Adjustable Boost Valve: Control & Performance

Hello!

During a test run with my 2000 ACV, I observed that the duty cycle of the boost pressure control valve was significantly below the specified values.

Time U/min setpoint/mbar actual/mbar duty cycle

,11.14,2264,1479.0,1336.2,12.8,,,,,,,,,,
11.58, 2244, 1479.0, 1336.2, 12.8, , , , , , , , , , , ,
12.00,2203,1479.0,1326.0,12.8,,,,,,,,,,
12.43,2224,1672.8,1336.2,12.8,,,,,,,,,,
12.84, 2203, 1785.0, 1438.2, 12.8, , , , , , , , , , ,
13.28, 2203, 1805.4, 1560.6, 12.8, , , , , , , , , , , ,
13.70, 2224, 1876.8, 1642.2, 12.8, , , , , , , , , , ,
14.14, 2264, 1876.8, 1744.2, 12.8, , , , , , , , , , ,
14.57, 2285, 1876.8, 1805.4, 12.8, , , , , , , , , , ,
15.01,2305,1734.0,1774.8,17.5,,,,,,,,,,
15.45, 2305, 1744.2, 1713.6, 15.9, , , , , , , , , , , ,
15.88, 2326, 1795.2, 1703.4, 12.8, , , , , , , , , , ,
16.32, 2326, 1795.2, 1723.8, 12.8, , , , , , , , , , , ,
16.75, 2346, 1795.2, 1734.0, 12.8, , , , , , , , , , ,
,17.19,2366,1795.2,1734.0,12.8,,,,,,,,,,
17.61, 2387, 1805.4, 1744.2, 12.8, , , , , , , , , , ,
4/18/2024, 2387, 1876.8, 1785.0, 12.8, , , , , , , , , , ,
18.46, 2428, 1876.8, 1846.2, 12.8, , , , , , , , , , , ,
18.89, 2468, 1887.0, 1907.4, 14.3, , , , , , , , , , ,
19.31,2489,1887.0,1938.0,16.7,,,,,,,,,,
19.74, 2530, 1887.0, 1989.0, 21.9, , , , , , , , , , ,
20.17, 2591, 1887.0, 1958.4, 26.3, , , , , , , , , , ,
20.60, 2652, 1887.0, 1927.8, 27.5, , , , , , , , , , ,
2021-02-21,2693,1887.0,1917.6,29.1,,,,,,,,,,
21.45,2754,1887.0,1907.4,29.9,,,,,,,,,,
21.87, 2795, 1887.0, 1897.2, 30.3, , , , , , , , , , ,
22.28, 2856, 1887.0, 1907.4, 30.3, , , , , , , , , , , ,
,22.71,2897,1897.2,1897.2,30.7,,,,,,,,,,
,23.14,2754,1499.4,1805.4,48.6,,,,,,,,,,
23.57,2101,1407.6,1479.0,46.2,,,,,,,,,,
24.00,1530,1315.8,1336.2,47.8,,,,,,,,,,
,24.44,2162,1836.0,1336.2,12.8,,,,,,,,,,
24.88, 2162, 1866.6, 1591.2, 13.1, , , , , , , , , , ,
,25.30,2183,1866.6,1876.8,14.7,,,,,,,,,,
,25.73,2224,1876.8,1958.4,21.5,,,,,,,,,,
26.15, 2244, 1876.8, 1968.6, 26.7, , , , , , , , , , ,
,26.59,2264,1876.8,1948.2,29.9,,,,,,,,,,
02/27, 2285, 1876.8, 1927.8, 31.9, , , , , , , , , , ,
27.44, 2305, 1876.8, 1907.4, 33.9, , , , , , , , , , ,
,27.88,2346,1876.8,1907.4,35.1,,,,,,,,,,
28.31,2366,1876.8,1897.2,35.9,,,,,,,,,,
28.74, 2387, 1876.8, 1887.0, 36.3, , , , , , , , , , ,
,29.16,2407,1876.8,1887.0,37.1,,,,,,,,,,
,29.59,2428,1876.8,1876.8,36.7,,,,,,,,,,
01/30, 2448, 1887.0, 1876.8, 36.3, , , , , , , , , , ,
30.44, 2468, 1887.0, 1887.0, 36.3, , , , , , , , , , , ,
30.87, 2468, 1887.0, 1876.8, 35.9, , , , , , , , , , ,
31.31, 2489, 1887.0, 1887.0, 35.9, , , , , , , , , , ,
31.74, 2509, 1887.0, 1876.8, 35.5, , , , , , , , , , ,
32.17, 2530, 1887.0, 1887.0, 35.5, , , , , , , , , , , ,
32.60, 2550, 1887.0, 1887.0, 35.5, , , , , , , , , , ,
,33.03,2550,1887.0,1887.0,35.5,,,,,,,,,,

A maximum value of 48.6 with a target maximum of 90 seems a bit low.

