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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 03-17-2008, 07:50 PM   #1 (permalink)
EcoMudder
 
Harpo's Avatar
 
Join Date: Mar 2008
Location: Gainesville, FL
Posts: 79

Harpo's Honda - '05 Honda Civic VP
90 day: 42.64 mpg (US)
Thanks: 0
Thanked 2 Times in 2 Posts
Running the AC during P&G - An observation

The Scangauge is waaayy cooool.

P&Ging around town, I noticed that my Civic reports zero fuel flow coasting in gear from 55mph to 35mph, then under 35mph, it's show's .32 gph. Dropping it in neutral from 30mph down gets it around .28 gph. If I keep it in OD, it feels as if around 30-35mph, the Torque Converter goes into a no load condition, about the same time the fuel flow returns.

I started thinking cool thoughts on the ride home, as our FL weather has started to all ready require some periodic AC usage. So, I used my AC in tandem with my P&G. I turned the compressor on only on decel (55mph to 35mph) which appeared to impose virtually no load. And during that time, the fuel flow still reported as zero! I kept it on RECIRC to retain dehumidified air as much as possible. Regeneration AC!

Level road conditions, fixed 30% TPS, shows about 4.5-5mpg less with AC operation. These little cabins can be cooled quickly, but even then, it's nice to do it without using fuel when possible.

__________________

Last edited by Harpo; 03-18-2008 at 05:48 AM..
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 03-18-2008, 10:09 AM   #2 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 21,713

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 53.56 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 66.29 mpg (US)
Thanks: 3,443
Thanked 6,267 Times in 3,240 Posts
This is the second report of A/C on decel only operation I've seen in the past few days. Interesting.... and not applicable to my situation (no A/C!).
__________________
Latest mods: 3-cylinder Mitsubishi Mirage. EcoMods now in progress...
Ecodriving test:
Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Old 03-18-2008, 11:12 AM   #3 (permalink)
Master EcoModder
 
tasdrouille's Avatar
 
Join Date: Jan 2008
Location: Mirabel, QC
Posts: 1,672

The Guzzler - '08 Hyundai Elantra GL
90 day: 33.12 mpg (US)

Got Soul? - '11 Kia Soul 2U
Thanks: 35
Thanked 83 Times in 55 Posts
Nothing comes free, chances are you are merely defeering the fuel use related to the A/C to your next pulse. You should do some tests, but I'm pretty sure you won't coast as far with A/C on than off.
__________________



www.HyperKilometreur.com - Quand chaque goutte compte...
  Reply With Quote
Old 03-18-2008, 05:54 PM   #4 (permalink)
I'd rather be biking
 
boxchain's Avatar
 
Join Date: Feb 2008
Location: New Orleans, LA, US Minor Outlying Islands
Posts: 127

Lexie - '98 Honda Civic LX
90 day: 39.46 mpg (US)

Beater Hauler - '92 Isuzu Pickup

Rentaclipse - '08 Mitsubishi Eclipse ?
90 day: 28.28 mpg (US)

Fahrt - '83 BMW R80 ST
Thanks: 0
Thanked 4 Times in 4 Posts
I often turn my AC off when accelerating...don't know if it helps FE any, but it alleviates the double load whammy, so it theoretically should. Now that I've got a manual, I'm gonna try turning the AC on during engine braking.

Got numbers on idle fuel flow with AC on/off?

Always use recirc with AC or def...no sense bringing in more hot humid air.
__________________

My bike runs on dihydrogen monoxide.
I like to use these acronyms
  Reply With Quote
Old 03-18-2008, 06:25 PM   #5 (permalink)
Master EcoModder
 
tasdrouille's Avatar
 
Join Date: Jan 2008
Location: Mirabel, QC
Posts: 1,672

The Guzzler - '08 Hyundai Elantra GL
90 day: 33.12 mpg (US)

Got Soul? - '11 Kia Soul 2U
Thanks: 35
Thanked 83 Times in 55 Posts
I would definately use the AC during engine braking, as it's energy I'm gonna waste anyway. So instead of totally wasting it in friction and heat on the brake pads, I'd use some to cool the cabin.

During P&G though, your goal is to carry your momentum as much as you can during a coast.
__________________



www.HyperKilometreur.com - Quand chaque goutte compte...
  Reply With Quote
Old 03-18-2008, 07:22 PM   #6 (permalink)
EcoMudder
 
Harpo's Avatar
 
Join Date: Mar 2008
Location: Gainesville, FL
Posts: 79

Harpo's Honda - '05 Honda Civic VP
90 day: 42.64 mpg (US)
Thanks: 0
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by boxchain View Post

Got numbers on idle fuel flow with AC on/off?

