Turbocharger Boost Hose: Connection & Oil Issues

Hello everyone,

I installed a boost pressure gauge in my Audi 80 1.9 TDI (model 1Z, manufactured in 03/94) and ran a pressure hose for it. In the engine, I connected it as shown in the picture. At this location, there was an outlet that had been capped with a blind plug.

Now I have a problem where oil is getting into the hose, which is clogging the sintered filter in front of the display and causing it to stop working.

- Did I connect the hose to the wrong place?

- Is my turbocharger faulty? (I've read that this can be a cause of oil in the air intake hose). However, everything else seems to indicate otherwise, as the engine is producing its full power and there are no unusual noises.

"Thank you!"

Hello Tino!
You can be completely sure that a certain amount of oil entering the intake manifold through the crankcase ventilation system is perfectly normal.
However, I'm a bit surprised that the oil is reaching your LDA, as there should only be a static column of air in the pressure hose, which is either compressed or decompressed. There shouldn't be any "flushing" of the hose, so the oil wouldn't normally be carried along unless you have a small leak somewhere in the area of the LDA.

It's possible that the problem is due to the fact that your connection point in the engine compartment is located very high, and the hose routing to the LDA (Lambda sensor) constantly slopes downwards. This means that gravity causes oil to slowly seep through to the LDA.
Furthermore, your outlet is located in a very unfavorable position from a fluid dynamics perspective because the airflow at this point is deflected downwards by 90 degrees. This causes particulate matter (oil droplets) to be separated by centrifugal force precisely on the side of the impeller where your connection is located.

My suggestion: Try connecting the pressure hose to a different, lower location. I'm not familiar with the 1Z engine. In my car, for example, there's an option near the cargo area outlet. From there, a pressure hose runs to the boost control solenoid valve (N75). If you disconnect this hose and use a T-connector to connect it to the LDA (Lambda датчик), the chances of eliminating oil leaks are quite good.

Regards,
Alex.

Okay, thanks... that's reassuring to know. Could it be that I'm actually tapping into the pressure line behind the EGR valve, and that's also causing some dirt to get in?

What is that small tube located at the bottom edge of the image, in the center? Is that the mass airflow sensor (MAF)? Is that location before or after the turbocharger?

Hello Tino!

Quote:

Could it be that I'm actually tapping into the pressure even behind the EGR valve, and am also adding dirt to the system in the process?

Yes, exactly! Directly across from your filling point is the membrane valve for the EGR (Exhaust Gas Recirculation) system operation.

The hose located centrally at the bottom of the image connects to the intake manifold before the turbocharger. Immediately after that, a branch from the crankcase ventilation system (KGE) is visible (the pipe coming from the right side of the cylinder head). From here, all the oil enters the intake tract!

It's a bit harder to see in the picture, but there's the pressure sensor of the turbocharger. Trace the hose that's connected to this sensor all the way to the solenoid valve. There are two more connections there. One is connected to the pressure side of the turbocharger, and the other is connected to atmospheric pressure (e.g., it vents into the air filter housing or the intake manifold before the turbo). If you install a T-piece in the line leading to the pressure side and connect your LDA to it, then your problems should be solved.

Regards,
Alex.

Can an oil-stained LDA (Linear Drain Array) be cleaned with a product like brake cleaner, or can it be serviced in any other way?

Follow-up question:

The blue hose visible in the picture comes from the "pressure sensor for the turbocharger boost control valve." The other end connects to the thing located at the bottom center, which is also connected to the small hose that leads to the intake manifold (that would be the ambient pressure).

Is this the "magnetic valve"? There's actually a third hose (red) on the bottom that could come from the turbo (at least it seems to lead there). I would need to tap into it with a T-connector, right?

Hello Tino!

Yes, exactly. You understood everything correctly!

