders came back in the 180s.

When I was on stock turbos, I was custom tuned by Dimitri from BQtuning. Here is a log when I was on stock turbos: https://datazap.me/u/rnmevo9/bq-v2-log-1?log=0&data=4-21

When I got my used rb next gen 15t, I got a base map from bq and here is a log: https://datazap.me/u/rnmevo9/base-bqe45rb?log=0&data=4-20-21

After I blew up the turbos and had it rebuilt by Rob, I took another log and I am still having the same boost dropping off: https://datazap.me/u/rnmevo9/ng?log=0&data=3-22

My car is a 2007 335i with about 119k miles. My father was the original owner and then I bought the car from him so I know most of its history. My car has the following modifications currently:

RB next gen plus turbos
RB external pcv valve
Mhd custom tuned by BQ on e45
Vrsf relocated aluminum inlets
Vrsf downpipes
Vrsf charge pipe with tial bov (black spring)
Psp 900 intercooler
Psp external oil cooler
Psp aluminum outlets
Relocated 335d coolant tank
Fuel it stage 2 lpfp 525 pump
EOSpeed bpm4 lpfp controller
Index 12 injectors
Precision raceworks fuel filter assembly (waiting to be installed)
Spool hpfp overdrive (waiting to be installed)

Thank you for your time.
 

RNM

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Jun 3, 2019
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I also wanted to add that I was experiencing 2a87 exhaust cam code every once in awhile after I had the rbs in. I changed the vanos solenoids and it still happened to pop up but less consistently. As of lately, it hasn't popped up but then again, I have not been very aggressive with the car as I know it still has a leak and do not want to go through the experience of sending back turbos in order to be rebuilt. It was suggested to me to have the cam ledge bearings checked out as well as the valves while they are in there.
 

JBacon335

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it's odd because wgdc goes way up while boost is going down. maybe a boost solenoid is taking a crap? have you tried replacing them yet as they should be ready to go at that mileage
 

NoGuru

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Jan 9, 2018
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Of coarse you know I have just about the same mods as you and chasing the same issue.
Lets skip the usual stuff like the plumbing as I will assume you have gone though all of it already and leak tests are not showing anything.

Something I was considering was putting the car on a Dyno. Then I would watch, and film the motor to see if I can pin point the leak.

Are you hearing the leak? I can hear mine as soon as it happens and it is very distinguishable.
 

Asbjorn

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Mar 10, 2018
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I feel your pain. I was struggling with boost leaks for almost a year. Finally now Dimitri says its the best he has ever seen. So keep fighting and don't give up. Here's a list of issues I had for inspiration:

-tmap housing leaked
-alu charge pipe leaked due to over-tightening the clamp near the fmic (the pipe was no longer round)
-the silicone hoses close to the turbos burnt or the clamps went loose several times.
-a brand new vacuum line leaked, but only intermittently. There was a cut in it that would shut tight most of the time, and only leak sometimes. We only found it by sheer luck.
-my car generally gains one +1psi during the first pulls and then goes back to hitting target spot on or slightly below when hot. It happens without touching anything, and confused me for a long time. It basically meant that we could change the rear wheel and then boost would become better just because the car had cooled down.
-exhaust flap randomly not opening as it should, causing the turbos to not spool up properly due to exhaust flow restriction

I want to let you know that smoke testing never helped me spot any of my leaks. I could hear my tmap leaking during one smoke test, but smoke never came out. So unless it is a huge leak, you have to use your ears more than your eyes if smoke testing. I wont say you have a huge leak when boost can get as high as +20psi at lower rpms. But your leak is big enough at high rpm that you should be hearing air whooosing out. If you dont hear anything, I cant help but think turbos/vaccum...

I have never had a leak that looks like yours. This means you can probably rule out most of my examples above, because they never looked like yours.

I thought about putting my car on a dyno and using leak detection spray everywhere so many times during my fustration. Some of my leaks could have been found that way, but not all.
 
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mikeseli

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May 23, 2017
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Purchase a hand held vacuum pump with a gauge and verify that the wastegate can hold vacuum by connecting directly to the vacuum hose that goes to the wastegate. Next, create a vacuum of 6-7" with the pump and confirm that both flapper on the turbo close, I recommend you remove the downpipes unless you can hear them close. If you need to create more vacuum 9" for them to close this is the issued why you have some delay to create boost.
 
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doublespaces

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Originally, I bought a set of used rb next gens to replace my perfectly working stock turbos.

Had these turbos ever been rebuilt prior?

One day, we (guy who sold and installed the turbos) were logging on the highway and the rear turbo shaft had snapped and there was lots of smoke coming out of the tail pipe.

