Does coasting in Neutral Work - Page 2 - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 11-04-2007, 07:32 PM   #11
Registered Member
 
1993CivicVX's Avatar
 
Join Date: Aug 2007
Posts: 1,066
Country: United States
Send a message via AIM to 1993CivicVX
I'd say for all you auto trannies out there that, unless you live in an area that is really flat, to just use the hills as P&G and the rest of the time leave it in drive. The fuel savings are not going to be wroth the extra wear on the tranny going from D to N to D all the time.

As for why P&G works, think of it this way: The amount of fuel pumped into the engine is not linear to the amount of power produced. So if you feather foot the gas pedal, you are using more fuel per horsepower produced than if you press the gas pedal down hard enough to be in the engine's "sweet spot" for efficiency. In other words, at 75% or near full throttle (closer to the engine's ratio of fuel efficiency to power sweet spot), you are going to produce the most horsepower per unit of fuel used. I don't know exactly what this sweet spot is on most cars, but the point is, holding constant speed, while requires little power, isn't requiring *that much less gas to maintain*: it's an inefficient use of fuel for the amount of power it's producing. So when you are accelerating moderately you are only using about 2 1/2 times more fuel than when you are maintaining constant speed, but it's allowing you to spend much more time coasting, which uses about 5-10+ times less fuel than constant speed. That is why P&G becomes less effective in situations where the car is slowing down quickly during the glide. If the car is slowing down quickly during the glide, it means it is requiring more power to maintain constant speed, and therefor is closer to the power/efficiency sweet spot which apparently is somewhere above 60% full throttle (although I think it is less than full throttle) Anyone know where abouts the sweet spot is?

To conclude the argument for P&G....

So instead of driving at a constant speed that is inefficient for the amount of power it is producing, keep the engine in its most efficient power to fuel ratio for as little time as possible, and try to have the rest of the time driving in neutral!
__________________

__________________
three stripes the charm!

Car mods are overrated. Just gotta adjust that nut behind the wheel for best mpg.



Forget about World Peace...Visualize using your turn signal.
1993CivicVX is offline   Reply With Quote
Old 11-06-2007, 10:34 AM   #12
Stay true to the Game!
 
popimp's Avatar
 
Join Date: May 2007
Posts: 303
Country: United States
It's not practical to do it for long trips! I got the same mpg using the engine on coasting technique at a 60mph average as I did with setting it at CC to 60 mph. I can say that speed does decrease mpg though. At a 70 mph cruise I only got between 24 & 25. So on this end I don't think it works. I'm gonna try and get together with Red and do some more testing.
__________________

__________________


popimp is offline   Reply With Quote
Old 11-06-2007, 12:20 PM   #13
Registered Member
 
Danronian's Avatar
 
Join Date: Aug 2007
Posts: 652
Country: United States
Has anyone tested this for the VX? I've been coasting down all hills in neutral lately, and it has netted me my best avg mpg (45-48) since owning the car, but I wonder if leaving it in 5th would be better...

For this car, the reason I don't resort to shutting it down, is because it takes most wideband sensors around 10 minutes to warm up, so I don't want to avoid being in lean-burn if I can help it.
__________________


On the never-ending quest for better gas mileage...
Danronian is offline   Reply With Quote
Old 11-07-2007, 12:13 PM   #14
Registered Member
 
Join Date: Nov 2007
Posts: 228
Country: United States
Only time I coast in neutral is when the engine is off, now that helps.

Usually before well known intersections, the light turns red, gear lever to N, engine off, coast to stop. It helps to be familiar with the light pattern, turn it on when the opposing light turns yellow (and mine is about to turn green), or if I have cars in front of me, by the time the 3rd car in front of me starts to move it is high time.

