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Adari,
What scanner are u using ? The 0299 Boost Pressure is too low DTC is not from Xentry if your engine is M276 3.0 Turbo with MED177V6LA engine computer.
Nevertheless here is how boost is actually measured by my engine computer :
#1 Pressure sensor before the throttle body and the #2 Manifold Absolute Pressure at the intake manifold which is after the throttle body.
So, it is not a single sensor job.
The 2 pressure sensors at the air filter housing also play a part, but not about turbo boost.
NOTE : Ambient pressure is a calcualted pressure using special strategy.
Boost pressure based on 2nd Xentry image is the one at the aftercooler, not the one at the intake manifold.....but....
You can't swap those two around, as they are part of the overall BOOST calculation, I am sure because they work at the boosted air region.
What separate them a part is one is after and one is before throttle body, so another X factor the engine computer need to calculate depending on throttle opening angle
They actually can be swapped. They are the exact same part numbers. So I did that and no change in engine operation. No other codes were set. So that just eliminated the possibility of a bad inlet pressure sensor.Thank you for providing a detailed explanation on the differences with each one of these pressure sensors. This sensor is the only one showing an inconsistent value at idle and when driving. What I found odd was the right side camshaft timing adjustment being -23 or so compared to the left side adjustment +32 or so. Hopefully this gets figured out. Soo frustrating.
I'm trying to upload a video showing exactly what is going on but this forum only accepts certain file extensions.
Yes the 2 pressure sensors can be swapped because they are the same P/N. I am just saying if either one is bad, DTC would still be triggered.
The autel screen shot somehow indicated in red for inlet manifold pressure or higher than it should be at that RPM and at that throttle opening value,
you best not worry too much. While it can mean vacuum leak or a bit poor cylinders suction, its too tiny a +13hpa overshot is.
========== What I found odd was the right side camshaft timing adjustment being -23 or so compared to the left side adjustment +32 or so
==========
I am in Bali at the moment and will be here for a month or so. My data laden PC is in Jakarta, so I will assist from memory.
Both banks have the same variable timing system for Intake & exhaust valve.
At 600ish RPM idle, Intake valve is +32 ish Exhaust is -23ish , in degrees.
I believe a 5 degree difference will trigger crank-cam correlation DTC already, so you best take a closer look at the Autel on the mentioned parameters as
your finding of -23 to +32 degrees difference between similar cam assignment on different bank is not possible and engine wont even start.
It seems you are mistaken and was seeing/comparing -23 exhaust at one one bank and +32 Intake on the other bank
5 degree is 1 jumped crankshaft tooth equivalent. Our cranksahft pulse wheel is 58 teeth and 2 empty = 60. 360/60 = 5 degrees per tooth.
Chain stretch can be seen using Xentry, I am sure Autel can too.
Out of spec 1.x degree is common. The accuracy of the camshaft sensor itself is about 1 degree, I scoped both banks inlet cam sensors once.
Do a search on this forum, I posted a few times technical manual for M276 3.0 turbo, it has the advance/retard degrees data for the variable timing.
Yes the 2 pressure sensors can be swapped because they are the same P/N. I am just saying if either one is bad, DTC would still be triggered.
The autel screen shot somehow indicated in red for inlet manifold pressure or higher than it should be at that RPM and at that throttle opening value,
you best not worry too much. While it can mean vacuum leak or a bit poor cylinders suction, its too tiny a +13hpa overshot is.
========== What I found odd was the right side camshaft timing adjustment being -23 or so compared to the left side adjustment +32 or so
==========
I am in Bali at the moment and will be here for a month or so. My data laden PC is in Jakarta, so I will assist from memory.
Both banks have the same variable timing system for Intake & exhaust valve.
At 600ish RPM idle, Intake valve is +32 ish Exhaust is -23ish , in degrees.
I believe a 5 degree difference will trigger crank-cam correlation DTC already, so you best take a closer look at the Autel on the mentioned parameters as
your finding of -23 to +32 degrees difference between similar cam assignment on different bank is not possible and engine wont even start.
