Better MPG

[noeligator]

On any bike I have ever owned, I always wanted a taller top gear. My 05 FZ6 spins around 5kRPM at 60 MPH.

I have changed out a countershaft (front) sprocket before to save the cash that the rear costs. I am looking to go a tooth up to a 17 or an 18 prior to stepping down a few teeth in the rear, but I am concerned with clearance of the larger front sprocket.

I have seen several owners here do the opposite for power, but I am looking to press the MPG envelope. Does anyone have any pearls of wisdom for me?

Thanks,
Mike

 

[Tailgate]

Mike, I hope somebody posts about this. Someday, I might do the same. I wonder how much increase MPG we could get, say, at 70MPH, where much of my riding hovers. And, we could always easily change the front sprocket back if we felt we needed to regain the normal acceleration. "HavBlue" has commented/done the math once on the reverse modification (lower gearing).

 

[BranNwebster]

I wonder if it would do anything for mileage. If you look at how much energy is required to push you and your bike down the road at 60 miles an hour if you change gear ratios wouldn't you be using about the same amount of energy just at a lower RPM?

 

[wolfc70]

I wonder if it would do anything for mileage. If you look at how much energy is required to push you and your bike down the road at 60 miles an hour if you change gear ratios wouldn't you be using about the same amount of energy just at a lower RPM?

It would drop the mileage a little. It takes more fuel to spin an engine faster due to increases in friction as rpms rise (I'm keeping it basic here). So dropping 1000 rpm at 70mph may yield a little better MPG. Dropping the revs too far will cause the bike to cruise out of it's powerband (decreased volumetric efficiency), then fuel usage would increase. I think a 500-1000 rpm drop at 70 mph would be ideal, it may increase MPG, but it will also get rid of the buzz in the bars.

 

[reiobard]

I wonder if it would do anything for mileage. If you look at how much energy is required to push you and your bike down the road at 60 miles an hour if you change gear ratios wouldn't you be using about the same amount of energy just at a lower RPM?

all the energy is used getting up to speed, but cruising is where the engine is using more gas than is needed to maintain speed just to keep the engine spinning and having available power for use.

 

[HavBlue]

Just a thought. if say 60mph is the target speed for the maximum effort on mpg and the bike is currently running 5,000rpm in top gear, the change to 17T could actually have an adverse effect at that speed while having a positive effect further up the scale. You will also note that while it may have a positive effect with a solo rider it could have a negative effect 2-up because the gearing will reduce the mechanical advantage at the lower speeds.

Please excuse the use of another bike but I have played with this much more on the Sporty. The Sporty has 3 available front sprockets which are 28T from the 883, 29T which is stock for the 1200 and 30T which is stock on the international models. With the stock 29T and while using 70mph as a target the bike had a best of 61mpg solo and 57mpg 2 up as it ran down the road at 2,900rpm. Switching to the 30T and again at 70mph the bike ran down the road at a bit over 2,500rpm and had a best of 63mpg solo and 60mpg 2 up but it was a real pain at lower speeds and roll on as you were constantly shifting both down and up. Running at a sustained 2,000rpm was forget it. The 28T offered awesome roll on, and ability to actually hold a sustained 2,000rpm in 5th solo or 2 up and at 70mph it was running down the road at 3,450 which is right at the maximum torque output for that engine. The result, the bike will pull 59mpg solo and just under 58 while 2 up and this is with combination riding where not all of it may be at 70 on the slab.

In general, the +1 will give you better fuel mileage but at what speed and at what cost in the overall scheme of your particular ride style.

 

[viper94bite]

To my understanding with most bikes you can usually go up or down a tooth in the front without having to have a different chain. I know some guys that went up a tooth on their zzrs and love it. Lower cruising rpms and I believe some got slightly better mileage. It is something I too would like to do with my fz6. It just is not on the top of my to do list.

 

[HavBlue]

To my understanding with most bikes you can usually go up or down a tooth in the front without having to have a different chain. I know some guys that went up a tooth on their zzrs and love it. Lower cruising rpms and I believe some got slightly better mileage. It is something I too would like to do with my fz6. It just is not on the top of my to do list.

