What's the difference between flywheels?

Bumping because I don't know shit about flywheels

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>tfw the teeth on my flywheel dont match up right with the teeth on my starter so every time i start the car it grinds to shit

Why are you contemplating this? Are you replacing the flywheel on your car? If so, what kind of car and what is your intended purpose for that car?

what dont you understand about heavy spinning objects?

the heavier they are, they slower they take to spin up
the lighter they are, they quicker they spin up

heavier things tend to stay spinning longer
lighter things tend to not spin as long


a heavier flywheel stores more momentum, and energy, that's what gives cars more torque, when you connect the trans the heavy flywheel will absorb some of those forces and allow the engine to keep its rpms.


imagine a fan. a plastic one, and a metal one. same size.

which do you think is harder to slow down?

>>14772124
Not trying to replace it. Its just that i am a mechanic student. And after i came to the realization that every single thing on a car has a physical reason and effect, i just want to learn WHAT exactly does everything does to the car, instead of going


"ok, this thing does that thing and it has that effect" i want to learn HOW that thing works, HOW is it built and HOW it does that.

In this case, all ive heard about flywheels just doesn't make any sense.

>>14772061
What are starter shims?

>>14772131
>what dont you understand about heavy spinning objects?
>the heavier they are, they slower they take to spin up
>the lighter they are, they quicker they spin up
>heavier things tend to stay spinning longer
>lighter things tend to not spin as long
That i already know, but it goes against everything ive heard.

"a heavier flywheel stores more momentum, and energy" But it only holds more momentum while the car is in gear and not using the gas, since after you open the throttle the heavier flywheel only removes power that could go diretly to the transmission.

>when you connect the trans the heavy flywheel will absorb some of those forces and allow the engine to keep its rpms.

Again, something the thrust bearing fixes if its good enough.

>imagine a fan. a plastic one, and a metal one. same size.

which do you think is harder to slow down?

But why do you want it slower to slow down if the metal one moves as much wind and its harder to spin up and requires more power?

>>14771815
Heavier flywheel, more inertia. Takes more throttle input to make a change in RPM, and has more of tendency to stay at a RPM.

Light fly wheel, less inertia, Less throttle input to change RPM and has less of a tendency to stay at a stable RPM.

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>>14772223
>has less of a tendency to stay at a stable RPM.
But why would you want it to make it stay at stable RPM if you are not accelerating it? this only has an effect if you keep it at a gear without using the gas nor breaking nor using the clutch, so what's the point?

>>14772167
The problem is that you think you know more than you really do, but you lack basic fundamental physics knowledge and so are completely out of your element, donny. Let me break it down for you:

>>Lighter flywheels are weaker
>Which makes sense if its all a single material etc
You don't know what you're talking about. Take a material science class and learn about alloy properties. There will be tradeoffs, and one guaranteed weakness of unobtainium is price.

>>Fucks up harmonics and vibrations in the car
>But shouldn't a good Axial rod bearing or a bigger engine deal with that crap?

LITERALLY WHAT. If "hurr better bearings" and "hurr bigger engine" made harmonics not matter, why would the bank angle of a V6 matter? Why would we have counterweights? Why would we care about firing order? Why would we literally do ANY of the things that have to be done to balance an engine?

Do you even understand how harmonic oscillation works? Hint: The frequency is based on the mass of the oscillator and its spring rate, and you're changing one or both of those when you change the flywheel.

>>since the revs stay in the same zone for longer its easier to shift without fucking the tranny
>Yeah but that's why you double-clutch/press the g

You don't know how to drive. You think you do, but you don't.

>>Easier on the hillclimb because it holds inertia better
>Yeah, this makes sense, but after you

They're not that much heavier you turd

>>heavier flywheels are better for low-end torque
>That doesn't make any sense, again, if you are pulling something the heavier flywheelare better for low-end torque

Where are you getting this shit?

http://www.uucmotorwerks.com/flywheel/there_is_no_torque_loss.htm

>>14772265
>You don't know what you're talking about. Take a material science class and learn about alloy properties. There will be tradeoffs, and one guaranteed weakness of unobtainium is price.
Now you are making things more complex


1 inch plate of aluminium is gonna be X strong, 2 inches is gonna be stronger. If a plate of the same material is half an inch wide, its gonna be weaker.

"If "hurr better bearings" and "hurr bigger engine" made harmonics not matter"

They dont make them not matter, they make them be less of an issue, if they didn't matter then the V8 would be the most stable engine in the world.