It seems you are mistaken and was seeing/comparing -23 exhaust at one one bank and +32 Intake on the other bank
5 degree is 1 jumped crankshaft tooth equivalent. Our cranksahft pulse wheel is 58 teeth and 2 empty = 60. 360/60 = 5 degrees per tooth.
Chain stretch can be seen using Xentry, I am sure Autel can too.
Out of spec 1.x degree is common. The accuracy of the camshaft sensor itself is about 1 degree, I scoped both banks inlet cam sensors once.
Do a search on this forum, I posted a few times technical manual for M276 3.0 turbo, it has the advance/retard degrees data for the variable timing.
Thank you! You were right. Looks like I am within specs. I do hear a slight tapping during cold start up so I think it's time to service the timing chains and replace the tensioners.
So watching a video related to my boost issue, i think i may have found the issue. That one way check valve when applyimg pressure slowly leaks down. Im only applying about 13 psi. But it does leak down. Vacuum however does not hold. Do I need to test from a different end when applying vacuum or vacuum and pressure can be tested from the same port?
So watching a video related to my boost issue, i think i may have found the issue. That one way check valve when applyimg pressure slowly leaks down. Im only applying about 13 psi. But it does leak down. Vacuum however does not hold. Do I need to test from a different end when applying vacuum or vacuum and pressure can be tested from the same port?
When testing we have to follow the air path/direction, hence I only test vacuum and pressure at that point as per video, the end which is for intake manifold.
The check valve in discussion basically for mine, is healthy for its vacuum capability, it open easy.
For pressure it leaks a bit as per video.
If your engine is the same as mine, M276.820 333HP , my turbo is a comfort turbo and not a performance one.
I mean, the turbo boost mapping/table by MB is not brute force/power oriented, but smoothness-comfort and longevity is the priority.
So, the specified up to 0.8 BAR or 11.6psi will only occur at mid RPM and not near redline RPM.
I attached a log, go and see for yourself the turbo boost vs RPM vs throttle opening.
Please ignore the AFR values, it is wrong direction , opposite in fact.
Banks Gauge the maker of my OBD2 gauge logger did not get the data conversion from Lambda value to AFR correctly.
The rest of the data is good.
There is vacuum/boost data field for PSI reader and Absolute Manifold Pressure (MAP) in BAR which is easy to convert to hpa.
The calculation for converting hectopascals (hPa) into bar can be derived as follows:
Do remember, Absolute means ambient air pressure is read. So 1.6BAR at MAP means 0.6 BAR only is the turbo boost. Our atmosphere is like 1 BAR at sea level.
If we want to be ****, 1 BAR = 0.986923 ATM
As to how the turbo boost mapping is like, I never seen the actual table.
I just want you to know and do not get confused if you see turbo boost always lowers down nearing 5,000 - 6,000 RPM usually.
There are many other parameters factored in by engine computer to choose boost value and at what RPM, its not a simple calculation for sure.
When testing we have to follow the air path/direction, hence I only test vacuum and pressure at that point as per video, the end which is for intake manifold.
The check valve in discussion basically for mine, is healthy for its vacuum capability, it open easy.
For pressure it leaks a bit as per video.
If your engine is the same as mine, M276.820 333HP , my turbo is a comfort turbo and not a performance one.
I mean, the turbo boost mapping/table by MB is not brute force/power oriented, but smoothness-comfort and longevity is the priority.
So, the specified up to 0.8 BAR or 11.6psi will only occur at mid RPM and not near redline RPM.
I attached a log, go and see for yourself the turbo boost vs RPM vs throttle opening.
Please ignore the AFR values, it is wrong direction , opposite in fact.
Banks Gauge the maker of my OBD2 gauge logger did not get the data conversion from Lambda value to AFR correctly.
The rest of the data is good.
