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On Probation
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Discussion Starter #1
Bike runs great but fuel milage is only 35-38 mpg all around hwy and city which seems low to me. By the numbers on my dyno sheet am I running too rich?
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Fat Guy on the Ultra
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I uavent had mine dynod but i also think mines running rich. May just be the difference in my new vs old bikes and mods. My 2010 had a 96" and i had slip ons and air cleaner, i could get about 250 on a tank. Now my 13 has the 103" and slipons and air cleaner but done the stage one download and xieds, its running great but at 215 miles i put 5.85 gallons in.....?

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On Probation
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Discussion Starter #3
Just comparing AFR numbers to others I have seen posted seems they are rich.
 

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Might be a hair rich at 4500ish RPM, but at 3000 RPM where you'd be cruising at, its spot on.

Even if you change the AF mixture at 4500 RPM, it won't affect your MPG cause you aren't cruising at that RPM.
 

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On Probation
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Discussion Starter #5
Might be a hair rich at 4500ish RPM, but at 3000 RPM where you'd be cruising at, its spot on.

Even if you change the AF mixture at 4500 RPM, it won't affect your MPG cause you aren't cruising at that RPM.
Sounds good......Thanks.
 

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i dont know this to be a fact as i havent done much looking into it but wouldnt the motor use the most fuel near peak TQ because this is where the motor is most efficiant...its pulling in more air and fuel at this point so wouldnt gas mileage suffer cruising at this speed...vs a motor of the same size making peak tq at say 4500??

it only takes a given amount of power to move your bike through the wind at 70MPH or any speed...and lets just say its like 50ft/lbs of tq for 70mph, so despite the motor build as long as you make 50ft/lbs at cruising rpm/speed then you should be able to maintain speed on the highway

so wouldnt you want to actualy make less power down low, and more power up top...this (in theory) should give better gas mileage

power is efficiency and efficiency means the motor is filling the cylinder to its max potential with air and fuel thus causing the drop in gas mileage

or am i over thinking it :)
 

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Thinking about it more than I am....

I just know that with the HD tuner you can tune at specific RPMs and different throttle positions at each of those RPMs.

I think it would be much less than 50 ft/lbs at cruising speed, a motor that makes less peak power at cruising RPM would just need to use a higher throttle position than a bike that makes more power at cruising RPMs.... Just think of all those small bikes that can do 70 MPH... Then my bike, I cruise at 70 MPH at maybe 1/8th to 1/4 throttle.
 

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Maddog
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Peak torque occurrs where the engine has the highest volumetric efficency. In your
case, that would be 3000-3500. So you should get the best gas milage between these
two rpm numbers.

your dyno guy should be able to tell you if you're too rich based on air/fuel readings...
 

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Bike runs great but fuel milage is only 35-38 mpg all around hwy and city which seems low to me. By the numbers on my dyno sheet am I running too rich?
View attachment 70977
The dyno sheet is 100% throttle at 100%+ manifold pressure. Your dyno sheet has nothing to do with everyday driving. Everyday driving is 5-40% throttle at 2000-3500. If the VE's are not set correctly and are making your engine run slightly rich, then you would use slightly more gas. A good tune is when "all" VE cells are correct, not just 100% throttle. Just my 2cents.
 

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Maddog
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what type of dyno did they use?

You really need an eddy current dyno to test things like this.
EC dynos provide a constant load under a variety of conditions.
I.e: part throttle crusing. They mimic road tests more accurately.

Allot of shops still use inertia dynos which are not ideal for setting
A/F ratios at anything other than wide open.

2 cents..
 

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nitro freak
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do it the old fashion way,check your plugs @ different cruising RPM`s
 

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On Probation
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Discussion Starter #12
do it the old fashion way,check your plugs @ different cruising RPM`s
Plugs look good, I guess I won't worry about it she runs great and I just got 41mpg twice on my Yosemite trip.
 

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Señor Member
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Plugs look good, I guess I won't worry about it she runs great and I just got 41mpg twice on my Yosemite trip.
I think it's a little wet. Not bad, but you could probably stand a little less fuel and probably gain some mpg.

My experience is limited, so don't bank on my opinion. Just my best guess comparing your sheet to mine.
 
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