Schwungscheibe erleichtern, AFN | Posts 16+

Hello,
With a smaller flywheel mass, it can sometimes 'hesitate' and stall more easily when starting.
Best regards,
Günther

Hello,

I didn't want to give the impression that changing the rotating mass affects the motor's torque.

But it's about the force acting between the tire and the road.
To change the rotational speed of the wheel, I need torque. This torque causes a change in the wheel's angular momentum. The angular momentum includes the moment of inertia.

So, I need torque just to accelerate the rotation of the wheel. This torque is effectively not available to accelerate the rest of the vehicle's mass.

"If you install wheels with a moment of inertia of 5 kg/m² on your car, you will be able to complete the acceleration test faster than with wheels that have a moment of inertia of 10 kg/m²."

Somewhere, that extra energy stored in the higher rotational momentum of the heavier rims has to go.

Best regards,
Georg.

Hello Georg_C,
Every motor has an efficiency, and that efficiency is always less than 1.
There are a few things that could be improved, but is starting with the flywheel really the best place?
Ulf has had more 'success' in that area so far!
Best regards, Günther.

Hello Günther,

That's not what I was talking about at all.
Only further up, before DonAlexo properly corrected things, was it possible to read that a heavier flywheel leads to more torque. That's when I wanted to add my two cents .

Best regards,
Georg.

Hi everyone,

I've certainly caused quite a stir .

I will have my flywheel lightened and balanced together with the clutch (of course, without the crankshaft & connecting rod, etc. - don't take everything apart ), and then I will report back on how the driving characteristics are.

So, according to what I've heard, increasing the engine's RPM improves performance, but I'll explain more about that later.

Regards,
DJ.

So, according to what I've heard, increasing the engine's RPM improves performance, but I'll explain more about that later.


In the lower gears, this is because the motor's moment of inertia is low compared to that of the wheels and the vehicle (gear ratio!).
You probably won't achieve the desired effect with the higher gears...

CU.

Hello!

Now, adding my two cents (with admittedly not complete knowledge about mass dynamics - is that the right term ), I recently rode in a car with a VTEC engine that had a flywheel installed that was almost half the weight of the original.

The driver says that smooth clutch engagement is slightly more difficult than before, but it's not dramatically bad. He notices a slightly rougher idle, but to me, as a passenger, it seemed normal - purring and with minimal vibration, as you would expect from a gasoline engine.

Regarding acceleration, it should be noted that this engine can rev up to 8,000 rpm from the factory. With an engine control unit that doesn't have a rev limiter, the engine exhibits an acceptable power drop-off up to 9,300 rpm, allowing it to effectively utilize this higher rpm range, especially in the lower gears. While this rpm can also be reached in higher gears, the effect is less pronounced there.
'Why?' one might ask. Either you read the explanation provided by the academics earlier in the thread, or you simply imagine it for yourself.

Torque represents the available force – in relation to mass, it determines acceleration. How much force does the motor need to apply to accelerate the flywheel from, for example, 1000 rpm to 9000 rpm in 2 seconds? In comparison, how much force would be needed to achieve the same acceleration in 10 seconds?
The same, but spread out over time. That's the key!
The 2 seconds for first gear and the 10 seconds for fifth gear suggest that, subjectively, the motor requires 'more' power in first gear to bring the flywheel up to its operating speed compared to fifth gear.
(Ugh... *already bracing for the lash*).

To continue the review:
In reality, better acceleration could be achieved in this vehicle. Besides the driver's enthusiasm, even as a passenger, you can feel that the first gear, which revs up the fastest, noticeably struggles to transfer its power to the road.
Is the slight increase in torque (at the wheel) or the altered 'waviness' of the torque oscillations responsible for the increased wheel spin?


The TDI, or diesel engine, provides more torque within a smaller RPM range compared to a gasoline engine. This means the flywheel is accelerated more easily, and less acceleration is required overall. Therefore, the tuning effect achieved through flywheel tuning is not as significant in diesel engines. This is likely the reason why it is not as widely used.


But perhaps someone will still enlighten us and share their promised experiences regarding the driving characteristics of a lighter flywheel here. ( dj1

Best regards.
Peter.

