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Discussion Starter #1
ok, ive got an 04 zx10r with kawasaki performance cams, pcIII, gi pro w/ atre, custom full exhaust, bmc filter, and a thinner head gasket.

i was driving it around daily getting about 35mpg city

i just had a vortex 520 sprocket kit put on and i went 2 down in the front.

i am getting the worst gas mileage now. idk how much bcuz i dont have a speedohealer yet but i can usually ride for about 4-7 days on a tank and now its like 2-3!!!

do i have to remap my pcIII bcuz of the new(front -2 down) sprocket???
 

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From what I have read on the subject of changing sprockets you will see two changes:

1. Speedo will be out by about 7% depending on change in gear ratio
2. Revs will be around 500rpm different for any given gear to achieve the same speed

As a result you will need to compensate with a speed healer to get correct mph and mileage. The engine will be running quicker and in a totally different area of the fuel mapping.. probably a richer area which would mean that you would be using more fuel.
Another big difference would be that it would change your style of riding which could well lead to higher fuel consumption.

Hope this sheds some light on it. :mrgreen:
 

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Discussion Starter #3
well im more concerned about the mpg right now then any of that bcuz its my daily driver and im gonna guesstimate that its only getting like 20 mpg!!! which is a BIG problem and i need to know if theres anything i can do rather then going back to my old gear ratio?
 

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Does the bike smell of gas or does it ever spit gasoline from the exhaust. If you have a power commander, is it working right? Consider getting it dynoed with an air/fuel ratio dyno. 20mpg does seem a bit rich, the gas has got to be going somewhere? Are the kids borrowing your gas for their mini bikes?
 

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first you should get a good figure for mpg... i reset my trip odometer every refill and i get about 38-40mpg. -1 up front. and a sprocket mod does not change engine speed.
 

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first you should get a good figure for mpg... i reset my trip odometer every refill and i get about 38-40mpg. -1 up front. and a sprocket mod does not change engine speed.
:dontknow:

He will be running higher rpms, but not high enough to cause mileage to go down that drastically. Something is wrong, I'd start checking fuel lines if really are going through that much fuel.
 

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Is your gas cap lock broken? Damn fuel thieves :dontknow:
 

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Do you have a custom tuned map or running a generic one? Most of the time tuners will tune lean to get more power and subsequentlly get you better MPG. A chain and sprocket conversion really should have no affect on your MPG.
 

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With no speeohealer, your mileage is way off if you went from a 17 to a 15 front sprocket. You are revving higher and burning more fuel to go the same distance than you were.

If you use this bike for commuting then why the drastic change in gearing? I would either change to a -1,+1 or go for mileage all together and stay stock or go down 1 or 2 in the rear with a stock front.

Tread
 

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Turn the GiPro ATRE off. With a geared bike there isnt any reason to have it. I have the GiPro ATRE and -1/+2 with a Speedohealer. With the GiPro "on" I get approx 75 miles per tank. With the GiPro "off" I get 105 miles per tank. I went through multiple tanks of gas to come to this conclusion. My bike was tuned with the GiPro "on" but that doesnt really matter as far as I know.

FYI most of my riding is in the mountains through the twisties at higher RPM's. And no I do not rev the shit out of my bike for the hell of it.
 

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Pretty simple really. If you go down in the fron tor up on the back your milage will go down. To look at it easily, consider a 10-speed bicycle. When you use the smaller gear in the front you have to pedal alot faster to go forward vs when you use the large sprocket in front you pedal slower. So by going down in the front you have to compensate by running at higher RPM's than you were doing before. More RPM = lesser fuel effeciency. But your taking off much quicker and wheelies are easier as well. :) Give and take.
 

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Discussion Starter #12
Pretty simple really. If you go down in the fron tor up on the back your milage will go down. To look at it easily, consider a 10-speed bicycle. When you use the smaller gear in the front you have to pedal alot faster to go forward vs when you use the large sprocket in front you pedal slower. So by going down in the front you have to compensate by running at higher RPM's than you were doing before. More RPM = lesser fuel effeciency. But your taking off much quicker and wheelies are easier as well. :) Give and take.
i am quite aware of of this, but i also can tell you that changing an end gear ratio from 2.29 to 2.60 is NOT gonna change my mpg from 35-40 all the way down to 20. i've seen gear ratio changes like this plenty of times and this is not the common result but thanks anyways
 

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I agree, I bet I could only use first gear and still average better mileage than that. Have you started tearing into it yet?
 

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Discussion Starter #14
I agree, I bet I could only use first gear and still average better mileage than that. Have you started tearing into it yet?
not yet, been a little too busy with school work. but i think im gonna disable the ATRE like the other guy said and go from there. if that doesnt work them im gonna get the damn thing remapped.

lots of great advice, thanks guys!
 

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not yet, been a little too busy with school work. but i think im gonna disable the ATRE like the other guy said and go from there. if that doesnt work them im gonna get the damn thing remapped.

lots of great advice, thanks guys!
If the mileage is as bad as you say it is though I don't think the remapping would help. If the map was that far off, you'd have noticed it in the way the bike ran. There is something more going on.
 

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not yet, been a little too busy with school work. but i think im gonna disable the ATRE like the other guy said and go from there. if that doesnt work them im gonna get the damn thing remapped.

lots of great advice, thanks guys!
Turn GiPro "off". A tune will not help get significantly better gas mileage, that isnt the purpose of it.
 
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