1Z Max Pressure 1500 mbar, Control Valve Blocked

'Hello, I'm having a problem with a 1Z engine where it's not exceeding 1500 mBar of boost pressure. Occasionally, I get the error code 'boost pressure control differential.' To rule out the boost pressure control valve as the cause, I disconnected the connector. However, the maximum boost pressure remains at 1500 mBar. I read in an article that the unregulated pressure should be 1.6 Bar, and it should be regulated to increase up to 1.9 Bar. My question is, how is the boost pressure supposed to be increased by this valve? If I apply pressure to the diaphragm, the valve opens. If not, shouldn't the valve be constantly closed? Does anyone have experience with this?'
Best regards, Harri.

Hi Harri,

(I'm now talking about reprints, not what you're referring to as absolute prints.)

You misunderstood the regulation regarding the turbocharger boost pressure on the 1Z engine.

When the valve is de-energized, the full boost pressure is present at the charger outlet and applied to the wastegate chamber. As you correctly read, this creates a pressure of 0.6 bar above atmospheric pressure.

The valve "mixes" the boost pressure from the turbocharger outlet with outside air (which is at zero bar).

For example, with a 50/50 mixture, the wastegate experiences a pressure difference of 0.3 bar, causing it to remain closed, which allows the boost pressure to continue to increase.

If you find yourself losing power and the pressure drops close to 0.6 bar, simply replace the valve.

028 906 283 F for approximately 30 EUR.

However, there is also a technical article about it that you can find through a search (see Fettnaepfchen).

I don't want to be like that: https://community.dieselschrauber.org/en/viewtopic.php?t=3101


m;

Thank you for the interesting information.
According to your statements, the wastegate shouldn't open if there are 0 bar of pressure at the pressure sensor. I'm going to disconnect the hose from the control valve to the pressure sensor. Then, the boost pressure should increase (hopefully not too much that something breaks). If the pressure increases, I'll replace the control valve. Otherwise, I'll measure the boost pressure again (I've already done this, but the barometer was vibrating a lot, so I need to dampen it first).
'If the pressure readings match what's displayed with VAG Com, I'll replace the turbocharger with the wastegate. I once bought a complete engine with turbocharger and fuel pump on eBay. Unfortunately, the turbocharger is very difficult to access, and I'm sure two more screws will break off, so I'll do that last.'
Thank you and best regards,
Harri.

HI.

I would NOT run the turbo without controlling the wastegate. That component is the only limit on the way to achieving maximum RPM!

It's cheaper to buy the 30 EUR valve than to risk destroying the turbo by disassembling it during this test (by over-revving it).

m;

Hello, with the pressure sensor hose disconnected, I'm getting about 600 mBar of overpressure. Still too low. I'm going to try sealing the EGR valve with a plate. Hopefully, that will improve things. Or what else could be the problem?
Best regards, Harri.

MOMENT!

Your turbocharger, without any limitations (meaning it operates with a completely pressure-free wastegate), only produces 0.6 bar.

Well then, it's definitely over for him!

Reasons for the turbocharger's zero output:
- Leaks (which should only be located at the crimp and be very noticeable).
- Can the EGR system significantly reduce the turbocharger's performance?
- Turbo failure (remove, inspect, rebuild).
- The engine is likely completely worn out (it's producing very little exhaust pressure - but I find that hard to believe).

How did you arrive at the 0.6 bar pressure? Please explain (ideally with a diagram) what changes you made compared to the original/standard configuration.

Did you measure the 0.6 bar under load, meaning *while the engine is working* - and not just "revving the engine while idling"? Otherwise, every turbo would be "broken."

m;

Hello,
Okay,
I disconnected the two pressure control valves (the upper one and the side one) from the three hoses. (This prevents the control valve from receiving any pressure). Then, I connected the Vag-com diagnostic tool, warmed up the engine, and drove it on a highway. The actual turbocharger pressure reading was a maximum of 1.6 bar (absolute, with a normal atmospheric pressure of 0.99 bar).
The engine is in good condition (compression is fine), and the acceleration is actually working.
When stationary, the barometer actually shows the same value as the external air pressure.
'That gives me something to do on the weekend; I'm going to swap the charger from the spare engine.'
Best regards, Harri.