coasting

[MetroMPG]

<b>the results:</b>

- <b>60.3 mpg</b> (US) - lap 1 "engine OFF while coasting"

- <b>53.4 mpg</b> (US) - lap 2 "engine idling while coasting"

[rh77]

As always, compliments on the experimentation. I've been using the idle at long-stops technique lately. I'd like to use an engine-off kill switch but with the automatic, I'd have to use the starter to get it going again...unless...

I haven't tried it, and I'm sure it would be murder for the transmission, but I wonder if it's possible move the transmission from N to possibly 2 or 1 -- would the momentum turn the engine to fire it back up, or would the TC be entirely disconnected and not translate the rotational energy back to the crankshaft? Just frustrated as usual with the automatic.

By the way, is it that windy all the time? I thought Kansas was windy...

RH77

[philmcneal]

welcome to my world, except you have a scangauge ;(!!!! Although that kill switch sounds nice but I wouldn't know where to start wiring :S

But my speedo comes right back on when I key on so I'm hoping my upcoming scangauge would too...

[JanGeo]

In the "old days" autotranny's could be bump started at about 25mph but I don't recommend it now - the hydralic pressure comes from the engine side of the torque converter so with the engine stopped no oil flow in the tranny. Seals cook pretty fast too.

[JanGeo]

Nice results! I took the long gentle down hill home last night in the fog, way weird coasting at 35-25mph using pulse and glid in the heavy fog but trip mpg rose for a 20 mile trip from 43mpg to 46.5mpg by doing P+G for a few miles. Was really weird when it hit the steeper down hill just before it levels out and starts up the steep hill at the end - no street lights but great to have the gps to "see" where I was. One thing I noticed is if you have to coast with the engine on the faster you are going the better the mpg - you are still burning gas at a constant rate at idle so going faster yields more mpg. Wish my idle would drop lower - think the torco may be changing the cleanness of the exhost forcing 800+ rpm idle?? Seen it as low as 650rpm when stopped. Seems mpg is a few less at night than day time too.

[MetroMPG]

Originally Posted by rh77

I've been using the idle at long-stops technique lately.

no engine-off stops at all? i don't mind using the starter once in a while, even in the manual shift car. 13 times in 9.7 km would be excessive, but i don't think 3 is. (it would have been 2 key starts, but i botched one of the clutch starts when i used my kill switch improperly.)

By the way, is it that windy all the time? I thought Kansas was windy...

um, there's almost always some wind, yes. but that day was windier than normal. i remember that last fall was particularly windy.

[MetroMPG]

Originally Posted by philmcneal

that kill switch sounds nice but I wouldn't know where to start wiring

my switch is wired into the positive wire to my distributor's pickup coil. (helps if you have a shop manual.) and your engine may use a different ignition approach, so i can't say for sure if it's applicable to your situation.

Originally Posted by philmcneal

But my speedo comes right back on when I key on so I'm hoping my upcoming scangauge would too...

that would be nice! but it seems to depend on what OBD protocol your car uses. if it's ISO, then interrupting the power to the scangauge will force it to wait while things re-initialize, and your data will be skewed by the delay.

another possibility that i didn't look at: krousdb suggested powering the scangauge independently of the OBD port.

as always: caveat experimentor! we modify our vehicles at our peril.

[MetroMPG]

since running this test, of course i've been shutting off the engine more for coasting than i used to.

my segment mileage, according to the scangauge, has shot way up. example:

68.1 mpg (US) over 30.5 km of sub/exurban driving (23 mph avg speed / 42 mph max; rain, wet roads; 6 C / 46 F ambient; 1.25 hrs EBH.)

this trip was actually above the 70 MPG level on the way back to the house, and then i got hit by 3 red lights in a row and a train crossing at the bottom of my best hill, and these things dragged it down to 68.1

i suspect that through using engine-off coasting more i'm going to see the "hybrid FE flip flop": where my non-highway driving FE is going to exceed my highway-only numbers.

[JanGeo]

That local driving better than highway is to be expected as air drag is a big factor of fuel use and low power engine use is the other big factor of fuel use. You usually get one or the other but not both at the same time - that is the reason I always got good mileage in my Geo no matter how fast I drive. SO by shutting down your engine at low speed you reduce the low power losses and get great results. The xB is a little different because of the additives helping the low power operation as well as the Variable Valve Timing at low speeds but air drag is the major factor over 40mph no matter what I do. That's why I think that a small electric motor power assist at low speed level operation would be the perfect solution - a small battery pack for less weight and small light efficient electric motor would propel the car at 20-30 mph without the ice running and could regen down hills and while stopping to recoup the energy losses. Just need to workout the connection to the wheel thing. Would love to tap into the input shaft of the tranny and on the Geo that could be done on the left side out the end of the case instead of the engine side.

[krousdb]

Originally Posted by MetroMPG

my switch is wired into the positive wire to my distributor's pickup coil. (helps if you have a shop manual.) and your engine may use a different ignition approach, so i can't say for sure if it's applicable to your situation.

Remebber that I removed my kill switch because my Honda will shut off the fuel pump if it senses that the engine has stopped. The only way to restart is to turn the key off then back on again, which defeats the purpose of the kill switch. I don't know if it is any different in a 2005 honda, but my guess would be that you will have the same issue.

If I were you Phil, I would consider going through a tank with your normal off while coasting technigue, and then calibrating the ScanGuage. As long as your off times and frequencies don't vary wildly from tank to tank, I would expect that you will get good results.