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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > Why is my boost hitting 22PSI on a stock map?



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      03-26-2021, 06:13 PM   #23
anjuna
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Quote:
Originally Posted by ky0u View Post
3.5mm inner diameter. get like 3ft. It's excess but vac hose is cheap and it's always better to have too much. Not to mention having spare vac hose on hand is never a bad thing with these cars
It should also be noted that true vacuum line is different than just regular line.

They usually have an internal liner to stop the collapse.
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      03-27-2021, 07:04 AM   #24
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Quote:
Originally Posted by anjuna View Post
Quote:
Originally Posted by ky0u View Post
3.5mm inner diameter. get like 3ft. It's excess but vac hose is cheap and it's always better to have too much. Not to mention having spare vac hose on hand is never a bad thing with these cars
It should also be noted that true vacuum line is different than just regular line.

They usually have an internal liner to stop the collapse.
Something like this would work?

https://germanoem.ca/vacuum-hose-3-5x2mm-contitech.html

I'm in Canada so I don't want to order from the US for a hose if I can help it.
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      03-27-2021, 07:36 AM   #25
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Originally Posted by jogill View Post
I replaced the solenoid and it did not fix the problem

The only other thing I can think it could be would be the actual wastegate actuator itself, maybe it's sticking and not releasing when commanded. I don't feel confident in this diagnosis since the exhaust pressure is pushing against it so for it to stick and overcome that pressure would be pretty significant. Although I don't know what else it could be.

On the N54 you can buy replacement actuators however on the N55 it's considered part of the turbo so you can't just buy the actuator, at least I'm not finding it. Anyone replace an actuator on a N55?

Many people seem to replace the vacuum lines however I don't see how that would contribute to overboost since the system requires vacuum to make boost. Although I'll likely just replace the line from the solenoid to the actuator if I'm going to replace the actuator anyway.

Anyone have any ideas?
I believe the N55 wastegate operates reverse of the N54. It needs vacuum to reduce boost. If there is no vacuum to the actuator, the wastegate is stuck closed.
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      03-27-2021, 10:30 AM   #26
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Originally Posted by MightyMouseTech View Post
I believe the N55 wastegate operates reverse of the N54. It needs vacuum to reduce boost. If there is no vacuum to the actuator, the wastegate is stuck closed.
No.

N55 is the opposite of conventional wastegate controls.

Typical wastegate controls (like, pretty much every turbo engine from any other manufacturer) use both a spring (to keep the wastegate closed to a certain PSI, like 6-7psi, after which the wastegate will open without outside forces, as you’re literally pushing it open with exhaust gasses) as well as the boost pressure from intake manifold routed to the wastegate to KEEP it closed. They modulate boost by BLEEDING pressure away from that intake-to-wastegate-actuator line to allow the wastegate to open. (Yes, I realize that external wastegate exist )

The N55 has two types:

EWG - easiest. You command a value and an electronic device modulates the wastegate position to an exact value regardless of boost/flow/etc.

PWG (the one most of us have) - has a spring as well, though the spring is something stupid low (2-4psi???? after which the wastegate will open without outside forces, as you’re literally pushing it open with exhaust gasses) and this is what may lead you to believe that “no vacuum means it’s closed.” That said, we DO use vacuum (produced by the vacuum pump) to PULL the wastegate CLOSED when boost pressure exceeds the wastegate spring. As such, you NEED vacuum to pull that wastegate closed under load/flow/boost. It’s also counter intuitive to say that the vacuum line “collapsed” and produced boost runaway, because we require MORE vacuum to keep the WG closed at higher exhaust flow (higher boost) because there is MORE pressure on the wastegate itself (because more exhaust flow).

If there is insufficient vacuum (no line connected, bad vacuum pump, bad solenoid, etc.), you will see no/little boost.

If there is excess vacuum (aka, really high WGDC [due to bad solenoid or poor tune]), you will see excessive boost.

