Nissan Almera Tino gönnt sich zuviel | Posts 16+

Hi,

You can certainly try it out, but I know that the car consumes less fuel at 1100 RPM than at 1800 RPM. It's quite obvious... the energy required to move the car is the same, but the resistance within the engine is higher at 1800 RPM, so more energy is needed to turn the engine.

Best regards,

January.

That raises the question of how the efficiency changes with the speed.

Okay, I understand. Please provide the German text you want me to translate into English. I will only provide the translation.

Thank you! Very interesting!

hello,
I'm not sure, but my impression is that Japanese people generally consume more.

I used to have a Skoda Fabia TDI with 100 horsepower, and on average, it consumed 5.3 liters per [unit of measurement - e.g., 100 kilometers/miles].

Then I made the mistake of relying on the supposedly reliable Japanese cars, and ended up with a Jw Mazda 626 station wagon with a 110 diesel horsepower engine. In my opinion, it also consumed quite a bit of fuel; never less than 6.5 liters, around 7 liters with air conditioning and normal driving, and about 8 liters at speeds of 140-160 km/h.
I found it to be far too much. Afterwards, I had a Mazda 3 with 68 horsepower... even that one couldn't be driven for less than 5 liters per 100 kilometers, not even with calm driving without air conditioning and on country roads.
However, at a speed of approximately 140 km/h on the highway, the fuel consumption was around 6.7 liters.

Okay, everything's clear about the Skoda...

I've now taken over my father's C220 CDI. It's still as fuel-efficient as I would expect for a car of this size. It uses about 5.8 liters per 100 km when driving at a steady speed of around 140 km/h on the highway, which is comparable to the smaller Skoda.

'Regarding the Mazda 626, everything was checked to rule out fuel consumption issues, including the EGR valve, turbocharger, mass airflow sensor, etc., but nothing was found.'

greetings
robs

Hi!

I've been familiar with the consumption map (see Rainer's link) for a while now and find it very interesting, but one could also represent the relationship between requested engine power and the most fuel-efficient speed in a simpler diagram.

y-axis: 'Speed at optimal efficiency'
x-axis: 'requested motor power'

Is the effective mean pressure in the performance map roughly equivalent to the torque, qualitatively speaking? Am I understanding that correctly?

If you connect the lowest points of each mean pressure-speed curve and swap the axes of the diagram, you initially obtain the torque-speed characteristic for the most economical fuel consumption. If you calculate the power for each torque and corresponding speed and plot it on a further y-axis, you obtain the aforementioned power-speed diagram for the most economical fuel consumption. Of course, this new y-axis must be linearized, as it is initially non-linear due to the power formula 2π*m*n/60. Furthermore, the curve only extends up to the power at maximum mean pressure. To continue the curve, one would have to find a continuation point in the fuel consumption map at the corresponding power level. However, this is not necessarily required, because if you compare the fuel consumption map with the full-load diagram and equate the maximum mean pressure with the maximum torque, the power-speed diagram extends up to approximately 2/3 of the maximum engine power (see full-load diagram). This is more than enough.

Have I understood this correctly, or is there a flaw in my reasoning?

Furthermore, a performance curve showing the relationship between power and speed should be included in every vehicle owner's manual, as I believe that many average drivers are unclear about these relationships. A second x-axis representing an equivalent speed for optimal efficiency during constant driving on flat terrain could also be added for general guidance.

Best regards,

Hi!

If you connect the lowest points of each mid-pressure speed curve and swap the axes of the diagram, you initially obtain the torque-speed characteristic for the most economical fuel consumption.

I've thought about it again: My previous statement regarding the low points is not correct.

Strictly speaking, one must plot a series of curves with different constant power values within this performance map. Using the effective mean pressure and speed, a combined formula should be used to determine the power output. If one fixes the power as a constant (and does so for a wide range of different power levels) and rearranges the formula to solve for 'mean pressure' (y), one obtains a fraction with a constant numerator (representing the power): y = 1/x -> this results in a hyperbolic curve.
http://de.wikipedia.org/upload/1/1b/Hyperbel.png

For different services, one now obtains various hyperbolas that are stacked like a set of bowls within each other, with the higher performance curves (the upper bowls) always being more gently curved.

At the point where the hyperbola intersects with the curve representing the lowest fuel consumption at a given mean pressure, you obtain the most fuel-efficient speed for that particular power output.

The resulting pairs of values for power and the most fuel-efficient speed can be plotted on a new graph, which then creates the power-speed diagram for the most economical operation.

And in my opinion, this is easier for the average car driver to understand than the consumption map (which, of course, contains more information, including consumption figures beyond the optimum).

Best regards,