Accelerate Rapidly for Better Gas Mileage
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From: Austin TX
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)."
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From: Bucharest, Romania
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)."
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I don't care for gas mileage, I just do it. 
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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
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That is way too much theory.... maybe a good theory but then tehre is the real traffic and roads..... 
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so you always drive in ds mode znod and accelerate fairly quickly? Do you have to replace the brakes more often? 
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From: So Cal, USA
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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.
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From: Central Massachusetts
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!" 
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From: Chicago
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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.
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From: Long Island, New York
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
