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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 11-12-2012, 03:39 PM   #1 (permalink)
The PRC.
 
Join Date: Oct 2009
Location: Elsewhere.
Posts: 5,304
Thanks: 285
Thanked 536 Times in 384 Posts
Question The big bad motorway vs the tiny car

A bit of advice from the assembled "expertness" if you please

I was trundling with George along the M9 motorway (aka freeway) last week. Normally I like to trundle along in the left hand (i.e. slow here) lane with the trucks so that a) I can get some limited draft effect (I don't tailgate) and b) so that people coming up behind apparently blind whilst driving at 85+ (limit is 70 but hey...) notice me and I don't get those last minute panic lane changes.

But on this occasion there were few trucks so I had to scurry along about 5-10 MPH faster than normal. That combined with changing wind direction (its a hilly area and it was stormy) and unfriendly inclines meant my MPG was low compared with recent averages, about 55-60 vs 70+ (imp).

I tried P&G but pulsing at these speeds (60+) is kind of limited before you have to do it again and George is just not that aero and is very light - the net result is falling MPG not steady - and of course I managed to pulse just before we hit another headwind of incline - Not sure if anyone has seen the old cartoon of Homer Simpson falling down a cliff and hitting everything on the way but it kind of felt like the ecomodder equivalent of that whien I tried stuff.

Eventually I decided on a DWL cruise with 60 as the minimum speed and anything over 55 as the MPG target, but ended up with a low-ball average of 56 for the round trip - not good.

So a question for the Metro-style folks - how to trundle at higher speeds (say 60-65) in the most efficient way in mixed conditions on an empty road except for speed freaks.

__________________
[I]So long and thanks for all the fish.[/I]
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 11-12-2012, 05:13 PM   #2 (permalink)
Administrator
 
Daox's Avatar
 
Join Date: Dec 2007
Location: Germantown, WI
Posts: 11,203

CM400E - '81 Honda CM400E
90 day: 51.49 mpg (US)

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

Daox's Insight - '00 Honda Insight
90 day: 64.33 mpg (US)

Swarthy - '14 Mitsubishi Mirage DE
Mitsubishi
90 day: 56.69 mpg (US)

Daox's Volt - '13 Chevrolet Volt
Thanks: 2,501
Thanked 2,585 Times in 1,553 Posts
P&G will always be the most effective driving method. However, if you're going into a head wind and are already at a decent speed the technique might be nearly moot. The purpose of P&G is to only operate the engine at its most efficient level - highly loaded. If you are already achieving a fairly high engine load because of the wind and speed you don't really need to glide as the engine will continually be loaded an adequate amount. I suggest watching the LOD gauge on the scangauge to determine when this is happening. By looking at a few BSFC maps, it seems anything over about 60% load is putting you pretty close to ideal BSFC and therefore the benefit of P&G is drastically reduced.
__________________
Current project: A better alternator delete
  Reply With Quote
Old 11-12-2012, 06:59 PM   #3 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,513

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

MPGiata - '90 Mazda Miata
90 day: 52.71 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 60.16 mpg (US)
Thanks: 4,058
Thanked 6,957 Times in 3,602 Posts
P&G doesn't work as well at high speeds in low-powered, unaerodynamic cars. The pulse is too long & the glide is too short.

As Daox points out, the headwind only makes things worse.

DWL or "target driving" to a reasonable (under the circumstances) MPG figure is the next best approach.
__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
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 11-13-2012, 03:40 AM   #4 (permalink)
The PRC.
 
Join Date: Oct 2009
Location: Elsewhere.
Posts: 5,304
Thanks: 285
Thanked 536 Times in 384 Posts
Gave DWL a better go on the comute this morning - will have to see how it hacks it on a longer trip with higher speeds. P&G (I still engine on most of the time) works well under 55.
__________________
[I]So long and thanks for all the fish.[/I]
  Reply With Quote
Old 11-14-2012, 09:27 AM   #5 (permalink)
Rat Racer
 
Fat Charlie's Avatar
 
Join Date: May 2011
Location: Route 16
Posts: 4,150

Al the Third, year four - '13 Honda Fit Base
Team Honda
90 day: 42.9 mpg (US)
Thanks: 1,784
Thanked 1,922 Times in 1,246 Posts
Terrain dictates, Mr. A, and on that road in your car the best you can hope for is for your mileage to not suck too badly. Look on the bright side- your worst is about twice as good as one of my bad days!
__________________

Quote:
Originally Posted by sheepdog44 View Post
Transmission type Efficiency
Manual neutral engine off.100% @MPG <----- Fun Fact.
Manual 1:1 gear ratio .......98%
CVT belt ............................88%
Automatic .........................86%

  Reply With Quote
Old 11-14-2012, 03:07 PM   #6 (permalink)
The PRC.
 
Join Date: Oct 2009
Location: Elsewhere.
Posts: 5,304
Thanks: 285
Thanked 536 Times in 384 Posts
Quote:
Originally Posted by Fat Charlie View Post
Terrain dictates, Mr. A, and on that road in your car the best you can hope for is for your mileage to not suck too badly. Look on the bright side- your worst is about twice as good as one of my bad days!
Yep - it's more an average thing, I could almost feel the pound notes being extracted from my wallet as petrol is $8+ US Gallon here.

I wish I could have gone slower but the 80+ muppets (I used to be one) don't notice anything small and slow.

__________________
[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