Jon Elson wrote:

BottleBob wrote:


sittingduck wrote:
Proctologically Violated©® wrote:

There was a brief ad campaign in NYC, to the effect that letting your
car idle more than **10 secs** wastes gas. Iow, the "cost" of
restarting your car is equivalent to only about 10
secs worth of gas.
NYC has pretty strict idling laws, which, iirc, limit the legal idling
to 3 minutes. I guess that could be whittled down to 30 sec!

One of my cars' engine shuts off instead of idling. It will kick back
on whenever it is needed. It's pretty slick.

PV & SD:

Well that's interesting. Just playing devils advocate here, but how
much gas would you have to save to pay for the labor & parts on a
possible early starter motor and/or flywheel ring gear change out?
I suppose the smaller the engine the less ring gear wear, but even
small engines would have small starter motors.


My Honda Civic has a "Brand New" starter motor, ie. it has never been
used in the life of the car. The integrated assist motor is used to
start the engine directly, as it is part of the flywheel. It is silent
and just about instantaneous. The 150 V battery doesn't have to strain
to crank the engine, either.

The 12 V cranking motor is only used if it is so cold the hybrid battery
would be harmed by cranking the engine (never gets that cold in MO) or
if you need to jump-start the car after killing both batteries. It is
also a backup if there is a major malfunction in the hybrid drive system.

The Honda Civic Hybrid, once warmed up, generally shuts the engine off
while coasting to a stop at about 9 MPH. If you confuse it by pulsing
the brakes, it will shut off after idling for 5 seconds. It also cuts
off fuel flow and closes all engine valves to allow a minimum-drag coast
anytime you take your foot completely off the gas pedal. It coasts
remarkably well in that mode.

I think you mean "opens all engine valves", as closing them would
provide maximum compression braking effect.

On Tue, 16 Jun 2009 16:27:45 -0500, "Pete C."
wrote:


Jon Elson wrote:

BottleBob wrote:


sittingduck wrote:
Proctologically Violated©® wrote:

There was a brief ad campaign in NYC, to the effect that letting your
car idle more than **10 secs** wastes gas. Iow, the "cost" of
restarting your car is equivalent to only about 10
secs worth of gas.
NYC has pretty strict idling laws, which, iirc, limit the legal idling
to 3 minutes. I guess that could be whittled down to 30 sec!

One of my cars' engine shuts off instead of idling. It will kick back
on whenever it is needed. It's pretty slick.

PV & SD:

Well that's interesting. Just playing devils advocate here, but how
much gas would you have to save to pay for the labor & parts on a
possible early starter motor and/or flywheel ring gear change out?
I suppose the smaller the engine the less ring gear wear, but even
small engines would have small starter motors.


My Honda Civic has a "Brand New" starter motor, ie. it has never been
used in the life of the car. The integrated assist motor is used to
start the engine directly, as it is part of the flywheel. It is silent
and just about instantaneous. The 150 V battery doesn't have to strain
to crank the engine, either.

The 12 V cranking motor is only used if it is so cold the hybrid battery
would be harmed by cranking the engine (never gets that cold in MO) or
if you need to jump-start the car after killing both batteries. It is
also a backup if there is a major malfunction in the hybrid drive system.

The Honda Civic Hybrid, once warmed up, generally shuts the engine off
while coasting to a stop at about 9 MPH. If you confuse it by pulsing
the brakes, it will shut off after idling for 5 seconds. It also cuts
off fuel flow and closes all engine valves to allow a minimum-drag coast
anytime you take your foot completely off the gas pedal. It coasts
remarkably well in that mode.

I think you mean "opens all engine valves", as closing them would
provide maximum compression braking effect.

No, closing the valves is correct. The cyl compresses the air, which
then pushes the piston back down like a spring. VERY efficient.

wrote in message
...
On Tue, 16 Jun 2009 16:27:45 -0500, "Pete C."
wrote:


Jon Elson wrote:

BottleBob wrote:


sittingduck wrote:
Proctologically Violated©® wrote:

There was a brief ad campaign in NYC, to the effect that letting
your
car idle more than **10 secs** wastes gas. Iow, the "cost" of
restarting your car is equivalent to only about 10
secs worth of gas.
NYC has pretty strict idling laws, which, iirc, limit the legal
idling
to 3 minutes. I guess that could be whittled down to 30 sec!

One of my cars' engine shuts off instead of idling. It will kick back
on whenever it is needed. It's pretty slick.

PV & SD:

Well that's interesting. Just playing devils advocate here, but
how
much gas would you have to save to pay for the labor & parts on a
possible early starter motor and/or flywheel ring gear change out?
I suppose the smaller the engine the less ring gear wear, but even
small engines would have small starter motors.