>Why would we care about firing order?

Because a crankshaft can break if all the force from the connecting rods is placed upon a single point. That's why usually smaller engines with smaller crankshafts can rev up higher.

>Why would we literally do ANY of the things that have to be done to balance an engine?
Because there is so much the thrust bearing can do since its just a small little piece of metal.

>Do you even understand how harmonic oscillation works?

Honestly not much.

>You don't know how to drive. You think you do, but you don't.

Are you mentally challenged? if you slightly hold the gas before relasing the clutch after upshifting there is less stress between the crankshaft and the input shaft of the tranny, making the car jolt less.

>They're not that much heavier you turd

They are heavier enough to make a difference.

>http://www.uucmotorwerks.com/flywheel/there_is_no_torque_loss.htm

Have seen the link. Did you even read the fucking article? the higher torque at first its because the dyno was taken while droping the clutch at higher revs.

If someone with a higher flywheel drops the clutch at 7k RPM he will have more torque in the crank than someone with a light flywheel.

That still doesn't prove how somehow the heavier flywheel helps produce more low-end torque.

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>this thread

>>14772414
I am not trying to make a thread to have a discussion with people. I just want to understand what's the positive to having heavier flywheels.

>>14772357
>Are you mentally challenged? if you slightly hold the gas before relasing the clutch after upshifting there is less stress between the crankshaft and the input shaft of the tranny, making the car jolt less.

Why the fuck would you want to hold the gas when upshifting. When you shift to a higher gear, the engine RPMs will be lower for any given speed the car is traveling at. That means you need to let off the gas and let the RPMs drop before releasing the clutch pedal for a smooth shift. A lighter flywheel lets the revs drop faster, allowing smooth shifts to be quicker.

>>14772433
>Why the fuck would you want to hold the gas when upshifting
Because you dont want tho jolt the fucking car, making everyone inside and you incluiding uncomfortable? ruining anything fragile that you had around your car? stopping your car from bleeding speed when upshifting? Same logic as slowly lifting the foot off the brakes when almost coming to a stop, so that you dont feel the jolt backwards when the car stops due to the G-force changing suddenly

>When you shift to a higher gear, the engine RPMs will be lower for any given speed the car is traveling at. That means you need to let off the gas and let the RPMs drop before releasing the clutch pedal for a smooth shift.

Because as soon as you press the clutch and drop the gas the revs will go down to idle RPM, which is less than the RPM for the next gear you are gonna shift at at that speed

>A lighter flywheel lets the revs drop faster, allowing smooth shifts to be quicker.

Not 100% true but whatever, my point with this thread is that i want to know why isn't everyone just using a lighter flywheel and be gone with it.

>>14772466
>>Why the fuck would you want to hold the gas when upshifting
>Because you dont want tho jolt the fucking car, making everyone inside and you incluiding uncomfortable?
You realize you can time it so that it doesn't jolt? You engage the clutch at the higher gear as RPM decreases.

>>14772534
>You realize you can time it so that it doesn't jolt? You engage the clutch at the higher gear as RPM decreases.
>timing
The ligher the flywheel, the quicker the timing, and i cannot shift in half a second, not unless i start practicing.

>you engage clutch on higher gears
Will just result in rising RPM just to make noise, and spend more fuel. Slightly pressing the gas while dropping clutch is what ive been thaught, what my dad does, and what everyone in my country driving a manual (95% of the population) does to make a smoother riding and making the clutch last longer. (yes, i know its riding the clutch for a little longer, but it makes a smoother connection between the clutch and the input shaft.

>>14771815
>Which makes sense if its all a single material, but since materials keep getting lighter and lighter without changing thoughness since alloy R&D gets better that's not a permanent deal-breaker
Unless they're making fly wheels out of plastic or aluminium, they're lighter because there's less material in them which also makes them theoretically weaker. Steel alloys are all so close in density that it's just pissing in the wind unless you're talking battleship sized amounts or something that even five grams could make a difference.

>>14772595
There are more materials than aluminium, plastic and steel, anon. There are a shit ton of alloys that could be made, if not an infinite amount, based on the chemical proportion of the metals.

>>14772569
Are you confusing higher gears for lower? And all that matters is getting the RPMs to match, which is why "riding the clutch" works

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>>14772614
>There are more materials than aluminium, plastic and steel, anon
I'm aware of that you smartass shit. But those other materials are very, very cost prohibitive to anyone that isn't some top tier racing team with a five million dollar car budget. And those that aren't don't fucking work as flywheels or you'd see them being sold. Thus, you've completely disregarded the practicality of both your question and my response just to go "Hurr but what if."

