Questions about the EDC calibration map architecture

Hello everyone.

As far as I understand the story so far, the determination of the injection quantity during operation generally works like this (please don't take the "equations" for the characteristic curve functions literally):

1. "Driver preference: Pedal position plus engine speed equals the desired fuel injection amount (and also acts as a limiter)."

2. "Boost pressure map: desired fuel injection quantity + engine speed = target boost pressure (which typically ensures a sufficient amount of air enters the cylinders for the combustion of the desired fuel injection quantity)."

3. Airflow map limitation: Air mass + RPM = Air limitation (maximum allowable injection amount at the current air mass per cycle, in order to keep the soot content within the exhaust values).

4. Torque map: Engine speed = maximum fuel injection quantity (limited for thermal/mechanical overload protection of the engine and powertrain).

Dynamic, keywords (example):
-> The driver presses the accelerator pedal while the engine is in idle, which triggers a specific amount of fuel injection.
-> The torque curve specifies the maximum injection quantity for each engine speed.
-> Initially, the mass airflow sensor (MAF) reports insufficient airflow, causing the air limiter to activate and reduce the fuel injection amount below the driver's desired setting.
-> At the same time, the boost pressure is increasing towards the target value. This increases the mass airflow rate, which in turn increases the air throttling, allowing the soot control system to gradually loosen its restrictions – until the air throttling exceeds the driver's desired setting or the torque limit.
-> Now, either the driver's desired setting or the torque limitation for the fuel injection quantity comes into effect, and the target state is (for the moment) achieved.

My questions:

1. Is this process generally correct?

2. What is the purpose of using a separate torque limit map (i.e., the absolute maximum limit: engine speed -> fuel injection amount) in this scenario?
If you precisely program the torque limit values for all engine speeds at full throttle into the driver-selectable performance map, could that performance map potentially take over the function of the (maximum) torque limit?

So, what is the purpose of the extra effort involved in using a torque curve?

It seems that for the first and second gears, some TDIs are designed to deliver slightly less power to protect the transmission.

DaBibo wrote:

I once heard...that this was done for the first and second gears, and that some TDIs have less power in those gears to protect the transmission.

Hi.
This would mean that the torque limit would vary depending on the vehicle's speed or the rate at which the engine speed is increasing. Can anyone provide more details on this (before I have to fire up my laptop again in the next few days to collect more data)?

The EDC generally has the capability of gait recognition.

As mentioned, this allows you to limit the speed in lower gears to prevent damage to the powertrain.

Similarly, at very low speeds, the torque is briefly held to prevent excessive stress on the bearings.
Similarly, it is possible to adjust this setting based on the current temperature (e.g., to protect a cold engine).

The torque curve can be influenced by many factors, which makes it difficult to replace or replicate.
'And the value changes dynamically with engine speed and gear, at least in my case. It especially drops below 1600 RPM. However, logging temperature-dependent data early in the morning seems like too much effort for me...'

Furthermore, there's no predefined profile for the driver's preference because it's already called a 'driver's *wish*.' The EDC then attempts to fulfill this wish based on the various available parameters.

'Starting with the EDC16 system, things work differently. It's designed as a torque-based system. In that case, the driver's input only serves as information. The system doesn't use injection amounts as a basis for calculation, but only the requested torque. It's much simpler and more comfortable.'

CU Gremlin.

Gremlin wrote:

The torque curve can therefore be made dependent on many factors, which is why it is not easily replaceable. and the value changes dynamically with engine speed and gear, at least in my case.

Hi Ralf,

This explains the purpose of a variable torque-speed characteristic curve, rather than simply programming a fixed maximum curve as a 100% profile (speed/quantity) for the driver's desired characteristic curve.

Does that mean that, for emergency operation, the system simply switches to a different torque curve with reduced torque values??

Can you perhaps also provide some information about Ben 1972's explanation of "summer slump"?
Okay, I'm ready. Please provide the German text you want me to translate.
Sure, please provide the text you would like me to translate from German to English. I will provide only the translation, without any explanations.

Ben1972 wrote:

I can give you a reason for the summer sluggishness. In this case, the exhaust gas temperature before the turbine is a limiting factor. . . . (At outdoor temperatures around 30°C), your intercooler no longer cools the temperature of the compressed air sufficiently, and the intake air temperature rises. If you have an intercooler that is not very effective, the intake air temperature can become so high that the exhaust gas temperature, at full injection, becomes so high that it can damage the turbocharger. Therefore, a correction map is then activated, which uses the intake air temperature to adjust the injection quantity by a factor < 1, thereby reducing the injection quantity. .

However, in my opinion, the fact that several attempts to artificially lower the LL temperature by about 20°C have failed to resolve the summer slump speaks against this approach.
I've tried something similar myself, but without success.
/viewtopic.php?t=706, post from July 15, 2002.

@Ben: What do you think about that?