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We just got our 2005 5-speed. In other manual transmission cars I have usually coasted in neutral to save gas going downhill. Would it be better in the Insight to coast in gear to maximize charging of the battery?
 

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On most modern cars (including the Insight), when you are completely off the gas, the engine goes into fuel cut mode. It pumps air until you either get back on the gas or the rpm's drop too low. Decelerate in gear.
 

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If you are going down a hill, you want to give it just enough gas to keep it from going into charge mode if you are looking for mileage. If you are coming up to a stop, then leave it in gear and touch the brake enough so the regenerative braking bumps the batteries, but be aware that when you get slow enough, the regen cuts out and you have to step on the brake harder.
robert
 

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yep coast in gear. You can see it on the FCD display, you'll want to find the spot where you just don't get charge and the FCD is at 150mpg. It's still possible you are using some fuel, though very minimal. If you switch the display over the metric it displays in liters per 100km so you can find the point where it displays 0L/100km, which can actually be pretty tricky to find sometimes.
 

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I've long suspected that coasting is the secret weapon of our hypermilers (their non-secret weapon is very high tire pressure) :roll: On my recent trip to Washington from California and back, going up those long mountain grades I tried to keep above 50mpg (down to 45mph sometimes). Coming down those same grades in neutral (but with the engine idling), the mpg display was locked at 150mpg for many many miles at a time, and it was so nice to see the trip mpg climb! Needed to put in gear and use my regen switch to slow down sometimes (have to blip the throttle first, or it doesn't work), but otherwise just let her roll along. Unless the battery is not charged, I don't see any reason to stay in gear when going down hills. JoeS.
 

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JoeMultihuller said:
<snip>
Coming down those same grades in neutral (but with the engine idling), the mpg display was locked at 150mpg for many many miles at a time, and it was so nice to see the trip mpg climb!

<snip>

Try switching to L/Km with the engine off (forced autostop) = 0L/Km = infinite MPG.
If you cost at idle in the L/Km mode you will see the difference.

Coasting at idle uses infinitely _more_ fuel. :twisted: :D


BEWARE loss of brake boost assist though :!:
 

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Yes, yes, I've been switching over to the L/100km reading and recognize the higher resolution down there; however, for me it's visually more satisfying to have that bar simply pegged at 150mpg. :)

Inasmuch as I'm still learning about the car, I've been somewhat reluctant to turn off the ignition (and, yes, click it back on after the engine stops) while coasting at 70mph. Understand the brake boost loss potential ...

I'm confused and guess that I need to go back and keep wading through all the postings, but is there a way to induce "autostop" at that speed (since the normal upper limit is around 19mph)? "Autostop" to me implies that the engine will automatically start up during this coasting if I push in the clutch, and associated with that is a solid green autostop light instead of it blinking. Like I said, I'm confused and still learning. :?

BTW, I always rev up the engine before putting it back into gear to minimize stressing the synchros.

Thank you for the education. JoeS.
 

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Sorry Joe if you took me too seriously.

Thought the twisted emoticon would make my intent clear, ever how accurate the rest of the information was.

A "forced" auto stop is simply turning the engine off with the key, then allowing sufficient seconds for it to spin down before key-on but not restarting.

The eventual loss of power brake boost, momentary loss of power steering assist, and (here in Tennessee) the illegal aspect of doing this makes it one for the MPG obsessed. AFAIK its illegal in part because of power brake boost loss. And yes it will be one of those forensic findings after the fact if your "caught". Might affect your heirs since you have likely paid the ultimate price in such a scenario.
 

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Now, that last sentence needed an emoticon! Thanks for the heads-up. Delighted to hear that I wasn't confused, but just slow... (after all, it was late). :idea: :oops:

From my teenage years I seem to recall a coasting law in California, but my '67 SAAB has freewheel, which means when you let off the gas pedal the car coasts - a transmission carryover from its two-stroke days, but also a great way to shift without using the clutch. It's illegal :?: (gosh, now they tell me...). :eek:

Didn't those laws get put in place in the '30's when brakes could easily fade, brake fluid could easily boil, and non-synchro transmissions meant you couldn't put it back into gear if the engine died? :(

Anyway, for the lawyers reading my will, I'll be performing the forced autostop controlled test on my own private road (read: long driveway). JoeS.
 