Sure, here's the translation:

"Just a few words for clarification of terms:"
The "thing" you refer to as a magnetic switch is an electromagnetic valve that modulates the pressure in the pneumatic control line to the turbocharger's pressure accumulator. This valve switches very quickly between ambient pressure and boost pressure, thereby creating an "arbitrary" pressure value between ambient pressure and boost pressure. The so-called duty cycle determines the duration within a period during which the valve is closed or open.
The pressure sensor on the turbocharger is mechanically connected to the wastegate valve on the turbine side via a linkage. The wastegate allows a portion of the exhaust gas flow to bypass the turbine, reducing the drive power. This is used for controlling the boost pressure.

Regards,
Alex.

Super Erklärung... "Thank you!"

One more question, so I don't end up with any silly ideas.

Why isn't the system "tuned" here to achieve a higher boost pressure? Would this damage the engine, or would it risk major engine failures if you were to "convince" the valve to generate higher pressure (by opening it for a longer duration, as I understand it)? Or is this approach completely nonsensical?

Hello Tino!

Increasing the turbocharger boost pressure alone, without simultaneously increasing the fuel injection volume, will not result in increased power output; instead, it can lead to reduced performance due to increased backpressure in the exhaust system.

It's certainly very easy to manipulate the boost pressure limit in this location. Try this test: disconnect the plug from the solenoid valve. Then take a drive and you'll notice that there's significantly less power. When the plug is disconnected, the valve is connected between the turbo outlet (boost pressure) and the pressure control diaphragm (safety function). The spring of the pressure control diaphragm is designed so that the wastegate opens at approximately 0.6 bar of overpressure. In this case, the boost pressure is regulated to 0.6 bar.

In the other case, if you disconnect the hose from the turbocharger pressure sensor (and seal the end of the hose to prevent vacuum loss in the system and keep dirt out), then the pressure sensor is always connected to atmospheric pressure, meaning the wastegate will remain closed.
If you drive like that, you can generate significantly excessive boost pressures at engine speeds above approximately 2000 RPM, which would be harmful to the engine and turbocharger. Therefore, the engine control unit intervenes and reduces the fuel injection amount in order to deprive the turbocharger of its power source. In most cases, the engine will then switch to limp mode (the glow plug indicator light illuminates), and you will only be able to move very slowly.

So, it's best to stay away from that!

Regards,
Alex.

I need to chime in here because I'm also planning to install an LDA (Linear Density Array) on my 1Z engine and I'm not entirely sure where it should go.

"In the picture, I've marked the hose with an arrow that I wanted to tap into using a T-connector. After following this discussion, I learned that this might not be ideal. However, I couldn't find the specific location they were referring to, or perhaps I missed something."

Can I connect the LDA using a T-connector to the hose marked with the red arrow?

If I understand correctly, this is the same location where I'm currently accessing my printer.

Do you have an engine from before '93? I saw in my "DIY Repair" book that the hose already connected there goes to a solenoid valve (possibly an EGR valve?), which is located behind the air filter housing.

I'm seriously considering relocating my "filling station" to the solenoid valve that was mentioned this afternoon.

but donalexo, wouldn't I be measuring the built-up boost pressure there? If the solenoid valve is always opening and closing, then the pressure isn't necessarily the same as what reaches the engine, right? Help - I'm confused again.

Edit:
I just saw that you have a '96 model... it seems like VW kept using that design for longer. In the Audi 80, they started putting a blind plug in that spot starting in '94. But basically, it should be the same location.

Hi,

The hose shown in the last picture connects from the 96 G3 1Z engine control unit to the motor and is used to measure the effective boost pressure (that's how it was on mine). If you want to connect a lambda sensor, this is the correct location.

Mmmhhh... and why isn't it "oily"? A control unit shouldn't like that at all!

Tino Kossmann wrote:

Mmmhhh.... and why doesn't it "get oily" - a control unit shouldn't like that at all!

Have you ever heard of pressure drop in a pipeline? Additionally, the pipeline has a "water pocket" – it first goes down and then continues upwards. Normally, an air column remains trapped in this section, so no air can pass through.

Thank you for the answer, Bertil. Now I can proceed with my work feeling more at ease .