Re: If you want to be invisible on a car lot...

frkrygow@xxxxxxxxx wrote:
Bill Baka wrote:
frkrygow@xxxxxxxxx wrote:
It's SIMPLE, all right, but it's wrong. At least, if you imagine it's
just piston ring friction at work.
Not friction, inertia. Lower RPM and more torque make better use of all
those cubic inches.

Inertia of the piston does not decrease engine efficiency.

Efficiency is decreased when energy is _lost_. That is, when it leaves
the system in an unproductive way. But the kinetic energy of a moving
piston doesn't leave the system. It just transfers to the next moving
piston, perhaps through the flywheel. When an engine runs at constant
speed, the total kinetic energy of its moving parts is almost exactly
constant.

Uh, huh. That may explain why engineers have been trying to get rid of pistons for over 60 years. The Wankel was an attempt, and a good one except that it would wind a zillion RPM and people did it and wore out the rotor seals.

The great bulk of the coast-down difference you described comes from
fighting the compression and the pumping losses of the engine, not just
the friction of the piston rings and other moving components.
No pumping losses when the throttle is closed, just piston losses.

Sorry, you're wrong. The throttle is never perfectly closed. There's
always some flow past it. Likewise, there's always some flow past the
valves. Anyone who's noticed exhaust gases escaping a decelerating car
should understand this.

A lot of those gases are oil from valve seals sucking it under the high vacuum conditions of a coast down. With even moderate RPM and a closed throttle there is not that much to pump.

Sure, it takes energy to accelerate a piston. That energy comes almost
entirely from the nearby piston which is decelerating. They are simply
trading kinetic energy back and forth.
Not so.

Well, depending on the engine design, the energy may pass through the
flywheel, which is just a temporary energy storage device. The
important point is, the kinetic energy of the piston is _not_ lost. It
does not leave the system.

Have you taken a thermo course? If so, imagine a control volume around
the engine. If your losses were just energy accelerating and
decelerating the piston, how would the energy leave the system?

Let me ask again: How would that energy leave the system?

Let's go to dumb ass simple. If you throw a ball does it heat up by the acceleration? If you sit in a jet airplane and it accelerates you to 600 MPH do you heat up?

You claim to be an electrical engineer. The electrical analog for
inertia (or mass) is inductance.

Capacitance. You can charge a capacitor and it will stay that way, the same as mass. You can't charge an inductor and leave it without maintaining a current source.

In an oscillating LC circuit, does
the inductance lose energy? No, of course not. It merely stores
energy, transferring it back to the capacitance and vice versa. Damping
the oscillation to zero requires insertion of a resistance BECAUSE the
resistor is a device which converts energy to heat. This allows the
energy to leave the system.

If the energy doesn't leave the system, the system has the same amount
of energy.

Damn, It is NOT rocket science.

Right. You should be able to understand this. First law of
thermodynamics. Easy stuff.

- Frank Krygowski


You guys all seem to think you are scientists but you are just proving your lack of knowledge.
Sorry,
Argue among yourselves.
I have made mods on two cars and seen a drastic increase in mileage in both cases, hence I have seen the proof.
Bye for this thread.
Bill Baka
.

Relevant Pages

  • Re: If you want to be invisible on a car lot...
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  • Re: If you want to be invisible on a car lot...
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  • Re: If you want to be invisible on a car lot...
    ... just rotating the engine. ... the friction of the piston rings and other moving components. ... Do the math and see how much energy it takes to make each 2 pound piston ... entirely from the nearby piston which is decelerating. ...
    (rec.bicycles.misc)
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