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Hey guys I seem to been able to make more than 7 psi on my M278.
So I took the tune out, and checked the boost... again 7 psi max.
No codes, and no CEL.
Can someone take a photo of both wastegates? One looks in a different position than the other one for some reason. And I am trying to find out what is normal.
I dont have a boost decrease as much as yours.
My engine is supposed to be a 0.8 BAR ( 11.6 psi ) boost, I am seeing 11 psi.
I have updated the thread on the boost controller, on how Xentry kinda fooled me.
Your engine if an M278 DELA46 ( E500, not E550 ) supposedly a 0.9 BAR boost or 13.05 psi
Don't blow 115 psi shop air into the boost controller, that solenoid is delicate. Even in a positive pressure mode application, I doubt any turbo will create boost more than 2.5 BAR or 36 psi.
Use vacuum pump to test, if you want to test.
AT THE SOLENOID ( boost controller ):
Smaller hose barb is to engine's vacuum pump.
Bigger hose barb is to the turbos using Y hose connector.
The small rectangular box near the 2 hose barbs is actualy a vent hole, like a 3rd airway.
This is a fail safe design when use in vacuum application, with no power the solenoid valve will "leak"...meaning no over-boost can occur.
When not applied PWM power to the solenoid, or not applied simple 12V power :
01. Sucking the big hose barb with a vacuum pump will get air from the vent.
02. Sucking the small hose barb and with the big hose barb plugged off, it will not hold vacuum...it will minor leak.
I have not tried above with 12V power applied to the solenoid.
This is not a simple OPEN/CLOSE solenoid, picture it as an adjustable air valve, the ECM via PWM signal/power commands the value of the opening of the valve like a push-rod, so to speak.
So the amount of suction can vary which, equals to more boost by manipulation of the wastegate round flap door at the turbocharger via the vacuum actuator unit.
NOTE 1 : Above scenario assumes a healthy turbo and a healty vacuum actuator unit and a healthy wastegate flap door + its bushing
NOTE 2 : I have not messed with the solenoid by appling simple 12V power.
Since 1 boost controller solenoid is connected to both turbos vacuum actuator unit, assuming all the vacuum hose from the solenoid to its Y split and then hoses to the turbo's vacuum actuator has no pin hole leak,
the pull movement distance of the vacuum actuator rod should be the same for both turbos.
These are my turbo vacuum actuators and the NEW boost solenoid "behaviour" as is.
BELOW : if you don't see max out 30 inchHG with engine idling, your engine's vacuum pump is probably worn out.
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.
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Below, vacuum pressure will hold for easy 3 minutes with only minor 10% drop* ( *minor leak from the hand-pump simple rubber valve) if there is no leak at the hoses/plastic tube and the vacuum actuators
VIDEO - Sorry it is kinda upside down , flip wrong during edit. My apology
I took the actuator out. And blew on both ends of the vaccum hose connectors, closing one end at the time, and I got a trumpet sound.
Trumpet sound while vacuum applied by engine's vacuum pump when you removed the hose for the turbos, means your valve is already weak ( could leak too ), and/or the magnetic coil is weak too aka not pulling enough.
Mine does that too if I tried a few times connecting & disconnecting the hose for the turbo.
ADD more info : This is also one of the reason it is good to replace the booster control solenoid, for my case. This is simple engine warm up. When I run engine long enough and hot enough, it would probably get worse. Below is at idle, from cold start.
Last edited by S-Prihadi; 12-05-2021 at 07:59 AM.
Reason: add info
...Nope, that is not normal.
The pull rod of the vacuum actuator should retract steady, like mine.
Get the cheapo vacuum pump like mine, or better yet, buy a GOOD one for long keeping :
Without a vacuum hand pump and its gauge, its kinda difficult to verify things vacuum related.
See if the other side/bank vacuum actuator has the same shake , if both the same, it means the boost controller solenoid internal valve is minor leaking.
If only 1 side shake like that, could be the diaghram of the vacuum actuator itself has a minor leak.
This is why the vacuum hand pump kit is a must have to assist and speed up troubleshooting.
