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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 03-11-2008, 10:41 AM   #1 (permalink)
bbb3108
 
Join Date: Feb 2008
Location: north brunswick, new jersey
Posts: 16
Thanks: 0
Thanked 0 Times in 0 Posts
Driving 55mph? (Is it the most efficient speed?)

Sorry if this is in many other threads... just was reading this article on BusinessWeek, and saw these comments:

http://www.businessweek.com/bwdaily/...n_id=rss_daily

# Gau Mar 11, 2008 3:16 PM GMT Actually no, 55 isn't the most efficient speed The best ratio for gas is just above minimum rpm in your highest gear. RPMs is what eats gas, not speed... t Generally older cars run from 45-60 depending on gears and ratio. However on a lot of newer higher end cars with 5 and 6 speed gears, those number goes up...

# Tobin Mar 11, 2008 3:09 PM GMT the difference between gas savings at 70 and 55 is negligible on today's vehicles, in fact some cars in overdrive have better MPG at 70 than at 40 or 55

Is this true?

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 03-11-2008, 10:49 AM   #2 (permalink)
Dartmouth 2010
 
SVOboy's Avatar
 
Join Date: Nov 2007
Location: Hanover, NH
Posts: 6,427

Vegan Powa! - '91 Honda CRX DX
Team Honda
90 day: 66.52 mpg (US)
Thanks: 92
Thanked 110 Times in 79 Posts
Send a message via AIM to SVOboy Send a message via MSN to SVOboy Send a message via Yahoo to SVOboy Send a message via Skype™ to SVOboy
The first one about the lowest you can be in top gear is generally considered a good gauge among ecodrivers, however, speed (and therefore aero drag) is a HUGE factor and that number is no where near where he has it. I think my most efficient measured speed was 35 in 5th...in my mom's cars it's probably somewhere closer to 30.
  Reply With Quote
Old 03-11-2008, 11:16 AM   #3 (permalink)
Administrator
 
Daox's Avatar
 
Join Date: Dec 2007
Location: Germantown, WI
Posts: 10,157

CM400E - '81 Honda CM400E
90 day: 39.62 mpg (US)

Daox's Grey Prius - '04 Toyota Prius
Team Toyota
90 day: 49.53 mpg (US)

Daox's 04 Civic - '04 Honda Civic DX
90 day: 41.58 mpg (US)

Daox's Insight - '00 Honda Insight
90 day: 64.33 mpg (US)
Thanks: 1,654
Thanked 1,944 Times in 1,193 Posts
I'd agree with SVOboy. #1 is true as per SVO's statement. #2 is false. Aero losses kill your mileage at higher speeds.
__________________
Current project: Heating the manual trans with engine coolant
  Reply With Quote
Old 03-11-2008, 12:41 PM   #4 (permalink)
EcoModding Apprentice
 
jwxr7's Avatar
 
Join Date: Dec 2007
Location: mid michigan
Posts: 136

the metro experience (retired) - '94 geo metro 4 dr HB
90 day: 66.44 mpg (US)
Thanks: 0
Thanked 1 Time in 1 Post
My geo definitly likes to go as slow as is practical in 5th gear. It has pretty low gearing.

There is also the effect of the engine's efficiency curve. Aero load goes up with speed but the engine may also be going towards a more efficient rpm to help offset drag (depending on gearing). I believe my GMC does this on the highway (it has a 5spd manual). It has pretty tall gearing. The scangage seems to average similar FE going either 55 or 65 on the highway. I can only attribute this to having something to do with the engine's efficiency range. Of course anything over 65 causes a decrease in mpg and speeds under 55 return better FE.
__________________


Best tank= 81.23 mpg on 07-01-2008
Longest range= 791 miles on 9.74 gallons
  Reply With Quote
Old 03-11-2008, 01:06 PM   #5 (permalink)
Banned
 
Join Date: Feb 2008
Location: california
Posts: 1,329
Thanks: 24
Thanked 158 Times in 106 Posts
It depends on the specific model. For some cars, the difference is negligible.
http://www.greencarcongress.com/2006...onsumptio.html
  Reply With Quote
Old 03-11-2008, 03:29 PM   #6 (permalink)
Master EcoModder
 
basjoos's Avatar
 
Join Date: Dec 2007
Location: Upstate SC
Posts: 1,032

Aerocivic - '92 Honda Civic CX
Last 3: 70.54 mpg (US)