My Honda Civic has a "Brand New" starter motor, ie. it has never been
used in the life of the car. The integrated assist motor is used to
start the engine directly, as it is part of the flywheel. It is silent
and just about instantaneous. The 150 V battery doesn't have to strain
to crank the engine, either.

The 12 V cranking motor is only used if it is so cold the hybrid battery
would be harmed by cranking the engine (never gets that cold in MO) or
if you need to jump-start the car after killing both batteries. It is
also a backup if there is a major malfunction in the hybrid drive
system.

The Honda Civic Hybrid, once warmed up, generally shuts the engine off
while coasting to a stop at about 9 MPH. If you confuse it by pulsing
the brakes, it will shut off after idling for 5 seconds. It also cuts
off fuel flow and closes all engine valves to allow a minimum-drag coast
anytime you take your foot completely off the gas pedal. It coasts
remarkably well in that mode.

I think you mean "opens all engine valves", as closing them would
provide maximum compression braking effect.

No, closing the valves is correct. The cyl compresses the air, which
then pushes the piston back down like a spring. VERY efficient.

Can't be that efficient. You'll be lucky if you break even. Laws of
thermo.
Which a
1. You cain't win
2. You cain't break even
3. You cain't even get out of the game.

But the point is well taken, that valves open or closed should in principle
be the same.

However, when they were experimenting with "variable cylinder cars", iirc
the trick was to leave the valves open, for non-compression.
--

Mr. PV'd

Mae West (yer fav Congressman) to the Gangster (yer fav Lobbyist):
Hey, Big Boy, is that a wad (of cash) in yer pocket, or are you just
glad to see me??

"Proctologically Violated©®" writes:

wrote in message
...

No, closing the valves is correct. The cyl compresses the air, which
then pushes the piston back down like a spring. VERY efficient.

Can't be that efficient. You'll be lucky if you break even. Laws of
thermo.
Which a
1. You cain't win
2. You cain't break even
3. You cain't even get out of the game.

But the point is well taken, that valves open or closed should in principle
be the same.

However, when they were experimenting with "variable cylinder cars", iirc
the trick was to leave the valves open, for non-compression.

I think the Cadillac 8-6-4-0 did that, but the Chrysler 5.7 leaves them
closed (is the 5.7 an interference engine? I don't know... if so, you
can't leave them open!).

On Tue, 16 Jun 2009 21:47:32 -0400, "Proctologically Violated©®"
wrote:



I think you mean "opens all engine valves", as closing them would
provide maximum compression braking effect.

No, closing the valves is correct. The cyl compresses the air, which
then pushes the piston back down like a spring. VERY efficient.

Can't be that efficient. You'll be lucky if you break even. Laws of
thermo.
Which a
1. You cain't win
2. You cain't break even
3. You cain't even get out of the game.

But the point is well taken, that valves open or closed should in principle
be the same.

However, when they were experimenting with "variable cylinder cars", iirc
the trick was to leave the valves open, for non-compression.
The MOST efficient way to turn an engine when not running.is with all
valves closed. Much more efficient than with the valves open as it
eliminates virtually all the pumping losses.

Open any one valve and it becomes a brake.

wrote: (clip) Open any one valve and it becomes a
brake.
^^^^^^^^^^^^^^^^^^
Yep. That's how the compression release worked on my old Yamaha enduro,
and, I believe, on those big trucks you hear decelerating by releasing
compression.

"Leo Lichtman" wrote in message
...

wrote: (clip) Open any one valve and it becomes a
brake.
^^^^^^^^^^^^^^^^^^
Yep. That's how the compression release worked on my old Yamaha enduro,
and, I believe, on those big trucks you hear decelerating by releasing
compression.

That's just downshifting/engine braking. They're not messing with valves,
afaik.

As far opening just one valve (presumably the exhaust valve), the piston
would just be fanning a little air, no real pumping losses. I can't imagine
those losses being greater than spring/friction losses with a closed valve
system.

Not to mention the greater wear and tear of a system under pressure.

--

Mr. PV'd

Mae West (yer fav Congressman) to the Gangster (yer fav Lobbyist):
Hey, Big Boy, is that a wad (of cash) in yer pocket, or are you just
glad to see me??

Proctologically Violated©® wrote:
"Leo Lichtman" wrote in message
...
wrote: (clip) Open any one valve and it becomes a
brake.
^^^^^^^^^^^^^^^^^^
Yep. That's how the compression release worked on my old Yamaha enduro,
and, I believe, on those big trucks you hear decelerating by releasing
compression.

That's just downshifting/engine braking. They're not messing with valves,
afaik.

