Smoking N54 on Decel and Boost

Maroon_e90

Specialist
Sep 30, 2021
57
11
0
23
Northwest Indiana
Ride
2009 335i - xdrive 6MT
I have recently swapped in a speed tech single turbo kit for my N54 motor. My car was showing signs of blown turbos (high amounts of smoke out of the exhaust). I have since changed the turbos hoping the problem would be resolved. It is not... I was hoping if someone with lots of experienence can confirm my suspicion.

The new turbo is in and the old turbos had excessive shaft play. The motor is still smoking under boost and especially under decel. My suspicion is valve seals. Here is a link which shows exhaust port 3 and 2 covered in oil/carbon. The spark plug in 3 is also very oily on the tip causing a misfire. Can anyone offer input to this? How difficult is it to replace valve seals?

Could this be a PCV issue? I have the FTP metal PCV and I have routed the PCV to the turbo inlet speedtech provides. I have capped the hard plastic vacuum lines which were used to control the boost for the twins. Would a crank case breather help or is this really too far advanced to where seals are definitly needed?

I also have brand a new valve cover and gasket as well as new index 12s. To offer further clarification I had to also remove my Oil catch can because water froze through all the lines and caused a really really REALLY bad smoking condition Im talking a quart in 5 miles could this have cause the valve seals to fail prematurely? I am at 72K miles.

Finally this is a bit more techincal but why does decel create a smoking condition? Does this increase crankcase pressure to cause the oil to blow through the seals? Whats the science behind it.

Thanks guys.
 

iminhell1

Sergeant
Jun 17, 2018
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204
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Decel is a low crankcase pressure situation, or should be. In an ideal situation the pressure in the valvecover and crankcase would be equal. But the way the PCV is setup on these engines that isn't the case always. You either need to leave the system stock. Or completely remove it / bypass it and block the vents to the intake ports. When you have half of each you create more problems than you think you solve.

But if you have a catchcan I'll go with you have things setup wrong and created a vacuum leak to the crankcase. The oil is coming from the vacuum pump.
 

Sava666

Corporal
Dec 14, 2020
141
19
0
1st thing is check for vacuum by opening the oil cap. It should open with woosh sound and sucked back strongly. 100% sure you don't have much vacuum if your smoking during decels. 2nd issue might be the high side valve (wicket) it could stuck in open pisition (ask me how I know, lol). Try to clean it with carb cleaner and be sure to install it VERTICALLY not under angle thus it shall operate correctly. As I understood all the PCV operation during decel is directly related to HIGH side considering your FTP is working correctly.
 

Maroon_e90

Specialist
Sep 30, 2021
57
11
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23
Northwest Indiana
Ride
2009 335i - xdrive 6MT
Okay I have opened the oil cap at idle and it is blowing vapor out pretty high like it's under pressure. Sounds like we're on to something here. What could cause the engine not to make vacuum? Where are the leak points because there's no leaks in the vacuum pump.
 

Sava666

Corporal
Dec 14, 2020
141
19
0
Its not related to vacuum pump. It creates vacuum by sucking air into cylinders. Its caused by blocked pcv either high side(remains open) or low side(stays blocked).
 

Maroon_e90

Specialist
Sep 30, 2021
57
11
0
23
Northwest Indiana
Ride
2009 335i - xdrive 6MT
Okay, so I've gotta lean towards the low side being blocked. Considering if the high side was left open there would still be vacuum created. There is absolutely no vacuum I could upload a video but the vapor is shooting out the oil cap like one of those old trains in the movies. The solution I assume is gonna be a new valve cover again?
 

RuskiRacer

Captain
Jul 17, 2019
1,209
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2009 e93 335i
Okay, so I've gotta lean towards the low side being blocked. Considering if the high side was left open there would still be vacuum created. There is absolutely no vacuum I could upload a video but the vapor is shooting out the oil cap like one of those old trains in the movies. The solution I assume is gonna be a new valve cover again?
I've had this issue before where my crank case wasn't being ventilated properly and my brand new 6266 precision was blowing clouds of smoke under acceleration. Oil doesn't drain properly from the turbo and it starts cooking it up and smokes
 

wheela

Lieutenant
Jun 4, 2021
539
302
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Twin Cities, MN
Ride
2015 e84 X1 35i Msport
If it's blowing out the engines's oil cap like an old train, is that a sign of bad piston blow-by? Hard to imagine how else that much pressure is in the crank case at idle🤷‍♂️?
 

Maroon_e90

Specialist
Sep 30, 2021
57
11
0
23
Northwest Indiana
Ride
2009 335i - xdrive 6MT
Any positive pressure in the crankcase is a nogo. Check the pcv system/catchcan. If youre still having issues, leakdown test
I do not have a catch can anymore, what could be a reason as to why my crank case is not creating Vacuum and creating positive pressure at idle?
 

iminhell1

Sergeant
Jun 17, 2018
420
204
0
Here is a video of idle with the cap off. Here. Has anyone watched the other video do the valve seals look okay?
Looks fairly normal to me, so long as the engine is fully warmed up. The 'smoke' is more water vapor than it is oil smoke. Throw a paper towel in the smoke and you'll see it get wet (don't cover the oil fill or it'll get sucked in).