At this point, the only thing I can think is that the WG actuator arm is not coming back to resting/open position. This can be due to a solenoid/line, or even physical issues like bends, rust/corrosion, bad actuator (damaged internals), bad turbo (as there is another pivot inside the exhaust side of the compressor), or uhhhhhhh something else pretty obvious (I haven’t had my coffee yet. It’s a Saturday mmmmmkay)

Last edited by anjuna; 03-27-2021 at 10:37 AM..
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      03-27-2021, 10:37 AM   #27
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Quote:
Originally Posted by MightyMouseTech View Post
Quote:
Originally Posted by jogill View Post
I replaced the solenoid and it did not fix the problem

The only other thing I can think it could be would be the actual wastegate actuator itself, maybe it's sticking and not releasing when commanded. I don't feel confident in this diagnosis since the exhaust pressure is pushing against it so for it to stick and overcome that pressure would be pretty significant. Although I don't know what else it could be.

On the N54 you can buy replacement actuators however on the N55 it's considered part of the turbo so you can't just buy the actuator, at least I'm not finding it. Anyone replace an actuator on a N55?

Many people seem to replace the vacuum lines however I don't see how that would contribute to overboost since the system requires vacuum to make boost. Although I'll likely just replace the line from the solenoid to the actuator if I'm going to replace the actuator anyway.

Anyone have any ideas?
I believe the N55 wastegate operates reverse of the N54. It needs vacuum to reduce boost. If there is no vacuum to the actuator, the wastegate is stuck closed.
According to this it's the same at the N54, vacuum to close the wastegate and build boost. I have too much boost which would indicate it's stock closed. I don't understand how that would happen but I cannot budge it and the lever position looks closed based on the angle.

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      03-27-2021, 10:48 AM   #28
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Quote:
Originally Posted by jogill View Post
According to this it's the same at the N54, vacuum to close the wastegate and build boost. I have too much boost which would indicate it's stock closed. I don't understand how that would happen but I cannot budge it and the lever position looks closed based on the angle.

You’re on the right track.

You can always drop your downpipe, inspect the wastegate flap, make sure it’s moving easily, and you can ALWAYS replace components of the mechanism with enough willpower.

No need to chunk a turbo if you’re just having issues with the wastegate, but if you decide to, id be happy to save it from the trash bin (I have been planning a few test fits of other compressor wheels and could benefit from having an extra “somewhat known good” turbskies)
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      03-27-2021, 11:42 AM   #29
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Quote:
Originally Posted by anjuna View Post
Quote:
Originally Posted by jogill View Post
According to this it's the same at the N54, vacuum to close the wastegate and build boost. I have too much boost which would indicate it's stock closed. I don't understand how that would happen but I cannot budge it and the lever position looks closed based on the angle.

You’re on the right track.

You can always drop your downpipe, inspect the wastegate flap, make sure it’s moving easily, and you can ALWAYS replace components of the mechanism with enough willpower.

No need to chunk a turbo if you’re just having issues with the wastegate, but if you decide to, id be happy to save it from the trash bin (I have been planning a few test fits of other compressor wheels and could benefit from having an extra “somewhat known good” turbskies)
I got under the car and I couldn't move the wastegate lever at all. I also tried to disconnect the actuator but the two nuts are too tight for me with the little working space. So because I can't disconnect it I can't tell if it's the actuator or the wastegate lever, but I hope it's just the actuator. Pure Turbos sells an N55 wastegate actuator so I'll buy one and take it to a shop to replace it since taking off the DP (xdrive) is also too much for me. I e replaced actuators on a 03 Jetta TDI but BMW left very little working space.
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      03-27-2021, 04:31 PM   #30
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Quote:
Originally Posted by jogill View Post
I got under the car and I couldn't move the wastegate lever at all. I also tried to disconnect the actuator but the two nuts are too tight for me with the little working space. So because I can't disconnect it I can't tell if it's the actuator or the wastegate lever, but I hope it's just the actuator. Pure Turbos sells an N55 wastegate actuator so I'll buy one and take it to a shop to replace it since taking off the DP (xdrive) is also too much for me. I e replaced actuators on a 03 Jetta TDI but BMW left very little working space.
Yes they did. I am X-drive. It may suck to pull the DP, but you'll thank yourself, as you'll be cussing when you pull it off as opposed to cussing while you're working on the compressor.
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      03-27-2021, 06:26 PM   #31
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Quote:
Originally Posted by jogill View Post
Something like this would work?

