Dan C wrote:
> On Wed, 02 Jul 2008 09:11:34 -0700, Dano58 wrote:
>
>> And I agree with the comment on coasting in neutral versus remaining in
>> gear. I typically roll up to a light in the highest gear I can, for as
>> long as I can until the engine starts to lug, before I disengage the
>> clutch and allow the car to go into idle. As noted, no fuel is delivered
>> while you're coasting in gear, but some is when you're coasting in
>> neutral (i.e., engine is idling).
>
> Of course there is fuel being used while coasting in gear. The engine is
> still running, is it not?

the engine is rotating, but that's because the momentum of the car is
pushing it. all the pistons are doing is pumping air - the injectors
are not releasing gas unless the ecu says to do so. and in this
situation it doesn't. when the revs drop below threshold again, /then/
it starts to inject, and thus the engine can run on its own. the
transition is seamless and the driver never notices.


> Therefore it's using fuel. No different than
> idling in neutral in that respect.

nope, it's completely different.

go to megasquirt.info and read through the source code for an injection
computer. all the modules are easy to follow and you'll find the
section where it specifically states the condition for over-run fuel cut
off. enjoy!

 

Tegger wrote:
> Tony Hwang <dragon40@shaw.ca> wrote in
> news:nEVak.73472$gc5.41373@pd7urf2no:
>
>> Tegger wrote:
>
>>> It's called "double-clutching". Look it up. It adds a lot of fun to
>>> driving a manual transmission.
>>>
>>>
>> Hmmm,
>> I thought doulbe-clutching was before the days of synchros.
>
>
>
> You think wrongly.
>
> Double-clutching is as relevant today as it was in 1920, and for the same
> reasons. But synchros now mask what failure to effectively double-clutch
> would have loudly and embarrassingly revealed in 1920.
>
> Part of the reason I got 255,000 miles out of my last clutch is because I
> double-clutch every downshift. And after 305,000 miles my synchros work
> almost as well now as they did when new.
>
>
>
Hi,
If you knit pick, you are right. Some cars even have a shift light on
the dash signalling time to shift. Tach is there for a reason. Then how
many real drivers are on the road these days? Most are motor vehicle
operators.

 

jim beam <spamvortex@bad.example.net> wrote in
news:lZKdnScH0bVXpPHVnZ2dnUVZ_sTinZ2d@speakeasy.ne t:

> Tegger wrote:
>> Tony Hwang <dragon40@shaw.ca> wrote in
>> news:nEVak.73472$gc5.41373@pd7urf2no:
>>
>>> Tegger wrote:
>>
>>>> It's called "double-clutching". Look it up. It adds a lot of fun to
>>>> driving a manual transmission.
>>>>
>>>>
>>> Hmmm,
>>> I thought doulbe-clutching was before the days of synchros.
>>
>>
>>
>> You think wrongly.
>>
>> Double-clutching is as relevant today as it was in 1920, and for the
>> same reasons. But synchros now mask what failure to effectively
>> double-clutch would have loudly and embarrassingly revealed in 1920.
>>
>> Part of the reason I got 255,000 miles out of my last clutch is
>> because I double-clutch every downshift.
>
> that bit's not true - it's because you don't slip the clutch. if
> anything, operating the springs/bearing twice as often as you need to
> /reduces/ life of the mechanical parts.



True, but it's the engine-rev during double-clutching that keeps the clutch
from slipping. I guess you could rev the engine without double-clutching,
but that won't help the synchros.

If there was any additional wear on any of the parts due to double-
clutching, it was undetectable when the old parts were removed. I checked
specifically for that when the clutch was changed.



>
>
>> And after 305,000 miles my synchros work
>> almost as well now as they did when new.
>
> that may be true, but it's much more likely that it's because you
> shift more slowly as a function of the above. synchros are very
> effective, and provided the clutch is disengaging properly, have very
> little load on shifting. unless raced and slammed prematurely,
> synchros last as long as the rest of the transmission.
>


Let me clarify my statement: Double-clutching extends the life of the
synchros far beyond what it would be if the lever had simply been dragged
into each lower gear without rev-matching. It's that which kills synchros
in addition to too-fast shifting.


