I can only imagine it has to do with American ingenuity ��

I have been reading through this thread since I received a used replacement turbo for my '91 350SDL FROM a '91 350 SDL. My old turbo does not have this extra gadget on the housing. The gadget I'm referring to is the part that looks like a vacuum line should be going to it. Make sense of this for me please.

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Was the pic any better?

From what I've learned from the person I purchased the turbo from this is a boost port. It reads manifold boost pressure and opens at high boost to protect the engine. It is my understanding that this connects to the intake.......somewhere.

What I DO Know:
Is that there would be no reason to connect the nipple,
in the location you describe it as being,
[The Turbocharger's Compressor housing] with the Intake manifold.
Since the Compressed Air (A.K.A. Boost) pressure in both is
the same,from the same source.

I believe there might have been a dis-enablement in communication
between yourself and the previous owner of the Turbocharger.

As soon as you get a little more illumination (light) on the subject of
your picture and Better resolution (Focus) it may be visible.

As it is now,who knows what, it is a picture of?

_________________________________________________________________

Straight answer (Por Favor):
Is there a hose connected from the Compressor Housing to the waste-gate Actuator?
Yes or No ?
Thanks

_____________________________________________________________________

The way you translated the P.O.'s (Previous Owner of the Turbo) information about
the "Mysterious" appendage to the "New to you" Turbocharger's Compressor housing
ALMOST sounds like the Boost Nipple necessary,to be connected to the Actuator.

_____________________________________________________________________

But,since you already have One(1) Turbo setup
(That came with the 126.135 350 SDL from Mercedes in Stuttgart)
You Should be able to make a Visible comparison of the New + Old (?).

__________________
'84 300SD sold
124.128

Yes, that was my attempt at sarcasm. Ha!

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The Black Rubber hose in the picture,to the right of the arrow,whose visible
end is plugged onto the Pressure operated waste-gate actuator's nipple.
Where is the other end of that hose ?
Is it Plugged into or onto anything?

Thanks?

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__________________
'84 300SD sold
124.128

Can you make out anything from this pic?

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So, the "push" actuator arrived. Installed it with the turbo on the engine.

With the fan/shroud/air-box-tube removed, there was just enough room to hold a drill against the round indent just below the flange at the top of the turbo. Used a 1/4 NPT tap (Harbor Freight) to make threads for a (Home Depot-sourced) 1/4" MIP brass barbed fitting. Stuffed microfiber rag in the top of the turbo first and shop vacuumed everything thoroughly after drilling and tapping.

Cut and threaded the actuator rod and installed with the waste gate lever pointing to the front of the car and tightened it down.

Swapped the "+" vacuum fitting on the driver's side for an "F" fitting. Swapped the EDS tube off the manifold/ALDA pressure circuit for a boost gauge tube.

Ran the boost tube with the other vacuum lines behind the display to a 15 psi VDO Vision boost gauge mounted in the center console (a whole other project involving a 2" hole saw, sandpaper, measuring and more measuring, and some anxiety).

So...THIS is what it is like to drive this car with a working turbo!

Boost tops out at 13-14 psi on downshift/WOT. Boost is responsive and comes on during acceleration and off on deceleration.

Much obliged for the good counsel ...

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Alright, well im not constantly flooring it but i do use my turbo. Like doing some pulls now and then. My 0-60 time is around 13 seconds so its not really faster then stock.

Im going to hook up a boost gauge so i can see what kind of boost im getting now with full vacuum to the wastegate.

That's a turbo from a 603.96 (86-87 SDL/D/TD) with ARV. The 603.970 in the 90-91 350SD/L didn't have ARV. There's no need to hook up ARV which IIRC is there to assist the trap oxidizer. Does the hose from the 350 air cleaner even hook up to that turbo? IIRC you can't just swap compressor housings to be rid of ARV since the 55 trim compressor in the 350 is bigger than the 50 trim compressor in the 300.

ARV gets a vacuum signal from the 'stuff' under the air cleaner as does EGR. Under specific circumstances, vacuum applied to the ARV opens a port that bleeds charge air from the compressor outlet to the compressor inlet. It's most definitely an emissions device rather than a performance device. The ARV in my SDL had a deformed plunger so there was a persistent boost leak even after the vacuum signal to the ARV was mysteriously disabled. I removed the ARV housing - no gasket to worry about - and set a freeze plug into the compressor outlet port to seal it. The port into the compressor inlet is an odd shape I couldn't easily seal so I left the ARV housing in place to keep it sealed.

You should have no problem running the 50 trim in the 350. It might seem peppier off the line with boost building sooner at the cost of less top end when the 50 trim runs out of breath. That's conjecture.

Sixto
MB-less

Nothing connects to the turbo from the air cleaner except the large air inlet pipe coming from the "box" under the air filter housing. Air comes into the air filter housing and flows downward through the box into the large pipe that connects to the compressor housing inlet. I've found nothing that would connect to this little "nipple."

That's the hose I suspect won't be a clean fit on the compressor inlet. My faded memory says the flange ends 20-30mm forward and is a few mm smaller. Your 350 won't have a vacuum amplifier nor an EDS signal to use ARV (not that you'd want to). You can use the turbo as is with ARV disconnected but I'd look into obtaining the correct turbo for your car. IMO, that one ain't it.

Sixto
MB-less

Could I just swap out the compressor housings? AFAIK the only difference is one has an ARV and the other doesn't.

Is this turbo from a newer 350 and would using it create more EGT'S? Less? This turbo supposedly came from another '91 350SDL.

You can try but I'll bet it won't work. Here are pictures from when I compared a 603.960 (87 300D/TD) 50 trim compressor housing to a 603.971 (92-95 SD) 55 trim compressor housing:

50 trim wheel in 50 trim compressor housing -



55 trim wheel in 50 trim compressor housing -



In your case you'd be fitting a 55 trim housing or a 50 trim wheel. It'll fit but you won't build much boost. As for the air inlet hose fitting properly:

Profile of 50 trim (left) and 55 trim (right) compressor housings -



I don't have clean pictures of the compressor inlet flanges. You'll have to measure those yourself.

You can see the ARV bleed port in the compressor outlet in the second and third pictures.

Sixto
MB-less

Thanks for the visuals Sixto! So the turbo, while not the stock turbo for a '91, will work in my car giving me more boost off the line but not so much when I'm at cruising speed. Correct? It's gonna take me longer to reach 120 mph with this turbo than the original. Correct? LOL!