Coasting up to Lights.

[antiqueshell]

Originally Posted By: bullwinkle
Originally Posted By: JHZR2
No need to have any semblance of thought
Describes about 3/4 of the people I deal with on the road on an average day!


I'd totally agree, could be more than that on any given day from what I've seen.

 

[crazyoildude]

here in nj everyone drives fast if you slow down and are lucky you may get the horn and maybe a bad gesture if you are unlucky you could be hit.

 

[hypervish]

Originally Posted By: crazyoildude
here in nj everyone drives fast if you slow down and are lucky you may get the horn and maybe a bad gesture if you are unlucky you could be hit.


Exactly. NJ has some crazy [censored] drivers. lol

 

[dave1251]

Originally Posted By: hypervish
Originally Posted By: crazyoildude
here in nj everyone drives fast if you slow down and are lucky you may get the horn and maybe a bad gesture if you are unlucky you could be hit.


Exactly. NJ has some crazy [censored] drivers. lol


This pretty much normal everywhere. Sad really.

 

[aquariuscsm]

Originally Posted By: George7941
I do it all the time. If I see a light up ahead turn red and I know it is not turning green soon, I will shift my manual transmission into neutral and coast up to the light.


Same here. I`ve always done this. I always laugh at the people who try to race you to the red light!

 

[dparm]

Driving instructors told us never to do that -- if you have to make an evasive maneuver or were to get hit, you'd have a problem.

I agree with Caterham that letting the engine's natural compression slow you down is healthy for the piston rings.

 

[01rangerxl]

I coast up to lights if traffic is light here, but if traffic is heavy you are probably going to get cut off or nearly rear ended. Many people can't comprehend that getting to a red light faster doesn't help you.

 

[PF52]

Originally Posted By: JHZR2
Heaven forbid I say it lest I be called an unknowledgable snob, but IMO ATs help to make these behaviors more common because it is so mindless to do it. With an MT, youre actually thinking about what gear you are in, thinking about how you MUST take it out of gear to prevent stalling, etc...


If only I had a nickel for everyone I've seen who forget their MT was in, say, 5th when they tried to take off from a stop sign, or lugged the engine in 5th when the light turned green just as they coasted to a stop, or fumbled to put it back in 1st because the light turned green while they were daydreaming...

Inattentive driving is inattentive driving. I can't see what difference the transmission makes. The same people who zoom up to a red light and slam on the brakes probably do it whether its in "D" or 5th.

 

[hooligan24]

so if you have a ecu that shuts down the injectors while coasting in gear above 1500rpm's, which would use more fuel?

1. coasting in nuetral for a 1/4 mile at 850 rpm's up to a red light

or,

2. driving at at 2400 rpm's and start coasting in gear at an 1/8 - 1/16th of mile away from the light?

(1/8 mile @ 2400 rpms + 1/8 mile coasting in gear)

 

[cchase]

My car shuts off the injectors above 1000 rpm when coasting in gear.

I typically coast in gear to save gas, then clutch to neutral as the rpm's approach the cutoff.

If I am going down a long and gradual hill, I coast in neutral. The injector cutoff isn't worth the dropping speed, in this case.

 

[George7941]

Originally Posted By: dparm
Driving instructors told us never to do that -- if you have to make an evasive maneuver or were to get hit, you'd have a problem.

I agree with Caterham that letting the engine's natural compression slow you down is healthy for the piston rings.


Caterham did not say that!

 

[George7941]

Originally Posted By: hooligan24
so if you have a ecu that shuts down the injectors while coasting in gear above 1500rpm's, which would use more fuel?

1. coasting in nuetral for a 1/4 mile at 850 rpm's up to a red light

or,

2. driving at at 2400 rpm's and start coasting in gear at an 1/8 - 1/16th of mile away from the light?

(1/8 mile @ 2400 rpms + 1/8 mile coasting in gear)



With 1, the first 1/8 mi is at 850rpm vs 2400 rpm and larger throttle opening with 2.
2nd 1/8 mi -- 2 wins this part from 2400 to 1500 rpm at no fuel consumption at all but from 1500 to 850 there is more fuel consumption because of higher rpm

Considering the above factors, my best guess is 1 uses less fuel.

 

[dparm]

Originally Posted By: George7941
Originally Posted By: dparm
Driving instructors told us never to do that -- if you have to make an evasive maneuver or were to get hit, you'd have a problem.

