balancing.

[jdbubb at ix.netcom.com (Dan Bubb)]

>  It takes energy, to save enregy...

You're going to have to explain this. I know it takes money to make money, but can't imagine how expending energy allows you to save energy

>   As you are cruising on the highway, it takes less effort to stay at a 
>constant speed with a stock flywheel, because you have built-up inertia...  
>Inertia is defined as the resistance to change it's present state of 
>motion...  In this case, if the flywheel is spun at 4K, it is going to resist 
>a change in speed, either up or down, IF it has more weight to it, yes? Then 
>that inertia will in fact save you more mpg, at a cost of mph...

So, if I understand this correctly, greater inertia helps you to maintain a constant speed better and because of this your throttle is more constant and therefore you get better mileage? Well, I can't argue with that but think it's such a small change you're never going to be able to measure it. The flywheel may represent a significant amount of the rotational inertia of the engine, but not a significant amount of the inertia (both linear and rotational) of the whole car, especially in the higher gears where the engine is only turning 3-3.5 times faster than the wheels.
>From a purely physics point of view, baring frictional effects, if a mass is at a constant velocity (linear or rotational) it takes no energy to maintain that velocity. Clearly it takes less energy to accelerate a lighter mass, but to maintain a constant speed requires no energy input so there is no difference between a light flywheel and a heavy one.
If you take into account frictional effects, bearing friction and aerodynamic drag, the lighter flywheel will have less bearing friction (insignificant) and the same aerodynamic drag (for all practical purposes), so, again, there is no practical difference between a light flywheel and a heavy one as far as energy input required to maintain speed and no difference in MPG.
Overall, I'd expect to see a slight increase in MPG from a lightened flywheel simply because you're accelerating less mass.

>   Do you know how heavy a Diesel flywheel is in comparison to a gas 
>flywheel?  Part of the reason is that they have a higher mpg is because of the 
>higher inertia they have once up to speed... 

I disagree. Diesels get better mileage due to the higher energy content of diesel fuel and the more efficient diesel cycle. The heavier flywheel is required because of the significantly higher CR of a diesel engine. More energy/inertia is required to get the engine through the compression stroke and maintain decent idle quality doing so.

>  The reasons you cited for having weight on the flywheel are good reasons as 
>well, but they are not the only ones...

Sorry, your original statement that a heavy flywheel would increase highway fuel mileage implied that was the Primary reason for a heavy flywheel which is incorrect.

>David

>PS  And while I read the Vortex quite a bit, I weigh that against hands-on 
>experience, as well as reading good technical sources (read that 
>as 'accredited'), as well as long conversations with a good friend of 13 years 
>who has been a mechanic for almost 40 years...  The one thing I will promise 
>each and every one of you is if you can prove me wrong, I will admit it, 
>period...  I don't know it all, nor do I pretend to (hopefully) :-)  I can 
>only ask that if you do not agree/understand, please ask questions...  I have 
>not insulted anyone here, nor will I throw jabs at someone, even if I 
>disagree, but especially if I do not understand...  I am here to learn, and to 
>share.  I thought that was that this list was for...  Did I misundestand? 

Ya know, I'm an engineer and I've spent way too much time thinking about and working on cars. Maybe, I'm overly concerned about trying to help make the Scirocco list technically correct and, hopefully, a huge step up on some of the laughable statements made on Vortex.

But, whatever.