With a cage gas mileage can become a real issue as 1mpg up or down can be say 20 miles on a tank where the tank is twenty gallons. On a bike that same 1mpg will net you maybe 4 miles and to what end in terms of relative performance? if you manage to get 2mpg better you may gain 8 miles on the run but to what end. Taking this a bit further, if you miss putting back the right amount of fuel (meaning you missed the starting level) by as little as a tenth of a gallon you will change your figures by 2mpg or a bit more either positive or negative. This is why I don't see changing the front sprocket for gas mileage as being all that great an idea as the difference in terms of mileage isn't real big.

 

[noeligator]

A continuously variable transmission would be ideal here with regard to reaching the powerband and staying there, but it isn't an option. I tend to double shift coming up in traffic as none of the big iron thingys has our power. Ultimately I am looking to broaden the range on the transmission; primarilly to reduce RPMs, and in doing so, increase gas mileage.

I am having a hard time filling up my TDI VW at $4.89/gallon for deisel with its 45 MPG. I stepped up from an 02 Ninja 250 with 68 MPG to the fz6 with what I thought was a realistic goal of 55 MPG. I commute over a 6 mile one way route that includes a stop light, a flightline gate, an air station main gate, and a yeild sign. Surely there is a way to get a fuel injected 600cc motorcycle to get 55 MPG under reasonable riding conditions, consistently. Gearing seems to be the $20 fix to that end.

 

[taki]

i commute 60 miles round trip, and have been averaging 51-52 mpg on stock gearing. My commute is at speeds between 45-70 mph. for your 6 mile commute, i suspect youre in some stop and go traffic, and thats going to hurt your goal of 55 mpg.

i considered changing out a sprocket, but im very happy with my mpgs (coming from a dl650 which i could only get 46-48 mpg from)...

 

[Hellgate]

Okay witness the Hellgate thought process here...most often I'm wrong...

One of the problems with the FZ is at 60 mph the things is spinning at 5,000 rpm. Soooo....our displacement is 599cc, so each minute we fill our displacement 2,500 times (four stroke remember?). That gives us a total volume filled per minute of - 1,497,500cc - a lot. This assumes a contant throttle.

Lets look at a 1,000cc bike that lopes at 4,200 rpm. 2,100 X 998cc = 2,095,800cc.

So where does this leave us???

I think the key to getting better mileage is to make the engine spin slower at a given speed. A one tooth increase is about a 6.25% increase in final gearing, right? So...I would think that one's mileage would go up about the same amount, or from 45mpg to 47.5mpg-ish.

Thoughts???

 

[mikebike]

I knew a guy

who recently rode 560 miles at speeds averaging 80-90 and got 52mpg

it was primarily 2 and 4 lane roads with about 90 miles of pure interstate (as he tells it)

I ....ahem....he said he would not drop a tooth when stock yields that kind of mpg

 

[Bowhunter]

Id love to get 52 MPG!! My current truck gets 7 mpg. Cant wait till I start driving the fz6!

 

[mdr]

Just a thought. if say 60mph is the target speed for the maximum effort on mpg and the bike is currently running 5,000rpm in top gear, the change to 17T could actually have an adverse effect at that speed while having a positive effect further up the scale. You will also note that while it may have a positive effect with a solo rider it could have a negative effect 2-up because the gearing will reduce the mechanical advantage at the lower speeds.

Please excuse the use of another bike but I have played with this much more on the Sporty. The Sporty has 3 available front sprockets which are 28T from the 883, 29T which is stock for the 1200 and 30T which is stock on the international models. With the stock 29T and while using 70mph as a target the bike had a best of 61mpg solo and 57mpg 2 up as it ran down the road at 2,900rpm. Switching to the 30T and again at 70mph the bike ran down the road at a bit over 2,500rpm and had a best of 63mpg solo and 60mpg 2 up but it was a real pain at lower speeds and roll on as you were constantly shifting both down and up. Running at a sustained 2,000rpm was forget it. The 28T offered awesome roll on, and ability to actually hold a sustained 2,000rpm in 5th solo or 2 up and at 70mph it was running down the road at 3,450 which is right at the maximum torque output for that engine. The result, the bike will pull 59mpg solo and just under 58 while 2 up and this is with combination riding where not all of it may be at 70 on the slab.

In general, the +1 will give you better fuel mileage but at what speed and at what cost in the overall scheme of your particular ride style.