But they are, PV:

http://en.wikipedia.org/wiki/Jake_brake
http://www.youtube.com/watch?v=z3bLqjPBlx8

--Winston

Pete C. wrote:

I think you mean "opens all engine valves", as closing them would
provide maximum compression braking effect.

That's what I thought, too, but Honda's video
explaining the scheme shows that the valves are
all made to close and stay that way. With the
valves closed, the pistons just go up and down,
compressing and expanding the same volume of air.
There is a tiny bit of adiabatic loss that way,
but less than dragging air in and out of the
cylinders. As long as the engine is above 1000
RPM, there's really a VERY minimal braking effect.

Big trucks have engine brakes that change the
valve timing to maximize pumping loss. Obviously
the valves are open at some part of the stroke to
cause that huge trumpeting noise.

Jon

Proctologically Violated©® wrote:

No, closing the valves is correct. The cyl compresses the air, which
then pushes the piston back down like a spring. VERY efficient.

Can't be that efficient. You'll be lucky if you break even. Laws of
thermo.
Which a
1. You cain't win
2. You cain't break even
3. You cain't even get out of the game.

But the point is well taken, that valves open or closed should in principle
be the same.

However, when they were experimenting with "variable cylinder cars", iirc
the trick was to leave the valves open, for non-compression.
Well, it really does work. First, you can feel
the car coasting very well, even coasting
pretty good up a slight hill. Also, I get 52 - 56
MPG tooling around town, WITH the air conditioning on.

Jon

Proctologically Violated©® wrote:
"Leo Lichtman" wrote in message
...
wrote: (clip) Open any one valve and it becomes a
brake.
^^^^^^^^^^^^^^^^^^
Yep. That's how the compression release worked on my old Yamaha enduro,
and, I believe, on those big trucks you hear decelerating by releasing
compression.

That's just downshifting/engine braking. They're not messing with valves,
afaik.

The federal highway law of 1986 required all
trucks over 12000 Lbs to have a "retarder". Fire
trucks use electric retarders (faraday brakes) as
they can be disabled by pulling a breaker and it
should be totally impossible for a bad electric
retarder to disable the truck.

Almost all other large trucks use "pneumatic"
retarders. Activating the retarder causes the
intake and compression strokes to happen normally,
but then the exhaust valves are opened at the peak
of compression. One system is the Jacobs brake,
sometimes called a "Jake brake" that uses an extra
lobe on the camshaft to trip the exhaust valve.

These devices have been built integrally into the
engines of large trucks for some years. The
federal law was due to a LOT of semi operators
disconnecting the front brakes to be sure to have
steering control in hard braking, and the rapid
wear of brakes (usually replaced every 10K miles!)
The retarders don't wear anything out, so the
truckers and owners love them.

Jon

"Winston" wrote in message
...
Proctologically Violated©® wrote:
"Leo Lichtman" wrote in message
...
wrote: (clip) Open any one valve and it becomes a
brake.
^^^^^^^^^^^^^^^^^^
Yep. That's how the compression release worked on my old Yamaha enduro,
and, I believe, on those big trucks you hear decelerating by releasing
compression.

That's just downshifting/engine braking. They're not messing with
valves, afaik.

But they are, PV:

http://en.wikipedia.org/wiki/Jake_brake
http://www.youtube.com/watch?v=z3bLqjPBlx8


OK, I think I got it:
Yyou allow the engine to compress, but by opening the valve at full
compression, you don't get any of the "spring back" from what was
compressed....
OK....

So Jon is also saying that *leaving* the valves open the piston will still
experience more drag than leaving the valves closed? At above 1,000 rpm, at
least.... Tough notion to get used to, but I guess that's what CdA is all
about, eh?

Live and learn....
Now I'm going to have weird dreams.... always happens when my intuitive
reality is disturbed....

--

Mr. PV'd

Mae West (yer fav Congressman) to the Gangster (yer fav Lobbyist):
Hey, Big Boy, is that a wad (of cash) in yer pocket, or are you just
glad to see me??






--Winston

On Tue, 16 Jun 2009 21:25:38 -0400, wrote:

On Tue, 16 Jun 2009 16:27:45 -0500, "Pete C."
wrote:


Jon Elson wrote:

BottleBob wrote:


sittingduck wrote:
Proctologically Violated©® wrote:

There was a brief ad campaign in NYC, to the effect that letting your
car idle more than **10 secs** wastes gas. Iow, the "cost" of
restarting your car is equivalent to only about 10
secs worth of gas.
NYC has pretty strict idling laws, which, iirc, limit the legal idling
to 3 minutes. I guess that could be whittled down to 30 sec!