I agree with Caterham that letting the engine's natural compression slow you down is healthy for the piston rings.


Caterham did not say that!


What I meant was to leave it in gear and let the engine help the brakes. I'm the one claiming it's good for the rings.

 

[rpn453]

Originally Posted By: dparm
Driving instructors told us never to do that -- if you have to make an evasive maneuver or were to get hit, you'd have a problem.


That's why I try to stay within the 5000 to 7000 rpm range at all times!

I don't coast in neutral, but I certainly don't have any useful power available when I'm coasting in 4th or 5th at 1000 to 1500 rpm. I'm not going to stay within the power band at all times while slowing just in case I don't have a second to spare in accelerating away from an idiot driver.

 

[Colt45ws]

Originally Posted By: JHZR2

I do too, and I am the owner of multiple original 200k+ mile ATs (yet I still dislike them as a whole). Yet some will say that it is bad to coast an AT when moving. Something about lube flow, IIRC. I personally prefer the feel of idling in neutral vs drive, but others likely have comments about that too.

Lube flow will only be an issue if you shut off the engine. Then you will lose the lube pump. Same exact thing as flat towing an automatic. But, as long as the engine is running, there will be no issue.

 

[rationull]

Originally Posted By: George7941

If my Scangauge is reporting accurately, fuel is seldom cut-off on my truck. The SG will occasionally display 0l/100km when I am overrunning the engine but it is very infrequent. It is probably because I seldom exceed 2500 rpm in city driving and my 3.23 rear has a lot to do with it. Most times I am under 2000rpm. If the fuel isn't being cut-off, I might as well take it out of gear.


IIRC SG reports DFCO (deceleration fuel cut-off) based somehow on throttle position. I remember learning about it at some point but don't remember the details anymore. IIRC there was some kind of calibration you could do to set the cutoff if it was inaccurate for your vehicle. Sorry I don't remember more details! But, if you can somehow find out when your vehicle is "supposed" to enter DFCO (I found it in the service manual for my previous car) then you might find it actually is cutting fuel more than you think. Or maybe not, of course.

 

[JHZR2]

Originally Posted By: George7941
Originally Posted By: Kiwialfa
Some engine management systems actually cut fuel to the injectors during engine braking. The Bosch ME.1.5.5 system in my Alfa Romeo does during engine braking over about 2200 rpm. So as coasting in neutral requires fuel to keep the engine idling, my car actually uses less fuel in gear. On a downhill run I will often change to a lower gear to keep the revs above 2200 rpm. Same applies for approaching lights.


If my Scangauge is reporting accurately, fuel is seldom cut-off on my truck. The SG will occasionally display 0l/100km when I am overrunning the engine but it is very infrequent. It is probably because I seldom exceed 2500 rpm in city driving and my 3.23 rear has a lot to do with it. Most times I am under 2000rpm. If the fuel isn't being cut-off, I might as well take it out of gear.


I would agree based upon the behaviors from monitoring the scangauge on my 98 S10 with the 4.3. Other cars go to zero routinely, while the 4.3 does not.

 

[Colt45ws]

You might have to adjust the fuel cutoff point. Factory setting is on the SGII 24. The correct setting, IIRC, is idle TPS reading plus four. My idle TPS is 20 so its correct from the factory but I imagine it has to be adjusted for some vehicles.

 

[Ross]

This is a very interesting conversation. I have a 2011 hyundai accent with a 5-speed. I have an ultra-guage hooked up to the ecm and have calibrated it.

The instant MPG will (depending on speed)show 80-120 mpg when coasting up to stop lights out of geer. In gear it will only show 40-60 mpg (depending of speed).

 

[E365]

I do this all the time. And I'll admit, I really started to do it when I started driving a manual transmission. It's just smart driving. I do think-ahead though to avoid blocking people. For example, if I'm approaching an intersection with seperate turn lanes. I try not to slow down too much, just in case the person behind me needs to turn, then they have unrestricted access to a turn lane. Either to make a turn on that red, or to trigger the sensor for the left turn arrow.

I think it's really funny when someone behind you gets mad you are slowing down and they quickly switch lanes. Then they floor it to get past you and move back into your (their original) lane. Usually about the time they get back into the original lane they are SLAMMING on their brakes because they are about to either run the red or rear-end the people already stopped at the light.