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OEM sprockets vs. +1/-2

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Old 06-29-2011, 03:08 PM
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Default OEM sprockets vs. +1/-2

Can't find the answer I'm looking for, so i'll post a new thread. My fuel economy is less than 30mpg. it might be my air filter, which someone suggested previously, but I also have the sprocket conversion done to my bike from the previous owner. Would this upgrade reduce my fuel economy a bit? I know it gives me lower-end torque but unsure if that is detrimental to my mpg. I'd like to have the bike up to the estimated 39mpg fuel efficiency if i can help it I'm not stunting this bike and don't think 'll need the conversion if its going to raise my fuel consumption by 8-10mpg.
 
  #2  
Old 06-29-2011, 03:13 PM
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Also, does anyone have the OEM part numbers for the chain and front sprocket?
 
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Old 06-29-2011, 03:21 PM
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I think you mean -1/+2? There is a chart somewhere that tells you gear ratios and how they will affect the bike. Try doing a search, it has been posted a few times.
 
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Old 06-29-2011, 03:22 PM
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going back to OEM sprockets will be good for gas mileage.

go to sprocket center and enter your bike's info and get 16tooth front sprocket and a 46tooth rear sprocket, you'll also have to get a 108 link chain, but it should be pretty easy to find the OEM set
 
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Old 06-29-2011, 03:30 PM
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Heres some quick numbers.
Stock gearing - 16/46 = 2.875 final drive ratio
Your gearing - 15/48 = 3.2 final drive ratio

3.2/2.875 = 1.11 So your engine will have to turn at 11% more times to travel the same distance as stock gearing, meaning approximately 11% more fuel consumption(its actually a little more because engines run less efficient at higher rpms) If you are currently getting 30 mpg, I would expect you would get at least 30 / (1-.11) = 34 mpg with stock gearing.

I have no experience with this in the real world, just messing around with numbers.
 
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Old 06-29-2011, 03:31 PM
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I highly doubt it will raise fuel economy 8-10mpg.
(17/44) / (16/46) = 1.11

Therefore when your on the highway you should gain about 11% fuel economy in theory so if your getting 30mpg you will get about 33mpg.

Edit: Kind of got beat to it.
 

Last edited by jeffjones; 06-29-2011 at 03:34 PM.
  #7  
Old 06-29-2011, 05:49 PM
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Default boost fuel economy?

is anyone out there running taller gears to try and boost fuel economy or for other reasons? if so what kind of mpg are you getting? i have stock gears and get 45-50 mpg on my 2002 F4i. im shocked to hear someone only getting 30 mpg but maybe its all city driving or something.
 
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Old 06-29-2011, 06:40 PM
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no it's mostly easy riding, averaging 40-60mph to and from work. i reset my trip meter this last fill-up(2nd fill up since i got it), i think i may have been short-selling my trip average. I'm about to order a new K&N air filter and see if the one I have now is dirty.
 
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Old 06-29-2011, 10:28 PM
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Originally Posted by Ragnar1x View Post
(its actually a little more because engines run less efficient at higher rpms)
Numbers are good but engine theory isen't. Engines run most efficiant at torque peak, which on a F4i is like 11,000rpm.
Below 40mpg when the bike is being ridden easily means there is something wrong. How many miles on the bike?
 
  #10  
Old 06-30-2011, 06:59 AM
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Originally Posted by F4iLOVE2RIDE View Post
is anyone out there running taller gears to try and boost fuel economy or for other reasons? if so what kind of mpg are you getting? i have stock gears and get 45-50 mpg on my 2002 F4i. im shocked to hear someone only getting 30 mpg but maybe its all city driving or something.

I would say Im more shocked to hear 50mpg thn 30mpg
 

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