Accelerate Rapidly for Better Gas Mileage
01-21-2006, 06:24 AM
#1
Contributors
Thread Starter
Join Date: Aug 2005
Location: Austin TX
Posts: 6,554
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2014 X5 xDrive 5.0 M Package Carbon Black Metallic/2008 M Roadster Imola Red
Hi Friends:
I have described my driving procedures before--which coincide for enjoying my car and for good mileage. I aways drive in DS--using a combination of manual and automatic shifting--with the emphasis on manual. I tend to get up to speed pretty quickly usually letting my engine get to 4k or 5k RPM before shifting. In this regard, I tend to maximize the time that my instantaneous MPG meter shows 20 MPG or better. It turns out that there is an explanation of why the rapid-acceleration part of my procedures may work. So, from Road and Track November 2005 we have:
"Full-Throttle Economy
If piston engines are most efficient at full throttle, won't we maximize fuel economy by flooring the pedal after every stop to get up to cruising speed? Or indeed any time we want to increase speed? (This is contrary to conventional wisdom which says that gradual acceleration is the best way to maximize economy.)
David Bookstaber
Berwyn, Pennsylvania
To oversimplify, yes. Given the practicalities of real engines, accelerating at three-quarter throttle (enough to reap a reduction in pumping losses but not enough to invoke wide-open-throttle fuel enrichment) returns excellent mileage. But in the real world of crawling traffic, such a rapid gain to cruising speed is not always practical. Also, this technique often results in acceleration to an unnecessarily high speed (especially between stoplights and other closely spaced impediments)."
I have described my driving procedures before--which coincide for enjoying my car and for good mileage. I aways drive in DS--using a combination of manual and automatic shifting--with the emphasis on manual. I tend to get up to speed pretty quickly usually letting my engine get to 4k or 5k RPM before shifting. In this regard, I tend to maximize the time that my instantaneous MPG meter shows 20 MPG or better. It turns out that there is an explanation of why the rapid-acceleration part of my procedures may work. So, from Road and Track November 2005 we have:
"Full-Throttle Economy
If piston engines are most efficient at full throttle, won't we maximize fuel economy by flooring the pedal after every stop to get up to cruising speed? Or indeed any time we want to increase speed? (This is contrary to conventional wisdom which says that gradual acceleration is the best way to maximize economy.)
David Bookstaber
Berwyn, Pennsylvania
To oversimplify, yes. Given the practicalities of real engines, accelerating at three-quarter throttle (enough to reap a reduction in pumping losses but not enough to invoke wide-open-throttle fuel enrichment) returns excellent mileage. But in the real world of crawling traffic, such a rapid gain to cruising speed is not always practical. Also, this technique often results in acceleration to an unnecessarily high speed (especially between stoplights and other closely spaced impediments)."
01-21-2006, 07:08 AM
#2
Senior Members
Join Date: May 2005
Location: Bucharest, Romania
Posts: 6,458
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Znod' post='227429' date='Jan 21 2006, 10:24 AM
Hi Friends:
I have described my driving procedures before--which coincide for enjoying my car and for good mileage. I aways drive in DS--using a combination of manual and automatic shifting--with the emphasis on manual. I tend to get up to speed pretty quickly usually letting my engine get to 4k or 5k RPM before shifting. In this regard, I tend to maximize the time that my instantaneous MPG meter shows 20 MPG or better. It turns out that there is an explanation of why the rapid-acceleration part of my procedures may work. So, from Road and Track November 2005 we have:
"Full-Throttle Economy
If piston engines are most efficient at full throttle, won't we maximize fuel economy by flooring the pedal after every stop to get up to cruising speed? Or indeed any time we want to increase speed? (This is contrary to conventional wisdom which says that gradual acceleration is the best way to maximize economy.)
David Bookstaber
Berwyn, Pennsylvania
To oversimplify, yes. Given the practicalities of real engines, accelerating at three-quarter throttle (enough to reap a reduction in pumping losses but not enough to invoke wide-open-throttle fuel enrichment) returns excellent mileage. But in the real world of crawling traffic, such a rapid gain to cruising speed is not always practical. Also, this technique often results in acceleration to an unnecessarily high speed (especially between stoplights and other closely spaced impediments)."
I have described my driving procedures before--which coincide for enjoying my car and for good mileage. I aways drive in DS--using a combination of manual and automatic shifting--with the emphasis on manual. I tend to get up to speed pretty quickly usually letting my engine get to 4k or 5k RPM before shifting. In this regard, I tend to maximize the time that my instantaneous MPG meter shows 20 MPG or better. It turns out that there is an explanation of why the rapid-acceleration part of my procedures may work. So, from Road and Track November 2005 we have:
"Full-Throttle Economy
If piston engines are most efficient at full throttle, won't we maximize fuel economy by flooring the pedal after every stop to get up to cruising speed? Or indeed any time we want to increase speed? (This is contrary to conventional wisdom which says that gradual acceleration is the best way to maximize economy.)
David Bookstaber
Berwyn, Pennsylvania
To oversimplify, yes. Given the practicalities of real engines, accelerating at three-quarter throttle (enough to reap a reduction in pumping losses but not enough to invoke wide-open-throttle fuel enrichment) returns excellent mileage. But in the real world of crawling traffic, such a rapid gain to cruising speed is not always practical. Also, this technique often results in acceleration to an unnecessarily high speed (especially between stoplights and other closely spaced impediments)."
