s4master1

Have you heard of lwfw? Light weight fly wheel.
You can have any Audi engine running without flywheel

mishar

This discussion has no sense.

s4master1

conveniently.
I was expecting a more technical/detail explanation of why is needed and why would the engine die without

mishar

As I said: "Yet they need a flywheel for exactly the same reason. On everything less than R6 (may be R5 counting mass of the crankshaft) total torque gets negative in the part of every rotation. No flywheel, or whatever you call it (may be even propeller), and engine would stop running."

May be it is too technical? That negative torque tend to stop crankshaft. In order to keep rotating it needs some energy. Kinetic energy stored in the flywheel, or may be propeller. Six (and more) cylinders do not have that negative torque so they can work without any flywheel but they still have them on both sides of a crankshaft to dump torsional rotations. There we can talk about dual mass and so on.

s4master1

[QUOTE=mishar;24305187]As I said: "Yet they need a flywheel for exactly the same reason. On everything less than R6 (may be R5 counting mass of the crankshaft) total torque gets negative in the part of every rotation. No flywheel, or whatever you call it (may be even propeller), and engine would stop running."

May be it is too technical? That negative torque tend to stop crankshaft. In order to keep rotating it needs some energy. Kinetic energy stored in the flywheel, or may be propeller. Six (and more) cylinders do not have that negative torque so they can work without any flywheel but they still have them on both sides of a crankshaft to dump torsional rotations. There we can talk about dual mass and so on.[/QUOTE
I totally agree on the kinetic energy, even some old manual hand crank machines had them to help keep momentum and make operation easier.
however on the negative torque you talking makes no sense on these engines.
give you an example that is even old at this point, is 4 cylinder and was/is the largest production 4 cylinder displacement engine on a passenger car.
PORSCHE 944S
it has no flywheel nor has a harmonic balancer. it does however has 2 balancing shafts, furthermore in the past I personally seen quite a few of them coming in with broken balance shaft belt and the only complaint was slight vibration at idle and around 2200 RPM, but they drove in all the time.

newer engines have quite shorter stroke and they are so much more balanced that you can have them running on a table and they won,t move at all.
look at old tractors, they had a huge flywheel on the side just to store a bit of energy and give momentum for the cylinders to start the cycle, those engine however had a very long stroke and were merely design for torque.
at this point the crankshaft has more than enough mass to get things going and even the cranks are getting lighter.

mishar

I always wonder if this is your way to ask something and not pop the question.

Here are some images of a non existing object:


Less mass and shorter stroke doesn't make a difference. Higher compression ratio and more intake air does. Making negative part (compression cycle) more negative. Turbo makes it worst.

P.S. Tractors have a huge flywheel so they can accumulate kinetic energy and add it to the max engine torque when needed.

s4master1

can you find a picture of the automatic?.
we all know the manual ones always need a surface for the clutch disc, and even those you can change to a light weight flywheel.
but if you find one for the automatic all you can see is the flex plate in that place.

mishar

We started this stupid discussion with this. Flax plate + torque converter = flywheel (rotating mass that accumulates kinetic energy and utilize it to smooth torque output). Physics is relevant, wording not.

s4master1

there was nothing stupid about the conversation, the guy just clarify that automatic A8 has no flywheel which is true.
you brought in the technical stuff and I just ask for a more detail elaboration, plus am not disagreeing on the function of a flywheel just stating the points where it does not quite make sense on these engines, my mistake on the 944S as they only came in manual but all the automatics don,t have a flywheel or harmonic balancer on the crank.
furthermore check the ferrari/maserati/porsche F1 clutch is so much smaller than your average clutch/flywheel assembly.
flywheels are not particular to engines, I remember an old McCormick manual corn grinder with huge flywheel to help you operated easier once it get going, however if/when something went wrong and you needed to stop it fast it was just not possible.
on these engine with the crank mass is more than enough to compensate.
and YES in automatics is not call flywheel is call flex plate or drive disc.

mishar

I think it is quite stupid because it is about irrelevant thing such is a name used for some part. There are more than 6800 languages in the world and many of them have their own word for a flywheel. These are German cars. Should we use Schwungscheibe instead?

For me it is technical, as this forum is. If it is about poetry than words would be essential.

On the other hand you are bringing up wrong examples. Mentioned cars have 8 or 12 cylinders. As I said everything above 6/5 doesn't need a flywheel. Even such engines, if designed for a luxury cars, would have one, whatever you name it and additional one at the front in order to smooth torque.