>>14772629
Ok. Good point. So the chance of getting a stronger yet lighter flywheel to an average steel alloy are minimal and getting a lighter one does reduce strenght on it.

Another disadvantage compared to the heavy ones?

I laugh at people who put light weight flywheels on there street cars. It's an expensive mistake.

>>14772718
W H Y
H Y W
Y W H
W H Y
H Y W
Y W H

>>14772730
Stop and go driving is why.

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>mfw this thread

Need to buy flywheel, not sure what to get

>>14772167
just look at a traction engine if you want to know about flywheels

>>14772167
>Its just that i am a mechanic student.
If you find this kind of stuff anything but intuitive, you should probably drop out now, other sports beckon.

Heavier flywheels make an engine feel smoother and in to a point make the engine more driveable because the revs won't die as quickly for taking off. Doesn't matter between gears because unless your shifting incredibly slow you will be close enough to the same revs that it won't matter. There is also noise and vibration. Had a lightened flywheel on my old car and it has chatter in neutral. Most people will find that annoying or think it's broken.
I did notice in low gears it was noticeably quicker. Strength is not a real issue with flywheels because they only really need to be strong along the axis they are spinning and there is enough area of material that it would only be a problem if you went incredibly light. Clutch will slip before any flywheel breaks

>>14772718
Not that guy, but I know that a lighter flywheel will make the car buck and shake a shitton at low rpm/idle because of the lack of inertia, aside from that, are there any other disadvantages? assume that the lighter flywheel is strong enough to handle whatever power is being put down no problem

>>14772755
So you want me to make an expensive mistake instead of telling me why its a mistake to do so?

>>14772783
If all you are saying its correct, thanks anon. You made me realize there is literally no advantage over heavier flywheels.

>>14772787
I know that a lighter flywheel will make the car buck and shake a shitton at low rpm/idle because of the lack of inertia

Could be fixed by slightly increasing the idle RPM tho.

>aside from that, are there any other disadvantages?

Considering that and that the previous anon stated the strenght only matters in the center (if he is correct) no. there isn't another disadvantage i guess.

It only sounds/feel weird at low RPM and makes the car lighter and more responsive.

>>14772814
well the nvh advantage is important if you're talking production rather than modification. an engine can be too responsive I guess, if a normie got into a car that had instant throttle response he'd wrap himself around a tree while complaining about the noise

>>14772797
Yes. I have been told my sense of humor is very "british".

>>14772822
Good point.

Now, another point. Is it true that a heavier flywheel is required to carry more torque from the engine to the input shaft? or has BeamNG and Initial D lying to me about "responsive throttle"?

>>14772787
Not the poster but, i think at higher gears a light flywheel will give less Top speed than a Heavy one. there for a light one is good for aceleration and fast shifts.
i guess the lighter will rattle more because of the emense weight. that's why land barges have V8s and heavy flywheels. to be alot smoother

>>14772843
>i think at higher gears a light flywheel will give less Top speed than a Heavy one.
Nope.

The engine might produce slightly less torque with a heavy flywheel but the top RPM and differential/tranny gears will stay the same, so the top speed will not change.

>>14772843
I suppose V8 need bigger flywheels because
1- back then there weren't ligher alternatives
2- engine vibrations would be greater.

>>14772814
Heavy flywheel is better highway mpg

>>14772830
Considering how much torque the old v10 formulas have and they use a super light flywheel I would consider that bullshit. Besides, BeamNG has great destruction but pretty shitty driving physics.

>>14773037
To add to this, Flywheel weight doesn't affect torque. It only affects engine inertia. Ok, engine inertia gives you 'torque' off the line through the kinetic energy contained within its mass, but you know what I mean.

Here's a better description http://www.superstreetonline.com/how-to/transmission-drivetrain/impp-1005-lightweight-flywheels-fact-or-fiction/

Good question though I enjoy this type of shit on /o/

>>14773056
I had thought it was just that the engine is not allays in a power stroke and the mass of the flywheel tides it over to the next compression
at lest that's what the blade on my lawn mower does the engine will not run without it

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>>14771815
A lot of that stuff isn't entirely true.

>flywheel strength
oem iron wheels are generally weaker, but you can get strong (safe for high revs) wheels in lots of different weights.

