Coasting vs. Engine Braking - Page 2 - Fuelly Forums

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

Reply
 
Thread Tools Display Modes
 
Old 12-16-2007, 07:52 PM   #11
Registered Member
 
Join Date: Dec 2007
Posts: 42
Country: United States
ok thanks.
__________________

caveatipse is offline   Reply With Quote
Old 12-16-2007, 08:13 PM   #12
Registered Member
 
skewbe's Avatar
 
Join Date: Jan 2007
Posts: 771
Country: United States
Well, it isn't as simple as JanGeo said. If you are engine braking (or any braking) you are bleeding off speed that took gas to make.

I suggest you look at installing a fuel injection kill switch and understand the pros and cons of pulse and glide ( EOC ) if you really want to maximize your mpg in your stickshift Yaris.
__________________

__________________
Standard Disclaimer
skewbe is offline   Reply With Quote
Old 12-16-2007, 08:17 PM   #13
Registered Member
 
Join Date: Dec 2007
Posts: 42
Country: United States
Quote:
Originally Posted by skewbe View Post
Well, it isn't as simple as JanGeo said. If you are engine braking (or any braking) you are bleeding off speed that took gas to make.

I suggest you look at installing a fuel injection kill switch and understand the pros and cons of pulse and glide ( EOC ) if you really want to maximize your mpg in your stickshift Yaris.
But if you are slowing down at all, you are bleeding off speed it took gas to make. If all other things are equal, if engine braking actually stops gas from flowing, and coasting keeps it flowing, how can it not be that engine braking saves more gas, all other things being equal??
caveatipse is offline   Reply With Quote
Old 12-16-2007, 08:33 PM   #14
Registered Member
 
skewbe's Avatar
 
Join Date: Jan 2007
Posts: 771
Country: United States
The most fuel efficient mode of operation for a gas powered vehicle that I know of:
http://metrompg.com/posts/xfi-pulse-and-glide.htm

The point is to avoid any sort of braking and to accelerate just enough to coast to the next stop. If you are engine braking you will have to accelerate more to cover the same distance, if you are just coasting you will travel farther after you get off the gas. If you can live with killing the injectors while coasting, even better.

We are trying to save gas here, right? Or are we here to debate hypotheticals with little return?
__________________
Standard Disclaimer
skewbe is offline   Reply With Quote
Old 12-16-2007, 08:35 PM   #15
Registered Member
 
Join Date: Dec 2007
Posts: 42
Country: United States
Quote:
Originally Posted by skewbe View Post
The most fuel efficient mode of operation for a gas powered vehicle that I know of:
http://metrompg.com/posts/xfi-pulse-and-glide.htm

The point is to avoid any sort of braking and to accelerate just enough to coast to the next stop. If you are engine braking you will have to accelerate more to cover the same distance, if you are just coasting you will travel farther after you get off the gas. If you can live with killing the injectors while coasting, even better.

We are trying to save gas here, right? Or are we here to debate hypotheticals with little return?
lol no I just do not understand and I want to understand. If I engine brake, why will I have to accelerate more? If I get off the interstate on an off ramp, for example, and I am going to have to come to a complete stop anyway, why not do so in a manner that completely shuts off fuel flow, rather than a manner that leaves some fuel flowing?
caveatipse is offline   Reply With Quote
Old 12-16-2007, 08:51 PM   #16
Registered Member
 
skewbe's Avatar
 
Join Date: Jan 2007
Posts: 771
Country: United States
the kill switch takes care of the fuel flow and allows you to cover more ground while using zero fuel. If traffic is light (or you just don't feel like being pushed) you can shut off the engine sooner and coast much farther than you can in gear.

If you are a fan of pool, you may understand that some shots require you to hit the ball just hard enough that it stops exactly where you want it. This is the same concept, you try and kill the engine at just the right speed and distance from the next obstruction that you roll to a stop where you meant to. Takes practice and some brakes are the norm (if I never use the brakes over 20mph I'm doing ok). But in that manner you do not over-accelerate and then throw that energy away in braking.
__________________
Standard Disclaimer
skewbe is offline   Reply With Quote
Old 12-16-2007, 09:00 PM   #17
Registered Member
 
Join Date: Dec 2007
Posts: 42
Country: United States
Argh lol but that is not what I am talking about. My Yaris shuts off the fuel flow completely under engine braking. So it is only logical that, if I have to slow down to a stop anyway, doing so with NO fuel is better than with a LITTLE fuel. How am I wrong? (pulls out own hair)
caveatipse is offline   Reply With Quote
Old 12-16-2007, 09:08 PM   #18
Registered Member
 
skewbe's Avatar
 
Join Date: Jan 2007
Posts: 771
Country: United States
What is your goal? Does it relate to this hypothetical question in a significant way?
__________________
Standard Disclaimer
skewbe is offline   Reply With Quote
Old 12-16-2007, 09:11 PM   #19
Registered Member
 
Join Date: Dec 2007
Posts: 42
Country: United States
Quote:
Originally Posted by skewbe View Post
What is your goal? Does it relate to this hypothetical question in a significant way?
lol my goal is to use the least amount of fuel possible when coming to a stop where I HAVE to stop.
caveatipse is offline   Reply With Quote
Old 12-16-2007, 09:27 PM   #20
Registered Member
 
skewbe's Avatar
 
Join Date: Jan 2007
Posts: 771
Country: United States
Quote:
Originally Posted by caveatipse View Post
lol my goal is to use the least amount of fuel possible when coming to a stop where I HAVE to stop.

Ok, then still look into pulse and glide and EOC . If you kill the engine with a kill switch it won't be burning any fuel, and you can get off the gas pedal sooner (I assume you can anticipate most of the stops) if you put in the clutch as your speed will not bleed off so fast as it would if you left it in gear. You may find that you can kill the engine way ahead of the off ramp and coast for miles with no fuel.

How much speed you carry into that stop that you HAVE to stop at is going to be the main determinant in how much energy you will lose at that stop by braking.

If it makes you feel better, then you are correct about the hypothetical situation where you could not anticipate the stop (or did not change wasteful driving habits) and managed to trick the engine into turning off the fuel for some portion of the deceleration by engine braking.
__________________

__________________
Standard Disclaimer
skewbe 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
Incorrect Milage Calcuatlion PatM Fuelly Web Support and Community News 4 07-17-2009 08:21 PM
ECT Analyzer/manual TC lockup GasSavers_Bruce Transmissions and Running Gear 60 04-01-2008 11:37 AM
How far do you drive daily? OdieTurbo General Fuel Topics 56 03-31-2007 02:49 AM
Switchable power steering idea dieselbenz Introduce Yourself - New member Welcome 11 03-08-2007 05:58 PM
State of the Union address touches on "oil addiction." Matt Timion General Discussion (Off-Topic) 31 02-06-2006 04:38 PM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 12:46 AM.


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