.
Yep. At steady state 35-55mph w/ AC fuel Flow is .20-.24 gph higher. On decel, from 55-30mph, with or without AC on Fuel flow is zero. It makes sense that I won't glide as far because there is additional engine load, albeit without fuel flow. At idle, in NEUTRAL, AC Fuel flow is .16gph higher (in my case - .25gph No AC to .41 gph W/ AC)

Today was a banner day, even with AC on decel this afternoon. 49.7 miles round trip. 40.7mpg or $4.11 for the trip.
__________________
  Reply With Quote
Old 04-11-2008, 11:33 PM   #7 (permalink)
I'd rather be biking
 
boxchain's Avatar
 
Join Date: Feb 2008
Location: New Orleans, LA, US Minor Outlying Islands
Posts: 127

Lexie - '98 Honda Civic LX
90 day: 39.46 mpg (US)

Beater Hauler - '92 Isuzu Pickup

Rentaclipse - '08 Mitsubishi Eclipse ?
90 day: 28.28 mpg (US)

Fahrt - '83 BMW R80 ST
Thanks: 0
Thanked 4 Times in 4 Posts
Quote:
Originally Posted by Harpo View Post
Yep. At steady state 35-55mph w/ AC fuel Flow is .20-.24 gph higher. On decel, from 55-30mph, with or without AC on Fuel flow is zero. It makes sense that I won't glide as far because there is additional engine load, albeit without fuel flow. At idle, in NEUTRAL, AC Fuel flow is .16gph higher (in my case - .25gph No AC to .41 gph W/ AC)
Thanks for the info Harpo. What's your rpm at DFCO trigger?

I'm going to assume that the same applies to my ride And I think I'm not far off, been trying DFCO for decel this tank and my odo at 1/2 tank (accurate I know) jumped from 225 to 280 this tank!

I also tried an AC/DFCO experiment. Coming down from a bridge (since we don't have hills ) I noticed that in gear there is definitely added drag when the AC is on. AC off, the car seems to slow down less quickly. I pushed the button several times going down and I could feel it. No good data, but I did A-B-A-B-A
__________________

My bike runs on dihydrogen monoxide.
I like to use these acronyms
  Reply With Quote
Old 04-11-2008, 11:45 PM   #8 (permalink)
Depends on the Day
 
RH77's Avatar
 
Join Date: Nov 2007
Location: Kansas City Area
Posts: 1,761

Teggy - '98 Acura Integra LS
Sports Cars
90 day: 32.74 mpg (US)

IMA - '10 Honda Insight EX
Team Honda
90 day: 34.76 mpg (US)

Tessie - '06 Acura TSX Base
90 day: 28.2 mpg (US)
Thanks: 31
Thanked 41 Times in 35 Posts
Quote:
Originally Posted by MetroMPG View Post
This is the second report of A/C on decel only operation I've seen in the past few days. Interesting.... and not applicable to my situation (no A/C!).
It's supposed to return to the low 30's again, so no worries yet on the A/C -- but I use the same kinda technique in the warmer months: manual cycling of the A/C on-off with recirc and med-hi fan depending on decel or highway downhill.

For me, last summer was the most operation without A/C since I had a car without it! Sweatin' for FE...

RH77
__________________
“If we knew what we were doing, it wouldn't be called research” ― Albert Einstein

_
_
  Reply With Quote
Old 04-12-2008, 03:33 AM   #9 (permalink)
EcoModding Lurker
 
Join Date: Apr 2008
Location: Grand Junction, CO
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
It's called DFCO or Deceleration Fuel Cutoff, when your instantaneous FE goes to zero. . What your fuel injectors do is when your engine is above some threshold rpm (~1500rpm) and you are applying no gas is it completely cuts the gas to the engine and just lets it turn from the car's momentum. However as the engine is still spinning your AC still works. However the AC is still causing drag, so it will shorten your "glide". I use quotes there because if you're P&Ging you should be gliding in neutral. If you're gliding with the engine on in neutral you'll see a significant decrease in FE as a idling engine with AC on uses a lot more gas than without.
  Reply With Quote
Old 04-12-2008, 03:45 AM   #10 (permalink)
EcoModding Minded
 
Chris D.'s Avatar
 
Join Date: Jan 2008
Location: Eagan, MN
Posts: 667

Lunar Mist - '02 Toyota Tacoma SR5
90 day: 25.31 mpg (US)

Silver Streak - '08 Toyota Corolla S
90 day: 38.25 mpg (US)
Thanks: 67
Thanked 25 Times in 12 Posts
Send a message via AIM to Chris D.
the SG shows fuel flow?!?

just got in on a group buy just in time!
cant wait for all this new instrumentation..
I love gadgets..

I still can't quite grasp this pulse and glide technique..

__________________


  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Small AC Conversion TomEV Fossil Fuel Free 4 02-06-2008 09:47 PM
AC Induction Motor used as Brushless DC? WaxyChicken Fossil Fuel Free 5 01-29-2008 09:26 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com