ASU - Idle speed not OK.

Hello,

zunächst großes Kompliment an den Macher dieser Seiten (Rainer) und die vielen fachkundigen Poster. Ein echte Sahnestück sind 'Rainers TDI-Seiten' und das Forum. NuKeep it up.

My question:
After installing a PSI powerbox in my 110 HP AFN Ibiza, the vehicle's mandatory technical inspection (ASU) was due shortly after. After receiving the inspection sticker, I checked the TÜV inspection certificate. What I read under 'Result' was: 'AA-DRZ 3670 U/min n.i.O' (where 'AR-DRZ' probably means 'rev limiter speed'). According to the inspection certificate, the target values for this 'AR-DRZ' are: 'min. 4500 max. 5200'.

Is this the maximum RPM for this AR-DRZ? If so, why is the minimum set at 4,500 RPM, as that's already almost in the red zone? And if it were to reach a maximum of 5,200 RPM, the engine would probably be ruined, right?

What do the measured values under the heading 'Free Acceleration' with the columns '1.', '2.', '3.' mean? I also find the note 'n.i.O' in the row 'nAR'. According to the certificate, the measured values are 4120 (revolutions, I think).

Can anyone help me decipher this cryptic certificate? And how should I interpret this certificate? So many questions...


Regards, Dilbert.

Can someone explain what an ASU inspection certificate is?

Hi.

das kleine n steht grundsätzlich für Drehzahl, t für Zeit. AlOkay, please provide the German text you would like me to translate.
nLL = Idle speed.
nAr = Maximum engine speed (achieved with the vehicle stationary).
k = Turbidity value ("soot number")
tB = Acceleration time, which is the time it takes for the engine to accelerate from idle to its maximum RPM after receiving a full-throttle command.

The rev limit for TDI engines is always around 5,000 rpm. Because operating at that speed during normal driving doesn't make sense (power output is practically zero, while wear and tear is high), the redline indicator starts a bit earlier.

If your car's accelerator pedal position sensor (throttle position sensor) reading is only 3670 when the engine is running normally, then either the sensor is incorrectly calibrated or defective, or there may be something obstructing the pedal, such as a floor mat.

Hello, thank you for the flowers .

The maximum engine speed that can be reached by pressing the accelerator pedal is called the rev limiter.
If your certificate shows "3670 min-1", it could mean the following:
- The examiner didn't push it to the limit.
- The measuring device was unable to determine the actual engine speed.
- Does your engine's idle speed, when the accelerator is fully pressed, really not exceed 3670 RPM?
In all 3 cases, you would not have actually passed the ASU, and the most likely scenario is point 2.

During the ASU (Abgasuntersuchung, exhaust emissions test), the soot emissions of the engine are measured under load by accelerating the engine's flywheel within a specified, short time period (free acceleration).

In a diesel engine, the amount of air available in the cylinder during combustion is limited. If more fuel is injected than can be burned, the engine will start to produce a significant amount of soot.
Even if the combustion is poor, for example, due to faulty fuel injectors (which prevents the fuel from being properly atomized in the cylinder), the exhaust will contain more soot.

The K-value is the indicator used to measure the opacity of diesel exhaust gases, and it primarily reflects the soot content. This is the key parameter in this context.
The K-value must be below a certain upper limit for the approval process. To achieve this, the following can be done:
- Take the car to the emissions test with an engine that doesn't produce excessive soot, meaning the engine is in good condition and the increase in fuel injection caused by the control unit is not too high.
- press the accelerator pedal as gently as possible, so that the engine injects less diesel per unit of time, thereby producing less soot.
- within the same time period, a lower rotational speed is achieved than the maximum allowed rotational speed.

The K-value, which is relevant for energy efficiency calculations (ASU), is calculated as an average of several measurements, which is why you see the 1st, 2nd, and 3rd values listed on your test certificate.

Best regards, Rainer.