Is coasting in neutral bad

MACK E-6 · Feb 18, 2017

MrEd said: ↑

I agree with ya completely. I'm not sold on any of this technology stuff. Never had a radar in a truck yet that worked properly. Knock on wood, I haven't had any issues with these automatics. But like you just said....I may only ever have the one!
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...And God willing that "one" won't lead to anyone getting killed.

Moosetek13 · Feb 18, 2017

MACK E-6 said: ↑

That much is a good thing, IF the technology is reliable.

I could well imagine a bad sensor or some other ancillary crapola causing one of these automatics to do that when it isn't supposed to, leading to unspeakable events.
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I'll let you know in the years to come.
This is my first truck with the auto, and with the radar.
So far the radar is more problematic than the auto.

I will be in this truck for the next 4 years or so, so I will get a good idea of how reliable they are over the long term.

AModelCat · Feb 18, 2017

Hulld said: ↑

from a practical stand point this does not prove to be true from what I have seen.
I have tried driving with my scanner hooked up and looking at injector pulse width modulation at coast and at idle the percentages are exactly the same.
If you have pulse width modulation then the injector is being fired.
So this is not to say that some sophisticated systems don't have this strategy programmed in them it's just not my practical experience that I have seem in the repair industry.
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So that right there basically says there is no fuel saving benefit to coasting in neutral if I'm reading what you wrote correctly.

scottied67 · Feb 18, 2017

MACK E-6 said: ↑

That much is a good thing, IF the technology is reliable.

I could well imagine a bad sensor or some other ancillary crapola causing one of these automatics to do that when it isn't supposed to, leading to unspeakable events.
Click to expand...

I have the same setup as Moosetek DD15/DT12. Got unloaded at a dock other night, the air was low from them running the forklift in and out and told me to move off. Normal truck/manual tranny you can move as soon as brakes are released. Not so with the DT12. Must build full air or the tranny will not go into gear. "Just another few minutes sir"

PermanentTourist · Feb 18, 2017

NorthernMechanic said: ↑

As long as the engine is turning the transmission should get lubrication. I can't see a benefit to it fuel economy wise. With your foot off the throttle the engine is in a no fuel condition anyways.
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As somebody pointed out earlier, it's not a matter of the truck using more fuel in gear versus idle. It's a matter of maintaining momentum by letting the truck gain more speed freewheeling downhill not encumbered by the transmission, and using that momentum to get higher up the next hill before the engine starts exerting effort.

And I understand I'm not going to get an extra two MPG doing it, but even a marginal percentage point fuel saving is nice, especially considering it's kind of fun to do on gentle rolling hills, so it's not like I'm suffering and wasting effort.

The one concern I have is that the wear and tear from extra clutch activation cycles will outweigh in the long term the couple of bucks per fill up I might save

PermanentTourist · Feb 18, 2017

snowwy said: ↑

The engine is getting fuel regardless or gear or no gear. Roughly .8 is burned idling when parked. Same theory when coasting down in neutral. Because the engine is idling.

CORRECT??????

I don't know about the out of gear vs. In gear. Does any of us know how the ecm software is programmed?????

But here's the big thing.

Get in an accident coasting down in neutral and guess what happens.

You failed to maintain control of your vehicle.

Also. How are you supposed to jake brake??????
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Consider the enclosed picture I took earlier today in Mississippi. (As a bonus, check out that pretty sky). I am talking about this kind of Hill, more of a dip really. Going down it in gear with 43000 pounds I was slowly losing speed without pressing the gas pedal. In neutral, I was slowly gaining speed. Even if the engine was using the same amount of fuel in both scenarios, gaining momentum obviously save fuel verses losing momentum. Physics and stuff. As for jake braking, would your Jake brake on this little dip? I wouldn't play the neutral game on any Hill much bigger than this, never mind an actual Jake brake grade.

