on the side of the intake just forward of the transmission dipstick there is a small plugged port, i am thinking about using that port to run the boost gauge to.

anybody know were we can get "banjo" fitting and bolts from? i asked the guy at napa and he has them on brake hose ends but nothing for this type of application. I had the plug with me and they don't didn't have anything straight thread that would work, he said this should work and handed me a fitting that was close but had a different thread pitch and was tapered.

hard tracking do stuff like this when you live in a small town

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"NEW" 1984 300D TD needs some love

I just teed into the ALDA line. No need to add another port to the intake.

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

I was wondering about doing that too, it is probably the easy way out, then started looking for parts for the other hole.....maybe go back to the ALDA line

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"NEW" 1984 300D TD needs some love

Plus if your boost gauge ever stops working you'll know that your ALDA line might be plugged.

-Rog

what kind of boost are your seeing?

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"NEW" 1984 300D TD needs some love

Stock I was seeing right at about 7-8 psi. I've searched and didn't find a definitive answer as to what it was originally supposed to be, but lots of people were reporting 7-9 psi, so that's probably close.

-Rog

I'm showing about 9.5 psi. max. I set my 0 pressure point at the house which is 1100 ft. So at sea level I generally show about .5 at idle. I guess that means I'm really at 9.0.

If you can find a 85 300D in the junk yard you can get the ALDA fitting with two connections. One connection is for the vacuum amplifier for the 722.4x transmission (the so called "blue flying saucer"). This makes the connection really simple.



Alternately, you can just use a simple T connector like I've used here. This Tees into the ALDA line ahead of vacuum switchover valve.



Why do I have two taps to the ALDA line? I'm actually running two boost gauges, one as part of my engine instrumentation project



and another one where I repurposed the vacuum gauge for a boost gauge by repositioning the needle to read 0-10psi vs 0-30 inches of vacuum.

Attached Thumbnails

   

__________________
Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

I just cut the line going to the valve on the firewall, i didn't think until now i should have put it after the valve to monitor if the valve is opening....... guess i need to crawl back under there, but at least i know that my power issues isn't the turbo as i am making the same, 9lbs of boost i'm at 3400ft, i have cycled the valve and i know it's working so maybe hold off on changing it just now, looks like it's injector time....

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"NEW" 1984 300D TD needs some love

Since altitude was mentioned, I'm just shy of 6,000 ft, so that may be a factor in my stock readings.

-Rog

Definitely. At 6000' you will be reading, on average, 3.1 psi less than at sea level. If you look at the typical boost/vacuum gauge, the zero point is not a line, but rather a "range" of 2-3 psi.

__________________
Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

so after it warmed up and on the way home I show the same as mach4 right around 9.5 almost 10 pounds of boost.

the guy with all the youtube videos talks about servicing the turbo and says that a properly functioning turbo is the different of being pushed back in your seat or not..... don't know that they did that off the showroom floor, but if you are building boost and it's pushed to the limit, aren't you pretty much just maxed out, not like a new turbo is going to give you more.

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"NEW" 1984 300D TD needs some love

That would be correct. If the turbo is putting out the max recommended boost, rebuilding that turbo will do absolutely nothing. The reason for rebuilding a turbo is generally related to leaks, worn bearings, damaged impellers or something similar.

It's amazing how reliable and trouble free turbos are given the speeds and temperatures that they operate at.

__________________
Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

that's what i was thinking, i have had them in a couple trucks and never had a problem with them but they didn't have as many miles as this car. Once i get the injectors taken care of i will check the turbo for end play, if OK will leave well enough alone.

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"NEW" 1984 300D TD needs some love

I figure as long as I am running a boost gauge I don't need the Alda.

I just plugged my boost gauge directly into the ALDA port at the back of the intake manifold.

Stock my car would not show boost until 60 mph and then it would go straight to 5-6. The max was 9. Turns out that in 85, Mercedes put an ARV valve on the car. The ARV basically bleeds the turbo pressure off without slowing the turbo.

Now even at 40 mph cruise I get about 3psi boost. At 55-60 I get 5 psi. Originally it maxed at 9 psi. I made a boost controller to trick the wastegate and could get it up to 14psi. I since have turned it down to 11 in deference to the age of the motor.

If you are pretty consistently at 6000 feet. The ambient air pressure is on the order of 10.8 psi instead of 14.7psi at sea level. Keep in mind that boost pressure is on top of ambient pressure.

What that means is that anything you can do to run an additional 2-3psi will make your car run like it was designed to.

I have threads on what I did a couple of years ago.

EDIT: Just read mach4s post. Guess we think alike.

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85 Merc 300D - Unwinding 31 years of wear
86 VW TD
Mahindra Diesel
Iseki Diesel

In 2007 I didn't own a diesel.