Leerlaufverbrauch

I agree with my predecessors and also believe that everything should be discussed in the forum.

However, unfortunately, one is sometimes forced to resort to private messages, especially when a topic is closed without the discussion having been concluded.

Such a sudden closing, in my opinion, is very unfair to the person who is then cut off and no longer has the opportunity to present their counterarguments.

Question for everyone: Who is allowed to close topics, and why are they usually closed? Can they be reopened?

The topic of 'downshifting' has recently been discussed. There, I no longer have a way to respond .

Since I'm not satisfied with my previous private message to Bertil (my discussion partner on this topic), I'm posting my response to Bertil's last comment here again. Ultimately, this is a forum, which is a public discussion platform.

Please provide the text you would like me to translate from German to English.

@Bertil: Hmm, it seems we were completely talking past each other. Perhaps I didn't write my text carefully enough.

In my case, the discussion was about 'coasting in neutral without brakes' versus 'rolling out with engine braking,' not... versus full braking.

Okay, let's do this using a case-by-case analysis; that's probably the safest approach. The vehicle is traveling at 100 km/h and is 800 meters away from a town on a flat, straight road. (The values are assumed and are for qualitative purposes only.)

Case1: The vehicle travels up to 400 meters before the town with a load (constant speed of 100 km/h), and then gradually decelerates using the engine brake in 5th gear, so that it reaches the desired speed of 50 km/h exactly at the town entrance. The EDC reduces the fuel consumption to zero during this 400-meter segment.

Case2 The vehicle begins to coast in neutral (with no braking effect) 800 meters before the town, and the engine idles during this time. At the entrance to the town, the vehicle reached a speed of 50 km/h due to the natural resistance of the road.

It is therefore evident that in case 1, the motor 400m was operated under load for a longer distance than in case 2. Now, regarding my statement that you may find laughable: 'The motor wastes energy through engine braking.' During those 400m, it wastes precisely the energy that it initially put into motion by maintaining a speed of 100 km/h during the first 400m. That's why I wrote about posthumous waste, not about holes in the tank. Your current fuel consumption display is misleading you when it shows a zero injection rate, while the motor can only achieve 'zero injection' because it is occupied with dissipating kinetic energy. Therefore, the reasoning 'The instantaneous power display shows zero -> I am not consuming anything during this time' does not hold. You are consuming energy that you previously obtained from the fuel. Kinetic energy, which is now being converted into frictional heat by 'dragging' the engine. However, your current power consumption display no longer shows the kinetic energy value.

Concluding remarks: The question is, which consumes more fuel: idling while gliding over 800 meters, or driving with a load (100 km/h) over 400 meters. But I believe the Eco driving program in the Lupo 3L already gives us the answer: In that mode, the vehicle is automatically set to coast (idle), not engine braking.

Hello idealist,

Unfortunately, all of the information you provided is completely incorrect. In the other threads as well, you've actually contributed more to entertainment than to a factual discussion.
Here in this forum, things like that are (fortunately) not well-received and are therefore blocked or deleted. It's also stated in the terms of service...

'In what way is it wrong?' Can you also address my individual arguments (with explanations)?

In which threads did I contribute to the entertainment? Was it when I asked about the intake manifold flap? Or what about when I suggested preheating with heating elements?

Hmm, I actually received substantive answers in both threads. There was no amusement to be found.

Hello,

Reason:
When the accelerator pedal is not depressed and the engine is running above a certain speed, the ECU shuts off the diesel injection. That's how simple it is. If no diesel fuel is injected, then none is consumed.
Before making claims and presenting them as facts (e.g., forced induction with a blower, despite the turbocharger being deactivated, engine preheating via glow plugs), please research the actual circumstances more thoroughly and avoid making unsubstantiated statements. That's what I meant by 'amusement.' And before you start throwing around terms like conservation of energy, please do some research and acquire the necessary knowledge.

If no diesel is injected, then none is consumed.

Okay, so that's how simple it is. Question: Have you ever manually rotated a diesel engine without fuel injectors by hand ? Yes? That was tough, wasn't it?

See, and it's precisely this friction (+cylinder pressure and intake resistance, which is added on) that slows down the vehicle when using engine braking. So, the vehicle loses speed. Where did this speed come from? From burning diesel fuel! And it's precisely this (now non-existent) fuel that the engine destroys, which is why the MVA (Motor Vehicle Analyzer) can show zero 10 times. So, if the engine is destroying a form of energy (kinetic energy) that it previously obtained from the diesel fuel, it's essentially a post-consumption. Because without this engine braking, the vehicle could have already been gliding without load much earlier. The kinetic energy is lost much more slowly when coasting in neutral than when using engine braking.

@ vr6:
Now you're misunderstanding the ideaAlist.
You must consider the entire distance traveled, not just the moment of deceleration!

He said that you need to accelerate for a longer period beforehand so that you can decelerate to the same speed using engine braking as you would in neutral. Because the fact is: When the vehicle is in gear, it brakes faster than when it's in neutral.



@ideeAlist + everyone
Nevertheless, this entire discussion certainly doesn't belong under the thread 'Forum Functionality - Replies and Private Messages,' which is marked as important, and should probably be deleted or at least moved by the admin/mods, as it really has no place here.

Normally, threads are only closed for a good reason. If someone feels unfairly silenced, they should first consider the possible reasons. Instead of simply continuing the discussion in a thread that is not related to the topic, they can, if necessary, start a new thread to discuss the issue. However, if the previous thread was closed for a valid reason (which, as I said, is usually the case), then the new thread will likely be closed or deleted fairly quickly as well.

