S-Prihadi

That is what I always remember when Cali explained his car improvement with his engine oil pump solenoid disconnected/defeated.

The last 24 hours I was looking at ways on how to buy alternative brake booster hose which MB has stop production for my RHD car with pariah engine M276.8 3.0 Turbo.
The sad story is here : https://mbworld.org/forums/e-class-w...cuum-hose.html

There then I realized that M276 3.5NA uses its vacuum pump to also feed vacuum power needs for the intake manifold 2 stage flapper of M276.9 3.5NA, just like M272 I think.
Even M278 has vacuum pump connection into its intake manifold.
So only M276.8 3.0Turbo does not use any vacuum suction support for its intake manifold. Vacuum pump purely only for brake booster and the small turbo wastegate actuators.

Here I am trying to understand how Cali got the improvement on his brake booster.

M278 - Vacuum pump hose/pipe going to the brake booster also has a tee connection to intake manifold.





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M276.9 3.5NA

1 in red is to vacuum pump. 2 in red I suspect to brake booster via firewall pipe-hose interface. Anyway, the point is vacuum pump get shared with 3 components.
Big port of vacuum pump shared by intake manifold and brake booster
Small port of vacuum pump also goes to intake manifold and I suspect it is the two small vacuum actuators called switch-over valves on the Left and Right side of M276 intake manifold assy.






The actual vacuum hose at vacuum pump looks like this, item #40.



Lesson learnt. Now I do not trust EPC hand drawn component shape. I came across many hoses and pipes drawn too simple and basically misleading aka wrong shape/bend/tee.
The only way is to go to Ebay and hope someone has a used one for sale and the actual P/N is shown on the component to verify.

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See, the Tee exist in the real vacuum hose/pipe but not in EPC drawing.






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I want to ask M276.9 3.5NA engine owners.
The intake manifold connection to vacuum pump BIG PORT one, is that for the SELECTOR DRUM of the intake manifold ?

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Back to the brake booster improvement for Cali M276.9 3.5NA engine with engine oil pump solenoid disconnected/defeated.
The vacuum pump uses engine oil not only to lubricate its moving parts, the oil is the actual deep vacuum agent. Without the oil film, the vacuum pump vane will leak and no deep good vacuum can occur.





Now it make so much sense when Cali is seeing improvement for his brake booster.
Now at low RPM his vacuum pump is getting good oil flow and hence is working better even at low RPM and that means the reserve capacity of vacuum power is good.
I do not know if that M276.9 intake manifold SELECTOR DRUM which I believe is using vacuum to operate, also now moves faster because of better vacuum supply and that aside
from VVT sprocket getting good oil at low RPM being very happy..... is making the so much improved engine response improvement for Cali's non turbo M276.

I wonder M278 vacuum pump port into the intake manifold, what does it actually do ?

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M276.9 3.5NA owners, please chime in.

JettaRed

iTrader: (1)

Here are some pics from my 2014 C350 (W204.057 M276 NA). The first two show the larger pipe running from the "T" in the vacuum circuit to the brake booster. The third just shows the other branch pipe connecting to the front of the intake plenum. Now that you explained your theory for the improve brake response, I do remember the brakes seeming a little touchy, but I just thought it was because I seldom drive the C350 when I have the SL400 available. I do believe the smaller hoses coming off the vacuum pump connect to the flap actuators. I recently replaced the spark plugs (what a pain in the butt!) and remember only pulling the small rubber hose off of the vacuum pump and not off of the intake.

I will say that having a GLB250 loaner while the SL is in the shop for a week and a half, driving the C350 is really a pleasure. The engine has substantial power and growl, where the little 4-banger in the GLB sounds (and feels) like a sewing machine.

CaliBenzDriver

The seal improvement of the piston rings working with oil leads to less crank ase pressure. We know the vacuum pump breath into the crankcase through a metallic reed valve, right?

Also the pump uses residual oil pressure for internal lubrication and dynamic seal.

We've seen how turbo engines have an habit to destroy the pump tiny check valve.

What was most interesting is how/when the shift from regular brake booster to have a nice touchy brake pedal. Many improvements took a long while to show up... that tells me it's not just the ECU software self-tuning. The piston rings were cleaning up and the results were welcome. Vacuum is the most direct connection between the engine and the brakes besides ESP CAN-C.


Lately the cold engine starts at very reduced 1200 RPM and quickly the high idles normalizes into the 600RPM idle. Way less than a month ago. I don't even think it has time to heat the two lambda PWM heaters to enter closed loop.
I think the ECU has enough data collected, the ECU is able to compute the perfect mixture and the engine can handle what the software throws at it. That GDI is tricky in a good way lately.

The rattlesnake idle is mostly gone. Its only oresent when cold now. The GDI idle sounds like a diesel. the torque at 1000.RPM is unreal because the cylinders are all balanced individually by the ECU.

These are just words to describes what I hope you will experience with your engine. This ECU is super responsive with all its sensors and self-adapted maps ... THAT'S A REAL LUXURY SW TECHNOLOGY

The heat management seams to be improving with its.learning of continuous cool8ng. Before the very engine core was not well cooled. I think Juan special MOTUL oil has veen very beneficial towards better cooling (no engine fan) and perhaps the improved cold idle RPM too. Honest viscosity really delivers easy improvements!!!
More power, less heat... sounds like improved ownership longevity.
PPL that were expected to get scalped are gona like a fantastic ride with minimal drama.

Unfortunately I picked up a front end vibration down the street. They must have been excavating for new service lines across the roadway with a poor temporary covering...
My driver side front wheel as veryical play between 12 to 6 only. Nothing horizontal from 9 to 3.
I have marked and rotated the wheels when I got all 4x genuine German CONTIs. Good thing is shaking did not follow the wheels.... good chance my ugly comfort wheels not bent after all . I need to rate driver front.

My short list involves
(bent front rims??)
lower ball-joints freeplay <<
front control arms
(not wheel bearings!)
At 55kMi I am going to commit to early front end maintenance - No problem! I had a swaybar links on hand already.

Just when that car was driving well.... bingo the weak parts creep in.

S-Prihadi

Thank you Jetta, that was very good photos for me to see how M276.9 LHD car vacuum hose/pipe set up is.

JettaRed

iTrader: (1)

Here's a pic of the large vacuum line coming off of the vacuum pump. The hard pipe runs under the edge of the intake plenum and branches off to the brake booster (as shown above) and to the front of the plenum (also as shown above). The rubber hose with the red X on it is not the vacuum line.

S-Prihadi

Aha, the LHD E350 W212 vacuum hose to the brake booster enters ( transition point ) the firewall/heatshield that much further away than in a RHD car.

JettaRed

iTrader: (1)

Vacuum pipe from passthru to brake booster.

Vacuum connection from pump line to booster.



Some more. The brake booster pipe runs under the strut brace to the booster.

JettaRed

iTrader: (1)

Vacuum to Booster.