Honda Car Forum

Brian Smith wrote:
> "gigelus2k3" <popescu.serban@gmail.com> wrote in message
> news:1184044534.276448.53530@x35g2000prf.googlegro ups.com...
>
>>What's up with all the advice to brake using downshifting instead of
>>coasting (manual tranny, of course)? I even heard this Sunday the two
>>clowns at cartalk claiming that downshifting is the way to braking
>>instead of bleeding off speed by only friction (when possible, of
>>course). Is there a downside to coasting?
>
>
> It's against the law in most if not all jurisdictions. It also lessens
> the amount of control one has over their vehicle.
>
>
>>I remember trying braking using downshifting and my mileage went down
>>by about 15% (city driving, from 35 to 30). Why would I want this?
>
>
> Then you're not doing it correctly.
>
>


So reducing fuel consumption by 75% for 25 feet saves more gas than
reducing it by 50% for 200 feet? Ok, if you say so. ;-)

"gigelus2k3" <popescu.serban@gmail.com> wrote in message
news:1184045978.808997.248490@j4g2000prf.googlegro ups.com...
> On Jul 9, 10:28 pm, "mjc13<REMOVETHIS>"
> <"mjc13<REMOVETHIS>"@verizon.net> wrote:
>> Using engine braking will virtually shut of the flow of fuel to the
>> injectors, making the engine use less fuel than in coasting. What the
>> above-mentiuoned clowns don't take into consideration is that unless you
>> are going down a pretty steep hill, engine braking will slow the car too
>> fast to save much gas. Coasting is the way to go on level roads or
>> gentle downhills. The main downside is that coasting in neutral is
>> illegal in many places, but when done carefully I think it's safer than
>> much of the legal stuff that people do while driving, and I've never
>> been stopped for it...
>
> What? I never heard of this... Where is coasting illegal? Man, you
> learn something everyday (and still die dumb)!
>
>
It's even stricter in commercial driving. I was preparing for a CDL (was
required by my employer until they found what it would do to my hours of
availability) and saw in the driving test study guide that at no time was
the rig allowed to travel more than 1 1/2 lengths without being in some gear
with the clutch out. That's probably the source of coasting laws - the
ability of a vehicle to get out of control on a downgrade. It's mostly
archaic but still the standard.

Mike

On Jul 10, 12:58 am, "Brian Smith" <Hali...@NovaScotia.Canada> wrote:
> It's against the law in most if not all jurisdictions. It also lessens
> the amount of control one has over their vehicle.

I really wonder if if that's so in California. Never heard of it being
illegal. Anyway, why would it lessen the amount of control I have over
the vehicle? I'm not talking about icy or rainy conditions or going
downhill on a steep slope, just day-to-day driving in the sunny
California.

> > I remember trying braking using downshifting and my mileage went down
> > by about 15% (city driving, from 35 to 30). Why would I want this?
>
> Then you're not doing it correctly.

That's possible too. Unfortunately I think I'm too old to learn new
tricks...

Michael Pardee wrote:
> "gigelus2k3" <popescu.serban@gmail.com> wrote in message
> news:1184045978.808997.248490@j4g2000prf.googlegro ups.com...
>
>>On Jul 9, 10:28 pm, "mjc13<REMOVETHIS>"
>><"mjc13<REMOVETHIS>"@verizon.net> wrote:
>>
>>> Using engine braking will virtually shut of the flow of fuel to the
>>>injectors, making the engine use less fuel than in coasting. What the
>>>above-mentiuoned clowns don't take into consideration is that unless you
>>>are going down a pretty steep hill, engine braking will slow the car too
>>>fast to save much gas. Coasting is the way to go on level roads or
>>>gentle downhills. The main downside is that coasting in neutral is
>>>illegal in many places, but when done carefully I think it's safer than
>>>much of the legal stuff that people do while driving, and I've never
>>>been stopped for it...
>>
>>What? I never heard of this... Where is coasting illegal? Man, you
>>learn something everyday (and still die dumb)!
>>
>>
>
> It's even stricter in commercial driving. I was preparing for a CDL (was
> required by my employer until they found what it would do to my hours of
> availability) and saw in the driving test study guide that at no time was
> the rig allowed to travel more than 1 1/2 lengths without being in some gear
> with the clutch out. That's probably the source of coasting laws - the
> ability of a vehicle to get out of control on a downgrade. It's mostly
> archaic but still the standard.
>
> Mike
>
>
>

I remember driving a big car transporter on a permit, back in the
'70's. The air brakes alone just wouldn't be enough to stop a vehicle
like that on a regular basis. You may be right about that being the
source of the laws.

"Hachiroku ????" <Trueno@AE86.gts> wrote in message
news:TgIki.5140$V35.1567@trndny03...
>
> Also,brakes are cheaper (and easier) than a clutch.

True.

> Of course, I downshift 90% of the time...