Yes, I feel unfairly dismissed in the 'Downshifting' thread, especially since a misunderstanding arose there.

Therefore, I would like to reiterate my request regarding the aforementioned. A reply has been added to Bertil's thread, 'Downshifting...'

Thank you to the admin or moderator who addressed my concern .

@everyone: This thread is a continuation or completion of the discussion in the thread 'Downshifting...'

In the future, I will probably have to try to formulate my arguments more precisely and unambiguously. Because Bertil initially misunderstood me, and that's something I didn't want.

Hello private sector,

Just to make sure we understand each other:

Many contemporaries, when approaching a clearly marked stop sign in a moving vehicle, do the following: They consistently downshift without any load, gear by gear, causing the engine to roar with each gear change (first the synchronizer ring, then the engine), and the vehicle jerks slightly each time.

And before you hit the brakes, you can use the remaining momentum to save on diesel. That was the point.

ideeAlist wrote:

Case 1: The vehicle travels up to 400 meters before the town with a load (constant speed of 100 km/h), and then gradually decelerates using the engine brake in 5th gear, so that it reaches the desired speed of 50 km/h exactly at the town entrance. The EDC reduces the fuel consumption to zero during this 400-meter segment. Case2 The vehicle begins to coast in neutral (with no braking effect) 800 meters before the town, and the engine idles during this time. At the entrance to the town, the vehicle reached a speed of 50 km/h due to the natural resistance of the road.

You're forgetting that both vehicles need to be accelerated to 100 km/h!
This energy is the same for both.
So, I'm able to travel 400 meters further on a flat stretch with an extremely low energy consumption. Ideally, I'm only overcoming air resistance and rolling resistance. This consumption is approximately 20-30% higher than the idle consumption.
Let's assume that the vehicles need 1 liter (a hypothetical value) to roll 400 meters in idle mode. In that case, in scenario 1, the car would need approximately 1.3 liters for the first 400 meters and 0 liters for the second 400 meters, resulting in a total of 1.3 liters. Case 2: Requires 2L!!

You are wasting fuel by letting your engine idle without actually moving forward. If you turn off the engine, the situation looks completely different.

You are right to point out that the idle consumption is crucial in this calculation.

But aren't you exaggerating a bit when you say that the fuel consumption at a constant speed of 100 km/h is only 20-30% higher than the idle consumption (at 100 km/h)? I haven't actually measured it myself, but it sounds quite extreme. Then, maintaining a speed of 100 km/h would almost require no power.

ideeAlist wrote:

Then, almost no power would be required to maintain a speed of 100 km/h.

That's right! You can achieve this with a vehicle weight of 1000 kg and less than 10 horsepower (assuming the air and rolling resistance are low).
If you drive at a constant speed of 100 km/h on a perfectly flat road, the MFA (Multi Function Display) will show surprisingly low values (2-3 liters per 100 km are not uncommon in that situation).
You wouldn't want to question the entire development of automobiles, would you? Twenty years ago, we introduced the "cut-off" system, which achieved approximately a 10% reduction in fuel consumption. Why is that?

@vr6

And before you press the brake, you can use the remaining momentum to save diesel. That was the point.

That's correct. My alternative is: Don't approach the stopping point too quickly, so that you don't need to brake at all (neither with the foot brake nor with the engine brake). This way, you can often maintain momentum without load, as the vehicle can use the remaining momentum without engine braking for a longer period. However, this only works if you know the route well and/or the route is very straightforward. You have to be able to see or know the stopping point well in advance.

@Bertil

Well, it's a shame I don't have a spare vehicle. I had one in my Trabant. Darn. It would have even fit in my SDI. However, it was a cheap iron with 7 LEDs, so there's nothing to do with power consumption measurements .

However, I would like to point out that the most powerful diesel motorcycle from Enfield, the 440, manages to reach a speed of 100 km/h with just 11 horsepower, and that's pushing it. This Enfield is really just a tiny little thing.

Is it really true that a car should only be able to maintain a speed of 100 km/h with just 10 horsepower? However, it must be optimized for fuel efficiency: This includes using low rolling resistance tires, ensuring they are properly inflated, keeping the windows closed, and avoiding roof racks, etc.

Ten years ago, manufacturers were already looking into reducing fuel consumption in idle mode. That's when the Golf TDI ecomatic was introduced. However, the ecomatic system (which automatically shuts off and restarts the engine) didn't really catch on. People were probably skeptical about it.

Hello,

If you want to maintain a speed of 100 km/h, it's not the mass that's the most important factor anymore.
Primarily, air resistance (or, more often, the coefficient of drag, cw) plays a role. And that's quite bad for a motorcycle.

Sure, the drag coefficient (cw-value) of the Enfield is bad, especially since it doesn't have any fairing. But on the other hand, the entire Enfield, including the rider, only has 1/4 of the frontal area of a Lupo. But it's possible that both vehicles have the same air resistance.

However, there's something else to consider: The Lupo has to overcome the friction of 4 tires and 4 wheel bearings, and these are even more robust than those on the Enfield.

Oh, and one more thing: The Trabant needed about 80% of its rated power to reach 100 km/h, which is roughly 20 horsepower. However, it also has a slightly worse drag coefficient (cw-value) than the Lupo. The Lupo might then need about 15 horsepower? You just need to measure it sometime.