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ProDigit · 10-28-2016, 06:07 AM

The R3 is geared very low.
It actually gets closer to 80MPG when in final gear, at about 35MPH.
The R3 is geared to go 30-35MPH in final gear for highest MPG. Below that the engine is lugging.

MPG is directly related to bike acceleration in final gear.
If you want a reasonable fun and snappy bike in final gear, you'll always hover around 50-66MPH, regardless of which bike.
The larger the bike, the lower that number.
If you have a large (sized) bike with an EPA estimate of 80MPG US, it will feel really sluggish in final gear.
Likewise, if you have a very modern, small bike, that's well tuned, but only gets 40MPG average, it's usually geared for acceleration (like dirt bikes).
The shorter the gear, the greater the acceleration, and the lower the MPG.

To compensate for the R3's lower power, and to be able to keep up at higher speeds, it needs to have high RPM to build more HP.
High RPM means MPG inefficiency, due to higher engine bearing and oil/watercooling pump frictions, and less efficient fuel burn in the piston due to very rapid exiting of the hot (often still not fully burned) gasses.

The following torque curve tells us that the best MPG range is from ~3-4k RPM, and the engine will lose a lot of efficiency beyond 9100 RPM.

If you want your R3 to have better gas mileage, you can change it's gears, by changing the sprockets.

The R3 comes stock with a 14/43 gearing, that gives an average of 56MPG.
56MPG is only because a lot of riders race the bike, or use it in town going from stop light to light.
If you ride it gently, you could get 66MPG out of it average.

Install a 15t front sprocket, and MPG goes up from the gentle riding 66 MPG, to 70.
Additionally, change the rear sprocket to a 38 tooth, and MPG in final gear is closer to 80MPG (which gives a very gentle acceleration in 6th).
It will also bring your top speed up by about +3 MPH.
From 110MPH at 11.2k RPM stock, to about 113 MPH at 10.8k RPM on a 15/38T setup, makes you hit the sweet spot of the engine's peak power output.
Another benefit will be a more useable first gear, since the stock gear is ok to let the bike idle in traffic, but is generally too short to accelerate from a dead stop.
a 15/38t gearing will increase the length of first gear, and allow you to actually cross an intersection before feeling the need to switch into second gear.
Your most efficient MPG is gained in final gear, at about 3k RPM. Stock that would be around 30MPH. With this setup, the bike's MPG won't be the only thing that has increased, it's speed to achieve that better MPG is also increased (from 30MPH to 35MPH).
Additionally this setup will require you to shift 1x less through the gears, as stock 6th gear seems to be almost identical to the modified 5th gear.
And, you have 1 extra gear; a '7th gear' so to speak compared to a stock bike, so it gives you more flexibility.

So the stock vs 15/38t might look more like this:

Stock: Modified
1: 1.2
2: 2.4
3: 3.6
4: 4.8
5: 6
6: 7.2

In this case, 5th gear modified is identical to a 6th gear stock, and 6th gear on a modified bike, would be like a stock bike having a 7'th (and something) gear.

If you want to go highest in fuel economy on an R3, you could try installing the largest front sprocket, and the smallest rear sprocket.
It will affect acceleration from a standstill (1st gear acceleration) a bit, might accelerate a bit slower, and in many cases also affect top speed; as the engine RPM at top speed, will in some cases fall outside the HP band.

If you want to keep the acceleration and top speed you get from a stock bike in final gear, you can install somewhere between a 15/39t for small people, and 15/40t for big people; and your 5th gear will be very close to a stock bike's 6th gear.
So on the interstate you'd have to shift down for passing power, while 6th will be a better overdrive gear.

Having to choose between both bikes, I'd say a Yamaha FZ-07 would perform better at 45-50MPH and up, while an R3 is more suited at speeds below 45-50MPH.

I find bikes with 35HP are usually most fun to ride between 30 and 75MPH.
The FZ-07 is better between 50-100MPH; because the engine's power is more tuned to these speeds.