There is vacuum/boost data field for PSI reader and Absolute Manifold Pressure (MAP) in BAR which is easy to convert to hpa.
The calculation for converting hectopascals (hPa) into bar can be derived as follows:
Do remember, Absolute means ambient air pressure is read. So 1.6BAR at MAP means 0.6 BAR only is the turbo boost. Our atmosphere is like 1 BAR at sea level.
If we want to be ****, 1 BAR = 0.986923 ATM
As to how the turbo boost mapping is like, I never seen the actual table.
I just want you to know and do not get confused if you see turbo boost always lowers down nearing 5,000 - 6,000 RPM usually.
There are many other parameters factored in by engine computer to choose boost value and at what RPM, its not a simple calculation for sure.
So checking vacuum and pressure from the intske manifold source as shown in the video should vacuum hold when applied with a vacuum pump? I can only test pressure and the gauge leaks down slower than the guy was showing in the video but does leak down. I don't have boost when driving. I can press the gas pedal to the floor and I have no power. Not sure what is going on.
I did. Both seals are good. I did not do any measurements as shown on the post. Here is a link to my YouTube channel showing live data as I am driving.
There is got to be a leak somewhere. I would start checking vacuum from the vacuum pump, and all the way to the t that splits one turbo to the other. That shaking indicates a mechanical leak.
There is got to be a leak somewhere. I would start checking vacuum from the vacuum pump, and all the way to the t that splits one turbo to the other. That shaking indicates a mechanical leak.
I'm going to dig deeper into what is causing this issue tomorrow. I have a few tools to regulate some air and see if I can find this leak.
Hahaha, thanks for the tip. I just bought my GL and I haven't got a chance to get her detailed and cleaned up yet. I definitely will get her cleaned up after I find this issue and replace both engine mounts that came in today along with a fresh oil change. There is so much to learn on all the features this beauty has to offer. I can't wait to really enjoy it. I'm hoping I solve this issue before 4th of July weekend.
Do a vacuum decay test.
From vacuum pump at Bank2 or Left side bank, the small plastic hose to Y split goes to two of the vacuum actuator.
See if both vacuum actuators can maintain vacuum, see if vacuum value produce equal pull on both vacuum actuator or not.
Tasos of Dubai has video showing vacuum actuator defective from oil inside it. Yep, oil from vacuum pump probably.
While at it , you can also and need to make sure your vacuum pump at Bank2 is healthy. This pump consumer is only the brake booster and the 2 turbo vacuum actuator.
See how stable is the vacuum reading at idle with brake pedal depressed a few times.
Here we are only discussing mechanical.
It could also be your issue is electrical, for example bad contact or wiring to the boost controller solenoid which produces intermittent action and that mean
boost leak will occur because boost controller solenoid is not allowing enough vacuum to pass thru to vacuum actuator at turbos.
Get MiytVac vacuum & pressure pump kit https://www.amazon.com/Mityvac-MITMV.../dp/B0002SQYUA
Do a vacuum decay test.
From vacuum pump at Bank2 or Left side bank, the small plastic hose to Y split goes to two of the vacuum actuator.
See if both vacuum actuators can maintain vacuum, see if vacuum value produce equal pull on both vacuum actuator or not.
Tasos of Dubai has video showing vacuum actuator defective from oil inside it. Yep, oil from vacuum pump probably.
While at it , you can also and need to make sure your vacuum pump at Bank2 is healthy. This pump consumer is only the brake booster and the 2 turbo vacuum actuator.
See how stable is the vacuum reading at idle with brake pedal depressed a few times.
Here we are only discussing mechanical.
It could also be your issue is electrical, for example bad contact or wiring to the boost controller solenoid which produces intermittent action and that mean
boost leak will occur because boost controller solenoid is not allowing enough vacuum to pass thru to vacuum actuator at turbos.
Thank you for providing me with some direction. I have a vacuum/pressure pump kit. I tested at the 3 way tee and vacuum is not holding. So I tested both wastegates individually and the driver side bank2 does not hold. Bad wastegate.