--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

 

Tegger wrote:
> jim beam <spamvortex@bad.example.net> wrote in
> news:lZKdnScH0bVXpPHVnZ2dnUVZ_sTinZ2d@speakeasy.ne t:
>
>> Tegger wrote:
>>> Tony Hwang <dragon40@shaw.ca> wrote in
>>> news:nEVak.73472$gc5.41373@pd7urf2no:
>>>
>>>> Tegger wrote:
>>>>> It's called "double-clutching". Look it up. It adds a lot of fun to
>>>>> driving a manual transmission.
>>>>>
>>>>>
>>>> Hmmm,
>>>> I thought doulbe-clutching was before the days of synchros.
>>>
>>>
>>> You think wrongly.
>>>
>>> Double-clutching is as relevant today as it was in 1920, and for the
>>> same reasons. But synchros now mask what failure to effectively
>>> double-clutch would have loudly and embarrassingly revealed in 1920.
>>>
>>> Part of the reason I got 255,000 miles out of my last clutch is
>>> because I double-clutch every downshift.
>> that bit's not true - it's because you don't slip the clutch. if
>> anything, operating the springs/bearing twice as often as you need to
>> /reduces/ life of the mechanical parts.
>
>
>
> True, but it's the engine-rev during double-clutching that keeps the clutch
> from slipping. I guess you could rev the engine without double-clutching,
> but that won't help the synchros.

it does. and that's what you should do. if you've changed gears
without the clutch, you'll find it only works when the engine revs are
in range.


>
> If there was any additional wear on any of the parts due to double-
> clutching, it was undetectable when the old parts were removed. I checked
> specifically for that when the clutch was changed.

the bits that would wear from double-clutching are the thrust bearing
and the pressure plate mechanism. the friction plates won't be affected.



>
>
>
>>
>>> And after 305,000 miles my synchros work
>>> almost as well now as they did when new.
>> that may be true, but it's much more likely that it's because you
>> shift more slowly as a function of the above. synchros are very
>> effective, and provided the clutch is disengaging properly, have very
>> little load on shifting. unless raced and slammed prematurely,
>> synchros last as long as the rest of the transmission.
>>
>
>
> Let me clarify my statement: Double-clutching extends the life of the
> synchros far beyond what it would be if the lever had simply been dragged
> into each lower gear without rev-matching. It's that which kills synchros
> in addition to too-fast shifting.

strictly speaking, too-fast and non-matching are the same thing. for
racing, one of the reasons for lightened flywheel is that engine revs
can change more quickly allowing quicker rev matching, and thus quicker
shifting.

i was reminded of this a few years back when i had both a 91 stick crx
and a 91 stick civic std. the std had a heavier flywheel than the crx,
and the time it took for revs to drop from any given rpm was about
double that of the crx with the lighter flywheel. and thus, you
couldn't shift as quickly. being able to compare the two "side by side"
was actually dramatic in contrast - you had to be considerably more laid
back in the std.

 

jim beam <spamvortex@bad.example.net> wrote in
news:lZKdnSQH0bUzpPHVnZ2dnUVZ_sTinZ2d@speakeasy.ne t:

