Single Turbo Setup Can't Reach Wastegate Pressure

Arrtus

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Apr 24, 2021
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Hey guys,

I originally had posted this in the N54Tech forum but got little to no help. I'm really stuck on and can't understand what is causing this problem.

This is a brand new DR700 setup and ever since making the swap, I am unable to reach more than ~9 psi (14 psi spring). The car is obviously way underboosting and I have no idea why. All the vacuum lines have been checked and are brand new. I have pressure tested from the turbo output all the way to the charge pipe and have found no issues. I also tested the compressor housing side of the turbo (and intake) and it did not leak whatsoever. I went through all the V-band connections and everything is on correctly and tightened to the max.

Symptoms: The car sounds different. I don't know if it's because of the single turbo but when going on WOT it doesn't sound like it's spooling. It's also very loud, like it just changes sound as soon as it starts building pressure.

With other maps, the wastegate (I think?) starts pulsing and sounding like it's hitting a rev limiter or 2-step while it's on WOT. It's most likely because of the mac that it's switching the air into the wastegate but it's not able to hold pressure or something. With maps aiming at higher PSI, it reaches ~12 PSI. What would cause the wastegate to do this? Can it be defective? It's a turbosmart gen V 45mm. I also checked the wastegate by putting some pressure on it and I can hear it open and closing. The MAC solenoid is also working just fine (which doesn't matter since it's not in use in map 0 and the problem is still there).

Log of a map 0 pull attached. Any advice or suggestions would be really appreciated!
 

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Arrtus

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Apr 24, 2021
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Did the fire ring in the wastegate get installed?
Yes it did. I think I found the problem though(?)

Took off the wastegate to test it and it works perfectly fine. However, the piston does not seal all the way. Can you verify if it should have a small gap or not? Small gap as in without the ring in (see images). I put the ring on and blew air into it with my mouth while holding it tightly and air just comes out the sides. The ring also seems to have a small amount of play. It looks like it's leaking judging by the black exhaust smoke marks too.

EDIT: After doing some digging around, looks like it's normal to have a gap but it is definitely leaking where the ring sits. The ring has some play in it when it is in position. It is ever so slightly too small. Would some gasket maker around the ring area be a good solution or will that blow out?
 

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Cruizinmax

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Maybe it's just the picture but that doesn't look right to me. Normally the fire ring protrudes slightly and when installed will slightly push on the wastegate valve to fully seal. It also looks like the tapered edge is facing away from the valve and in my experience that normally faces towards the valve.

Perhaps another photo of the fire ring itself?

If the wastegate is in fact sealing properly the next thing to look at would be the turbo inlet side. How is your air filter set up? Filter straight on the turbo or is there silicone piping involved before the filter?
 
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Arrtus

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Apr 24, 2021
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Maybe it's just the picture but that doesn't look right to me. Normally the fire ring protrudes slightly and when installed will slightly push on the wastegate valve to fully seal. It also looks like the tapered edge is facing away from the valve and in my experience that normally faces towards the valve.

Perhaps another photo of the fire ring itself?

If the wastegate is in fact sealing properly the next thing to look at would be the turbo inlet side. How is your air filter set up? Filter straight on the turbo or is there silicone piping involved before the filter?

Thank you for taking the time to reply! Here are some more images.

The fire ring does stick out and it does get pushed in when installed. However, it stills leaks from all around the outer wall of it (between the fire ring and wastegate housing. I think the play in it may be why. I can't find my caliper to measure the OD and ID on each but I would say around 0.5mm

Here's a video showing the play:

I'm thinking maybe if I can find something to put around the wall before installing, it might work. Something that would harden with heat or cure hard. I was going to try the gray gasket maker since that's rated for high temperatures but I'm afraid it may blow out given its flexibility after curing.
 

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Arrtus

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Apr 24, 2021
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After doing some more research, I think the wastegate may be leaking because of the way I am installing it.

I have been putting the ring in the WG, then the WG onto the manifold, and tightening it really hard. I had been under the impression that the V-clamp would pull the two pieces together but that may not be the case. I'm going to try to feed the valve continuous pressure to keep it open then tighten it so that the plates mate before the valve pushes against the ring and see if that helps.