>harmonics
Thats true. I lighter flywheel will make your idle feel rougher because there is less inertia that would encourage the engine to stay at a constant rpm. This is especially true of 4 cylinders.

>easier to shift
I guess that it would be easier to float shift if the revs don't jump around as quickly. But for most people that's not a big issue.

>better for low end torque
idk wtf that is about. heavy flywheels are better for clutch dumps on drag cars though.The extra stored energy can be put to the tires in addition to the engine's power.

Flywheels are just energy storage, nig. If you get a light flywheel then expect your engine to rev quicker in neutral, but also stall easier and feel rougher at idle.
As for improved acceleration; you might feel a difference in 1st and 2nd.

>>14773037
>BeamNG has great destruction but pretty shitty driving physics.
BeamNG has fantastic driving handling considering all the cars are not real. It does needs an upgrade in the tunning department

>>14772797
>Being this retarded.

>>14774626
>there is a reason why you are wrong but i am not gonna explain it lol ur retarded

jew go and pls stay go.

>>14772261
You underestimate how much staying at stable rpm matters for engines at low rpm. With a really light flywheel they tend to lose too much speed between ingintions, making them run like shit. Maybe imagine it with a 1cyl-engine to make the problem more obvious.
>>14772357
bearings do absolutely nothing about that though. They cannot eat up torque and release it a moment later. A flywheel does just that. As the combustion delivers power, the engine will speed up a little (mostly by deforming stuff), the flywheel's inertia stores that energy rather than directing it right to the wheel. Then, as combustion doesn't yield power, the flywheel releases the stored power, thus steadying the power-flow.
Obviously more cylinders reduce the problem, but it can't be quite overcome.

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>heavier flywheels increase torque

>>14774959
But it all goes again to the fact that the flywheel gives less power than what it ate. I understand the thing about engines with little power, but again, shouldn't the problem also be eliminated if it has a light flywheel and the engine can produce more torque for the same RPM?

What's the point of a dual mass flywheel? Why are they so fragile, and why do they cost a ton to replace?

>>14775367
>14775367
They dampen vibration by using springs making clutch engagement smoother.

It's basically two flywheels that are sprung against each other.


As such they cannot be milled and reused like single mass flywheels

>>14772061
You know that paper thin metal strip that goes between the starter and the car? It's really important to have.

>>14775300
The flywheel will give less power than what it ate because it's not a frictionless environment. Even a lighter flywheel will do the same. A lighter flywheel will have less rotational mass and will store less rotational inerta. This means it can rev up faster as there is less rotational inerta to fight but won't idle correctly because the flywheel can't store enough energy to allow it to idle at its normal idle speed. Increasing the idle speed will help a bit, but that's it. It doesn't change torque or horsepower ratings, it just allows you to rev faster, which might make you a little faster through 1st, but that's it.

>>14772167
Yes, I'm sure the combined trillions of dollars/shekels spent on engine R&D has totally overlooked your ideas. Perhaps if you write to them to let them know where they're going wrong?

>>14775829
I am thinking about benchracing, so the "accelerating faster" is kind of a big deal to me

>>14775863
>i want to learn why shit happens
>R&D teams obviously overlook your ideas

what?

>>14771815
A lighter flywheel makes the engine respond faster, it gains and loses revs faster. There is less stored energy in the lighter flywheel at the same given rotational speed so the engine is less resistant to rev changes, this means it can be trickier to start off on a hill or in other situations like that. I found that it was tough to get my car to not stall when I clutched in or went to neutral at the same time as the AC kicked on, I had to add a bunch of ignition advance in the bins just below idle revs.

>>14775968
Doesnt look like you're trying to learn much of anything, since all you want to do is argue.

Alot of physics work counter intuitively, like countersteering on a bike, or lift on an airplane wing.

>>14775625
>TFW your car wasnt engineered by a carpenter and the starter bolts on and works as intended with no silly adjustments.

>>14776445
>Alot of physics work counter intuitively, like countersteering on a bike, or lift on an airplane wing.
That's not counter intuitive.

All effects on physics have a purpose and a reason to happen. I am just trying to learn why it happens

>>14776570
Anyone who has taken even middle school level physics would understand it, I think you're being dense. It's called inertia, a heavier flywheel has more of it, how does it apply to the behavior of an engine? Use your fucking brain and figure it the fuck out!

>>14776656
Anyone with middle school level of physics would understand that the heavy flywheel needs more power to rotate than the power it gives with the inertia. My point isn't wether or not the heavy flywheel has inertia since that's a stupid question, my point is if there is an advantage of having a heavy flywheel with the inertia that isn't fixed by just having a light flywheel with better throttle response.