One of my cars' engine shuts off instead of idling. It will kick back
on whenever it is needed. It's pretty slick.

PV & SD:

Well that's interesting. Just playing devils advocate here, but how
much gas would you have to save to pay for the labor & parts on a
possible early starter motor and/or flywheel ring gear change out?
I suppose the smaller the engine the less ring gear wear, but even
small engines would have small starter motors.


My Honda Civic has a "Brand New" starter motor, ie. it has never been
used in the life of the car. The integrated assist motor is used to
start the engine directly, as it is part of the flywheel. It is silent
and just about instantaneous. The 150 V battery doesn't have to strain
to crank the engine, either.

The 12 V cranking motor is only used if it is so cold the hybrid battery
would be harmed by cranking the engine (never gets that cold in MO) or
if you need to jump-start the car after killing both batteries. It is
also a backup if there is a major malfunction in the hybrid drive system.

The Honda Civic Hybrid, once warmed up, generally shuts the engine off
while coasting to a stop at about 9 MPH. If you confuse it by pulsing
the brakes, it will shut off after idling for 5 seconds. It also cuts
off fuel flow and closes all engine valves to allow a minimum-drag coast
anytime you take your foot completely off the gas pedal. It coasts
remarkably well in that mode.

I think you mean "opens all engine valves", as closing them would
provide maximum compression braking effect.

No, closing the valves is correct. The cyl compresses the air, which
then pushes the piston back down like a spring. VERY efficient.

Kind of like perpetual motion?

Proctologically Violated©® wrote:

(...)

Now I'm going to have weird dreams.... always happens when my intuitive
reality is disturbed....

But we're cheaper than anchovy pineapple pizza!

--Winston

Jon Elson wrote:

Proctologically Violated©® wrote:
"Leo Lichtman" wrote in message
...
wrote: (clip) Open any one valve and it becomes a
brake.
^^^^^^^^^^^^^^^^^^
Yep. That's how the compression release worked on my old Yamaha enduro,
and, I believe, on those big trucks you hear decelerating by releasing
compression.

That's just downshifting/engine braking. They're not messing with valves,
afaik.

The federal highway law of 1986 required all
trucks over 12000 Lbs to have a "retarder". Fire
trucks use electric retarders (faraday brakes) as
they can be disabled by pulling a breaker and it
should be totally impossible for a bad electric
retarder to disable the truck.

Almost all other large trucks use "pneumatic"
retarders. Activating the retarder causes the
intake and compression strokes to happen normally,
but then the exhaust valves are opened at the peak
of compression. One system is the Jacobs brake,
sometimes called a "Jake brake" that uses an extra
lobe on the camshaft to trip the exhaust valve.

These devices have been built integrally into the
engines of large trucks for some years. The
federal law was due to a LOT of semi operators
disconnecting the front brakes to be sure to have
steering control in hard braking, and the rapid
wear of brakes (usually replaced every 10K miles!)
The retarders don't wear anything out, so the
truckers and owners love them.

Jon

12,000# in which way? My latest truck is 13,000# GVWR and does not have
any sort of "retarder", "jake brake", etc.

Jon Elson wrote:
Proctologically Violated©® wrote:
"Leo Lichtman" wrote in message
...
wrote: (clip) Open any one valve and it becomes
a brake.
^^^^^^^^^^^^^^^^^^
Yep. That's how the compression release worked on my old Yamaha
enduro, and, I believe, on those big trucks you hear decelerating by
releasing compression.

That's just downshifting/engine braking. They're not messing with
valves, afaik.

The federal highway law of 1986 required all trucks over 12000 Lbs to
have a "retarder". Fire trucks use electric retarders (faraday brakes)
as they can be disabled by pulling a breaker and it should be totally
impossible for a bad electric retarder to disable the truck.

They USED to use this style. Many today use either a hydraulic retarder
in the transmission OR an exhaust retarder (just a pneumatic damper in
the exhaust pipe really) However as fire engines are usually considered
an "off highway vehicle" they are also exempt from that law.


Almost all other large trucks use "pneumatic" retarders. Activating the
retarder causes the intake and compression strokes to happen normally,
but then the exhaust valves are opened at the peak of compression. One
system is the Jacobs brake, sometimes called a "Jake brake" that uses an
extra lobe on the camshaft to trip the exhaust valve.

These devices have been built integrally into the engines of large
trucks for some years. The federal law was due to a LOT of semi
operators disconnecting the front brakes to be sure to have steering
control in hard braking, and the rapid wear of brakes (usually replaced
every 10K miles!) The retarders don't wear anything out, so the
truckers and owners love them.

Jon


--
Steve W.