> Tegger wrote:
>> googamooga <googamooga@gmail.com> wrote in
>> news:871cad1c-4e6b-43ee-a73c-
>> 275fcb96e225@m36g2000hse.googlegroups.com:
>>
>>> Ok what if I am going down a slight hill (not mountain hills) at 40
>>> mpg, then shift to neutral...ride it out for a few seconds then back
>>> in gear so I can go up the next hill? I would stay in gear but that
>>> slows me down so I can't take full advantage of the hill and the
>>> momentum.
>>>
>>> How would being in neutral while riding would wear anything out?
>>> Can someone explain that to me in full detail please.
>>>
>>
>>
>> It's not the neutral part that wears things out, it's the getting
>> back into gear afterwards that does.
>>
>> Ever notice how it takes a bit of pushing before the lever will drop
>> back into gear again? That's your synchros grinding themselves into
>> powder.
>
> no dude, it's a cone clutch - cone clutches lock solid in next to no
> time, incur /very/ little wear, and are incredibly reliable. if you
> had a porsche-type baulk ring synchro, you'd be a little more correct
> because the wear rate is higher, but again, they last a /long/ time
> when everything is working right.



All synchro friction surfaces are cones. All synchros have been cones,
and have operated on the same friction principles, ever since the first
ones were installed in the 1928 Cadillac.

All synchro assemblies have baulk/blocker rings of some kind that
prevent engagement of the dog teeth until the two synchro halves are
immobile relative to each other (i.e.: matched). Baulk/blocker rings are
separate from the friction surfaces of the cones, although the female
half of the synchro does form one half of the baulk ring assembly. There
are many, many designs of blocker rings, but all of them operate on
identical principles.

If you feel the lever hang up a bit (or a lot) before dropping into
gear, you are experiencing the baulk/blocker rings in action, protecting
the dogs from the damage they would incur as a consequence of speed
difference relative to each other. The greater the difference in
friction surface rotational speeds, the more drag the synchro friction
surfaces must apply before they are matched, and the longer the baulk
rings will delay dog engagement. Excessive drag from excessive speed
difference can actually burn through the oil film seaprating the two
halves of the cone and cause metal-to-metal wear, which /dramatically/
shortens synchro life.

If the lever drops in immediately under very light pressure, the two
synchro halves were closely matched in speed, and have become quickly
immobile relative to each other. This means the synchros have had little
work to do, and the baulk/blocker rings were not long subject to the
rotational forces that caused them to prevent dog engagement.

The upshot: Proper double-clutching extends the life of the synchro
friction surfaces.

--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

 

jim beam <spamvortex@bad.example.net> wrote in
news:BqWdnXRJg9RYU_HVnZ2dnUVZ_oDinZ2d@speakeasy.ne t:

> Tegger wrote:

>
> the bits that would wear from double-clutching are the thrust bearing
> and the pressure plate mechanism. the friction plates won't be
> affected.


There was no unusual wear to any part of my clutch assembly. The pressure
plate was replaced on principle because it was 255,000 miles old, not
because anything was specifically wrong with it.

Riding the clutch - or neglected adjustment - will cause far quicker and
more severe wear than double-clutching.


--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

 

jim beam <spamvortex@bad.example.net> wrote in
news:lZKdnSYH0bWJp_HVnZ2dnUVZ_sTinZ2d@speakeasy.ne t:

> Dan C wrote:
>> On Wed, 02 Jul 2008 09:11:34 -0700, Dano58 wrote:
>>
>>> And I agree with the comment on coasting in neutral versus remaining
>>> in gear. I typically roll up to a light in the highest gear I can,
>>> for as long as I can until the engine starts to lug, before I
>>> disengage the clutch and allow the car to go into idle. As noted, no
>>> fuel is delivered while you're coasting in gear, but some is when
>>> you're coasting in neutral (i.e., engine is idling).
>>
>> Of course there is fuel being used while coasting in gear. The
>> engine is still running, is it not?
>
> the engine is rotating, but that's because the momentum of the car is
> pushing it. all the pistons are doing is pumping air - the injectors
> are not releasing gas unless the ecu says to do so. and in this
> situation it doesn't. when the revs drop below threshold again,
> /then/ it starts to inject, and thus the engine can run on its own.
> the transition is seamless and the driver never notices.



They've really screwed down the fuel-cutoff since 1995. All Honda engines
now shut off the injectors on decel at or below 1,000 rpm. There's one
Civic engine where they shut off on decel above 850rpm. Can't remember
which one just now, though...

