Go Back   EcoModder Forum > EcoModding > Hypermiling / EcoDriver's Ed
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 11-27-2013, 02:03 PM   #51 (permalink)
NightKnight
 
NachtRitter's Avatar
 
Join Date: Dec 2008
Location: Placerville, CA
Posts: 1,594

RippinRoo - '05 Subaru Legacy Wagon 2.5 GT
Subaru
90 day: 21.16 mpg (US)

Helga - '00 Volkswagen Jetta TDI
TEAM VW AUDI Group
Diesel
90 day: 53.91 mpg (US)

Olga - '03 Volkswagen Jetta Wagon
90 day: 46.24 mpg (US)
Thanks: 303
Thanked 311 Times in 186 Posts
Quote:
Originally Posted by bikenfool View Post
Minor nit: you are misusing the term acceleration, "In physics, acceleration is the rate at which the velocity of a body changes with time" https://en.wikipedia.org/wiki/Acceleration. Of course, you are correct the engine doesn't know the difference.
No, I don't believe I am... the wiki page you linked discusses g as acceleration as well... in order to rise vertically at a steady speed, you will need an upward force that directly counteracts the downward pull of gravity, or, since F = ma, you would need ma = mg and since mass is equal, a = g. I don't know how that is a misuse of the term?

I would suggest removing the arbitrary flat section (how much of a flat section? what is the total travel time / total travel distance?); this just muddles things. Just focus in on the hill section only, base to crest. There are already more than enough variables in that short section. If you assume the starting and ending speed are the same, which approach is better. Then what if you assume the average speed from bottom of hill to crest is the same (which would mean Method 2 starts out slower), which approach is better. I don't have the answer, but that's how I would constrain it.

From my own perspective, I wouldn't drive differently on the flats just because I *might* choose DWL or choose P&G when I encounter a hill. I would wait until I encounter the hill then choose what I believe to be the best method depending on the size of the hill, the grade, and the current conditions (traffic, etc). Heck, I might even change from "pulse" to DWL in the middle of my climb and then back to "pulse" depending on changing conditions. All of that would be SOP (seat of pants) because I'm sure as heck not going to stop, measure the parameters of the hill, plug them into a formula or script and then use the approach that calculates out to a 0.001% (or whatever) fuel savings.

And with a different car, I would probably do it differently. As they say, YMMV.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 11-27-2013, 03:46 PM   #52 (permalink)
EcoModding Lurker
 
Join Date: Nov 2013
Location: lakewood, co, usa
Posts: 53

subey - '99 Subaru Impreza Outback Sport

rav4 - '07 Toyota Rav4
Thanks: 3
Thanked 1 Time in 1 Post
Quote:
Originally Posted by NachtRitter View Post
No, I don't believe I am... the wiki page you linked discusses g as acceleration as well... in order to rise vertically at a steady speed, you will need an upward force that directly counteracts the downward pull of gravity, or, since F = ma, you would need ma = mg and since mass is equal, a = g. I don't know how that is a misuse of the term?
I don't want to argue that in this thread since it doesn't matter to this subject.
Quote:
Originally Posted by NachtRitter View Post
I would suggest removing the arbitrary flat section (how much of a flat section? what is the total travel time / total travel distance?); this just muddles things. Just focus in on the hill section only, base to crest. There are already more than enough variables in that short section. If you assume the starting and ending speed are the same, which approach is better. Then what if you assume the average speed from bottom of hill to crest is the same (which would mean Method 2 starts out slower), which approach is better. I don't have the answer, but that's how I would constrain it.
If you remove the flat section, & the total time is not the same then you're answering the question "which is the lowest fuel cost method to get up the hill". This is a good question for a hypermiler & I'd like to know the answer too, & I agree the answer probably won't be constant speed, but my question is more practical. In the real world most of us trade off fuel consumption with time, so fixing the time variable, what is the most fuel efficient way to drive?
The starting and ending speed must be the same or it isn't a relevant test.
There are a lot of inputs, such as the length of the flat section, & the length & grade of the climb, but I don't see a way to eliminate the flat section and have a good comparison.

Quote:
Originally Posted by NachtRitter View Post
From my own perspective, I wouldn't drive differently on the flats just because I *might* choose DWL or choose P&G when I encounter a hill. I would wait until I encounter the hill then choose what I believe to be the best method depending on the size of the hill, the grade, and the current conditions (traffic, etc). Heck, I might even change from "pulse" to DWL in the middle of my climb and then back to "pulse" depending on changing conditions. All of that would be SOP (seat of pants) because I'm sure as heck not going to stop, measure the parameters of the hill, plug them into a formula or script and then use the approach that calculates out to a 0.001% (or whatever) fuel savings.