https://germanoem.ca/vacuum-hose-3-5x2mm-contitech.html

I'm in Canada so I don't want to order from the US for a hose if I can help it.
I know its from the USA, but I have a friend here in Canada that bought these for his N54 which had a leak and they seem to work good.

https://www.verociousmotorsports.com...ld-by-the-Foot
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      03-27-2021, 08:15 PM   #32
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Quote:
Originally Posted by TheGoodTheBadTheUgly View Post
I know its from the USA, but I have a friend here in Canada that bought these for his N54 which had a leak and they seem to work good.

https://www.verociousmotorsports.com...ld-by-the-Foot
I redid my vac hoses 2 years ago and used the Verocious product. Works fine. No problems.
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      03-29-2021, 02:35 PM   #33
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Quote:
Originally Posted by TheGoodTheBadTheUgly View Post
I know its from the USA, but I have a friend here in Canada that bought these for his N54 which had a leak and they seem to work good.

https://www.verociousmotorsports.com...ld-by-the-Foot
These are the exact ones I replaced my vac hoses with too
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      04-15-2021, 09:31 PM   #34
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Quote:
Originally Posted by jogill View Post
I got under the car and I couldn't move the wastegate lever at all. I also tried to disconnect the actuator but the two nuts are too tight for me with the little working space. So because I can't disconnect it I can't tell if it's the actuator or the wastegate lever, but I hope it's just the actuator. Pure Turbos sells an N55 wastegate actuator so I'll buy one and take it to a shop to replace it since taking off the DP (xdrive) is also too much for me. I e replaced actuators on a 03 Jetta TDI but BMW left very little working space.
Did you ever get this sorted?
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      04-19-2021, 08:46 AM   #35
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Originally Posted by wheela View Post
Did you ever get this sorted?
Not yet, still waiting for the wastegate actuator to show up. Soon I hope. I'll update once I have replaced it and it is hopefully working properly.
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      04-29-2021, 12:05 AM   #36
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This is common on Mhd n55e flashes. They abandoned the platform to work on the n55 ewgs. Theres nothing wrong with your car its the tune. I went custom tune just for this reason.

You cant log intake (after throttle valve) with mhd .. You can with Protools. The pressure you are seeing is before throttle body and once the throttle closes you would see a increase in pressure before (which you see) and a decrease in psi after throttle .. Its only like a decrease of 1 to 2 psi though.

Its really just bad maps .. Its been documented many times. Any n55e mhd map log you will see the throttle closure then excess boost.

Last edited by TunafishE93; 04-29-2021 at 12:20 AM..
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      05-03-2021, 07:36 AM   #37
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Quote:
Originally Posted by TunafishE93 View Post
This is common on Mhd n55e flashes. They abandoned the platform to work on the n55 ewgs. Theres nothing wrong with your car its the tune. I went custom tune just for this reason.

You cant log intake (after throttle valve) with mhd .. You can with Protools. The pressure you are seeing is before throttle body and once the throttle closes you would see a increase in pressure before (which you see) and a decrease in psi after throttle .. Its only like a decrease of 1 to 2 psi though.

Its really just bad maps .. Its been documented many times. Any n55e mhd map log you will see the throttle closure then excess boost.
This is one of my frustrations with MHD - they shifted to adding funky weird CAN / ethanol / aftermarket bs instead of getting the standard data points, like valvetronic (I'm assuming this is what you mean by 'intake after throttle body')

That said, valvetronic does not deviate from the programmed table. See my N55e EWG valvetronic table below.

Stock Valvetronic table for N55e


My changed table
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