10-28-2016, 06:07 AM	#8 (permalink)
ProDigit EcoModding Apprentice Join Date: Jun 2012 Location: Florida Posts: 222 Thanks: 0 Thanked 22 Times in 18 Posts	The R3 is geared very low. It actually gets closer to 80MPG when in final gear, at about 35MPH. The R3 is geared to go 30-35MPH in final gear for highest MPG. Below that the engine is lugging. MPG is directly related to bike acceleration in final gear. If you want a reasonable fun and snappy bike in final gear, you'll always hover around 50-66MPH, regardless of which bike. The larger the bike, the lower that number. If you have a large (sized) bike with an EPA estimate of 80MPG US, it will feel really sluggish in final gear. Likewise, if you have a very modern, small bike, that's well tuned, but only gets 40MPG average, it's usually geared for acceleration (like dirt bikes). The shorter the gear, the greater the acceleration, and the lower the MPG. To compensate for the R3's lower power, and to be able to keep up at higher speeds, it needs to have high RPM to build more HP. High RPM means MPG inefficiency, due to higher engine bearing and oil/watercooling pump frictions, and less efficient fuel burn in the piston due to very rapid exiting of the hot (often still not fully burned) gasses. The following torque curve tells us that the best MPG range is from ~3-4k RPM, and the engine will lose a lot of efficiency beyond 9100 RPM. If you want your R3 to have better gas mileage, you can change it's gears, by changing the sprockets. The R3 comes stock with a 14/43 gearing, that gives an average of 56MPG. 56MPG is only because a lot of riders race the bike, or use it in town going from stop light to light. If you ride it gently, you could get 66MPG out of it average. Install a 15t front sprocket, and MPG goes up from the gentle riding 66 MPG, to 70. Additionally, change the rear sprocket to a 38 tooth, and MPG in final gear is closer to 80MPG (which gives a very gentle acceleration in 6th). It will also bring your top speed up by about +3 MPH. From 110MPH at 11.2k RPM stock, to about 113 MPH at 10.8k RPM on a 15/38T setup, makes you hit the sweet spot of the engine's peak power output. Another benefit will be a more useable first gear, since the stock gear is ok to let the bike idle in traffic, but is generally too short to accelerate from a dead stop. a 15/38t gearing will increase the length of first gear, and allow you to actually cross an intersection before feeling the need to switch into second gear. Your most efficient MPG is gained in final gear, at about 3k RPM. Stock that would be around 30MPH. With this setup, the bike's MPG won't be the only thing that has increased, it's speed to achieve that better MPG is also increased (from 30MPH to 35MPH). Additionally this setup will require you to shift 1x less through the gears, as stock 6th gear seems to be almost identical to the modified 5th gear. And, you have 1 extra gear; a '7th gear' so to speak compared to a stock bike, so it gives you more flexibility. So the stock vs 15/38t might look more like this: Stock: Modified 1: 1.2 2: 2.4 3: 3.6 4: 4.8 5: 6 6: 7.2 In this case, 5th gear modified is identical to a 6th gear stock, and 6th gear on a modified bike, would be like a stock bike having a 7'th (and something) gear. If you want to go highest in fuel economy on an R3, you could try installing the largest front sprocket, and the smallest rear sprocket. It will affect acceleration from a standstill (1st gear acceleration) a bit, might accelerate a bit slower, and in many cases also affect top speed; as the engine RPM at top speed, will in some cases fall outside the HP band. If you want to keep the acceleration and top speed you get from a stock bike in final gear, you can install somewhere between a 15/39t for small people, and 15/40t for big people; and your 5th gear will be very close to a stock bike's 6th gear. So on the interstate you'd have to shift down for passing power, while 6th will be a better overdrive gear. Having to choose between both bikes, I'd say a Yamaha FZ-07 would perform better at 45-50MPH and up, while an R3 is more suited at speeds below 45-50MPH. I find bikes with 35HP are usually most fun to ride between 30 and 75MPH. The FZ-07 is better between 50-100MPH; because the engine's power is more tuned to these speeds. Last edited by ProDigit; 10-28-2016 at 06:25 AM..