ADVrider

Go Back   ADVrider > Bikes > GSpot > Parallel Universe
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-26-2015, 04:11 PM   #1
Excite-Bike OP
Gnarly Adventurer
 
Excite-Bike's Avatar
 
Joined: Jun 2011
Location: San Francisco, CA
Oddometer: 177
Any data out there on MPG lost per pound of weight added?

Whether it be luggage or a passenger?
Excite-Bike is offline   Reply With Quote
Old 03-27-2015, 04:19 AM   #2
Snowy
Beastly Adventurer
 
Joined: Dec 2008
Oddometer: 1,817
it's more about speed than weight in my experience. There's a point where aerodynamics turn to shit.
Snowy is online now   Reply With Quote
Old 03-27-2015, 06:51 AM   #3
GREWUPIN_D11
GREWUPIN_D11
 
GREWUPIN_D11's Avatar
 
Joined: Feb 2010
Location: Northern VA
Oddometer: 135
Quote:
Originally Posted by Snowy View Post
it's more about speed than weight in my experience. There's a point where aerodynamics turn to shit.
+1 on Snowy's comment. Aerodynamic forces at highway speed are greater than rolling resistance. So adding farkles that increase frontal area and/or coefficient of drag has greater effect on fuel consumption than adding a pound that doesn't affect aerodynamics. Power required to overcome aerodynamic force is proportional to speed cubed. So increasing cruising speed from 60mph to 80mph requires (80/60)^3 = 2.37 times more power to part the air!
GREWUPIN_D11 is offline   Reply With Quote
Old 03-27-2015, 07:02 AM   #4
TheProphet
Zen Rider
 
TheProphet's Avatar
 
Joined: Mar 2014
Location: North / Central Illinois
Oddometer: 715
Agreed. I would be more concerned with the activity of the throttle hand, as well as frontal area, aerodynamics.

Once you exceed about 55 MPH, your biggest obstacle to decent MPG is pushing the bike - and yourself - into the oncoming air. Fairings (decently designed ones) windshields (Ditto) and so on help, as do reducing YOUR frontal area by leaning down. Streamline the front of the bike, and you should see some improvement.

As far as Weight Vs. HP, I believe it is something like every ten pounds added reduces the effective HP by 1, and the reverse - removing ten pounds is the equivalent of making another HP available. All theoretical, and to a certain limit of course.
__________________
When you come to a fork in the road... take it.
TheProphet is offline   Reply With Quote
Old 03-27-2015, 10:21 AM   #5
Captain Excellent
+ll+
 
Captain Excellent's Avatar
 
Joined: Sep 2011
Location: North Vancouver, BC
Oddometer: 197
Here's an over simplification, but a good way to think of this none the less.
If you assume a given rate of consumption at say 100kph, then to achieve 120kph would require 120% fuel consumption. Faster equals more fuel.
The only way to a ascertain the impact of mass (more $%@# on the bike) would be to measure fuel consumption during acceleration from 0 to a given speed in a given time.
__________________
!
Captain Excellent is offline   Reply With Quote
Old 03-27-2015, 10:45 AM   #6
Rgconner
Beastly Adventurer
 
Joined: Mar 2014
Oddometer: 1,559
Quote:
Originally Posted by Captain Excellent View Post
Here's an over simplification, but a good way to think of this none the less.
If you assume a given rate of consumption at say 100kph, then to achieve 120kph would require 120% fuel consumption. Faster equals more fuel.
Wind resistance is a squared function.

To go from 100 to 120 is double the HP, approximately.


http://phors.locost7.info/phors06.htm
__________________
Undersecretary of the Ministry of Silly Posts.
Rgconner is offline   Reply With Quote
Old 03-27-2015, 12:48 PM   #7
97707
Go Long
 
97707's Avatar
 
Joined: Aug 2014
Location: Oregon, USA
Oddometer: 72
hills

Also the mpg penalty for adding weight isn't constant. Its bigger in hill country than on the flat, f'rinstnce.

There are so many variables, I don't think you can find a formula that will give you useful results. A large engine is going to show less increase in fuel use with added weight, compared to a small one.

Weight flattens tires, which increases roll resistance a bit. How much might depend on the tire.

Probly the best way to find an answer, for your application, is to do a test. Check your mileage loaded light and then load up and check it again. For a meaningful result, you'd have to make sure you didn't change the air resistance in the process. No doubt the difference will vary with speed.

.
__________________
Today's subliminal message is . . .
97707 is offline   Reply With Quote
Old 03-27-2015, 01:49 PM   #8
GREWUPIN_D11
GREWUPIN_D11
 
GREWUPIN_D11's Avatar
 
Joined: Feb 2010
Location: Northern VA
Oddometer: 135
Quote:
Originally Posted by Rgconner View Post
Wind resistance is a squared function.

To go from 100 to 120 is double the HP, approximately.


http://phors.locost7.info/phors06.htm

Rgconner - both of your statements are true, but they are not equivalent. Wind resistance (which is a force) increases as the square of airspeed. Power required (horsepower) to overcome the air resistance for constant-speed cruise requires multiplying force by speed. This then results in the cubed relationship for power required as a function of airspeed. And the cube root of 2 is about 1.2, as your example indicates.

