Fuel Efficiency: Optimal Consumption & Start Time

Hi,


It would be interesting to know what the initial fuel injection timing needs to be set at in order to achieve an optimal fuel consumption rate . My pump is currently set a bit too early (between the middle line and the upper tolerance line). Surprisingly, since I changed it from "too late" to "a bit too early," there has been no change in fuel consumption .

Best regards, Christian.

Sure, here is the translation of the text from German to English:

"Hi,"
"It's not funny at all. Under partial load conditions, which is likely the most common operating state, the injection timing is significantly shifted towards later by the EDC (Electronic Diesel Control). Therefore, the pump would need to be adjusted so that the control system reaches its limit. Or even better, a tuning modification could be implemented. However, I'll leave it up to the specialists to determine the best approach."

... read this (@haehnlein):
http://www.dieselschrauber.de/esp.html

You still haven't understood the injection startcontrol .
This is not a control.

Best regards, Rainer.

Rainer K. wrote:

You still haven't understood the injection startcontrol. This is not a control.

Hi Rainer,

Why? If the pump is statically set to an early timing, then, for example, the control system might not be able to adjust sufficiently late in partial load operation... etc.
Why does adjusting the fuel injection start time from late to early result in a performance increase? Is it because the engine's efficiency changes in this case (apparently)? I just want to know how the static fuel injection start time is related to the engine's efficiency. Or are you telling me that the pump always has a constant consumption regardless of its position?

Best regards, Christian.

Oh man...


wake up, the sun is shining .

Christian, we have a system in place. No matter what setting you choose on the pump, the EDC (Electronic Diesel Control) will always try to reach its programmed target value. The adjustment range of the pump is greater than what you can achieve by manually twisting it. If you turn the pump as far as possible towards 'early' and the EDC cannot reach its programmed 'late' setting, there will simply be an error message and/or a limp-home mode activated.

This only works with fully mechanical pumps.

The question of optimal fuel consumption is moot. Once the overtorque threshold is exceeded, the full combustion pressure needs to be applied, to put it simply. As everyone knows, this depends on engine speed and load (as well as temperature, boost pressure, etc.), which is why it's controlled via a map in TDI engines, rather than being roughly adjusted based solely on engine speed, as was done in the past.

Again: twisting the pump doesn't achieve anything in a TDI engine. The only solution is to modify the adaptation channels.

CU Gremlin.

Gremlin wrote:

wake up the sun is shining

.

Sure, here is the translation of the text from German to English:

"Hi Gremlin,"

.....I'm sorry... maybe I'm too stupid for it .

Gremlin wrote:

Christian, we have an AGREEMENT. No matter what setting you choose on the pump, the EDC will ALWAYS try to reach its characteristic curve data. The adjustment range of the pump is greater than what you can achieve by twisting and bending. If you now turn it as far as possible to "early" and the EDC cannot reach its target value of "late," there will simply be an error message and/or a failsafe mode.

A flawless explanation... I think I understand it now (hopefully).

Gremlin wrote:

This only works with fully mechanical pumps.

...I'm just an old timer when it comes to TD .

@Rainer: Just delete the topic... it might only confuse other people.


Best regards, Christian.

Hi Christian,

1. I don't believe you are too stupid.
"You're just still looking at it through the lens of traditional design. That's the difference between mechanics and electronics."
3. Even if the post isn't directly relevant to everyone, it might still be educational for others. I think many people who are switching from traditional development methods are having problems with the technology.

Hello,

The real problem is understanding the difference between control and regulation.

A regulation always compares the desired value (setpoint) with the actual value of the controlled variable. If the actual value deviates from the setpoint, adjustments are made continuously until the actual value equals the setpoint.
Example: Injection start control for TDIs with distributor injection pumps. The target value is stored in the EEPROM of the ECU and is read/calculated for each operating condition (speed, load).
The actual value is determined by the needle lift sensor via the EDC (Electronic Diesel Control). So, when the injector needle lifts, the EDC detects this and knows that fuel is being injected.
The EDC then adjusts the actual value to match the target value by varying the injection timing via different control ratios at the injector control valve (solenoid valve) of the fuel injection pump.

The control system does not compare actual values to target values; instead, it would adjust a device like an injection limiter based on factors such as speed and/or load. The resulting outcome is not verified in the process.
Example: The injection control system mentioned for VAG TDI engines. The internal pressure in the fuel injection pump increases with increasing engine speed.
The hydraulic control element in the TD distributor injection pump moves against a spring force, adjusting the start of injection to occur earlier as the pump speed (internal pressure) increases.

Best regards, Rainer.

The explanations regarding the electronic injection start control using a lookup table were very informative.

Here's another minor point regarding the regulation: It's clear that determining the correct injection start time, as defined by the characteristic map, involves a control loop. The characteristic map defines the target value, the needle lift sensor and the crankshaft angle sensor are measuring devices, and the injection timing adjuster is the actuator.

But globally considered, it is a characteristic map-conforming control of the injection start, where disturbances (adjustment and tolerance of the static injection start, tolerance and aging of the electric injection adjuster, fuel viscosity) are eliminated using a control system (measuring element needle lift sensor).

Why control? The characteristic map is permanently etched into the EEPROM of the EDC, and injection timing is rigidly set according to this map. What actually results from this is not taken into account. The optimal characteristic map was previously determined on a test engine that represents all examples of this engine type. Ultimately, it's a compromise between fuel consumption, maximum power, NOx emissions, and smooth running.

A possible solution would be to measure the engine's efficiency, NOx emissions, and vibrations in real time and compare them with the driver's preference (maximum power or partial load with fuel consumption optimum?). In this case, there wouldn't be a static map, but each engine would calculate its own individual optimum for every operating and aging condition. Each engine would have its own momentary characteristic curve at any given time, which is influenced by thousands of individual factors: the condition and wear of the injectors (spray pattern), compression losses, air quality, fuel properties, valve timing tolerances, etc. However, this doesn't exist because it is too expensive, too complex, or not feasible.

In summary, the injection start adjustment technique can be described as a map-controlled injection start with controlled control range.

Best regards,