Couldn't have said it better than HavBlue did. :thumbup: I toyed with the idea of going +1 but I sometimes cruise pretty leisurely on Virginia's more scenic backroads (4000 RPM) and I was afraid it would lead to a marked increase in the amount of shifting down to 5th or even 4th to make a brisk pass. I'm finding the stock gearing to be a pretty decent compromise and any increase from current 55 mpg is going to be minimal - just do the math like HavBlue suggests.

 

[HavBlue]

A continuously variable transmission would be ideal here with regard to reaching the powerband and staying there, but it isn't an option. I tend to double shift coming up in traffic as none of the big iron thingys has our power. Ultimately I am looking to broaden the range on the transmission; primarilly to reduce RPMs, and in doing so, increase gas mileage.

I am having a hard time filling up my TDI VW at $4.89/gallon for deisel with its 45 MPG. I stepped up from an 02 Ninja 250 with 68 MPG to the fz6 with what I thought was a realistic goal of 55 MPG. I commute over a 6 mile one way route that includes a stop light, a flightline gate, an air station main gate, and a yeild sign. Surely there is a way to get a fuel injected 600cc motorcycle to get 55 MPG under reasonable riding conditions, consistently. Gearing seems to be the $20 fix to that end.

Read what you have written and then understand the conditions you have just described. Going up 1 under those conditions will likely hurt you more that help. You are riding a mere 6 miles and there are more than a few places along the way you are slowing down and speeding up which means you will be in the lower end of the power band. Now, you will reduce the gearing to a final drive of 2.70:1 and expect better results than you had at 2.87:1. I would like to know how this turns out as it would appear, based on the run profile, -1 may actually do better as the slower speeds can take advantage of the gearing. Mine will get 55 but on the tour at speed.

 

[Avalon786]

Speaking of MPG is it better to shift through all the gears or to stay in like 3rd or 4th for city riding?

 

[HavBlue]

Okay witness the Hellgate thought process here...most often I'm wrong...

One of the problems with the FZ is at 60 mph the things is spinning at 5,000 rpm. Soooo....our displacement is 599cc, so each minute we fill our displacement 2,500 times (four stroke remember?). That gives us a total volume filled per minute of - 1,497,500cc - a lot. This assumes a contant throttle.

Lets look at a 1,000cc bike that lopes at 4,200 rpm. 2,100 X 998cc = 2,095,800cc.

So where does this leave us???

I think the key to getting better mileage is to make the engine spin slower at a given speed. A one tooth increase is about a 6.25% increase in final gearing, right? So...I would think that one's mileage would go up about the same amount, or from 45mpg to 47.5mpg-ish.

Thoughts???

That's pretty good Pete but spinning slower can lead to it's own share of problems. An engine is merely the force behind motion and the respective drag caused by any particular vehicle can have an adverse effect on that force so slowing the engine down could actually make things harder to overcome. If you drive my wifes car at a sustained 60-65mph it will get roughly 25.5mpg. Averaging 68-72mph along the same daily run the car will get almost 28mpg. The Lambo Countach will get about 11mpg trying to maintain 65mph yet it will get almost 20mpg up near the century mark on a sustained run. You can get to a point the lower rpm will actually cause the engine to work harder in an effort to maintain the same speed however, with any particular gearing and while actually increasing rpm it gets easier for the engine to overcome drag hence an increase in fuel efficiency.

Try this, get out on a flat, straight piece of road with no relative wind in a cage or on a bike and run that thing up to about 85mph then throw it into neutral or clutch it and watch that speedo really close. As it slows down it will, for a brief moment, almost stop at a point on the way down. This is the optimum speed and while that speed on most modern cages or bikes will likely be above the speed limit this is your target speed to match aerodynamics and drag.

 

[08fz6]

what i was thinking was possibly what maybe saving 10 cents per fill up so it will take you what 40,000 miles to make back the money you paid for that sprocket?

 

[HavBlue]

what i was thinking was possibly what maybe saving 10 cents per fill up so it will take you what 40,000 miles to make back the money you paid for that sprocket?

Very good thought...

 

[sideslider]

Speaking of MPG is it better to shift through all the gears or to stay in like 3rd or 4th for city riding?

I wonder this as well... I have heard that 4k rpm is borderline lugging the engine and is not too good for the bike.. anyone?