AerocivicLB - '92 Honda Civic CX
Team Honda
90 day: 61.34 mpg (US)
Thanks: 6
Thanked 526 Times in 257 Posts
My car has a fuel consumption curve that is flat from 30mph to 65mph, and drops only slightly at 70mph. My Cd is low enough that the slight increase in aero drag from 30 to 65mph is offset by the increase in ICE efficiency as I increase the load on it. It is actually easier for me to get good mileage at 65mph than at 30mph because at the lower ICE loadings (barely above idle), the throttle/mpg relationship becomes super sensitive. I have to use the hand throttle to consistently keep getting the better mileages at the lower speeds.
__________________
aerocivic.com
  Reply With Quote
Old 03-11-2008, 04:14 PM   #7 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 8,270
Thanks: 10,001
Thanked 4,313 Times in 2,386 Posts
Driving 55

I'm also in the "it depends" camp.I think every vehicle has a sweet spot.There's no question that loads increase with speed,however,how the powerplant reacts to increased load may be counterintuitive,as in my case with the Dodge D-100.It's mileage is better above 55mph,so in it's particular case,it's brake specific fuel consumption hits the "sweet spot" at 65mph,not true for any of my other vehicles.Experimentation may be the only means to discover peak efficiency for each vehicle.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 03-11-2008, 04:23 PM   #8 (permalink)
Bicycle Junky
 
NoCO2's Avatar
 
Join Date: Jan 2008
Location: Atlanta, GA
Posts: 464

Putsaround - '96 Toyota Camry LE
90 day: 32.74 mpg (US)

The Commuter - '07 Trek 1000SL
90 day: 617.28 mpg (US)

Zippy - '91 Honda Civic DX
90 day: 33.29 mpg (US)
Thanks: 0
Thanked 5 Times in 4 Posts
between 60 and 65MPH seems to be the most efficient for my car, however, it's also an automatic so if I slow down, it will downshift, I don't have a choice...However, I also noticed that at 65MPH I'm at 2100 but the minimal RPM for that gear is around 1500RPM but I can only go around 45MPH at that RPM....what gives? Maybe I'm just confused or something.
__________________
  Reply With Quote
Old 03-11-2008, 06:21 PM   #9 (permalink)
Pokémoderator
 
cfg83's Avatar
 
Join Date: Dec 2007
Location: Southern California
Posts: 5,864

1999 Saturn SW2 - '99 Saturn SW2 Wagon
Team Saturn
90 day: 40.49 mpg (US)
Thanks: 439
Thanked 520 Times in 349 Posts
aerohead -

Quote:
Originally Posted by aerohead View Post
I'm also in the "it depends" camp.I think every vehicle has a sweet spot.There's no question that loads increase with speed,however,how the powerplant reacts to increased load may be counterintuitive,as in my case with the Dodge D-100.It's mileage is better above 55mph,so in it's particular case,it's brake specific fuel consumption hits the "sweet spot" at 65mph,not true for any of my other vehicles.Experimentation may be the only means to discover peak efficiency for each vehicle.
I think we need a "BSFC Topo Map Collection" sticky. It would be a cool way to compare engine behavior. There could be little "X marks the gold" spots on it for MPG, .

CarloSW2
__________________

What's your EPA MPG? Go Here and find out!
American Solar Energy Society
  Reply With Quote
Old 03-11-2008, 07:40 PM   #10 (permalink)
Master EcoModder
 
Big Dave's Avatar
 
Join Date: Jan 2008
Location: Steppes of Central Indiana
Posts: 1,275

The Red Baron - '00 Ford F-350 XLT
90 day: 27.99 mpg (US)

Impala Phase Zero - '96 Chevrolet Impala SS
90 day: 21.03 mpg (US)
Thanks: 0
Thanked 153 Times in 108 Posts
My old diesel has a very flat BSFC curve from 800-2000 RPM. That plus its outrageous low-end torque allows me to think of truly radical gearing.

With an add-on overdrive I can cruise 70 MPH @ 1350 RPM and 60 MPH @ 1050 RPM. Aero mods will reduce the road load at these speeds and I'll have good roll-on capability even at ridiculously low RPM.

__________________
2000 Ford F-350 SC 4x2 6 Speed Manual
4" Slam
3.08:1 gears and Gear Vendor Overdrive
Rubber Conveyor Belt Air Dam
  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
News: Utah Considers Joining 80 MPH Speed Limit Club MetroMPG General Efficiency Discussion 68 11-04-2009 07:25 PM
Field Weakening Experiment for Speed Increase TomEV Fossil Fuel Free 12 04-10-2008 03:53 PM
Series Motor - Speed vs Torque TomEV Fossil Fuel Free 3 03-02-2008 12:27 PM
Video: Driving with a Steady Speed, or a Steady Accelerator? Peakster Hypermiling / EcoDriver's Ed 22 01-11-2008 10:22 PM
Basic EcoDriving Techniques and Instrumentation SVOboy Instrumentation 2 11-17-2007 11:38 AM



Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com