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Couldn't find a crossed out eyes, upside down, tongue hanging to one side emoticon <VBG>

I think you've got it in regard to the origination of the anti coasting laws. And brake fade can still be a deadly consequence today :!: Especially on mountain grades in the west, use caution.
 

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There is one spot locally where I can coast for almost two miles on gradual slopes. It is tempting to shut down the engine and then turn it on again. In Canada we have day time lights. How much energy does it take to run the lights and the electronics? If these loads drain more energy from the battery than the amount of energy supplied by the IMA when the engine is idling, then there really is absolutely no reason to shut off the engine. This lost energy will have to be returned later decreasing the efficiency, perhaps preventing "lean burn". Therefor in my opinion the answer is far from clear cut.
 

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Two scenarios

b1shmu63 said:
Therefore in my opinion the answer is far from clear cut.
I'll agree it's not clear cut. Let's consider two scenarios:

1) Coasting on a gentle grade where the slope is just enough to keep you at the speed you want.

In this situation, I think it is most efficient to:
A) shut off the engine and coast in neutral.
The other options are:
B) 5th gear, lean burn or zero fuel. In either case, you've got the added friction of the engine to overcome, whether you are overcoming it by going slower, or by adding a little fuel.
C) Engine on, idle. This might use a little less fuel if the engine speed is slower, and so there's less friction to overcome, but the engine is not operating at a very efficient point (it can't do lean burn idling, can it?).
So I think A) is always most efficient, with B) most efficient at lower speeds and C) most efficient at higher speeds.

As to whether you should keep the engine on idle to power the lights, etc., I think that the engine is operating at a poor enough efficiency point in that case that you are better waiting until you are next running the engine.

2) Coasting on a grade that is steep enough that you accelerate unless you use brakes, regen, or engine braking to slow down.

In this situation, either engine braking or brakes will simply throw away energy, whereas regen will capture it. So you certainly want to use regen unless the battery is full. The question is what gear to use. I think the answer is to use as high a gear as "possible" to minimize engine braking and thus maximize regen, unless you hit maximum regen and still want to slow down more, or if the engine speed gets too low so you lose regen. In those cases you shift down.

Finally, if the batteries are full, and you need some braking, then it's just like any other car--it's better for the brakes to use engine braking. And presumably what others have said is correct, that the fuel use can go to zero in that case.

That's mostly from theory--I've only had my insight for a month. So please correct me. I've tried to lay out all the scenarios here for clarity, not because I know everything for sure.

Of course, I'm only describing efficiency here--consider also the safety issues others have raised.

Charlie
 

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On my semi daily "lunch" commute there's a detour through a neighborhood that allows for gradual hill engine off key on coasting. I've done it repeatedly. Its worth about +1% to my daily MPG.

Guess this puts me in the MPG obsessive category <VBG>
 

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I’m a bit confused by the messages in this topic. Since safety is apparently involved, it seems appropriate to both offer and request clarification.

Optional coasting with the engine idling was introduced as a feature on American cars in 1932. It was called “Free Wheeling In”.

Coasting with the engine idling was an energy saving requirement for cars in Sweden in the 70’s. I don’t know if the laws have since changed.

Many cars go into a “rich burn” mode when that car is going down hill by its own momentum (foot off the accelerator pedal) and the drive train is engaged. This results in more fuel consumption than if the car would be in neutral (drive train disengaged).

The Honda Insight with 5 speed manual transmission has a “fuel cut” feature which in many cases, effects less fuel consumption going down hill with the drive train engaged, than if the car were in neutral, or clutch disengaged, with the engine idling. When the ignition switch is on, the Insight’s ECM keeps the engine turning, either by the car’s momentum, or combustion, except when the car is stopped or at very low speed. This ensures that the power brakes and power steering are active while the car is in motion. (The experts may clarify the specific speeds and conditions.)

Turning off the ignition switch while the car is in motion is inherently UNSAFE. The power brakes, power steering, and possibly the anti-lock braking system and airbags may not be active. (Even if the airbags are not disabled in this mode, it would seem that they could be more likely to be required as a result of possible, undesirable events!)

Please clarify specifically what is not legal in some states:
-Coasting with the engine idling;
-Coasting with the ignition switch off.
 

