Wie fahre ich Sprit sparend? (Solution) | Posts 16+

Hello hansemann2.5,
Your argument sounds logically sound and is also difficult to refute. However, my statement was primarily based on a diagram from the MTZ article, which shows the maximum combustion pressure over engine speed (at full load). This diagram shows an M-shaped curve, with an increase from low engine speed to a maximum at approximately 1600 rpm, followed by a nearly linear decrease to an engine speed of 2700 rpm. Then, the pressure increases again to an engine speed of 4000 rpm, but does not reach the maximum of 1600 rpm. Above 4000 RPM, the pressure drops very sharply.
If we consider the maximum pressure occurring in the cylinder chamber as an equivalent measure of the mechanical load on the engine, it can be deduced that the highest main bearing load occurs at a speed of 1600 rpm.
Of course, the resulting mass forces of the crank mechanism are not taken into account, which contribute significantly to the bearing load, especially at high speeds (due to a quadratic relationship).
In your argument, you are basing your reasoning on the performance, but the decisive factor for the load on the bearing is the applied radial force. This is more proportional to the delivered torque and not to the power (power = torque x angular velocity (RPM)).
At low engine speeds, the combustion process is largely isochoric, meaning it occurs at a constant cylinder volume, which would result in a higher pressure increase compared to higher engine speeds. It is precisely this relationship, in combination with the thin lubricating film in the main bearings, that leads to a critical load on the engine.
In simple terms, the crankshaft receives a massive impact with each ignition when running at full load and very low RPM, and this impact is stronger than when running at full throttle and maximum RPM.
To clarify this connection, one would need a better understanding of the design and function of the main bearings in TDI engines.
Fundamentally, hydrodynamically lubricated plain bearings only exhibit sufficient load-carrying capacity at certain minimum rotational speeds.

Without specific knowledge, we are unlikely to reach a conclusion. For my part, I prefer to be cautious and only give it full throttle when the RPMs are above 1600.

Regards,
Alex.

Please provide the German text you would like me to translate.
AUDI A3 1.9 TDI, engine code AGR, 66kW, everything original.

Hi,

My fuel efficiency record is 3.7 liters per 100 kilometers with the 1Z engine.

First, fully fueled, then driving at 90 km/h in the...
Drafting behind trucks to get to the university, and doing the same thing on the way back in the evening.
So, the distance is 65 km each way, 80% highway, with 2 cold starts.
While driving, I kept the accelerator pedal pressed lightly and shifted gears at 2000 RPM.
After filling up the tank, I chuckled at the cashier's dumb expression as I paid for 4.8 liters of diesel.
The normal fuel consumption was always around 5.2 liters.

I haven't tried that with the AAT yet.
However, it has always consumed 6.5 liters, regardless of how I drive.
For a 2.5-liter engine, 115 horsepower, a weight of 1,500 kg, and a development stage from the late 1980s, but okay.

Hello,

Here's the email I received from Alex:

Quote:

A crucial foundation for this is the precise knowledge of the... Consumption characteristic curve of the respective engine, in order to determine the specific... To be able to determine the fuel consumption at each specific engine operating point. Fortunately, I have the (somewhat dated) article from MTZ. Issue No. 57 of 1996, which featured the introduction of Volkswagen's new TDI engine. is being. It's likely a 66kW engine with the MKB AGR designation, operating at 4000 RPM. 210Nm at 1900 rpm), which is also installed in my AUDI A3, manufactured in December 1996. In this article, you will find information on the consumption curve (specific... Fuel consumption as a scallop diagram, depending on... (Speed and mean pressure), it's also a very interesting full-load diagram. (Power, torque, specific...) Fuel consumption and soot level as a function of engine speed. as well as a diagram of the cylinder pressure (max. (Combustion pressure) above the... Speed. The latter reflects the mechanical stress on the engine very well. again.

[img]https:/verbrauchskennfeld.png[/img]
[img]https:/volllastdiagramm.png[/img]
[img]https:/zylinderdruckverlauf.png[/img]
Source: MTZ 57/1996

Best regards, Rainer.

Oldy but goldy: Fuel efficiency Optimizing fuel consumption to travel more cost-effectively.

dieselschrauber wrote:

Oldy but goldy: Fuel saving Optimize fuel consumption to travel more cost-effectively.

2.30 EUR per liter... those who pay attention to the consumption data displayed will save money!