Leaking on the forced induction side from turbo>>aftercooler>>intake manifold is another possibility, aside from that shaky-shaky vacuum actuator of the wastergate.
Thanks to you ( coz I ended up doing Amazon search on vacuum pump )... I just ordered the GOOD vacuum hand pump kit, that MityVac. It can also do pressure...YIPEEE.
Swapped wastegates solenoid/actuator. No more shaking of the wastegate rods. Will go for a drive this evening to see how it runs, and get some datalogs.
Well problem is still there. The shaking on the wastegates stopped, and I can visually see the rod moving back and forth when I plug and unplug the actuator and hose. Smooth movement. But still the car shakes hard, very random. It can vary from slight to hard throttle. AFR commanded, and realtime looks good. No knocks on history on any cylinder.
I gonna have to wait for the pump.
It's frustrating because, most people with the same problem (same engine)disappear or are cryptic with the solution.
If you remember my other post, I had some bad motor mounts, which broke the driver side axle boot.
I took it to the dealer which fixed the mounts, and boots.
When I picked it up it was super cold (for Florida) 32f. I laid on the car, and the whole car shook hard (once). I thought they had screwed up something on the repair.
As I tried to slowly try again, and the car started to feel smooth again. To the point that when I got back to the dealer is was back to normal.
I attributed it to the rubber being new, and the weather being cold, it was causing the car to shake.
I told them if the issue came back I would let them know.
Now 2 weeks later, I am driving the car to work, and I noticed the car feels slower than usual.
Down the road I laid on hit hard, and it shook like when the dealer gave me the car.
No check engine lights, so I figured it was a drivetrain issue, but then I got thinking: why is the car feeling slow.
So I started datalogging, and noticed when the car ran smooth (but slower than usual) it would not get past 7.8PSI, and if it got past 7.8PSI it would shake violently.
So I started from there, since the car is not throwing any codes.
Also I want to throw this just in case. There is oil inside the line coming between the vacuum pump (rear of the engine), and the solenoid actuator. Isn't the check valve on the picture below supposed to stop that from happening?
I do not know about this check valve, but I seen from the below video, a senior mechanic in Dubai called Tasos, the wastegate vacuum actuator can get a lot of oil inside it :
Well I may have troubleshot this, and it may have been unrelated.
So my car is now on full boost, but the shaking continues.
The shaking seems to be related to a job done, by the dealership. (where they swapped the driver axle and motor mounts).
Now they tell me the shaft that holds the axle needs replacement, and told them why the tech did not tell me about while he was swapping the boots on the same side he was working.
I am livid. Is there a decent MB dealer around. They are going downhill quick. I think these cars are getting to complicated for them.
I had to explain to the service advisor that the part he just to quote me for, directly connects to the part the tech just worked on.
So the boost controller your replaced and now the full boost you are getting ( excluding the shaking ), was it only the boost controller or what else was the issue ?
I’ve been hunting down my positive high fuel trims for a while and what you guys discuss may be the solution. The car acts like it has an air leak. Smoke test showed nothing, exhaust has no leaks. 2 dealerships and 1 Indy Mercedes’ shop couldn’t diagnose it.
Also, I couldn’t tell I’m missing boost since it does that since I bought it used. I thought it had full power.
At boost I get somewhere around 45 inHG. Car is a 2012 E550 coupe with 63k miles.
Upon inspecting the actuator, I found out that it is shaking at start and most likely not sealing properly. Also it has a little play as you can see. Videos below.
I plan to clean/replace the solenoid and take it from there. How hard is to fix the play of the rod?is it normal to have a little play?
The rod having little play is normal, wastegate normal rattle is like that. Don't mess with the pull rod, unless the vacuum actuator need to be replaced.
The sound suggest the boost controller is the bad boy. https://mbworld.org/forums/e-class-w...76-3-0-tt.html
45 inch HG at boost is 1.5 BAR manifold absolute pressure or 0.5 of it is turbo boost, 1 BAR of it is our atmosphere at sea level.
M278 max boost is 0.9 BAR, so your manifold absolute pressure would read 1.9 BAR.
My M276 3.0 Turbo is supposedly 0.8 BAR of turbo boost, but this is max and 0.7BAR is what I usually get.