97707 then adds in the unknowns about rolling resistance. Which is why everyone's real-world fuel consumption increase with speed doesn't match the very simple model above which only deals with wind resistance.

GREWUPIN_D11 screwed with this post 03-27-2015 at 04:20 PM
GREWUPIN_D11 is offline   Reply With Quote
Old 03-27-2015, 03:29 PM   #9
inbred
Gnarly Adventurer
 
inbred's Avatar
 
Joined: Jan 2011
Location: Weedsport, NY
Oddometer: 187
Never has so much intelligence gathered since Max Fritz dined alone in Munich, Bavaria.
__________________
Some wanna wire their seats to provide warmth to their taints, I just want the option of operation without light.
inbred is offline   Reply With Quote
Old 03-27-2015, 04:26 PM   #10
Excite-Bike OP
Gnarly Adventurer
 
Excite-Bike's Avatar
 
Joined: Jun 2011
Location: San Francisco, CA
Oddometer: 177
Sorry, I should have made my question more concise.

If the bike with its 4 gal tank plus my 2 gal Camel tank has a range of around 300 miles till I must refuel, what might be a decent guess of how much shorter that range would be with my 105lb girlfriend on back plus about 50lb of luggage?
Excite-Bike is offline   Reply With Quote
Old 03-27-2015, 04:26 PM   #11
GREWUPIN_D11
GREWUPIN_D11
 
GREWUPIN_D11's Avatar
 
Joined: Feb 2010
Location: Northern VA
Oddometer: 135
Quote:
Originally Posted by inbred View Post
Never has so much intelligence gathered since Max Fritz dined alone in Munich, Bavaria.
Friz
GREWUPIN_D11 is offline   Reply With Quote
Old 03-27-2015, 04:36 PM   #12
Boon Booni
Red Clay Halo
 
Boon Booni's Avatar
 
Joined: Aug 2003
Location: Richmond, Va
Oddometer: 13,679
Quote:
Originally Posted by Excite-Bike View Post
Sorry, I should have made my question more concise.

If the bike with its 4 gal tank plus my 2 gal Camel tank has a range of around 300 miles till I must refuel, what might be a decent guess of how much shorter that range would be with my 105lb girlfriend on back plus about 50lb of luggage?
Don't worry about your range, she will have to pee first.

Boon Booni screwed with this post 03-27-2015 at 06:20 PM
Boon Booni is online now   Reply With Quote
Old 03-27-2015, 04:58 PM   #13
GREWUPIN_D11
GREWUPIN_D11
 
GREWUPIN_D11's Avatar
 
Joined: Feb 2010
Location: Northern VA
Oddometer: 135
Quote:
Originally Posted by Excite-Bike View Post
Sorry, I should have made my question more concise.

If the bike with its 4 gal tank plus my 2 gal Camel tank has a range of around 300 miles till I must refuel, what might be a decent guess of how much shorter that range would be with my 105lb girlfriend on back plus about 50lb of luggage?
Not enough info. Is 300 mile range with empty baggage attached? What was the average speed for while achieving this range? Will your average speed change with passenger and luggage onboard? I've noticed higher fuel consumption in very cold temperatures, possibly due to increased air density therefore higher wind resistance at same indicated speed. So what was the temperature when you achieved 300 mile range? Will the temperature be different for your upcoming trip? And on and on . . .

IF the ONLY change is adding GF and filling the bags, which you always have attached, with luggage, I'll go out on a limb and say . . . range of 290 miles.
GREWUPIN_D11 is offline   Reply With Quote
Old 03-27-2015, 05:05 PM   #14
Excite-Bike OP
Gnarly Adventurer
 
Excite-Bike's Avatar
 
Joined: Jun 2011
Location: San Francisco, CA
Oddometer: 177
Quote:
Originally Posted by GREWUPIN_D11 View Post
I'll go out on a limb and say . . . range of 290 miles.
That's what I was looking for and your guess surprises me. Why such a small drop?

I would have guessed something like 30-40 mile difference rather than 13-14, so I guess I am overestimating the difference weight makes?
Excite-Bike is offline   Reply With Quote
Old 03-27-2015, 05:09 PM   #15
flei
cycletherapist
 
Joined: Apr 2013
Location: Western Mass.
Oddometer: 996
OP- Does your girlfriend always stay in a good tuck behind you, or does she sometimes create more wind resistance by peeking out around you? What does she weigh after a big meal vs. a small one? With a starting weight of only 105, eating a Whopper would increase that by quite a large % and effect your mileage! Does she have long hair, and if so does she wear it down, because that would increase wind resistance. Does she ever wave at others? The more waving, the more wind resistance and the worse your mileage. How much more air do you add when you have the girlfriend and luggage? How often does she pass gas? The more often, the more likely your mileage will be increased by the extra propulsion. Wow, this gets really complicated! Please do research on this and report back with your findings.
__________________
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
flei is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 09:55 PM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2015