In 1991 it was 1,500 rpm.


--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

 

Tegger wrote:
> jim beam <spamvortex@bad.example.net> wrote in
> news:BqWdnXRJg9RYU_HVnZ2dnUVZ_oDinZ2d@speakeasy.ne t:
>
>> Tegger wrote:
>
>> the bits that would wear from double-clutching are the thrust bearing
>> and the pressure plate mechanism. the friction plates won't be
>> affected.
>
>
> There was no unusual wear to any part of my clutch assembly. The pressure
> plate was replaced on principle because it was 255,000 miles old, not
> because anything was specifically wrong with it.

i didn't say there was, but by definition, the more times you operate
it, the closer it gets to its limit. you're operating it twice as many
times as other people, that's all.


>
> Riding the clutch - or neglected adjustment - will cause far quicker and
> more severe wear than double-clutching.

quicker wear of the friction plate and thrust bearing, yes indeed.

 

Tegger wrote:
> jim beam <spamvortex@bad.example.net> wrote in
> news:lZKdnSQH0bUzpPHVnZ2dnUVZ_sTinZ2d@speakeasy.ne t:
>
>> Tegger wrote:
>>> googamooga <googamooga@gmail.com> wrote in
>>> news:871cad1c-4e6b-43ee-a73c-
>>> 275fcb96e225@m36g2000hse.googlegroups.com:
>>>
>>>> Ok what if I am going down a slight hill (not mountain hills) at 40
>>>> mpg, then shift to neutral...ride it out for a few seconds then back
>>>> in gear so I can go up the next hill? I would stay in gear but that
>>>> slows me down so I can't take full advantage of the hill and the
>>>> momentum.
>>>>
>>>> How would being in neutral while riding would wear anything out?
>>>> Can someone explain that to me in full detail please.
>>>>
>>>
>>> It's not the neutral part that wears things out, it's the getting
>>> back into gear afterwards that does.
>>>
>>> Ever notice how it takes a bit of pushing before the lever will drop
>>> back into gear again? That's your synchros grinding themselves into
>>> powder.
>> no dude, it's a cone clutch - cone clutches lock solid in next to no
>> time, incur /very/ little wear, and are incredibly reliable. if you
>> had a porsche-type baulk ring synchro, you'd be a little more correct
>> because the wear rate is higher, but again, they last a /long/ time
>> when everything is working right.
>
>
>
> All synchro friction surfaces are cones. All synchros have been cones,
> and have operated on the same friction principles, ever since the first
> ones were installed in the 1928 Cadillac.

not true - and we've had this conversation before. the porsche type
synchro is a large annular ring with a couple of springs inside. it
has steel-to-steel contact, unlike the bronze cones of the more
traditional type.


>
> All synchro assemblies have baulk/blocker rings of some kind that
> prevent engagement of the dog teeth until the two synchro halves are
> immobile relative to each other (i.e.: matched). Baulk/blocker rings are
> separate from the friction surfaces of the cones, although the female
> half of the synchro does form one half of the baulk ring assembly. There
> are many, many designs of blocker rings, but all of them operate on
> identical principles.

not so. the porsche type is simply a friction fit. if you want to race
it and over-ride the blocking action, you can.


>
> If you feel the lever hang up a bit (or a lot) before dropping into
> gear, you are experiencing the baulk/blocker rings in action, protecting
> the dogs from the damage they would incur as a consequence of speed
> difference relative to each other. The greater the difference in
> friction surface rotational speeds, the more drag the synchro friction
> surfaces must apply before they are matched, and the longer the baulk
> rings will delay dog engagement. Excessive drag from excessive speed
> difference can actually burn through the oil film seaprating the two
> halves of the cone and cause metal-to-metal wear, which /dramatically/
> shortens synchro life.

while they spin, they're hydrodynamically separated by oil.


