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Old 03-12-2015, 04:14 PM   #1 (permalink)
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Yamaha R3 (56mpg) vs Yamaha FZ07 (58mpg)

How is the 321cc R3 less efficient than the ~700cc FZ07? Both are two cylinder if that helps. R3 is probably horsepower oriented and FZ07 is a torque monster. 56mpg vs 58mpg. I want an FZ07 now

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Old 03-12-2015, 07:00 PM   #2 (permalink)
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an R3 is less efficient than a FZ07 . EPA test in

Does it lead every day as in the EPA test?

if driving different. has different consumption.

if you can. tests the two motorcycles , compare consumption.
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Old 03-12-2015, 10:54 PM   #3 (permalink)
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A way to compare engines of different displacements is to multiple the displacement times RPM at peak torque to determine rate of flow. Flow in a 350 cc at 10,000 rpm equals that of a 700cc at 5,000 rpm. The compression ratios of the two engines are similar as are the weights. A V star 250cc is rated at 78 mpg.

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Old 03-13-2015, 10:18 AM   #4 (permalink)
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That is odd...

You would have to look closely at the test procedures and see how they compare to real world riding.

I would expect the R3 to have much more potential to go significantly beyond its rated MPG compared the the FZ.

If you compare the test results from a CBR250R or Ninja 250/300 to what some of the riders are getting for MPG you should see the potential MPG of the R3.

The R3 is still significantly smaller and lighter than the FZ, so it really depends on what is important to you as a rider.
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Old 03-13-2015, 11:09 AM   #5 (permalink)
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I have owned both a Ninja300 and a CBR 250r. The CBR easily beat the Ninja by a large margin in fuel mileage.

I think it's more a function of bore to stroke ratio and gearing. Look at the redline on the bike in question The R3 is supposed to produce 41 HP out of a litte over 20 cubic inches.
I'd bet it revs to over 12k rpm, maybe even close to 14k, while the longer stroke engines will have a much lower rev limit, like 10 k give or take. Also a single cylinder with longer stroke to bore ratio is going to be the more economical in a bike.

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Old 03-14-2015, 12:25 AM   #6 (permalink)
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Quote:
Originally Posted by Old Mechanic View Post
I think it's more a function of bore to stroke ratio and gearing. Look at the redline on the bike in question The R3 is supposed to produce 41 HP out of a litte over 20 cubic inches.
I'd bet it revs to over 12k rpm, maybe even close to 14k, while the longer stroke engines will have a much lower rev limit, like 10 k give or take. Also a single cylinder with longer stroke to bore ratio is going to be the more economical in a bike.
Then, with higher torque at lower RPM, it's possible to run a taller gearing without much harm to throttle-responsiveness.
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Old 03-14-2015, 10:29 AM   #7 (permalink)
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Precisely.

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Old 10-28-2016, 06:07 AM   #8 (permalink)
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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..
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Old 11-02-2016, 07:09 AM   #9 (permalink)
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I was able to get slightly over 80 mpgUS on my combined highway commute with my R3 before changing the tires which gave 12% to my CBR250R when I put the Michelin Streets on it. If you want fuel economy then you want one of the Honda 300, 500, or 700cc world bikes.
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Old 11-17-2016, 08:27 AM   #10 (permalink)
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I think, all other factors being equal, your best economy is going to come from the bike with the largest cylinders turning at the slowest speed. That's just physics giving the advantages to the greatest volume with the least surface area, and time enough in the cylinder stroke to actually use up all the fuel.

Make the gearing changes to move the engine's torque peak (or the "island of efficiency," if you can find a BSFC map for the engine) to your usual cruising speed.

"All other factors being equal" is the limiting factor here, since bikes don't generally offer engine options in the same chassis.

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