A properly maintained and well tuned engine helps as well, very embarrassing if it won't start now, preferrably it should start with just a 'kick' of the key, 1-2 revolutions at the most.
__________________
A FE gauge should be standard equipment in every vehicle.
8307c4 is offline   Reply With Quote
Old 11-07-2007, 12:52 PM   #15
Registered Member
 
1993CivicVX's Avatar
 
Join Date: Aug 2007
Posts: 1,066
Country: United States
Send a message via AIM to 1993CivicVX
Quote:
Originally Posted by Danronian View Post
Has anyone tested this for the VX? I've been coasting down all hills in neutral lately, and it has netted me my best avg mpg (45-48) since owning the car, but I wonder if leaving it in 5th would be better...

For this car, the reason I don't resort to shutting it down, is because it takes most wideband sensors around 10 minutes to warm up, so I don't want to avoid being in lean-burn if I can help it.
But your o2 sensor isn't going to cool down in one or two minutes. If my CE light is any indication, it takes 5 minutes of the engine off for it to cool down.
__________________
three stripes the charm!

Car mods are overrated. Just gotta adjust that nut behind the wheel for best mpg.



Forget about World Peace...Visualize using your turn signal.
1993CivicVX is offline   Reply With Quote
Old 11-07-2007, 01:18 PM   #16
Registered Member
 
JanGeo's Avatar
 
Join Date: Jan 2006
Posts: 2,442
Country: United States
Send a message via Yahoo to JanGeo
Part of the problem is that the engine still is burning probably 0.5gph at idle so you do not save much fuel coasting then the added automatic tranny losses offset the savings. Best to keep a light foot on the pedal and keep the body surface clean. Think of it this way, if you turned off the engine for an hour you would save 0.5 gallons of fuel at idle so coasting for an hour would save you ??? . . . not much.
JanGeo is offline   Reply With Quote
Old 11-07-2007, 01:32 PM   #17
Registered Member
 
Sigifrith's Avatar
 
Join Date: May 2007
Posts: 135
Country: United States
Location: Illinois
Quote:
Originally Posted by JanGeo View Post
Part of the problem is that the engine still is burning probably 0.5gph at idle so you do not save much fuel coasting then the added automatic tranny losses offset the savings. Best to keep a light foot on the pedal and keep the body surface clean. Think of it this way, if you turned off the engine for an hour you would save 0.5 gallons of fuel at idle so coasting for an hour would save you ??? . . . not much.
Isn't the question how much I save in that hour of coasting VS what I'd burn at 55 MPH?
__________________
[SIGPIC][/SIGPIC]
Sigifrith is offline   Reply With Quote
Old 11-07-2007, 02:18 PM   #18
Registered Member
 
Danronian's Avatar
 
Join Date: Aug 2007
Posts: 652
Country: United States
Quote:
Originally Posted by Sigifrith View Post
Isn't the question how much I save in that hour of coasting VS what I'd burn at 55 MPH?
Yeah, that's what I'm wondering. Here's an example of what I'm wondering:

Going down a long hill, where no throttle is needed (a few minutes of coasting), would it be better to be in 5th gear, which would have the motor at about 1500 RPMs or would it be better to be in neutral at 600 RPM?

For the VX, I'm wondering if idling wastes more gas than being in lean-burn?

As soon as this tank is over (and I get a base-line for my car with my shift light now functioning and following those points), I'm going to stop coasting in neutral and keep it in 5th instead. If there is a difference in MPG, I would assume the VX would prefer to be in gear going down hills.
__________________

__________________


On the never-ending quest for better gas mileage...
Danronian is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
UK MPG/US Gallons bl4desman Fuelly Web Support and Community News 3 07-14-2011 07:08 AM
More SMS Requests zbret Fuelly Web Support and Community News 16 02-03-2011 01:09 AM
electric vehicle (bike/motorcycle) on the cheap? skewbe Electric and Solar powered 16 07-12-2007 10:56 AM
Using the "Engine Load" number from OBDII... GasSavers_root General Fuel Topics 5 07-01-2007 07:06 AM
Switchable power steering idea dieselbenz Introduce Yourself - New member Welcome 11 03-08-2007 05:58 PM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 10:08 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.