Okay, here's my question: Is a duty cycle that's too low really an indication of a faulty boost pressure control valve? That darn thing costs a whopping €106 (which is still €90 for me).

Before I just blindly replace it, I'd like to know if something else might be negatively affecting this valve.

Best regards, Peter.

P.S.: The test drive was, of course, longer, but this excerpt is representative of the entire test drive.

Could it perhaps also be due to the length of the rod used for the VTG adjustment?

ACV has a wastegate.

That's right!
But the wastegate actuator also has a range of adjustment, and it could be set too long or too short.

Really, did she ????

I need to put my 1Z to the test right away.

I thought the rod was fixed (in length)?

m;

It is already adjustable, but nothing has been changed on mine. Of course, this could explain the constant boost pressure I'm experiencing, if this rod was incorrectly adjusted from the beginning??????????????

Greetings, Peter.

P.S.: I generally don't want to change anything that doesn't need to be changed.

Quote:

Of course, this could explain the constantly unchanging boost pressure,

Huh ??? It's not always the same!

High key values seem to reduce the charging pressure. And the fact that this control loop works can be seen in the log.

Based on the values, I don't see any need for changes.

m;

Hi!

Assuming a constant boost pressure, I meant the consistently maximum boost pressure. It's not possible to achieve anything more than 0.7 bar consistently. According to the target value table, up to 0.92 bar should be achievable. In conclusion, there's a lack of air in the full load range, which is why it's producing soot. That's how I see it, but I could be wrong. I don't know in which direction the duty cycle needs to adjust for low or high boost pressure, but since the duty cycle increases with increasing engine speed, it should be around 90% at full load and the target engine speed (according to the target value table). However, that's not what's happening. An error is not ruled out.

Greetings, Peter.

P.S.: Mass airflow sensor (MAF) is new, but the solenoid valve is still the old one. A test drive with the new valve has not yet been carried out for timing reasons.

Hello!

I don't understand quite a few things.

Quote:

Under constant boost pressure, I meant that the maximum boost pressure remains the same. It's not possible to achieve more than 0.7 bar consistently. According to the target value table, values up to 0.92 bar should be achievable.

You had a target boost pressure of 1897.2 at time 22.71, and even an identical actual boost pressure value.

Shortly after switching on (at time 26:15), there's even an overshoot of 1968.6.

One thing to consider is the relatively slow pressure build-up.
at the beginning of the log and after switching (similar to what I see in my AFN, which is why I'm also interested in this thread).
The duty cycle values seem indeed low (similar to what I'm seeing in my AFN), especially because the maximum value of 48% probably still needs to be disregarded, as you were likely in the middle of the switching process at that point (meaning no load).

Greetings,
Klaus.

Is the charge air cooler leaking?

Let's put that into a visual representation.

I would like to log more information than just a single switch event.

Could you please do a DZT (maybe in different keys)?

Something like that (but now with air masses).



m;

Hello!

My log is just a snippet, but it's typical of the entire test drive. I've now replaced the valve and will be taking another longer trip this weekend. Now, a really simple question: How do I get a logged diagram? Am I too stupid to find it?

@ Rainer

An optical visual inspection revealed that the intercooler is okay. I will test it again using soapy water. Perhaps I will then see some bubble formation.

Greetings and thank you to you all.

Peter.

@Clause

"I installed a boost pressure gauge. Now the question is, is the gauge faulty, or is it the boost pressure sensor? Something's not right here. But what is it? And who's responsible? How can I figure this out? Should I replace the boost pressure sensor? If it's not expensive, I might just replace it. However, if I could test the sensor under controlled laboratory conditions, applying 1.0 bar and then measuring it with VAG COM, I could definitely check it. But that's not really feasible right now..."

Hi Peter,

The diagram was created using common, readily available tools (Open Office or other similar products ).

VAG-COM only outputs CSV files (which you can create ).

m;

Hello!

You couldn't have known that you would suddenly start talking about your LDA after providing the logged data...

Good luck with the leak detection.

Greetings,
Klaus.

Sure, the boost pressure gauge is only there for monitoring. However, if it's not displaying correctly, it's obviously difficult. It's a Razimex gauge, with a range of -0.5 bar to 1.5 bar. A 0.815 gauge typically has a deviation of a maximum of 2.5%, which means at 0.7 bar, the actual reading would be a maximum of 0.7175 bar and a minimum of 0.6825 bar, a difference of 0.035 bar. This difference shouldn't normally matter given the difference between my actual and target boost pressure, as I'm operating with a difference of 0.2 bar.

Could it really be that the boost pressure sensor is broken???

Greetings, Peter.

P.S.: The next log will be visually enhanced.