Die Crux der niedrigen Drehzahl | Posts 16+

@Jochen
wegen die Verbrauchsenkung, siehe Antwort von Roger, so kenne ich das auch eher. And because of:

If the system is sluggish, you cannot briefly accelerate with full power and then use the thrust cutoff while rolling.

The regulation is not becoming any slower, is it? We can't possibly be talking about seconds, can we?

Of course, I'm familiar with that as well, just like Roger is with gasoline engines. Here, as is common, the goal is to reduce throttle losses.

Regarding the regulation, I sometimes need 2 or 3 seconds after a period of low load before the regulation kicks in.
Okay, Uwe's car consumes an extra liter, and that won't be achieved through this rule change, I agree with you on that.
However, you'll start to notice a difference in the 1/10-liter range, whether you accelerate more or less aggressively.

I do have one more idea, although I find it to be quite far-fetched:

AHF has a VTG loading system.
The VTG turbocharger can use its exhaust flow to provide braking force. To achieve this, it is operated at a boost pressure of 0.1 bar.

Here's my speculation:
The turbocharger is operated at precisely this boost pressure because it achieves a rotational speed where its moment of inertia has the most significant effect, and it optimally brakes the exhaust flow.

If Roger frequently uses the turbo in this range, he needs more energy to power it. If soot then accumulates on the turbine blades, this effect is amplified, and the fuel consumption increases further, until the blades are 'cleaned' again.

If my speculation is nonsense, just ignore it .


Best regards, Jochen.

@ Jochen

The VTG brake exerts a pressure significantly higher than just 0.1 bar.

See segment "B" on this Leon ASV.

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In my opinion, for example, the fuel consumption advantage of the 110PS TDI compared to the 90PS TDI in the Seat Leon is...

When it comes to the 90 horsepower Leon, you need to check whether it's an AGR (wastegate) or ALH (variable turbine geometry) TDI engine.

It's clear that the 'Waster' version consumes more fuel. That's why the G3 with 90 horsepower consumes more than its 110 horsepower counterparts (in the G3, the 90 horsepower version was always considered the 'Waster' version).

m;
In the Leon, there was always a VTG loader installed - it's news to me that the AGR was also available in the Leon - it was available in the Toledo, yes, but not in the Leon?
I'm familiar with that process, just like Jochen was with my previous TDI-powered cars.

Oops.
I believe we've discussed the AGR Leon before. My "reliable source" claims it existed, but it probably wasn't actually a thing... or perhaps it was only available in certain regions.
Just like in Germany, the Ibiza ASV was the only model marketed as a "sport" version, but Jan has a Dutch "Signo" model that also has the ASV designation.

m;

Uwe wrote:

Since I switched to one more gear, not only has my driving style changed, but also the engine speed has changed dramatically. It now takes hardly more than 2,000 RPM, and my tachometer only shows 3,000 RPM in exceptional cases, while the speedometer next to it shows a solid 180 km/h. "In normal traffic flow, I average around 1,600 RPM. I initially assumed that, in addition to the car's characteristics, the fuel consumption would also adapt to the conditions. Unfortunately, things didn't quite go as planned. At first, I saw a savings of about 10 to 15%. However, it seems that some kind of residue is building up inside the engine, which leads to increased fuel consumption after a few tankfuls, rather than less. Only after I can use a stretch of open highway does my fuel consumption return to normal. However, those types of roads are not very common in my area." The difference is approximately one liter. What is the reason for that? What can I do about it, besides giving up my sixth gear?

*ausgrab*

Hi Uwe,

Are there any more recent (or more reliable) consumption data available?
Did you also experience a similar difference between "blown out" and "slowly driven" with the 5-speed gearbox?


I'm also a bit frustrated with the fuel consumption of my Polo compared to the AFN-G3: an average of about 4.3 liters per 100 km is not terrible, but with the G3, I usually got around 3.8 - 4.0 liters per 100 km with the same driving profile (mostly country roads and small towns).

I understand that a PD-ASZ (common rail injection system) tends to have a lower efficiency at low engine speeds compared to a VP-TDI (injection pressure at the injector).
However, I also suspect the transmission. It has two bevel gear output shafts (for gears 1-4 and 5, 6, R) that are constantly engaged with the differential. This means that one unloaded shaft is always spinning faster than in a 5-speed transmission, and this undoubtedly consumes power, which increases fuel consumption.
Does anyone here happen to know the approximate additional power requirement (depending on the speed) that this causes?

Hi Ulf!

The starting situation is still the same, with no significant changes. I'm just getting on the highway a little more often, but unfortunately, still not frequently enough to cover sufficient distances.

During my highway drives, I've noticed that after driving at high speed for an extended period, the next morning when I start the car, my entire surroundings are completely fogged up. It's always a rather unpleasant experience. However, everything is fine again with the next start.

I wouldn't logically expect it to be hot, as there are several kilometers between the highway and the parking lot. However, I noticed that the fog light under the hood was on during the subsequent cold start. I'm also not entirely sure if it's diesel or oil. I suspect it's diesel, though.

