Short Answers Not Allowed Here | Posts 48+

Hi Uwe,

j.weimann wrote:

You can see the power on the speedometer, and the torque pulls you backward.

Despite all the ambiguity, there's definitely some truth to it.
"When supplemented in the direction of..."
"Good torque pulls you forward without having to rev the engine excessively."
then we end up back at the TDI .

You already described it with...

Quote:

Ultimately, the higher performance wins, not the maximum power, but rather the currently available power. And this happens precisely when as MUCH POWER as possible is applied to the current engine speed.

What I would like to add is:
The lack of torque must be compensated for by high engine speeds to achieve rapid acceleration, which means downshifting into the maximum power range. Drivers of normally aspirated engines in cars with the weights that are unfortunately common today can certainly attest to this.

Anyone who imagines the effort it takes to move a motor even just one rotation by hand, with the glow plugs or spark plugs removed, can imagine the amount of energy that must be drawn from the fuel for each rotation in order to keep the engine running at all.

If you then imagine that gasoline engines operate at a roughly 50% higher RPM range compared to diesel engines (with the corresponding high power loss!), which is absolutely necessary for noticeable acceleration, then I "see" what you mean.
- the vortex in the tank.
- to secretly applaud the finance minister.

What is also clearly confirmed by the actual consumption figures...

When it comes to the combination of driving pleasure through torque and good fuel efficiency, TDI engines and their relatives are likely unbeatable for the time being.
Apparently, even high-tech features like FSI and similar technologies do not change this (according to relevant test reports). These features seem to be more fuel-efficient only in the lower performance range compared to conventional gasoline engines, but this advantage is rarely utilized given the general power requirements for reasonably fast movement (except when going downhill or with a tailwind ).

Assuming a motor produces 400 Nm of torque at 2,000 RPM, 266 Nm at 3,000 RPM, and 200 Nm at 4,000 RPM, with 100 Nm at 8,000 RPM, then it would always produce the same power output (114 horsepower) at 2,000, 3,000, 4,000, and 8,000 RPM. In that case, it wouldn't matter which gear you use to accelerate; the acceleration would be the same for a given speed!


That sounds very reasonable.


The winner is always the one with the higher power output, not necessarily the maximum possible power, but rather the power currently available. This happens precisely when as much power as possible is applied at the current engine speed.


'AT THE SAME SPEED, you said earlier. And that's important. A car with a higher maximum RPM simply has more engine revolutions per minute in the same gear. Therefore, a vehicle with, for example, a redline of 4000 RPM at 50 km/h will have 2000 RPM and, with, for example, 200 Nm of torque, will produce approximately 57 horsepower.'
A car traveling in the same lane with an engine speed of 6000 RPM and a speed of 50 km/h then operates at 3000 RPM. To achieve the same power output and therefore the same acceleration at 50 km/h, it only requires 133 Nm of torque.

And that finally explains the real purpose of this thread. Adrian asked why a diesel engine has to produce so much more torque in order to achieve the same pulling times.
And that can now be explained using torque and gear ratio.
Or with power at speed.

Here's the translation:

Power = Torque * Speed / Gear Ratio.

Or: Speed = Power / (Torque * Gear Ratio)

I think the way Ulf did it in the DZR with the torque is the best because it provides acceleration in the most straightforward and easily understandable way.
'And this acceleration should be relatively constant. (That is, the power output should increase with engine speed because the power demand also increases with speed). A slightly better acceleration at lower speeds wouldn't hurt... that's how most everyday cars are designed. However, in higher performance classes, a constant torque curve is often optimized for driving dynamics. See models like the Audi RS4, RS6, or Bugatti Veyron.'
A vehicle with constant power output across the RPM range (meaning immense torque at low speeds) would feel like it's constantly accelerating at its maximum rate, because the acceleration would decrease proportionally with speed: 10 m/s² at 10 km/h and 1 m/s² at 100 km/h.

Best regards,
Ernst.
There's no judgment between diesel and gasoline... it's simply a matter of understanding the laws of physics, and I have a pretty good grasp of those after four years of studying mechanical engineering with a focus on vehicle technology.

And that can now be explained using torque and gear ratio.
Or with power at speed.

Okay, here's the translation:

Power = Torque * Speed / Gear Ratio.

Or: Speed = Power / (Torque * Gear Ratio)

That's what I meant. 1 watt = 1 nm/s, where 'n' refers to the turnip and 'm/s' refers to the speedometer. This is without considering the mass of the turnip or any gear ratios. In the future, I will refrain from using kinematic/kinetic approaches.
best regards, j.

Performance can be seen on the speedometer, and torque pulls you backward.

1 watt = 1 nm/s, where 'n' refers to the turnip and 'm/s' refers to the speedometer.



Okay. Then you need to correct your first sentence.
'...and the force pulls your lower back backwards.' Because Newton's law still applies: it's about force, not torque.

But then I really like that sentence .
Best regards, Ernst.

