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balancing.



Quoting "T. Reed" <treed2@wsu.edu>:

> I'm gonna trim out all the parts we basically agreed on for conciseness.
> 
> > > 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."
> 
> > I still have not found where I said this...  If I did, then I really did
> > step in it...  What I was TRYING to say is the decreasing F/W can decrease
> > mpg...
> 
> Well, close enough. Saying that decreasing flywheel weight hurts mileage
> implies that increasing it helps mileage. The result of increasing the
> flywheel weight is an increase in inertia. Therefore the arguments are
> functionally equivalent.
> 
> I'm not saying a heavier flywheel does nothing to help, I'm just saying it
> does nothing to help mileage (on the contrary, it hurts mileage).
> 

Depending on your driving style...  Cruiser, vs. racer...  I should have been 
more specific when I responded the first time...

> [more snippage]
> 
> > "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."
> >
> > Now I am losing you again, methinks...
> 
> Let me try to clarify.. you are driving up a hill then back down again.
> On the way down there is lots of wind opposing you. A car with a heavier
> flywheel takes more fuel (I think we've agreed on this) to get up the hill
> because it stores more energy in its flywheel. If, without stopping, both
> cars proceed down the hill, letting off the throttle completely (lets
> pretend this shuts off fuel flow completely), the car with the heavy
> flywheel will have traveled further, but it will have burned more fuel
> (say, 200 mL more) than the car with the light flywheel. The car with the
> light flywheel simply has to burn another 200 mL and it will catch up.
> Therefore the additional flywheel weight offers no fuel savings in this
> scenario.
> 

I will have to look to find some evidence of this, but my impression is that 
there is more of an energy savings by keeping that flywheel spinning...  
Centripetal force, something, blah blah...  I know that I am losing a bit of 
credibility, but I AM going to have to look for an excuse here...


> > "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."
> > But, the AFM does not drive the car, the T/B does...  The T/B is what
> > affects the AFM, not the other way around...
> 
> The TB does affect the AFM, but there is not a rigid mechanical
> correlation between the two. If the engine is off and you jumper the fuel
> pump and step on the gas pedal, nothing happens. If you jumper the fuel
> pump and lift the air flow plate, fuel is sprayed from the injectors. The
> fuel spray is directly controlled by the air flow plate and indirectly by
> the throttle body (i.e. only under certain circumstances, and not
> necessarily with fast response).
> 
> The TB "suggests" how much fuel to deliver, and the AFM makes the final
> decision. I think we agree on this, I just did a crappy job of stating it
> in my previous e-mail. My fault!
> 

I agree with you now, no sweat on the confusion....  :-)

> > 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.
> > This is true, if you have no fuel flow while on the highway, it will act
> > differently than if you were coasting with it in gear...  So, we would
> have
> > to both agree that there is some fuel flow, perhaps the same amount that
> > flows when the car is idling?  Or close to the same amount, depending on
> > relative RPM?
> 
> Yeah, my guess is that the fueling drops to some amount greater than idle
> fueling rate, then steadily decreases to idle fueling rate.
> 
> So back to my original point, the longer it takes the engine to wind down
> to idle fuel levels, the more fuel it burns during the wind down process.
> It winds down faster with a light flywheel, and so burns less fuel.
> 

Yes...

> [snip]
> 
> > Well, if I built the Titanic, I would not have admitted it after it sunk,
> > but I am slowly getting a sinking feeling here...  I still cannot let it
> go
> > just yet, but I feel that there is something I am missing to make it work,
> > or even to let it go...
> 
> Hmm.. I'm still puzzled by the 'how' behind added weight helping mpg. I've
> rattled my brains and I still can't think of any scenario with a
> heavier flywheel that would result in fuel savings.. unless of course the
> flywheel was already spinning before you started measuring fuel
> consumption :P
> 

I will ge looking for this, I may not find it, but I will be looking....

> > The flywheel, OTOH, I'm sure about :)
> >
> > OTOH?
> 
> Sorry, "On The Other Hand".. one of them internet abbreviations ;)
> 
> -Toby
> 
Of course!  (Homer Simpson voice)...  "Stupid military and their 
A.C.R.O.N.Y.M.S...."  

David