You don't need to use a clutch to shift gears. Just to pull away and to
come to a stop.

On Tue, 10 Jul 2007 22:52:01 +0000, Brian Smith wrote:

>
> "Hachiroku ????" <Trueno@AE86.gts> wrote in message
> news:TgIki.5140$V35.1567@trndny03...
>>
>> Also,brakes are cheaper (and easier) than a clutch.
>
> True.
>
>> Of course, I downshift 90% of the time...
>
> You don't need to use a clutch to shift gears. Just to pull away and
> to
> come to a stop.


I've only used that method when the cable broke or one of the cylinders
went bad.

Yeah, it works...sometimes...

"mjc13<REMOVETHIS> @verizon.net>" <"mjc13<REMOVETHIS> wrote in message
news:nOEki.2665$CJ4.1081@trndny08...
> gigelus2k3 wrote:
>
>> On Jul 9, 8:45 pm, "mjc13<REMOVETHIS>"
>> <"mjc13<REMOVETHIS>"@verizon.net> wrote:
>>
>>>* Coast when possible and safe, rather than going back and forth between
>>>the gas and brake pedals.
>>
>>
>> What's up with all the advice to brake using downshifting instead of
>> coasting (manual tranny, of course)? I even heard this Sunday the two
>> clowns at cartalk claiming that downshifting is the way to braking
>> instead of bleeding off speed by only friction (when possible, of
>> course). Is there a downside to coasting?
>>
>> I remember trying braking using downshifting and my mileage went down
>> by about 15% (city driving, from 35 to 30). Why would I want this?
>>
>
>
> Using engine braking will virtually shut of the flow of fuel to the
> injectors, making the engine use less fuel than in coasting.

According to the ScanGauge readouts, it uses up to twice the fuel of
coasting when you downshift. For example, 0.7GPH is the fuel rate at idle.
It will jump up to 1.2GPH if downshifted to 2nd at ~35mph. Shifting into
neutral and braking will maintain the 0.7GPH. Maybe the ECU is lying, I
dunno.

--
Phil

Phil wrote:
> "mjc13<REMOVETHIS> @verizon.net>" <"mjc13<REMOVETHIS> wrote in message
> news:nOEki.2665$CJ4.1081@trndny08...
>
>>gigelus2k3 wrote:
>>
>>
>>>On Jul 9, 8:45 pm, "mjc13<REMOVETHIS>"
>>><"mjc13<REMOVETHIS>"@verizon.net> wrote:
>>>
>>>
>>>>* Coast when possible and safe, rather than going back and forth between
>>>>the gas and brake pedals.
>>>
>>>
>>>What's up with all the advice to brake using downshifting instead of
>>>coasting (manual tranny, of course)? I even heard this Sunday the two
>>>clowns at cartalk claiming that downshifting is the way to braking
>>>instead of bleeding off speed by only friction (when possible, of
>>>course). Is there a downside to coasting?
>>>
>>>I remember trying braking using downshifting and my mileage went down
>>>by about 15% (city driving, from 35 to 30). Why would I want this?
>>>
>>
>>
>> Using engine braking will virtually shut of the flow of fuel to the
>>injectors, making the engine use less fuel than in coasting.
>
>
> According to the ScanGauge readouts, it uses up to twice the fuel of
> coasting when you downshift. For example, 0.7GPH is the fuel rate at idle.
> It will jump up to 1.2GPH if downshifted to 2nd at ~35mph. Shifting into
> neutral and braking will maintain the 0.7GPH. Maybe the ECU is lying, I
> dunno.
>

I was repeating what I knew of how EFI systems worked years ago. If
you are correct, then the Car Talk Clowns are completely, 100% wrong,
not just 75% wrong. ;-)

"mjc13<REMOVETHIS> @verizon.net>" <"mjc13<REMOVETHIS> wrote in message
news:eezmi.2439$4J4.1750@trndny05...
> Phil wrote:
>> "mjc13<REMOVETHIS> @verizon.net>" <"mjc13<REMOVETHIS> wrote in message
>> news:nOEki.2665$CJ4.1081@trndny08...
>>
>>>gigelus2k3 wrote:
>>>
>>>
>>>>On Jul 9, 8:45 pm, "mjc13<REMOVETHIS>"
>>>><"mjc13<REMOVETHIS>"@verizon.net> wrote:
>>>>
>>>>
>>>>>* Coast when possible and safe, rather than going back and forth
>>>>>between
>>>>>the gas and brake pedals.
>>>>
>>>>
>>>>What's up with all the advice to brake using downshifting instead of
>>>>coasting (manual tranny, of course)? I even heard this Sunday the two
>>>>clowns at cartalk claiming that downshifting is the way to braking
>>>>instead of bleeding off speed by only friction (when possible, of
>>>>course). Is there a downside to coasting?
>>>>
>>>>I remember trying braking using downshifting and my mileage went down
>>>>by about 15% (city driving, from 35 to 30). Why would I want this?
>>>>
>>>
>>>
>>> Using engine braking will virtually shut of the flow of fuel to the
>>> injectors, making the engine use less fuel than in coasting.
>>
>>
>> According to the ScanGauge readouts, it uses up to twice the fuel of
>> coasting when you downshift. For example, 0.7GPH is the fuel rate at
>> idle. It will jump up to 1.2GPH if downshifted to 2nd at ~35mph.
>> Shifting into neutral and braking will maintain the 0.7GPH. Maybe the
>> ECU is lying, I dunno.
>>
>
> I was repeating what I knew of how EFI systems worked years ago. If you
> are correct, then the Car Talk Clowns are completely, 100% wrong, not just
> 75% wrong. ;-)
>

