Do lightweight flywheels make much difference?

[jdgFirefly]

Thanks for the DMF video, vary descriptive. If a picture is worth a thousand words whats a video worth?

[jdgFirefly]

Originally Posted by steffen707

I saw something like this before, very good video.

So the link to our ongoing debate/discussion would be that a heavier flywheel like those big ones in the video store more power or store the power longer? Than say a lighter flywheel, completely disregarding what autoteach had explained earlier about the distance of mass to center of rotation?? ???

What auto tech said still applies. Basically the farther you get from the center line the higher the velocity at a given rpm. Put the mass where the velocity is higher and you will have more inertia. Notice in the video how the flywheels are constructed, they are both massive and have a large diameter with most of the mass at the edge of the wheel. using the same amount of material they could have made the flywheel more compact (smaller dia but thicker) however it would be far less effective.

[autoteach]

So, now I am being confused with someone named Red Herring? whatever...

I know that a single cylinder needs a specific amount of flywheel to run effectively. That is, more or less, the point. Could you get to a point where the number of cylinders is high enough to negate the necessity of a flywheel? Sure! Does a higher CR require more mass (inertia in this case)? Absolutely. Will a lightened flywheel show significant fuel savings in P&G? I will argue no. Before I will, I would like to assume (yep, got it) that most of us would say that steady state cruising will not be affected positively by a lightened flywheel. This is assuming a statistical thesis that lightened flywheels will increase MPG. Without a doubt, your significance that you will show in this will be low.

Onto the P&G debate (oh no, you didn't realize that we were having one? Just started) Lets assume that you are doing a highway pulse and glide of 55mph to 65mph with an rpm change of 1000 (generous). What is the amount of power (or fuel, whatever) that is consumed in accelerating the FW compared to the total amount of accelerated bits and pieces? I will go on a limb here (and piss someone off) and say that the percentage of fuel consumed in accelerating this piece is low, like in the realm of <1%. Assuming that you have a 185-65-15 tire, you would be dealing with a tire that is 26.5" tall (bigger than a flywheel and x4), a brake rotor that is about 10-12 inches in diameter (and dragging nonetheless, as removing drag from this is nearly impossible but we can discuss if necessary), a ring gear, tranny gears, rotating assembly, and all the accessories, not to mention rolling resistance and drag.

Can we find better places to spend our money? Yes.
Does this mean I am giving in (NO! The flywheel IS NOT drag on the engine)
Is there a reason that I am switching to a stock flywheel on my motorcycle? Hmmmmm, na, couldn't be.


I will tell you this, the main reason that I am enjoying this "debate" is that, no matter what is said in against this, you are most likely going to do it anyway. So, I could have said it was a good idea, which could have caused you to order a flywheel yesterday, or I could try to be the sense of reason that makes you think before you do. I am certain, in no particular scientific way, that you will not gain from going with a 7lb flywheel. Than again, I do know what cold starts in an acura integra are like with a "lite" (so light that you cant use the g and h cause they are farther down the periodic table of letters).

[ShadeTreeMech]

I've often wondered about adding an electric motor to run the water pump and power steering pump; as you said a steady rpm would be all that is necessay, and in the case of the PS pump you really only need it during slow driving and parking or emergency maneuvers. Wonder what the fuel savings would be on using an electric motor for the water and PS pump.....

Only other accessory running off the crank is the AC and alternator, neither of which I intend to delete (I'm a big baby when it comes to sweating )

This discussion nearly makes me want to add some lead weights to the flywheel to see how it goes.

[steffen707]

Originally Posted by autoteach

Can we find better places to spend our money?

Originally Posted by autoteach;

no matter what is said in against this, you are most likely going to do it anyway. So, I could have said it was a good idea, which could have caused you to order a flywheel yesterday,

You do not read well, as stated NUMEROUS times, I already own BOTH flywheels. I'm not wasting money, i'm only wasting time if the light flywheel loses mpg. Your theories will not influence me either way, people's real world experiences like the turbo miata guy and the guy that lost mpg will.

[steffen707]

Originally Posted by ShadeTreeMech

I've often wondered about adding an electric motor to run the water pump and power steering pump; as you said a steady rpm would be all that is necessay, and in the case of the PS pump you really only need it during slow driving and parking or emergency maneuvers. Wonder what the fuel savings would be on using an electric motor for the water and PS pump.....

Only other accessory running off the crank is the AC and alternator, neither of which I intend to delete (I'm a big baby when it comes to sweating )

This discussion nearly makes me want to add some lead weights to the flywheel to see how it goes.

Well considering metrompg gained 10% mpg from 70 to 77 in deleting his alternator, you could be hopeful that power steering robs a lot as well. This is an easy test as well cuz you can simply take the power steering pump off, the problem is if you don't loop the PS lines, it will be much harder to drive, but if you just do a small test then it shouldn't be so bad.

i'm in the same boat as you, I LOVE AC and won't be without it, I know it robs MPG probably a bunch more than this heavier or lighter flywheel thing would help or hurt, but its not a sacrifice I will make.