>>14777047
Yes, the extra inertia smooths power delivery and makes the engine harder to stall. As another anon in this thread mentioned, it is possible that with a very light flywheel the engine may want to stall under certain loads as the revs drop. When tuning a car with a newly installed lightweight flywheel you frequently run into issues with it stalling in neutral if you let the revs drop too fast because there isn't that extra inertia to keep the revs from dropping too far. You have to be sure to test these conditions under loads like AC on and power steering being used.

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>>14777072
But that's just a minor fucking issue. I want to know if there is a REAL advantage to having heavier flywheels, if its cheaper, if it increases reliability, if it makes the engine last longer, if there is anything other than bullshit shitty reasons to keep it other than stability at lower RPM and maybe slightly being stronger

>>14777093
READ

It smoothes power output and basically increases usable torque at idle or during coast down because more inertia is equivalent to more torque.

>>14777101
>more inertia is equivalent to more torque.
Holy fucking shit and you want to try and explain to me anything about physics?

The engine has to POWER MORE INERTIA, it has to move SOMETHING HEAVIER, its LOSING TORQUE with a heavier flywheel, you dont even need to search far into google to find out articles and people posting results of heavier flywheels taking torque off the car.

It is going to make your power delivery seem smoother since it will make it spin up/down easier. It will also make it harder to stall.

If it's of any significance to you, dirt bike riders install flywheel weights on their bikes to tame down the power delivery to make them easier to ride and get better traction.

>>14777131
I don't think you get it, dumbshit. More inertia means when a load occurs the engine is more resistant to rpm drop. The only time the heavy flywheel is additional load is while rpm is CLIMBING, you dense piece of rat shit. If RPM is constant or falling, more inertia is equivalent to more available torque. When revs are climbing the load of spinning the flywheel up is not significant, when they are falling or constant and low, the additional inertia of the flywheel provides quite a bit of extra load capacity.


Holy fuck you're stupid.

>>14777131
>The engine has to POWER MORE INERTIA, it has to move SOMETHING HEAVIER, its LOSING TORQUE

Thats not how Inertia works.

>>14777214
>If RPM is constant or falling, more inertia is equivalent to more available torque
WHY THE FUCK would i want MORE TORQUE when i am not accelerating?

>the additional inertia of the flywheel provides quite a bit of extra load capacity.

What did you pull out of your ass this time and why is it brown?

>The only time the heavy flywheel is additional load is while rpm is CLIMBING

AKA: When the lighter flywheel matters more

>When revs are climbing the load of spinning the flywheel up is not significant

That's not what most people who used both flywheels have to say

>>14777231
Yes. Yes it is.

The inertia from the flywheel doesn't come from thin air, the engine has to bleed power by spinning it up. power that could be delivered directly to the input shaft and slightly increasing the power of an engine instead of spinning a disc that will have little to no advantage.

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>this fucking thread
>everyone calling each other a retard
>mfw OP is going insane over fucking flywheels

The only positives to a heavier flywheel are strength and smoother idle. For normies a stock flywheel is best. For not normies a light flywheel is better.

>>14777421
/thread

>>14777385
Are you fucking illiterate? Why the fuck do you keep ignoring EVERYTHING I SAY?

I'm done, I have told you everything you wanted to know but you are WILLINGLY ignoring it. Fucking retard

>>14777789
>Are you fucking illiterate?
Ad hominem

>Why the fuck do you keep ignoring EVERYTHING I SAY?
Strawman. I dont ignore what you say, i only counterargue.

>I'm done, I have told you everything you wanted to know but you are WILLINGLY ignoring it. Fucking retard

If that's all you've got to tell me then i have come to the conclussion that there is literally no good reason to keep heavy flywheels in anything but comfort cars.

>>14777832

You have your answer now, can you stop bumping this thread?

>>14777853
No. YOU stop bumping this thread.

>>14772718
I daily a 8lb fly wheel feels great and is responsive on the street and the on the track but then again in not a cuck and know how to shift

>>14777396
Christ you are retarded,

Once the flywheel is at a set speed, there's very little forces that will slow it down, that IS the inertia at work. Yes when you increase the speed of the flywheel the engine will lag but at any constant rpms you lose no power.


the reason the car has a flywheel is for its inertia, if you take it away or reduce its weight the engine has a harder time fighting the frictional forces and runs like shit.