01-21-2006, 07:19 AM
#3
Contributors
Join Date: Sep 2005
Location: Hong Kong
Posts: 3,585
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: In a place where the Mercedes density is the highest in the world (no. of MB per square kilometer) I choose a Bimmer, why? because of one thing "The Ultimate Driving Experience"
My Ride:
523i Steptronic, Silver Grey Exterior, Black Interior with Black Dakota Leather and Maple Wood Trim. Chrome Grill, Style 123 rim, Airbags everywhere, PDC, Rain sensor, Auto lights, Moveable front armrest, Advance Climate Control, Glass Sunroof, Auto dimming interior and exterior mirror with foldable functions, Extended Lights package, 6 CD changer in glove box, Power seats with memory, Power adjustable steering wheel, Power rear sunblinds.
Add ons: 123 wheels, chrome grill, K&N Hi flow filter, Eibach Pro Kit, e60.net decal and 24,000km
Past rides:
2001 Nissan Xterra SE
1999 E39 523i
1999 E46 323i
1996 Acura Integra LS
I don't care for gas mileage, I just do it. 
01-21-2006, 07:21 AM
#4
New Members
Join Date: Nov 2005
Location: UK
Posts: 117
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 520d M-Sport
Model Year: 2013
I worked this out a few years back in my e39 and it really does return pretty good economy figures.
I've concluded that it simply is based on the fact that the increased engine efficiency as revs increase rapidly is more than the addition fuel used to reach the desired speed, ie. get the acceleration bit out of the way quickly then you can get on with economical driving. Doesn't half make driving economically more fun
I've concluded that it simply is based on the fact that the increased engine efficiency as revs increase rapidly is more than the addition fuel used to reach the desired speed, ie. get the acceleration bit out of the way quickly then you can get on with economical driving. Doesn't half make driving economically more fun
01-21-2006, 08:15 AM
#5
Contributors
Join Date: Apr 2005
Location: Prague, Czech Rep. - Europe
Posts: 1,934
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2004 BMW 530I steptronic, Orient Blue, Dakota Black Leather, Finishers Aluminium with Wave Cutting interior, NAVIgation, Radio PROFESSIONAL, CD in-dash, Hi-Fi extended sound system, PDC system, Bi-Xenons lights with washers, cruise-control, heated seats, Extended AC, auto"shade" mirrors, auto lights sensors, rain/wiper sensor, M-tech leather multifunction steering wheel, side airbags rearseats, sliding armrest, smoker's package (I don't smoke!), velour floor mats, spare wheel and jack, 122 style rims winter setup, M135 style rims summer setup
[color=red]Mods:[/color]
[color=blue]M tech sport steering wheel with M5 SMG paddles working retrofit done !
Trunk lid opening button retrofit done.[/color]
[color=blue]3M window 35% tint done
Chrome grilles
E60.net Clings
[/color]
That is way too much theory.... maybe a good theory but then tehre is the real traffic and roads..... 
01-21-2006, 11:27 AM
#6
Senior Members
Join Date: Nov 2005
Location: western Canada
Posts: 570
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2006 550i Titanium Silver, Black Dakota Leather, Aluminum Cube Trim, M Sport Pkg, Premium Pkg, Comfort Access, Head Up Display, Steptronic, Comfort Seats, Rear Heated Seats, Through Load, Park Distance Control, Navigation , HK Logic 7, etc
so you always drive in ds mode znod and accelerate fairly quickly? Do you have to replace the brakes more often? 
01-21-2006, 11:40 AM
#7
Contributors
Join Date: Oct 2004
Location: So Cal, USA
Posts: 14,776
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 545iSMGSilver GrayAuburn Dakota LeatherLogic 7 Premium SoundSports Package
Originally Posted by AC_S5' post='227442' date='Jan 21 2006, 08:19 AM
I don't care for gas mileage, I just do it.
01-21-2006, 11:47 AM
#8
Contributors
Join Date: Aug 2004
Location: Central Massachusetts
Posts: 1,717
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: Now Driving a Freakin' Prius!
Was...
2004 545i | SMG | White/Black | Sport | NAV | Logic 7 | PDC | Fold-down Seats | Adaptive Headlights | Cold Weather Pkg | Clear-again Bra | Mud Flaps | Bluetooth | Coat Hangar | Aux Input | All Weather Mats | 18"X8.5" BBS RK w/ Michelin Pilot Alpin's (winter) | New steering rack @ 1.2K & 17K miles| Software V.19.1 | B&B Exhaust (vrrrroooooommm!) <---Click.
Well at least now when my wife asks my why I drive the way I do, I have something to come back with besides "'cuz it's fun!" 
01-21-2006, 12:32 PM
#9
Contributors
Join Date: Aug 2004
Location: Chicago
Posts: 493
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: #1: 2004 545i; 6-speed manual; Sport Package; Mystic Blue with a gray leather interior and Anthracite wood; CWP; Logic 7.
#2: 2010 535xi Touring; Automatic.
I thought I had heard something about the Valvetronic Double-VANOS system in the 545 reducing these pumping losses.
See the attached, http://www.bmwworld.com/technology/valvetronic.htm, which talks about this engine's reduction of those typical partial-throttle power losses.
So the point may still be true, partially, it may not make much difference, or any, on my car.
But I won't tell our wives if you won't. I like an excuse for the jackrabbit starts, too.
See the attached, http://www.bmwworld.com/technology/valvetronic.htm, which talks about this engine's reduction of those typical partial-throttle power losses.
So the point may still be true, partially, it may not make much difference, or any, on my car.
But I won't tell our wives if you won't. I like an excuse for the jackrabbit starts, too.
01-21-2006, 03:21 PM
#10
Contributors
Join Date: Sep 2005
Location: Long Island, New York
Posts: 1,624
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2005 525i Titanium Silver Metalic and 2003 325xi Jet Black with the Premium Package in both cars.
Well I see I learn something new, each and every time I read this forum. Good info....thanks