I hope it is the Y771/1 Boost Pressure Actuator.........otherwise it will be expensive
Good luck...
Got back from the dealer yesterday. They were able to replicate the issue with hard shifting to the 4th gear and their diagnostics see no other code than P029900, which is low boost pressure of turbocharger (driver's side). Guided test showed Y77/1 valve does not have correct duty cycle. Vacuum tested waste gates and found the left side internally leaks down. Offered solution - replace the left turbo, which is almost $4K, including everything. No TCU codes or anything related to the tranny. They explain that there's not enough air to provide smooth shifting and this is the culprit. I can buy this when I'm accelerating and it shifts down from 5th to 4th to have more power, but when I'm decelerating and it goes from 7th to 4th I'm wondering how it happens at all.
I doubt this is going to help, but who knows... The only concern now is the price. I saw some used turbos from junk yards are around $500 (up to 70K miles on them), plus labor. So thinking of doing that in a few weeks maybe.
Any suggestions or thoughts?
Are there any ways to fix that internal leakage? Or the part is worn out an need to be replaced?
Got back from the dealer yesterday. They were able to replicate the issue with hard shifting to the 4th gear and their diagnostics see no other code than P029900, which is low boost pressure of turbocharger (driver's side). Guided test showed Y77/1 valve does not have correct duty cycle. Vacuum tested waste gates and found the left side internally leaks down. Offered solution - replace the left turbo, which is almost $4K, including everything. No TCU codes or anything related to the tranny. They explain that there's not enough air to provide smooth shifting and this is the culprit. I can buy this when I'm accelerating and it shifts down from 5th to 4th to have more power, but when I'm decelerating and it goes from 7th to 4th I'm wondering how it happens at all.
I doubt this is going to help, but who knows... The only concern now is the price. I saw some used turbos from junk yards are around $500 (up to 70K miles on them), plus labor. So thinking of doing that in a few weeks maybe.
Any suggestions or thoughts?
Are there any ways to fix that internal leakage? Or the part is worn out an need to be replaced?
In red is my remark, on your statement: let me explain.
DO NOT trust Xentry duty cycle of 70% and up for Y77/1 if at engine idle and not boosting the turbo. 45% duty cycle is a good brand new boost controller and all vacuum pump + wastegate actuator healthy, but at idle.
Read here and go to Number 2 subject on how Xentry is sometime misleading. https://mbworld.org/forums/e-class-w...rors-note.html
Ancore wrote : Vacuum tested waste gates and found the left side internally leaks down.
How do they test the wastegate coin shape flap ? It is not easy to test wastegate coin flap without un-doing a lot of parts. Example of the wastegate is below :
At best they can only test the vacuum actuator which is the one pullling the actual coin shaped wastegate.
This is the vacuum actuator and indeed, use vacuum to test it is the proper way and sometimes it may have lots of oil inside from the check valve failure at vacuum pump.
Read the test here , the actuator for wastegate section: https://mbworld.org/forums/e-class-w...rity-test.html
We need to make sure that you are getting a proper and honest diagnostic.
Thank you for the reply.
They took the car for a day to complete the diagnostics. What they ended up with is the actual error code that sits in the memory, P029900. So they did the diagnostics (whatever they had to do).
This is what I heard from them that day. Below you see the message that was left as a solution from them.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
OK, how does the waste gate "leak down" since it is a simple mechanical door controlled by the actuator. My understanding is that our waste gates are normally OPEN to avoid a failure in the vacuum line causing engine destruction. With NO VACUUM, the waste gate will be open and is only closed on command as long as there is adequate vacuum and the controller signals the actuator to close. Unless the waste gate flap has broken off, it's not a wear part that should "leak". Otherwise, you would have NO boost from the left turbo.
While the waste gate may not be separately available from Mercedes, I would be interested to see if the manufacturer (Garrett?) offers it separately. Also, you may want to contact Weistec since they modify and rebuild our turbos (at least for the M276.8XX engines).
Were you thinking of doing the work yourself with a used turbo? If so, I would definitely try to find a replacement part first.
12-04-2021, 12:59 AM
, flip wrong during edit. My apology