I don't think they got that wrong; it's practically mandated by emission
concerns. Cleaning up marginal combustion conditions is a lot tougher than
turning off the fuel altogether when it isn't needed. On my 1993 Chevy work
truck I could feel the cutout happening on descents. The engine drag would
suddenly increase at some RPM level and then switch back when the RPMs
dropped.

In the Yahoo! Prius-Technical-Stuff forum there is a lot of discussion about
engine operation compared to the OBDII bus info, and it's apparent the bus
info is not quite right all the time. In particular, the injector open time
is way off at idle (the same indications that would be used to calculate
idle fuel flow). That makes sense as the info is there for diagnostic
purposes. Personally, I suspect the ScanGuage is operating on bogus data. As
you say, the ECU is telling little white lies.

Mike

Michael Pardee wrote:
> "mjc13<REMOVETHIS> @verizon.net>" <"mjc13<REMOVETHIS> wrote in message
> news:eezmi.2439$4J4.1750@trndny05...
>
>>Phil wrote:
>>
>>>"mjc13<REMOVETHIS> @verizon.net>" <"mjc13<REMOVETHIS> wrote in message
>>>news:nOEki.2665$CJ4.1081@trndny08...
>>>
>>>
>>>>gigelus2k3 wrote:
>>>>
>>>>
>>>>
>>>>>On Jul 9, 8:45 pm, "mjc13<REMOVETHIS>"
>>>>><"mjc13<REMOVETHIS>"@verizon.net> wrote:
>>>>>
>>>>>
>>>>>
>>>>>>* Coast when possible and safe, rather than going back and forth
>>>>>>between
>>>>>>the gas and brake pedals.
>>>>>
>>>>>
>>>>>What's up with all the advice to brake using downshifting instead of
>>>>>coasting (manual tranny, of course)? I even heard this Sunday the two
>>>>>clowns at cartalk claiming that downshifting is the way to braking
>>>>>instead of bleeding off speed by only friction (when possible, of
>>>>>course). Is there a downside to coasting?
>>>>>
>>>>>I remember trying braking using downshifting and my mileage went down
>>>>>by about 15% (city driving, from 35 to 30). Why would I want this?
>>>>>
>>>>
>>>>
>>>> Using engine braking will virtually shut of the flow of fuel to the
>>>>injectors, making the engine use less fuel than in coasting.
>>>
>>>
>>>According to the ScanGauge readouts, it uses up to twice the fuel of
>>>coasting when you downshift. For example, 0.7GPH is the fuel rate at
>>>idle. It will jump up to 1.2GPH if downshifted to 2nd at ~35mph.
>>>Shifting into neutral and braking will maintain the 0.7GPH. Maybe the
>>>ECU is lying, I dunno.
>>>
>>
>> I was repeating what I knew of how EFI systems worked years ago. If you
>>are correct, then the Car Talk Clowns are completely, 100% wrong, not just
>>75% wrong. ;-)
>>
>
>
> I don't think they got that wrong; it's practically mandated by emission
> concerns. Cleaning up marginal combustion conditions is a lot tougher than
> turning off the fuel altogether when it isn't needed. On my 1993 Chevy work
> truck I could feel the cutout happening on descents. The engine drag would
> suddenly increase at some RPM level and then switch back when the RPMs
> dropped.
>
> In the Yahoo! Prius-Technical-Stuff forum there is a lot of discussion about
> engine operation compared to the OBDII bus info, and it's apparent the bus
> info is not quite right all the time. In particular, the injector open time
> is way off at idle (the same indications that would be used to calculate
> idle fuel flow). That makes sense as the info is there for diagnostic
> purposes. Personally, I suspect the ScanGuage is operating on bogus data. As
> you say, the ECU is telling little white lies.
>
> Mike
>
>
I didn't say that, but it sounds apt. I remember that the last of
the street-legal two-stroke motorcycles used a novel way to get through
the EPA emissions cycle: IIRC a butterfly valve blocked off the exhaust
port(s) when the throttle was closed. With fuel injection it's even
easier to virtually shut off the fuel flow for deceleration...