[autoteach]

Originally Posted by steffen707

You read well, as stated NUMEROUS times.... Your theories will influence me.

Be careful on what portions you edit when you quote. Your quote of me does not read well, and it doesn't make sense. What I state is not merely theory, but if you have the two flywheels, show the results. Like you said, it would merely be a waste of time, not a waste of money. Do the test and show the forum whats what when it comes to flywheels. I think everyone could appreciate that.

[steffen707]

Originally Posted by autoteach

Be careful on what portions you edit when you quote. Your quote of me does not read well, and it doesn't make sense. What I state is not merely theory, but if you have the two flywheels, show the results. Like you said, it would merely be a waste of time, not a waste of money. Do the test and show the forum whats what when it comes to flywheels. I think everyone could appreciate that.

Well what I quoted wasn't meant to fabricate a completely different sentence as your quote clearly has, if you want to be an a$$hole and start a pissing match, You have succeeded.

And owning both flywheels I do intend to try both out, unless I read about somebodies detailed test results.

[autoteach]

Originally Posted by steffen707

Well what I quoted wasn't meant to fabricate a completely different sentence as your quote clearly has, if you want to be an a$$hole and start a pissing match, You have succeeded.

And owning both flywheels I do intend to try both out, unless I read about somebodies detailed test results.

I anxiously await your results, as I already have mine. They contradict your thoughts. I know that in your eyes I have become (or am, but I am okay with that) an A-hole. But your lack of time searching the internet to cover this topic makes you look...well, I found answers that support more than the "at full throttle, xHP are added".

A little story, which you could give a crap about... I once led a student group to an automotive build and competition. I was the first to get it to go in 2 years of trying, and it went every year I led the group. I graduated and they didnt make it the next 2-3 years. While I was there, I took a group of 40 aspiring engineers and auto enthusiast and whittled it down to 5-8 guys through enforcing expectations of deadlines, research, design, and follow through. Many of those 40 young men have poor opinions of me. Many of them never had the follow through or wherewithal to make it to the big show. Do I feel bad that they don't like me? No, and that is because if I had fought for there friendship, I would never have succeeded.

What does this mean to you? It should give you an idea of my expectations from my students as well as my feelings (or lack there of) when it comes to offending people in the pursuit of getting to the right answers or to the end product. I have worked in performance automotive and powersports shops for 6 years, 2 years building ground up race cars, and teaching automotive education for 6 years. Your time is valuable, but you are in search of proving me wrong, so let me give you some pointers for your testing to maximize your chances of proving me wrong:

1. When you go to the lite FW(low inertia), give yourself an oil change worth of time on it before starting your test. You will need to acquaint yourself with its nuances.
2. Test multiple driving conditions. City, hwy, CC, P&G, EOC, etc. It is plausible that one of these might net you the results you are looking for (although most of them will not).
3. Test over some significant amount of time (2 months) to get the best data possible.
4. Separate #2 tests from your regular driving numbers. Do this so that the data is not commingled and distracting from the pure state of each test.
5. If you switch back to the heavy FW(high inertia), make sure that you give yourself some time to reacquaint yourself with it before testing. This will likely take less time than the other FW.
6. Check you tire pressures regularly throughout this so as not to soil data one way or the other (in the case of weather changes- Sept, Oct temp drops)
7. Realize that in large tests of this nature, tire wear will play a part in number changes. And whatever you do, resist all other changes that would effect mpg. If you are tempted to make other changes, makes sure that those changes are well documented within your testing.

oh yeah, big secret, minimize engine load...LFW will be very picky for mpg's surrounding higher engine loads. This may mean that, for you to maximize your numbers, that you run a lower gear to keep rpms up.

Well, if I wasn't an A-hole before, I am sure that I am now.

[steffen707]

Originally Posted by autoteach

But your lack of time searching the internet to cover this topic makes you look...well, I found answers that support more than the "at full throttle, xHP are added".

Searching the internet isn't all its cracked up to be, because you often get answers like your original one, "HEAVIER IS BETTER". If i relied on many internet forums with blind faith for all my questions, i would never get anywhere. And on the contrary, I have searched the internet, about 50 different webpages, and many of them where people said they changed to lighter flywheels has increased their mpg. I could cite sources, but i'll take a page out of your book and just say, if you don't believe me I don't give a crap, and you can blindly believe what i say is true.

Originally Posted by autoteach;

A little story, which you could give a crap about...

Correct, i don't give a crap about it.

Originally Posted by autoteach;

Your time is valuable, but you are in search of proving me wrong

And wrong again, i'm in search of more mpg, and the knowledge of what works and what doesn't. If I was in search of proving you wrong, I would just post on here 2 weeks from now a complete lie with fake results to say "YOU WERE WRONG". And then you would call me a liar because there is no way a teacher of blah years could ever be wrong or miscalculate something. Because that would hurt your ego. Sure it wouldn't "prove" you wrong but if all I cared about was proving a stranger wrong on the internet, i would settle for lying to you. lol

I will probably end up doing the test myself because there isn't a hands down this has been done before, you will lose mpg for sure consensus.