EVERY engine will act just like that, puffing out the oil fill cap. It's due to the imbalance of air pressure in the crankcase of piston engines. Remember how the piston speeds change based on the rod angle and position? That is why and why there is a PCV system ... the reburn portion is due to EPA ... the physical design is due to engine physics though.

This is a 4cylinder (zetec specifically). The center purple line is what the PCV would be designed to relieve, the pressure imbalance. As RPM increases the frequency of that wave would increase. The amplitude would not, unless there is a leak (vacuum or pressure), a blockage, a volume change (more or less oil in the pan).
When we modify cars and add power we tend to forget this fact. If we stuff more air in the cylinder there tends to be more blow-by. but the PCV system was not designed to handle that additional volume (CFM). So we created a imbalance of higher pressure than designed, thus smoking.


I'm not trying to fix your car. I'm trying to educate you so you understand how to fix the system.
 

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Maroon_e90

Specialist
Sep 30, 2021
57
11
0
23
Northwest Indiana
Ride
2009 335i - xdrive 6MT
There is absolutely no suction after taking this cap off I can feel it pulsing out vapor otherwise I would know that this isnt the issue. I would like to understand why it is not creating suction. so possible problems are the head ports are plugged, the the low pressure side PCV is plugged, or there is extremely excessive blowby. Also that was on a cold start if that means anything. I suspect I need to get a compression test...
 

wheela

Lieutenant
Jun 4, 2021
539
302
0
Twin Cities, MN
Ride
2015 e84 X1 35i Msport
Looks fairly normal to me, so long as the engine is fully warmed up. The 'smoke' is more water vapor than it is oil smoke. Throw a paper towel in the smoke and you'll see it get wet (don't cover the oil fill or it'll get sucked in).

EVERY engine will act just like that, puffing out the oil fill cap. It's due to the imbalance of air pressure in the crankcase of piston engines. Remember how the piston speeds change based on the rod angle and position? That is why and why there is a PCV system ... the reburn portion is due to EPA ... the physical design is due to engine physics though.

This is a 4cylinder (zetec specifically). The center purple line is what the PCV would be designed to relieve, the pressure imbalance. As RPM increases the frequency of that wave would increase. The amplitude would not, unless there is a leak (vacuum or pressure), a blockage, a volume change (more or less oil in the pan).
When we modify cars and add power we tend to forget this fact. If we stuff more air in the cylinder there tends to be more blow-by. but the PCV system was not designed to handle that additional volume (CFM). So we created a imbalance of higher pressure than designed, thus smoking.


I'm not trying to fix your car. I'm trying to educate you so you understand how to fix the system.
Now I want to try that with my car. In that video it sure looks like there is net more vapor/smoke exiting on the pulses that getting sucked in on the pulses. At idle, there should be little blow-by, to the extent that the intake vacuum overcomes all blow-by producing a net vacuum on the crankcase via the pcv system. So idling with the cap off, more air should be getting sucked in through the cap than gases blowing by the pistons. At idle, this should also be true on a mofified engine, right? Unless you've got higher clearance piston rings (more blow by), but even then the pcv should still be able to keep up at idle, right?

OP - out of curiosity, what was the outside temp when that idle video was taken? I'd imagine it would have to be pretty cold for water vapor to condense into visible steam like that? Seems like a lot of water vapor. The main combustion byproducts are CO2 and water vapor, so it seems to me that video suggests excess blow-by🤷‍♂️ I hope not though for your engine's sake.
 

Maroon_e90

Specialist
Sep 30, 2021
57
11
0
23
Northwest Indiana
Ride
2009 335i - xdrive 6MT
Well it would seem that this post predicted my future. I did not blow the turbos. I guess I should have known that the turbos wouldn't just blow after a pull it would have been more progressive.

If anyone sees anything fishy from that pull's log please let me know haha

Here are the results of the compression test:

cyl compression.jpg


We can see there is a problem with some cylinders, 1 is a little low and 3 is atrocious. The odd thing is I did not hear anything weird during that pull, just smoke. I will assume the rod is slightly bent as the motor still runs.

Thanks for everyone's help!

We do have a few goodies (full build I think...) laying around so I guess they will have to be installed, my only issue is no garage... lol

20220521_202451.jpg
 

RuskiRacer

Captain
Jul 17, 2019
1,209
749
0
Ride
2009 e93 335i
Well it would seem that this post predicted my future. I did not blow the turbos. I guess I should have known that the turbos wouldn't just blow after a pull it would have been more progressive.

If anyone sees anything fishy from that pull's log please let me know haha

Here are the results of the compression test:

View attachment 68622

We can see there is a problem with some cylinders, 1 is a little low and 3 is atrocious. The odd thing is I did not hear anything weird during that pull, just smoke. I will assume the rod is slightly bent as the motor still runs.

Thanks for everyone's help!

We do have a few goodies (full build I think...) laying around so I guess they will have to be installed, my only issue is no garage... lol

View attachment 68623
thats a pretty good batch of parts I've used those pistons and rods and bearings with good success. The ringland could be cracked as well not sure how bad the smoke is. Typically when they are cracked they make the car missfire pretty bad
 
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