Update: Installed the WG and it didn't seem to fix the issue. I'm going to have to step away from the car for a bit, I'm so tired of working on it and trying to fix this problem. It could still be the turbo to header connection even though I took that apart and re-installed it and made sure it was extra tight.

Update 2: I pulled off the hose that feeds into the bottom portion of the WG which opens the WG when the spring pressure is reached and went out for a drive and the car hit more than 16 psi. The reason I did this was mainly to see if the leak is bad enough to keep it from creating enough boost. Could the reference signal to the WG be too high causing it to open too soon? I am using the compressor housing location which comes with it pre-installed from Precision. Even if it was too high, why wouldn't the MAC be able to keep it closed instead of sounding like a pressure cooker/2 step when on other maps?
 
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doublespaces

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Update 2: I pulled off the hose that feeds into the bottom portion of the WG which opens the WG when the spring pressure is reached
This means your top ports aren't getting boost to hold the gates closed. This could be due to a pressure leak, incorrect plumbing, broken mac solenoid, solenoid getting reversed PWM signal? Did you wire the solenoid up yourself or did it come PnP? Try disconnecting the mac solenoid entirely and see if that works.
 

Arrtus

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Apr 24, 2021
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This means your top ports aren't getting boost to hold the gates closed. This could be due to a pressure leak, incorrect plumbing, broken mac solenoid, solenoid getting reversed PWM signal? Did you wire the solenoid up yourself or did it come PnP? Try disconnecting the mac solenoid entirely and see if that works.
Here is how I have it wired and an image of what it looks like. It's a plug and play MAC I purchased from BMS. There are no leaks in the hoses, I've tested that. Also, for map 0, the MAC is not in use and would strictly be based on WG spring.

The only thing I can think of would be in a scenario where there is a boost leak some point after the compressor housing (since that's where my reference to WG is). This would make the pressure output from the turbo higher than the actual pressure reached/read at the TMAP. For example, if there was a post turbo leak and I am reading 10 PSI at the TMAP, then that would mean the turbo is being over worked and is actually producing 14+ PSI which causes the wastegate to open and would appear that it is opening too soon.

Going to get a pressure gauge tomorrow and do a proper boost leak test post-turbo.
 

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doublespaces

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I embedded your datalog, which you can do at: https://www.spoolstreet.com/graphs/

Additional information

FirmwareInterfaceEngineTMAP_VAvgIgnDWPMethTriggerModeFFMethSafeModeMethAddMethScaleMethPSIVINE85_SetupVFF_Offsetfuel_30fuel_35fuel_40fuel_45fuel_50fuel_55fuel_60fuel_65fuel_70
30/139//2JB4 Android A330E Series - N541.945.47005000600.0............NONE0000000000

BoostSafetyPID GainAutoShiftRedFuel_OLFUA1st_limiter2nd_limiter3rd_limiterOptionsN20_TMAP6CylModeLastSafetyduty_15duty_20duty_25duty_30duty_35duty_40duty_45duty_50duty_55duty_60duty_65duty_70
21.025607600.00.00.0NONE153000000000000
 
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Cruizinmax

Corporal
Jul 18, 2018
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After doing some more research, I think the wastegate may be leaking because of the way I am installing it.

I have been putting the ring in the WG, then the WG onto the manifold, and tightening it really hard. I had been under the impression that the V-clamp would pull the two pieces together but that may not be the case. I'm going to try to feed the valve continuous pressure to keep it open then tighten it so that the plates mate before the valve pushes against the ring and see if that helps.

Update: Installed the WG and it didn't seem to fix the issue. I'm going to have to step away from the car for a bit, I'm so tired of working on it and trying to fix this problem. It could still be the turbo to header connection even though I took that apart and re-installed it and made sure it was extra tight.

Update 2: I pulled off the hose that feeds into the bottom portion of the WG which opens the WG when the spring pressure is reached and went out for a drive and the car hit more than 16 psi. The reason I did this was mainly to see if the leak is bad enough to keep it from creating enough boost. Could the reference signal to the WG be too high causing it to open too soon? I am using the compressor housing location which comes with it pre-installed from Precision. Even if it was too high, why wouldn't the MAC be able to keep it closed instead of sounding like a pressure cooker/2 step when on other maps?
All that you are describing with the installation sounds normal. I have seen cases where the wastegate flange gets warped in the welding process. It does appear you are leaking some exhaust around the wastegate flange based on the exhaust soot on the manifold.