I really dislike how companies classify a failure. A lot of times I feel like unless it is without a doubt a manufacturing defect, its considered 'unknown cause' and they don't put it down as 'failed' and therefore everyone's track records are nice and neat.

I'd be curious to know what percentage of turbo sales resulted in replacement, upgrade or rebuild, for any reason.

With that aside, I'm with @mikeseli on this one, test the wastegates manually and see what is going on there. It may also be worthwhile to investigate your vacuum pump and vacuum canisters. If there is a crack in the housing or something odd going on with your crank case pressure(where the vacuum pumps air into) then perhaps that is causing an issue somehow.j

Also, check the lines going to your brake booster and also the one that goes to the muffler, in case your golf tee fell out :)
 
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RNM

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Jun 3, 2019
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Had these turbos ever been rebuilt prior?



I want to say I really dislike how companies classify a failure. A lot of times I feel like unless it is without a doubt a manufacturing defect, its considered 'unknown cause' and they don't put it down as 'failed' and therefore everyone's track records are nice and neat.

I'd be curious to know what percentage of turbo sales resulted in replacement, upgrade or rebuild, for any reason.

With that aside, I'm with @mikeseli on this one, test the wastegates manually and see what is going on there. It may also be worthwhile to investigate your vacuum pump and vacuum canisters. If there is a crack in the housing or something odd going on with your crank case pressure(where the vacuum pumps air into) then perhaps that is causing an issue somehow.

The turbos were rebuilt prior before I purchased them initially.

Thanks again for all of the suggestions as I will do that promptly as soon as I get a chance.
 

Asbjorn

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I got a problem today that reminded me of your boost leak.

I was running MHD stage 0 for a few weeks, then upgraded to MHD v1.8 and wanted to go back to my old custom tune. I had a hiccup during the flash, and had to reflash. When I WOT logged, it showed a weird "boost leak" that looks a bit similar to yours:


Just like yours it would hold boost to around 5000rpm, and then start to fall off. Yours is more violent, but could it have been caused by a similar bad flash?

To solve this I went back to mhd v1.72b. Then I renamed the 2mb bin file in the mhd folder, flashed back to stock, then re-flashed the custom tune (full write), and reset adaptations afterwards. Now car is back to normal:


Im still waiting for my tuner and MHD to comment on this, so the above is all the info I have at this point.
 
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martymil

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I got a problem today that reminded me of your boost leak.

I was running MHD stage 0 for a few weeks, then upgraded to MHD v1.8 and wanted to go back to my old custom tune. I had a hiccup during the flash, and had to reflash. When I WOT logged, it showed a weird "boost leak" that looks a bit similar to yours:


Just like yours it would hold boost to around 5000rpm, and then start to fall off. Yours is more violent, but could it have been caused by a similar bad flash?

To solve this I went back to mhd v1.72b. Then I renamed the 2mb bin file in the mhd folder, flashed back to stock, then re-flashed the custom tune (full write), and reset adaptations afterwards. Now car is back to normal:


Im still waiting for my tuner and MHD to comment on this, so the above is all the info I have at this point.

I found similar flashing problem issues too and reported it and they just ignored me.

We had two tuners tuning the same car but with different files for different fuels for a specific reason, you couldn't flash one tune directly over the other to switch, you had to flash back to stock every time and load the other tune and vice versa.

If you did not weird crap happened and the car would not run right.
 

Asbjorn

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I found similar flashing problem issues too and reported it and they just ignored me.

We had two tuners tuning the same car but with different files for different fuels for a specific reason, you couldn't flash one tune directly over the other to switch, you had to flash back to stock every time and load the other tune and vice versa.

If you did not weird crap happened and the car would not run right.

yeah no response from mhd on this, maybe it has been solved with 1.91

@RNM glad you found the problem. How did you find it, what does it look like exactly and what was the solution. I dont understand what inlet collapsing on turbo means exactly.
 

RNM

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Jun 3, 2019
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yeah no response from mhd on this, maybe it has been solved with 1.91

@RNM glad you found the problem. How did you find it, what does it look like exactly and what was the solution. I dont understand what inlet collapsing on turbo means exactly.

Here is a picture of what a collapsing inlet looks like:
 

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SlowE93

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I found similar flashing problem issues too and reported it and they just ignored me.

We had two tuners tuning the same car but with different files for different fuels for a specific reason, you couldn't flash one tune directly over the other to switch, you had to flash back to stock every time and load the other tune and vice versa.

If you did not weird crap happened and the car would not run right.
I too have had this happened. MHD kinda laughed and said there was no need to do full writes. Just 2 min flash and you are good.
But yeah, same experience here.