Ok, u meant the vacuum actuator.... not the wastegate itself.
In MB EPC this actuator is not sold stand alone, it is part of the turbo.
Maybe ask Tasos, where he sourced his vacuum actuator.
I don't mind keeping 2 for spare too, rubber membrane WILL fail overtime, it is given.
Some learning, membrane based vs o-ring based vacuum actuator, but aftermarket ones
Ok, u meant the vacuum actuator.... not the wastegate itself.
In MB EPC this actuator is not sold stand alone, it is part of the turbo.
Maybe ask Tasos, where he sourced his vacuum actuator.
I don't mind keeping 2 for spare too, rubber membrane WILL fail overtime, it is given.
Some learning, membrane based vs o-ring based vacuum actuator, but aftermarket ones https://youtu.be/GnOE_JpQzpQ
I meant the wastegate itself. Removing the small vacuum hose attached to the nipple on the wastegate and applying vacuum does not hold. I did the same test on the passenger side bank 1, and as you see, vacuum is stable. The membrane inside the wastegate no longer holds vacuum
OK, it seems you got the name of the component wrong.
Waste gate is this item : sample only, not unit for our engine
Vacuum actuator for wastegate is the leaking one you speak of ...correct ? :
Vacuum actuator is a common device used for many applications, not only for turbo's wastegate actuation.
OK, it seems you got the name of the component wrong.
Waste gate is this item : sample only, not unit for our engine
Vacuum actuator for wastegate is the leaking one you speak of ...correct ? :
Vacuum actuator is a common device used for many applications, not only for turbo's wastegate actuation.
Yes the acuator. Not the wastegate flap.. Even though the flap does have a good amount of play. I'm sure as soon as i remove the actuator rod from the flap, i will be abje to wiggle it around. The process to replace the flap seems pretty straightforward but a good deal of work. Any idea where I could find a replacement vacuum actuator or an updated version? I found some mamba style ones but I'm not too sure if they will work on our turbos. At this point, I'm considering just replacing both turbos or have them rebuilt, whatever way is cheaper lol
I think ask Tasos of Dubai where you can buy the vacuum actuator, he buys alot for the AMGs
Wastegate flapping around when not being pulled tight by actuator does not mean it is a leaking unit.
I think ask Tasos of Dubai where you can buy the vacuum actuator, he buys alot for the AMGs
Wastegate flapping around when not being pulled tight by actuator does not mean it is a leaking unit.
Not sure which ones you have, but the ones in the M278/M157 are Honeywell/Garrett.
The M276 was build a bit after the M278, and it looks like the actuators are completely removable.
yes, they can be replaced. They are not available to purchase separately from MB, of course they want you to buy the whole turbo. I'm trying to find a used turbo in the market place or someone parting out. So far no luck. Im in Michigan so I might find someone.
Curious If the m278 turbos are direct bolt on to our m276 engine? When it comes to upgrading, are the Garrett's the next option? The reason I ask is because I found a set of used turbos off of a gl550 and now that I think about it, I'm wondering if I can use just the wastegate vacuum actuators or install the turbos.
Curious If the m278 turbos are direct bolt on to our m276 engine? When it comes to upgrading, are the Garrett's the next option? The reason I ask is because I found a set of used turbos off of a 2018 gls550 and now that I think about it, I'm wondering if I can use just the wastegate vacuum actuators or install the turbos. I read that the gls550 use a Garrett turbo. Any help would be appreciated
2016 E400 4Matic, 1994 Mercedes Benz E320 Sedan (Sold), 1995 E320 Wagon (Sold)
This thread is awesome! Thank you @S-Prihadi! My E400 has always had a fluttery acceleration issue since I bought it with 46,000 miles. Is there a way to definitively test the boost pressure actuator using Xentry? Or a way to test it with a vacuum pump?
06-23-2022, 10:30 PM