Also I always recommend getting your boost reference from the intake manifold. Otherwise any restriction in your intercooler will make you underboost.

Have you checked your vacuum lines to the BOV? Is your BOV possibly opening under boost?

Don't give up! Really nothing too difficult here. Just double checking a few little things. 🙂
 
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doublespaces

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I don't know jack about the Jb4 so I can't really help there. But if you want to isolate the mac solenoid wiring and jb4 from the equation, just unplug the EV1 connector. That would be my first recommended troubleshooting step.
 

Cruizinmax

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I don't know jack about the Jb4 so I can't really help there. But if you want to isolate the mac solenoid wiring and jb4 from the equation, just unplug the EV1 connector. That would be my first recommended troubleshooting step.
Nothing the Mac solenoid is capable of will allow the car to hit less boost than the wastegate spring.
 
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doublespaces

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Nothing the Mac solenoid is capable of will allow the car to hit less boost than the wastegate spring.

With a broken/malfunctioning mac solenoid blocking the top port, you'd have 10 psi of boost on the bottom of the wastegate diaphragm and zero on top. You don't think that would help crack it open on a 1 bar spring stack combined with the exhaust back pressure itself?

This may not be the issue it's just the first thing I'd check. Saying it's on map 0 doesn't actually eliminate any of those potential causes but unplugging it does which is why I suggested it.
 

Cruizinmax

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With a broken/malfunctioning mac solenoid blocking the top port, you'd have 10 psi of boost on the bottom of the wastegate diaphragm and zero on top. You don't think that would help crack it open on a 1 bar spring stack combined with the exhaust back pressure itself?

This may not be the issue it's just the first thing I'd check. Saying it's on map 0 doesn't actually eliminate any of those potential causes but unplugging it does which is why I suggested it.
All good! The situation you are describing is exactly what happens at 0% duty cycle which is the same as unplugging the solenoid. All the boost is sent to the bottom of the gate and 0 to the top. A 1 bar wastegate spring doesn't necessarily crack open at 1 bar of pressure. Normally it's slightly higher for the reason you are stating. It's to counter the pressure in the exhaust manifold.

Say hypothetically your Mac valve was faulty and keeping any air from going in or out of the top port of your wastegate, that would also raise boost because it wouldn't allow the gate to open.

You can do the unnecessary steps of unplugging the solenoid if you want but I can promise you the solenoid has NO way to lower boost below your wastegate spring.
 
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doublespaces

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Say hypothetically your Mac valve was faulty and keeping any air from going in or out of the top port of your wastegate, that would also raise boost because it wouldn't allow the gate to open.

I follow you now. I think I've been away from my car too long and I'm trying to be smart.

I get my reference from a manifold barb so I know my wg follows my TMAP as closely as possible, but plenty of people get their reference from the comp housing port and don't seem to have issues. Maybe a charge pipe leak like mentioned... or improper n20 sensor scaling? 10 psi wg spring? Just throwing mud at the wall now.

Either way the boost curve looks pretty wobbly, something definitely seems off.
 

martymil

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If you can hit spring pressure with the Mac solenoid disconnected there is a problem with your wastegate period.

Either your wastegate is stuffed or your v bands are warped not letting the wastegate fully shut to fully hit spring pressure.

The least amount of boost you should see is 12psi with a 14psi spring if the mac solenoid is electrically disconnected
all the way through the rev range
 
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Arrtus

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Apr 24, 2021
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Thank you everyone that has been providing suggestions and feedback, I really do appreciate it.

Today I did another leak test, except this time I got a pressure regulator hooked up so it was more controlled and consistent. I fed ~25 PSI into the system and saw that the charge pipe was leaking air, sounding like a small vacuum. I put a new o-ring from BMS in it but the leak is still there. I guess the CP is just junk? I think it's an ARM CP but I don't know if that's even a good brand or not judging by the way it's leaking.

I know a small amount of air may be normal to leak from around that area but this just seems like too much.. I tried to have the JB4 read the boost electronically from my phone with the ignition on but it didn't seem to work. Anyway, I guess I will purchase another CP and see if that fixes it. Hopefully it does so I don't have to keep bothering everyone on here. :tongueclosed:


 
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