Interestingly, I only experienced this effect on my trip last weekend, only on the outbound journey, about 200 km away. In the morning, I had once again "contaminated" the parking lot. When I started the return journey in the evening, I drove those 200 km in 1 hour and 20 minutes, mostly using cruise control at 200 km/h. In the morning, everything was probably completely cleared out, and it started without any fog.

My fuel consumption is usually around 5.3 liters, but after cleaning, it was about 4.7 liters for several tankfuls. On the highway trip this weekend, it was almost 8 liters.

By the way, I also have the DRW gearbox with the double set of wheels installed. Obviously, the power consumption is quite low.

Hi,

I've also made a small contribution; my car has a slightly longer 5th gear ratio compared to the others.

Initially, I experimented with different driving styles to achieve fuel efficiency. I found that driving at low RPMs (up to 2000 RPM) and accelerating gently resulted in high fuel consumption. Similarly, accelerating with nearly full throttle also increased fuel consumption.

After increasing the RPM to 2500 RPM and accelerating with approximately 3/4 throttle to reach speed as quickly as possible, I drive more efficiently. That means: in 1st gear, only start moving (otherwise it becomes uncomfortable and puts too much strain on the tires ); in 2nd and 3rd gear, use 3/4 throttle; in 4th gear, reach top speed, and then shift into 5th. For example, you can reach speed within a few tens of meters when exiting a town and then maintain that speed for the rest of the journey.

"I'm saving about 0.5 liters of fuel and, overall, the engine is running a bit smoother. I've experienced some issues with the clutch, and the dual-mass flywheel also started to vibrate..."

Best regards.

M3mph15

Hi,

What is Blue Motion's approach here? They supposedly have extremely long final stages, yet they are still incredibly fuel-efficient.

Perhaps it would be an idea to combine the very long gear ratios, or a 6-speed gearbox, with a corresponding software (SW) modification for this purpose...

Perhaps Rainer's Spritspar-Tuning is actually a perfect fit for that.

Best regards,

Jan.

BM models don't just have long gearboxes.

They mostly have various aerodynamic modifications.
I wouldn't approve of that for all models with different engine configurations.

For example, the Passat does not have any air ducts for brake cooling in the front bumper.
Sure, they cause quite a stir - but I also want that when braking hard from 220 km/h.

In addition, he closed 2 cooler fins - at full throttle at 35 degrees, I also want to see those open .

m;

Hi Uwe,

How many kilometers has your car been driven? Could it be that the injectors are no longer in perfect condition and are causing carbon buildup at partial load?
A back pressure, if it's causing the catalytic converter to break down, could only be coming from the mufflers, but the openings in those should be relatively large.
Or is it simply that the cat no longer uses it, despite the geometrically perfect monolith?

I believe that increasing the turbocharger boost pressure is not beneficial. Even if it does provide any improvement, it likely leads to increased fuel consumption due to the poor efficiency at closed throttle, which would negate any potential fuel savings.

"Before my trip, the tire pressure was 0.5 bar when fully loaded, between ATL and Kat. After the trip, it was 0.3 bar. The fuel consumption decreased by 0.5 liters per 100 km, although the wind conditions might have played a role. Also, the onboard computer now shows lower values for fuel consumption during city and highway driving, especially when accelerating quickly."

Hi,

Quote:

BM models don't just have long gearboxes. They mainly feature various aerodynamic modifications.

Of course, I know that. Initially, the discussion was about the negative effects of operating at very low speeds for extended periods due to the very long gearbox. That's why I mentioned that the problem Uwe is experiencing is likely also present in BMWs (because they also have very long gearboxes) or that a production solution has been found for it there.

Best regards,

Jan.

christians wrote:

How many kilometers has your car been driven? Could it be that the injectors are not working perfectly and are causing carbon buildup at partial load? A back pressure, if it exists after the catalytic converter has been destroyed, can only come from the mufflers, but the openings in the mufflers should be relatively large. Or is it simply that the cat no longer uses it, despite the geometrically perfect monolith?

The engine has approximately 150,000 kilometers on it. The nozzles are probably not in the best condition anymore.

Counter pressure shouldn't be an issue for me. There isn't much there where dirt could accumulate .

Hello!

No offense, but what do you actually expect when you operate the engines far below their optimal RPM? Even if you were to force enough air in with an external supercharger, the fuel consumption would still be higher than if you ran the engines at their optimal RPM. And neither variable valve timing nor anything else will fundamentally change that. That's just the nature of the internal combustion engine; get used to it.

Perhaps they should also print a green sector on the tachometer in cars...

BYE
TDI mechanics.

tdi-schrauber wrote:

but what do you actually expect when you operate the engines far below their ideal RPM?

I expected to save about 5% by upgrading to a 6-speed transmission. However, I achieved a fuel consumption reduction of over 10%.

What exactly is "ideal engine speed"?

For me, the speed range around the peak torque is the ideal speed for fuel efficiency.
The ideal speed for mowing is found within the range between the stall torque and the maximum power.
Going uphill, shift to a higher gear; going downhill, shift to a lower gear (but this requires a gear ratio that's too long).

teileklaus wrote:

The area around the maximum torque is, for me, the ideal speed for fuel efficiency,

It's possible. For me, it's 120 km/h. Unfortunately, the many cars in front of me don't know that.