In the Lupo (with an AMF of approximately 260 nm), I like the combination of being very small and having a lot of power. Cars like this, often referred to as 'organ grinders,' have existed for a long time (like the Mini Cooper or Abarth), but a diesel version? Well, the Golf... it's not really that small anymore. However, the three-cylinder engine makes quite a racket, almost like a fishing boat, and the power delivery gives you a guilty conscience on the highway.
See you soon.
j.

Hi Ernst!

Ich glaube, wir haben es nun geschafft. Thank you.

ulf wrote:

... then I "see" it. - the vortex in the tank.

Thank you again for the well-crafted wording. I see it exactly the same way.

To add another praise for the TDI engine, here's a testimonial:
A while ago, I test drove a BMW 530 diesel, the current model, unfortunately with an automatic transmission. I expected massive torque and powerful performance, but what I experienced was a heavy, sluggish vehicle with average performance that doesn't suit a three-liter turbo diesel at all. The automatic transmission prevents the engine from reaching RPMs below 2,500 until you reach 100 km/h because the torque converter has too much slippage. It only engages the torque converter lockup *at most* around 100 km/h, and then you can finally drive at 2,000 RPM. Overall, the performance is significantly worse than my chipped 1.9 TDI. All in all, it's a nice car, but it certainly can't compete with a TDI in terms of engine performance.

Best regards,
Uwe

No one has said that BMW builds good automatic driving systems.

I also experienced something similar in a 520i with Steptronic, or whatever they call it. It feels less responsive than the old fully hydraulic automatic transmission in my 'old-man's car.' By the time it reacts to acceleration or deceleration, the corner is already gone.

drive the 'TDI' 3.0 with a manual transmission .

CU Gremlin.

Hi!

It's possible that the automatic transmission is working better now, but - on a "reference incline," the 530 with kickdown only reached 120 km/h, while mine exceeded 150 km/h. How much fuel should the automatic transmission be consuming?

Best regards,
Uwe

Good question...

Although I've modified the software for my transmission, the wastegate closes at speeds above 60 km/h in 3rd gear, and it remains closed unless you accelerate very aggressively. Then, the car pulls forward like a TDI. The wastegate also stays closed during gear changes into 4th (at approximately 135 km/h).
If BMW leaves the natural aspiration open to its maximum extent, it will negatively impact forward momentum.

CU Gremlin.

Hello,

Thank you for the interesting contributions. I think the 'problem' is now solved. Unfortunately, I didn't understand everything immediately (I'm not a mechanical engineer), so I'll go back and reread some parts to let them sink in.

Best regards,

Adrian.

I don't think you can compare TDIs with gasoline engines.
You don't compare apples and oranges!

The gasoline engines discussed here were all naturally aspirated, making it an 'unfair' comparison.
TDI engines have a turbocharger, which is why they produce such high torque.



'If you compare the diesel engine with 150 hp to the 1.8-liter gasoline engine with 150 hp, it looks quite different. That would probably be a fairer comparison.'


Just as an example:

A gasoline-powered Polo with 60 horsepower (naturally aspirated engine) versus a diesel Polo with 60 horsepower – it's probably not even a question that the gasoline version will outperform the diesel one by a significant margin.
Just as a random 'sucking' sound...


Best regards,
Ingo

'Just compare the diesel engine with 150 hp to the 1.8-liter gasoline engine with 150 hp, and you'll see that it looks quite different. That would probably be a fairer comparison.'




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

GOLF IV TDI-PD 110 kW.

0-100 km/h - 8.6 seconds.
80-120 - 8.4s


GOLF IV 1.8T 110kW

0-100 km/h - 8.5 seconds.
80-120 - 12.0s


GOLF IV V5, 126 kW, 220 Nm.

0-100 km/h - 7.6 seconds.
80-120 - 11.1s


CU Gremlin.

Hmm, is this from the same source as the other values mentioned above?


As far as I remember, the 1.8T was superior in terms of responsiveness, at least that's what it said in 'Gute Fahrt' magazine.

It doesn't really matter anyway...

The 1.8T engine in the A3 was significantly less flexible and responsive than the 130 horsepower common-rail (PD) diesel engine.

CU Gremlin.

Hello!

Comparison of two turbocharged engines with 150 horsepower.
Here's the data from the final run. The top speed for both was 216 km/h, so that's a good match. Enter the torque values into the driving chart and you'll get the result...



In situations where you need maximum power (from 150 km/h to top speed), the gasoline engine performs slightly better.
If one were to perform an elasticity test at speeds of 50-100 km/h in the highest gear... poor TDI driver.

If all the gears were listed, the TDI would be in the lead... it has 6 gears, while the gasoline engine only has 5, resulting in a poorly spaced transmission for a top speed of 216 km/h.

P.S. We could also start a new thread sometime; this one is getting a bit 'cluttered' and doesn't really have anything to do with Adrian's question anymore.

Based on what I've seen so far, I would either buy the 130 hp TDI or the 150 hp gasoline engine. The 150 hp TDI is more for 'enthusiasts.'


Okay, I would first sit in it, test drive it, and then decide whether to buy it.

theory and reality often differ SIGNIFICANTLY .

CU Gremlin.