PROPANE · Feb 18, 2017

PermanentTourist said: ↑

As somebody pointed out earlier, it's not a matter of the truck using more fuel in gear versus idle. It's a matter of maintaining momentum by letting the truck gain more speed freewheeling downhill not encumbered by the transmission, and using that momentum to get higher up the next hill before the engine starts exerting effort.

And I understand I'm not going to get an extra two MPG doing it, but even a marginal percentage point fuel saving is nice, especially considering it's kind of fun to do on gentle rolling hills, so it's not like I'm suffering and wasting effort.

The one concern I have is that the wear and tear from extra clutch activation cycles will outweigh in the long term the couple of bucks per fill up I might save
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that might be a worry in a big rig,

but think of how many times you wouldn't have to push the clutch in, in a car.

I can literally skip the first 3 gears in a 5 speed just by coasting and using gravity/momentum going down hill. thats 3 times I didnt have to push the clutch in.

as long as its done right, using the clutch to engage/disengage/change gears/etc, wouldnt be any more wear and tear than if you were disengaging just to downshift or upshift as opposed to disengage the clutch just to coast.

PermanentTourist · Feb 18, 2017

Moosetek13 said: ↑

I'll let you know in the years to come.
This is my first truck with the auto, and with the radar.
So far the radar is more problematic than the auto.

I will be in this truck for the next 4 years or so, so I will get a good idea of how reliable they are over the long term.
Click to expand...

This might be very Blasphemous to say, but I sort of miss the little radar. This owner op truck I just bought doesn't have it. I certainly didn't like that obnoxious beeping, but it was nice knowing how fast people ahead of me were going so I could plan my passing strategies in advance or just leave them alone. And the automatic following cruse would be useful if I could change the gap settings and make it follow closer.

It was also fun to clock insane Maniacs cutting me off in their Mustangs at 120 mph and write them imaginary tickets.

Of course mine was actually properly calibrated, as opposed to some other guys whose radar would confuse exit signs for imminent death danger

Aradrox · Feb 18, 2017

Toomanybikes said: ↑

The whole concept of coasting is stupid. The theory is if you use the potential energy stored up at the top of the hill without dissipating it with the engine or brakes, you can see a return on your energy investment with better fuel milage. The key is you don't dissipate that energy with brakes or engine and you let the car/truck run free to recover that energy and momentum. Of course you have to discount the damage to the car/truck, the ticket, and the damage to your driving record to recover that little bit of fuel.

So goes the mentality of the auto driver. As such, despite what Moosetek's reply, I have no problem picking up or hunting any gear in a manual, I know that is not the case for guys starting out though. I have also had automated manuals and trucks screw up while hunting for gears after going into coast mode.
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Some engines rpm limiters make it difficult aswell I've had engines I can downshift to 9th at 60 and ones that won't let me rev over 1400 rpm In Neutral

Moosetek13 · Feb 18, 2017

PermanentTourist said: ↑

This might be very Blasphemous to say, but I sort of miss the little radar. This owner op truck I just bought doesn't have it. I certainly didn't like that obnoxious beeping, but it was nice knowing how fast people ahead of me were going so I could plan my passing strategies in advance or just leave them alone. And the automatic following cruse would be useful if I could change the gap settings and make it follow closer.

It was also fun to clock insane Maniacs cutting me off in their Mustangs at 120 mph and write them imaginary tickets.

Of course mine was actually properly calibrated, as opposed to some other guys whose radar would confuse exit signs for imminent death danger
Click to expand...

The adaptive cruise is nice for when someone is going just a bit slower than me. It will gently back off my speed to keep me at around 300 feet. It is set to 3.5 seconds of following distance.

And there is a way to override the system. Just click on the engine brake to the lowest setting. That will let you get as close as you want before passing, with no warnings or hard braking by the system.

I do get collision warnings for overhead signs, quite often.
But it just beeps.

The real annoyance is when someone is going a LOT slower in the lane next to me. Full engine brake, with service brakes thrown in as well.
I've learned to cancel the cruise control when I am approaching that situation.

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