Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Do lightweight flywheels make much difference?

autoteach · 06-12-2010, 09:05 PM

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).

06-12-2010, 09:05 PM	#63 (permalink)
autoteach Master EcoModder Join Date: Apr 2010 Location: belgium, wi Posts: 262 Bus - '94 Ford School Bus huge Stupid - '01 Chevy Blazer LS 90 day: 21.38 mpg (US) hawk - '00 Honda Superhawk Thanks: 2 Thanked 24 Times in 19 Posts	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).