Quote:

But perhaps someone will still enlighten us and post their promised experiences regarding the driving characteristics of a lighter flywheel here. ( dj1 icon_wink.gif )

"For extremely high-revving gasoline engines, where power is primarily derived from high RPM, this works wonderfully. However, these engines tend to be rough at low RPM. In my old GTI 1.8 with approximately 140 horsepower (with the flywheel partially removed), you had to give it a bit of gas when starting, otherwise the engine would stall immediately, which could even cause you to lurch forward. However, the throttle response was excellent."

However, I believe this is counterproductive for diesel engines. Firstly, they are inherently sluggish, so the effect will hardly be noticeable (Force = Mass x Acceleration). Secondly, they need that rotational inertia to run relatively smoothly.
I think that with a significant reduction in flywheel mass, the machine would essentially become a vibrating plate and would be more suitable for road construction. And let's not even talk about the durability of the timing belt and other auxiliary components.

Yesterday, I installed a G60 flywheel along with a Sachs Performance clutch in my ALH engine because of a faulty dual-mass flywheel (DMF).
From some reports I had read, the G60 EMS with clutch was said to be 3kg heavier than the ZMS with clutch.
After I had taken everything out (it was a lot of work), I weighed it, and it turned out that the EMS and ZMS had exactly the same weight!
The only unfortunate thing about the whole story is that I had the EMS system lightened by 3 kg and finely balanced to compensate for the weight reduction.
In plain terms, this means that instead of the 14.3 kg of the old flywheel and clutch assembly, I now only have 11.3 kg of rotational mass.
During my first drive within the town, I noticed that it responded noticeably better to the accelerator and revved more freely. There were no vibrations or any other loss of comfort that I could detect.
BUT!!! On the way home, I drove 70 km on the highway, and I have to say that it doesn't perform as well at high speeds.
For example, when I pressed the accelerator at 180 km/h, I felt a surge of power and noticed that the car was still accelerating strongly. I'm calling it the "turbo push," which is something you feel with a gasoline engine when it kicks in. That feeling is now gone. The car still reaches 200 km/h just as quickly as before, but that feeling of being pushed forward is no longer there. As a result, the acceleration feels subjectively slower.
Despite the expectation that the small flywheel, which serves as an energy storage device according to the principles of mechanics, would store and release less energy, leading to a decrease in performance, the device maintains the same values as before.
It's also possible that I experienced some slight headwinds last night during the ride from Kassel to Paderborn, which happens quite often, and that could explain why I didn't feel like I was pushing myself as hard.
I will observe the entire process and will probably reinstall an original G60 flywheel so that I can get back to my original weight of 14.3 kg.

"The behavior cannot be explained using formulas from dynamics, but the point mentioned above regarding charge transfer work, etc., might still be relevant to the overall system. Perhaps it's too complex for me, as a machine builder, who can only calculate stationary cyclic processes and dynamic relationships. In that case, an expert in the field of internal combustion engines would need to be consulted to provide meaningful results."

Wishing you a wonderful holiday season and a happy start to the next decade.


Regards,
Patrick.

Anything you observe at high speed is most likely not related to the flywheel.

Can you also provide some justification for that? I can just throw out random phrases if I wanted to.

I assume that the motor, especially at high speeds where there are fewer "grains" (presumably referring to fuel or energy units) available, draws energy from the flywheel to maintain a certain level of performance. When further acceleration is attempted, 1. the energy from the flywheel can better maintain the speed, requiring less motor power, and 2. the increased inertia of the flywheel makes it easier to accelerate further because only work is required to accelerate, not to maintain the speed.

Quote:

Could you perhaps provide some justification for that? I can easily just throw out some random phrases if I wanted to.

Think about which 'masses' come into play when, in the final gear, the crank shaft is almost directly linked to the wheels with a 1:1 ratio.

Okay, let's add up gears, shafts, rims, tires, etc., consider their radii, and then think about whether 3 kg of rotational inertia is significant. Just considering the wheels alone, the impact of a lighter flywheel is laughably small.

Best regards, Rainer.

patrick8549 wrote:

Can you somehow justify that?

I can explain that for you, acting as a representative.

The flywheel stores kinetic energy, which in German is called "Schwung."

When the speed changes, the flywheel releases or absorbs its kinetic energy accordingly, depending on whether the speed is increasing or decreasing.

When you're driving on the highway in the highest gear, there's no significant decrease in engine speed, which would cause the flywheel to release energy.

In other words, the flywheel has no effect on the engine's power output.