And with a different car, I would probably do it differently. As they say, YMMV.
All true, & traffic typically forces the issue anyway. But if you knew what the best solution was for a typical grade wouldn't you at least try it?
  Reply With Quote
Old 11-27-2013, 03:57 PM   #53 (permalink)
Master EcoModder
 
euromodder's Avatar
 
Join Date: Jul 2010
Location: Belgium
Posts: 4,683

The SCUD - '15 Fiat Scudo L2
Thanks: 178
Thanked 652 Times in 516 Posts
Quote:
Originally Posted by bikenfool View Post
Perhaps you guys are right and I'm an idiot, perhaps it works for some cars, or some conditions. For now, I remain skeptical.
You've ended up here, so you're not

You may be skeptical, it's a good attitude, but these things have been tested over and over by people here and elsewhere on fuel-efficiency forums
__________________
Strayed to the Dark Diesel Side

  Reply With Quote
Old 11-27-2013, 04:18 PM   #54 (permalink)
EcoModding Lurker
 
Join Date: Nov 2013
Location: lakewood, co, usa
Posts: 53

subey - '99 Subaru Impreza Outback Sport

rav4 - '07 Toyota Rav4
Thanks: 3
Thanked 1 Time in 1 Post
Quote:
Originally Posted by euromodder View Post
You've ended up here, so you're not

You may be skeptical, it's a good attitude, but these things have been tested over and over by people here and elsewhere on fuel-efficiency forums
Great, point me to the tests!
  Reply With Quote
Old 11-27-2013, 06:43 PM   #55 (permalink)
NightKnight
 
NachtRitter's Avatar
 
Join Date: Dec 2008
Location: Placerville, CA
Posts: 1,594

RippinRoo - '05 Subaru Legacy Wagon 2.5 GT
Subaru
90 day: 21.16 mpg (US)

Helga - '00 Volkswagen Jetta TDI
TEAM VW AUDI Group
Diesel
90 day: 53.91 mpg (US)

Olga - '03 Volkswagen Jetta Wagon
90 day: 46.24 mpg (US)
Thanks: 303
Thanked 311 Times in 186 Posts
Quote:
Originally Posted by bikenfool View Post
There are a lot of inputs, such as the length of the flat section, & the length & grade of the climb, but I don't see a way to eliminate the flat section and have a good comparison.
OK

Quote:
Originally Posted by bikenfool View Post
All true, & traffic typically forces the issue anyway. But if you knew what the best solution was for a typical grade wouldn't you at least try it?
If your question here is related to the two methods you describe, which include an arbitrary length of flat section and an arbitrary fixed amount of time to cover both the flat section and the hill, then my answer would be no. If instead you are asking only about the best method (which in this context means getting the best FE) for getting up a grade from base to crest, then I think it would be interesting academically but my intuition tells me that there wouldn't be enough of a difference to change my behavior. I would still do what feels right at the time based on the conditions (choosing between P&G and DWL), since I know either approach will be better than using cruise control or flooring the pedal to maintain speed uphill.
  Reply With Quote
Old 01-04-2014, 02:12 AM   #56 (permalink)
EcoModding Apprentice
 
Join Date: Jun 2009
Location: pacific southwest
Posts: 147
Thanks: 7
Thanked 4 Times in 3 Posts
Quote:
Originally Posted by Old Mechanic View Post
since engine braking consumes no fuel,
which vehicles are you referring to, please?
  Reply With Quote
Old 01-04-2014, 01:21 PM   #57 (permalink)
Master EcoModder
 
Join Date: Aug 2010
Location: Philippines
Posts: 2,173
Thanks: 1,739
Thanked 589 Times in 401 Posts
I'm pretty sure that's just about everything with computerized fuel injection. There are those that still inject a miniscule amount during engine braking, but it's a tiny percentage of what you use while idling.
  Reply With Quote
Old 01-11-2014, 07:47 AM   #58 (permalink)
EcoModding Lurker
 
zingaro's Avatar
 
Join Date: Jan 2014
Location: NC
Posts: 17

z - '13 Honda CRZ

Global - '12 Dodge Ram Cargo Van
Thanks: 3
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by 3-Wheeler View Post
Driving with load allows the gas engine to run in a more efficient regime.

If you can find it, look for a fuel consumption map for your particular engine.

HTH, Jim.
So where does one find this map??
  Reply With Quote
Old 01-11-2014, 04:04 PM   #59 (permalink)
EcoModding Lurker
 
Join Date: Nov 2013
Location: lakewood, co, usa
Posts: 53

subey - '99 Subaru Impreza Outback Sport

rav4 - '07 Toyota Rav4
Thanks: 3
Thanked 1 Time in 1 Post
Quote:
Originally Posted by zingaro View Post
So where does one find this map??
In general, they are not available. There's a thread &a wiki page on this site with the best collection of them.
  Reply With Quote
Old 01-17-2014, 06:32 PM   #60 (permalink)
The PRC.
 
Join Date: Oct 2009
Location: Elsewhere.
Posts: 5,304
Thanks: 285
Thanked 536 Times in 384 Posts
Question. In your challenge you seem to suggest an either/or choice of DWL vs P&G ? Is that correct ?

In your scenario I would use P&G on the flat part and then use an extra strong Pulse just before the hill Once the speed bleeds off I would then maintain a minimum until the top and I would expect to gain again on the following flat or descent.

If it has been a long journey or I feel lazy then I would maintain a minimum speed / MPG combination on the flat as that requires less effort but still speed up just before the hill to get a push and then again maintain a minimum speed.

The instrumentation available - built in or add in - isn't accurate enough to determine which is better in one run or a collection of runs really but they give a guide, better than nothing.

__________________
[I]So long and thanks for all the fish.[/I]
  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com