balancing.

[treed2 at wsu.edu (T. Reed)]

> "Tell me what's wrong with this argument:
>
> When you climb a hill in a car, you're not going any faster, the road is
> just more vertical. So, the acceleration at the flywheel is zero; it is
> still moving at a constant speed. The engine is just working harder than
> it was before you started climbing the hill, it's not spinning any faster
> or slower.
>
> Therefore I conclude that the flywheel weight has no effect when
> climbing hills. This is based on our previous agreement that the flywheel
> weight doesn't matter when you're moving at a constant speed."
> Okay...  Here is another argument, as I cannot think of a way to work within
> that one...

Hmm, I wonder why you can't heheh ;)

> Two cars, going 70, side by side...  One is 2000lbs, the other is 3000lbs...
> You two both approach a hill...  Neither one of you attempts to accelerate,
> or to maintain the same speed...  Which one will go further up the hill?

The one with more potential energy stored. (i.e. the 3000 lb car or the
car with the stock flywheel)

But that energy is not free; I think that's what you're not getting here.

You've already converted it from stored energy (gasoline) to stored
energy (flywheel). So yes, it may (will) help you go up a hill
->with no throttle<- but no more so than just stepping on the gas and
burning that same amount of fuel would in a car with a light flywheel. And
I don't know anyone who (on a regular basis) lets off the throttle
completely and coasts "up" hills.

Even if that was your driving style you'd use the same amount of fuel,
because like I said, you've already converted the energy from gasoline to
rotational inertia. You can't convert it backwards like regenerative
braking in an electric car.

With a stock flywheel you're shopping at Costco and with a lightened one
you're buying single items. Every time you stop you have to throw away
everything you've bought. So yes, if you don't stop, shopping at Costco
could save you trips to the store. But those trips don't take any
additional time or effort (the engine is already running when you're
driving) so there is really no benefit. You just waste a lot more.

> This is the whole of my argument...  More spun weight carries more inertia,
> which will, under some circumstances, benefit the driver...  Does that one
> make sense?

Yes, and I agree with it 100%. Under some circumstances more inertia will
benefit the driver (like driving through a brick wall, or mangling a
pedestrian). But your original argument was that more interia would
increase fuel mileage. That's what I disagree with.

Conservation of energy says you can't create energy out of nowhere.

If you watch the Simpsons, this is like the episode where Homer buys a
bunch of bacon and cooks it in the frypan, feeds the bacon to the dog and
then collects the bacon grease in cans to take in for recycling:

GREASE MAN: Four pounds of grease...that comes to sixty-three cents.
HOMER: Woo hoo!
BART: Dad, all that bacon cost twenty-seven dollars.
HOMER: Yeah, but your mom paid for that.
BART: But doesn't she get her money from you?
HOMER: And I get my money from grease. What's the problem?

> "As far as driving up one side of a hill and then back down again, this is
> similar to the braking energy explanation. You're storing potential energy
> in the mass of the car as you drive up the hill. A car with a heavier
> flywheel is just storing more energy on top of that. As you drive down the
> hill you will have to use the brakes to dump the energy from the extra
> flywheel mass as well as from climbing the hill."
> Not necessarily...  Actually what happens at highway speeds is that you have
> such wind-drag and friction forces working against you, that you would
> instead of breaking, not have to have the throttle down nearly as much, you
> coast more, which is again the benefit of the stock flywheel...

Okay, lets try a money analogy. It costs $1 to drive up a hill with a
lightened flywheel, and $2 to drive up a hill with a stock flywheel.

It doesn't matter where the money goes (to charity or to McDonalds)... to
wind drag or friction, you already spent it climbing the hill.

Even if, after cresting the hill, the stock flywheel car can coast twice
as far before coming to a stop.. all you have to do is spend another $1
(well, actually less than that since you're not going 'up' anymore) to go
the same distance in the lightened flywheel car.

> "Which brings up one more thing-- the fuel dumped in to the engine is
> determined by the air flow plate position, not the throttle position."
> Actually, it is the other way around...  If you take your foot of the
> throttle at 70mph, and decelerate, there is no fuel entering the engine...
> With your statement above, if that were true, then a lot of air would go
> through/around the throttle butterflies, which it cannot do...  If it could
> it would not do any good to have a butterfly there at all...

[air flow plate shenanigans snipped]

Okay, now you are misunderstanding *me* :) and I think that's my fault
because of how I said this.

Read the first line again: Fuel dumped in to the engine is determined by
the air flow plate position, not the throttle position.

That is 100% correct. Look at where your fuel distributor is located. On
the throttle body? Didn't think so.. it's above the air flow plate.

As far as deceleration, I may have been a bit off. I don't know the exact
dynamics. You state "The airflow plate is not lifted at coast at all...".
I don't know conclusively if this is true or not true.

I do know that when I'm driving in my 16v and get off the throttle to
start to coast, the car responds slightly differently than if I reach down
in to my fusebox and pull the fuel pump relay.

You may be correct, and this may just be my imagination.. but I have the
opinion I have based on observation and some mild thinking.

My thoughts are -- yes, the TB is closed when you're coasting, but there
is a TB bypass path (this is how the engine gets air when it's at idle).
Furthermore, the amount of vacuum at a motor's intake is proportional to
the rpm the motor is turning at. Therefore I say that at 7000 rpm there is
more vacuum at the intake than at idle. Greater vacuum with the same sized
bypass can pull more air (think of this as one compressed air line at
30psi and one at 90psi.. the one at 90 can move more air through the same
sized hose) and as a result create more vacuum above the air flow plate
than when the engine is at idle. Not -as much- vacuum as with the
butterflies open, but more than at idle. So you're still burning fuel.

Again, this is purely theory and unscientific observation. I may be
wrong, but perhaps not. I'm not going to stick up for this opinion the way
you're sticking to your guns about the flywheel thing because I don't feel
like I can back it up.

The flywheel, OTOH, I'm sure about :)

-Toby