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Old 07-12-2009, 01:29 AM   #1 (permalink)
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Lightbulb Best way to eco-drive an automatic

I'm starting this thread in the hopes that it can become a 'sticky' that helps those of us crippled with automatic transmissions.

Besides shifting into 'N' ( neutral ) when coasting down a long hill*, what else can we all do ?

* engine running

Shutting off the engine on an automatic, and trying to restart while moving doesn't seem to work, at least not with the car I drive - A 1993 Civic.
I have to pull over and apply the brake before shifting back into 'D' ( drive )

I haven't tried lightly tapping the brake with enough pressure to let me shift, but then this wouldn't be practical in any sort of traffic anyhow.

Is there anything we can do to increase the efficiency of our transmissions, such as adding lower weight fluid ( Hey - it works for manual transmissions )

If any of you have any tips please share them here. Thanks !

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Old 07-12-2009, 09:31 AM   #2 (permalink)
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I like the idea of this thread. with automatics being so popular it is getting harder to find used cars with manual shift transmissions.

Synthetic trans fluid is available and can be used in most makes of car cd.

I always wondered about coasting. If I coast in gear my engine revs is 200rpm lower than if I am in nuetral. Once I stop the rpms go right back to the factory set idle. My question is.. Is the engine load of being in gear (foot off pedal) worse than the additional rpm caused by (I am assuming) a ram air effect of the car moving forward. I have seen this in a few cars even my old 95 civic.
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Old 07-12-2009, 10:36 AM   #3 (permalink)
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I don't think it's a ram air effect so much as a computer compensation.

I think what happens is that the VSS tells the ECU that the car is moving, but the engine is not under load, so the ECU opens the IACV to help compensate for where the engine should be, in case it gets a sudden load.

I could be spitting canal water, here, but that's what I've always thought was happening, cuz it never happened on any of my carbies.
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Old 07-12-2009, 11:08 AM   #4 (permalink)
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That sounds like a better reason to me.. LOL I'll use that one.
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Old 07-12-2009, 12:16 PM   #5 (permalink)
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Yeah I pretty much am in neutral about 10% of each drive I take. If I drive 8 miles, I'm probably in neural about 2 miles of it..(which I know is 20%~~leave me alone~~)
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Old 07-12-2009, 02:06 PM   #6 (permalink)
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The most efficient thing to do would be to shut the engine off so no fuel is being burned.....The safest thing to do is leave the motor running so you can steer easier saying you have power steering.....Most newer vehicles when coasting down hill in gear with very low load will actually go into fuel cut which means that the motor is still running but no fuel is being injected. This can be seen with an air/fuel monitoring device. and a scan tool or something similar to monitor load. I have no clue if the older vehicles do this as well.....The down fall to coasting in gear is that the vehicle is slowing down vs not slowing or actually gaining speed when in neutral. So will you slow down too much to make it over the next rise? So you see this can get quite involved.....Cd, Can you make the car think that the brake is pressed at all times so that you can start up on the go vs having to stop?
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Old 07-12-2009, 02:25 PM   #7 (permalink)
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Quick, for our cars it makes a difference if you're neutral coasting or in-gear coasting. I do better neutral coasting downhill, unless there's a stop sign or another impediment to slow down for. I find I actually gain speed going down a steep enough hill, and gradual declines are enough to let me maintain speed. We don't have a fuel cut, it simply uses less. Where our air boxes are isn't much good for ram air. Sure does a good job drawing in ambient air. I'm blocking the frame opening off this winter for higher air temperatures and reduced knocking. My car doesn't like 15*F air...

For our cars, once they're warm idling in gear or in neutral uses the same amount of gas. 0.45 gph according to my ScanGauge.

Also, upgrading to lighter-weight ATF ought to make a difference. For us GM drivers, Dexron-VI has much better cold-flow properties than Dexron-III. And it's part-synthetic to meet the spec. I'm going to do it one of these days when I have nothing better to do.
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Old 07-12-2009, 06:47 PM   #8 (permalink)
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Quote:
Originally Posted by nubbzcummins View Post
The most efficient thing to do would be to shut the engine off so no fuel is being burned.....The safest thing to do is leave the motor running so you can steer easier saying you have power steering.....Most newer vehicles when coasting down hill in gear with very low load will actually go into fuel cut which means that the motor is still running but no fuel is being injected. This can be seen with an air/fuel monitoring device. and a scan tool or something similar to monitor load. I have no clue if the older vehicles do this as well.....The down fall to coasting in gear is that the vehicle is slowing down vs not slowing or actually gaining speed when in neutral. So will you slow down too much to make it over the next rise? So you see this can get quite involved.....Cd, Can you make the car think that the brake is pressed at all times so that you can start up on the go vs having to stop?
Have you ever lost your power steering at >30MPH? There's no need for power steering when you're moving. It was invented for scrawny kids in parking lots.
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Old 07-13-2009, 12:56 PM   #9 (permalink)
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I coast in neutral as much as possible, usually up to 25% of my commute. I also Pulse and Coast (as I call it) on flat ground or slightly rolling terain. When I can't coast, I just keep the speeds down low enough to not make other drivers too mad. I also accelerate briskly to get torque converter lock asap. When I am coasting, I will re-engage the gear at a speed above torque converter lock, so I can get it locked asap again then pulse and repeat. I just coast as much as is possible. I have found, just thru observation not with any instrumentation, that the pulse and coast for my car is extremely effective at any speed below 60mph. My car will idle at 1000-1100 rpm when coasting in neutral, it's normal idle is 750rpm, my presumption is that the IAC is attempting to rev things up a bit in case I drop it back into gear. Also, a tackometer is vital in rev. matching to coast as much as I attempt to. You can check my fuel log to see the results once I started to coast more and then as I have gained skill at at it.
I also run full synthetic (generic brand) ATF, it didn't seem to make much of a difference to mpg, but I do have trans overheating problems when coasting a lot and having a full grill block, the syn. deffinatly helps relieve those heat related issues.
I also have a trans pan heater to get things warm for the morning, it deffinatly helps get things shifting quicker in the morning.
I also have upped the line pressure in my trans for firmer/quicker shifts. It doesn't seem to have helped mpg any, but it is more reasssuring feeling the shifts.

I'm ready to swap to a manual transmission, the ATX is a big limiting factor for taking my car much further up the mpg charts. I have made a switch box to maually shift my automatic so I can hit gears sooner, but it doesn't have much of a possitive effect on mpg and is difficult to use in traffic. I've tried about all there is I can do with the ATX and have gotten some good results.
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Old 07-13-2009, 09:56 PM   #10 (permalink)
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I'll have to try brisker acceleration. It's not a problem for my car. I just hate the low numbers on the ScanGauge while accelerating. Also my Tcc locks at ~30 mph. Is that too high to accelerate briskly to?

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