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In the case of the Insight, the power steering is electric.
It takes a couple of seconds for the electronics to settle when restarting, and that is definitely a safety issue.
The amount of fuel used going down hill is minimal, and with the driving I do, 1% isn't worth the risk.
robert
 

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Agreed engine-off coasting can be very hazardous to your health (and others health).

AFAIK most "modern" fuel injection engines have a fuel cut mode. High manifold vacuum and low throttle opening will cause the fuel system to temporarily turn off the injectors. And agreed that a carburated engine will consume more fuel with higher manifold vacuum typically caused by engine on, foot off gas pedal while in gear downhill "coasting". If I'm understanding you correctly what your calling "rich burn".

As you are aware legal opinions are "illegal" in most states unless given by an attorney licensed in the state the opinion is for. With the legal disclaimer above in place, in TN its illegal to do either of your posted questions. I think the "technical" issues surrounding the reasons behind such laws have been sufficiently addressed.

HTH! :)
 

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On a 50 mile trip 1% would save about 2 cents. :shock: Well, that's my 2 Cents worth. :wink:
 

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b1shmu63 said:
On a 50 mile trip 1% would save about 2 cents. :shock: Well, that's my 2 Cents worth. :wink:
:lol:

We, the MPG obsessed, can chuckle about your calculation. But there are about 3 other segments of my lunch commute that I haven't tried the forced autostop coasting, yet :!:

Maybe it'll be worth 5% :!:

If I can lol about it is there still hope for me :?: :D <rhetorical>
 
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Hi All:

___Hypermilers do indeed use ALL the coasting techniques to improve their FE.

___On a similar note, most forced Autostop’s I use come at speeds well below 19 mph when the Auto-stp logic isn’t made up when it should be. As for high speed, electric power steering isn’t needed given how light our Insight’s are. From high speed, you do not use hypermileage techniques willy nilly. You use them when it is safe to do so. A key off to reboot takes less then 3 seconds. You can lock up the brakes without assist at any time with or without the ICE running although you will have a much different feel.

___Originalbadbob, I cannot say whether 1% is a good figure or not but I can say 92.5 lmpg using all the techniques is well worth it vs. most others?

___As for forcing autostop in regular automobiles, here is a great start … I use it sometimes (long red’s locally) but not always given the wear and tear on the ICE and the Starter.

Japanese Government to Promote Manual “Idling Stop”

Kyodo News reports that the Japanese government is planning to take its “idling stop” campaign from buses and taxis and other commercial vehicles to the general car-owning population in an effort to save fuel and reduce greenhouse gas emissions.

The proposed idling-stop campaign is the low-tech version of a hybrid stop-start system: manually turning off the engine when the vehicle is stopped for more than a very short time in traffic or at an intersection.

Although vehicles equipped with automatic idling stop devices are on the increase (such as the hot-selling Toyota Vitz—earlier post), and the Japanese government extends subsidies to commercial firms which use such vehicles, there is no such incentive for private cars.

Automatic idling-stop (or stop-start) systems save a significant amount of fuel, especially in cities.

The Energy Conservation Center of Japan, affiliated with the Ministry of Economy, Trade and Industry, carried out a three-week test in the summer of 2002 using two cars of the same make and model—one with an automatic idling cut-off and the other without it.

On open roads between cities there was not much difference between the two vehicles in fuel-saving because stops were few, but even so, the vehicle with the idling-prevention device used 3.4% less gasoline that the other car. In cities, however, fuel consumption dropped 13.4%.

A center official said that since the saving on fuel was large, “Operators of buses running on regular routes in cities, those of home-delivery trucks, and taxi companies have begun to actively introduce the practice.”

However, impatient drivers do not like to turn off their engines at traffic light stops because they want to get off to a fast start when the lights change.

With improved efficiency in starters and batteries, turning off the engine for a short time poses almost no problem, but even so many drivers find it a heavy psychological burden to deliberately turn off the engine by using the key.

The idea of drivers shutting of their vehicles to spare the air is not new. The state of Oregon, for example, advises drivers to turn off their engines after more than 10 seconds of idling on Clean Air Action Days.

This sounds like it might be the first broad-based national initiative to undertake the practice—at least recently.


___Insightful_Trekker, have you any links to the illegalities of Autostop?

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:2y19ja5u][email protected][/email:2y19ja5u]
 
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