>
> If the lever drops in immediately under very light pressure, the two
> synchro halves were closely matched in speed, and have become quickly
> immobile relative to each other. This means the synchros have had little
> work to do, and the baulk/blocker rings were not long subject to the
> rotational forces that caused them to prevent dog engagement.

actually, all it means is that the two are in sync. nothing else. it
won't drop in [under normal usage] unless they are. if it takes time to
sync, it doesn't matter because the real syncing comes from rev matching
if relatively low mass components - two cogs, two shafts and a clutch
friction plate.


>
> The upshot: Proper double-clutching extends the life of the synchro
> friction surfaces.
>

not so you'd notice. really, the blocker mechanism is excellent and
lasts as long as the rest of the transmission unless forced. and that
includes defective clutch and/or over-zealous shifting. my crx had 306k
miles on it and the synchros were perfect - no crunchiness at any speed,
in any gear.

 

Tegger wrote:
> jim beam <spamvortex@bad.example.net> wrote in
> news:lZKdnSYH0bWJp_HVnZ2dnUVZ_sTinZ2d@speakeasy.ne t:
>
>> Dan C wrote:
>>> On Wed, 02 Jul 2008 09:11:34 -0700, Dano58 wrote:
>>>
>>>> And I agree with the comment on coasting in neutral versus remaining
>>>> in gear. I typically roll up to a light in the highest gear I can,
>>>> for as long as I can until the engine starts to lug, before I
>>>> disengage the clutch and allow the car to go into idle. As noted, no
>>>> fuel is delivered while you're coasting in gear, but some is when
>>>> you're coasting in neutral (i.e., engine is idling).
>>> Of course there is fuel being used while coasting in gear. The
>>> engine is still running, is it not?
>> the engine is rotating, but that's because the momentum of the car is
>> pushing it. all the pistons are doing is pumping air - the injectors
>> are not releasing gas unless the ecu says to do so. and in this
>> situation it doesn't. when the revs drop below threshold again,
>> /then/ it starts to inject, and thus the engine can run on its own.
>> the transition is seamless and the driver never notices.
>
>
>
> They've really screwed down the fuel-cutoff since 1995. All Honda engines
> now shut off the injectors on decel at or below 1,000 rpm. There's one
> Civic engine where they shut off on decel above 850rpm. Can't remember
> which one just now, though...
>
> In 1991 it was 1,500 rpm.

sure. absolutely no point injecting if the momentum of the car is still
turning the motor.

 

jim beam <spamvortex@bad.example.net> wrote in
newsLydnSDANuaz4_DVnZ2dnUVZ_u2dnZ2d@speakeasy.ne t:

> Tegger wrote:

>>
>>
>>
>> All synchro friction surfaces are cones. All synchros have been
>> cones, and have operated on the same friction principles, ever since
>> the first ones were installed in the 1928 Cadillac.
>
> not true - and we've had this conversation before. the porsche type
> synchro is a large annular ring with a couple of springs inside. it
> has steel-to-steel contact, unlike the bronze cones of the more
> traditional type.
>


Then Honda synchros are cones. We're talking Hondas here, not Porsches.



--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

 

On Fri, 4 Jul 2008 01:20:30 +0000 (UTC), Tegger <tegger@tegger.c0m>
wrote:

>They've really screwed down the fuel-cutoff since 1995. All Honda engines
>now shut off the injectors on decel at or below 1,000 rpm. There's one
>Civic engine where they shut off on decel above 850rpm. Can't remember
>which one just now, though...
>
>In 1991 it was 1,500 rpm.

Interesting. One change I noticed in my 2007 Accord 4 auto over the
2004 is that with foot off gas it almost seems to decelerate like an
old-style drive-by-linkage manual!

On the other side, I notice GM is advertising a car that (apparently)
shifts to neutral while waiting at a light. Oh, technology! I often
do that myself when I catch a long cycle, can be two minutes at some
major intersections. I just get tired of standing on the brake that
long, besides saving a few drops of gas.

J.