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Thread: MPG poll
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Old 08-01-2006, 06:45 PM   #125
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What I Drive: '99 M Roadster, '10 speed3, '04 ZX3

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well i must diasagre, if you shift in the low RPM range, you will hurt your MPG and your enige, why? simple, look at a dyno chart, you have half(or less) HP and tourque at 1.5-3k rpm(this is where my cars shift light comes on) which this means, your enige will have to work harder to acelarate, gas milage is soly based on the amount of fuel the engine burns, nothing more. so if you shift at low rpms, to get any sort of acel, you must give the car a fare amount of gas, and also for a longer time,

if we shift at the the 5k range, then you will have more Hp to use, thus needing less fuel to get the same amount Hp out of it... then you are using less gas and also you will have to acel for far less time!

so basicly, the amount of time you have your foot down on the pedal, wheather its at 3k or 5k rpm, is what truelly is afecting your MPG, sure in theroy you should use less gas at lower rpms, due to the engine having to fire less often, HOWEVER!!! if you have to use more gas per cylnder to acel, then well you aint gaing anything.

a cool way to prove this yourself (if you have a stick) is to go out the freeway, when your doing 60, be in whatever gear it takes to be in the 3.5-4.5k range rpm range, then just drop the pedal to the mettle till you get to 70-80, im pretty sure its not going to take you very long.
NOW slow down to 60, and shift to whatever gear wil lget you in a LOW rpm range ( idle to 2k) NOW i want you to floor the gas again, till you get to the same speed....

we all know that it will take far longer to acel the second time, thus its taking you WAY more fuel.....

i also know this from this, when i acel i have my foot in nearly the same spot everytime, when i would shift at the low rpm range, say the 3k shift point, id get 27-29mpg

then i started to shift at the 4.5-5.5k range, i will get an xtra 3-5mpg, i get (as said 31-32)

this is of course with my car with my gas etc..... its posible its just my car with my driving style... however the best way to do it, drive one way for 2-3 tanks, check your mpg, drive the other for a few, check your mpg, then jsut run whatever gives YOU the best for YOUR car.

so i say this, weahter my above text is flawed or not, so be it, but after typing this, jsut drive your car shifting at a spesific rpm, per tank of gas, check your MPG each time, when you find the sweet spot, RUN IT!!! heck, it could be at 2k it could be at 6k, who knows, im guessing every varible posible determines the swet spot for your car. but hey, if you get 35mpg shifting at 2krpm, dang, do it lol.

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