Adventure Bike Rider Forum

Out on the bikes the other day, son on the XT660Z and me on the S10, so same mileage and speed.
Fuel consumption was Xt660Z 29.6 Km/ltr and the S10 23.7 Km/Ltr.
Assuming that the different engines have a similar efficiency, is the 6 Km/litre difference in fuel consumption due to the 60 Kg difference in the weight carried, or maybe the way the bikes are ridden?
Data attached.

also how the power is generated, braking and accel energy, tyres loads of small things can add up

steve

There is a whole host of things that affect fuel consumption - for example from practical stuff like weight of the rider :woohoo: through to technical stuff like engine design and millions of things in between.

However in this instance I would suspect the biggest influence to be the way the figures were measured. For a good comparison you would need a lot more than just one "snap shot" figure.

I would say Davecon is right.

I have been looking at fuelly.com and both of you have beat the average for both bikes by a long way. So you need to get some more data to level out fuelling inconsistencies.

I think 10 tanks will start to give you a better picture. Then when you have that done and established a baseline for each of you on your own bike you would need to go do it all again on each others bikes to run out the different riding styles.

But why is there such a difference I can't say with any authority, but weight will be a big factor, if you have a lot of speed changes. Pity we can't get COG figures for bikes, because it would be interesting to see if the baby Ten has a better aero than the S10. I would have thought the S10 is more streamlined, but maybe not.

In these days of speed cameras I am becoming increasing in the game of getting the best mpg I can.

My current NC750x.
http://www.fuelly.com/motorcycle/honda/ ... nge/319745

My old XT660z.
http://www.fuelly.com/motorcycle/yamaha ... nge/165237

i think it is mostly down to fuelling set up.

a racing bike will always use more than eg a commuter (same capacity same use mode)

its how the power band is set out, fuel input (jetting/injectors), timing etc, is set up.

more power needed = more fuel inputted

identical engines can be tuned differently.
high rev and more fuel input, or more torquey at lower revs.

the same capacity engine can have a different engine layout, or different bore stroke.
a under square piston will be set up to rev more than an over square piston setup, but use more fuel.


i have found that fuel consumption has very little to do with weight or aerodynamics.

of course, there is also air filter condition etc and tune and wear

If aerodynamics didn't matter so much we would not see so much effort but into developing cars with lower cd figures.

Wind resistance is the biggest factor in fuel consumption. Wind resistance doubles in relation to speed.

Just look at a Prius for example Toyota spent a lot of time even making sure the wheel trims minimise aero drag.

Look on some of the economy website you will see the massive difference aero make to cars and bikes. With people making sleak shells to but around motorbikes.

Like this https://www.wired.com/2010/01/streamlined-honda-innova/

or on bicycles you have velomobiles....capable of much higher average speeds for the same power, also an efficiency measurement.

http://www.velomobiles.co.uk

650ginge wrote:I would say Davecon is right.

I have been looking at fuelly.com and both of you have beat the average for both bikes by a long way. So you need to get some more data to level out fuelling inconsistencies.

I think 10 tanks will start to give you a better picture. Then when you have that done and established a baseline for each of you on your own bike you would need to go do it all again on each others bikes to run out the different riding styles.

But why is there such a difference I can't say with any authority, but weight will be a big factor, if you have a lot of speed changes. Pity we can't get COG figures for bikes, because it would be interesting to see if the baby Ten has a better aero than the S10. I would have thought the S10 is more streamlined, but maybe not.

In these days of speed cameras I am becoming increasing in the game of getting the best mpg I can.

My current NC750x.
http://www.fuelly.com/motorcycle/honda/ ... nge/319745

My old XT660z.
http://www.fuelly.com/motorcycle/yamaha ... nge/165237

We were not going very fast, 70 MPH on the motorway and not much more than 50 MPH on the minor roads.

Strangely,sometimes more power can prove more efficient? A few years back,myself and two friends went up to N.Wales for a weekend trip. I was on my Daytona Super3,one friend on a VTR1000 Firestorm,and one on an ER6. When we got up there,we filled up to calculate the mpg. Even though the Daytona was the heaviest,and most powerful,it came top..
About 140 odd miles covered.
Daytona 63mpg
VTR1000 61
ER6 59

650ginge wrote:If aerodynamics didn't matter so much we would not see so much effort but into developing cars with lower cd figures.

Wind resistance is the biggest factor in fuel consumption. Wind resistance doubles in relation to speed.

Wind resistance goes up with the square of the increase in speed (half x density of air x velocity squared).
The biggest factor is wind resistance assuming you are travelling over (approximately) 80mph and constantly.
All the quotes about CD figures and "slippery aerodynamic cars" are, on the whole, a marketing ploy for anything except for high end supercars.
I remember when they first brought out the Rover SD1 (low sleek saloon car), it had the same fuel consumption as a the similar engined Range Rover (side of a house) if my memory serves me rite :laugh:
Aerodynamics come into play on bicycles and other human powered vehicles because we are so puny as engines usually with nothing in reserve and needing all the help we can get

650ginge wrote:If aerodynamics didn't matter so much we would not see so much effort but into developing cars with lower cd figures.

Wind resistance is the biggest factor in fuel consumption. Wind resistance doubles in relation to speed.

Just look at a Prius for example Toyota spent a lot of time even making sure the wheel trims minimise aero drag.

Look on some of the economy website you will see the massive difference aero make to cars and bikes. With people making sleak shells to but around motorbikes.

Like this https://www.wired.com/2010/01/streamlined-honda-innova/

or on bicycles you have velomobiles....capable of much higher average speeds for the same power, also an efficiency measurement.

http://www.velomobiles.co.uk

at high speeds, aerodynamics are going to make a big difference, especially as you approach 200mph, when wind force increases dramatically.
at low speeds and low fuel or energy input, then every bit of wind deflection counts.
but for the same speeds in the real world (70 + 50 quoted now) I don't believe there is much difference between a faired or naked. .. just my personal observations.



sorry, did not read DaveCon's reply .... and yes its a marketing ploy, innit.