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  #1  
Old 30 Aug 2010
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fuel consumption in different power modes

It looks like many new Adv bikes are coming with 2 or 3 power modes.

Never ridden one myself but I wonder if anyone's established whether fuel consumption varies much in these modes. After all, some drop power by 30%.
Could that mean 30% better economy? My impression is a low compression ratio and normal power (< 100hp/litre) often adds up to good mpg, carb or efi.

I imagine for overlanding after a while you'd put your 600cc+ bike on the lowest power mode.

Chris S
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Old 30 Aug 2010
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I hope someone has established the numbers. There is no reason these bikes shouldn't turn in 70 mpg at real world speeds (Ted Simons Jupiter was capable of this in 1973). If the modes are just fast acceleration/studpidly fast acceleration/Impress the journalist acceleration there is going to be a gap in the market for chips/patches with a proper economy mode.

Still, what do I care, the brick seems to do 30 mpg regardless, but it does have a fridge and somewhere to stow the gin

Andy
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  #3  
Old 31 Aug 2010
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I recently rode the new Ducati 1200S Multistrada. We tried the 3 power modes but never kept track of fuel economy. (we only got it for a day) But MCN (American magazine, not the UK Scandal sheet) did test the economy as part of their testing. In low power the Multi got 42 mpg (US gallons) which did not compute to the 15% improvement Ducati claimed in low power mode. I liked full power mode best, had the best drivability.

The BMW is most likely better, as they do seem to get fuel economy right.
No idea on the new Yamaha 1200 Tenere'.

I can't believe that about the best I can get on my DR650 Suzuki is 50 mpg (US gallons). Now that is a bike that would benefit from F.I. Seems even if I'm pooching along at 45 mph and never goose it ... it still doesn't get much above 50mpg. Head winds and deep sand and even panniers suck gas. Add a typically overloaded bike and your predicted range is shot.

I could take a 250 or 400 but I'm too old and too spoiled by the comforts of my DR. I love the 250's in technical stuff, sand, mud, rocks. I love the 70 mpg. But over all, as a day-in-day-out travel bike ... for me? No joy. Just have to pay the price and plan carefully regards range and attempted destinations.

Last edited by Mickey D; 1 Sep 2010 at 06:46.
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  #4  
Old 31 Aug 2010
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Compression

Quote:
Originally Posted by Chris Scott View Post
My impression is a low compression ratio and normal power (< 100hp/litre) often adds up to good mpg, carb or efi.
That I guess has more to do with the overlap of the valve timing (time that both inlet and exhaust valves are open). I expect there will be a correlation between compression and valve overlap. High compression and little overlap should result in best fuel economy.
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Old 31 Aug 2010
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42 US for the Ducati = 50.4 Imp. MPG or 17.8 km/litre. *

Looks pretty good to me seeing as a recent Brit mag came up with 37 Imp. MPG (30.8 US!) in high power for the Multistrada.
And they said the new Yamaha 1200 Tenere was worse! It does weigh over quarter of a tonne, but can that be possible?

Never thought of valve overlap; it does seem like a recipe for wasting fuel. Do most modern high-revving engines have more overlap then an old BSA 21 for example?

Even then, I've always thought an advantage of low comp for overlanding is an ability to run OK on low-octane fuel.

That's assuming you can't electronically retard the ignition as you can on some bikes since many years. Is that what a low power mode will be on these latest bikes? Or is it lots of things in the system from throttle to exhaust?

Chris S

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Old 31 Aug 2010
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Quote:
Originally Posted by Chris Scott View Post
Never thought of valve overlap; it does seem like a recipe for wasting fuel. Do most modern high-revving engines have more overlap then an old BSA 21 for example?
Old engines generally have less overlap.
I wouldn't say that increased overlap has to increase fuel-consumption. It might increase, but it can also decrease. Personally I think choosing the right cam-shaft is a very important task to fit the bike to your needs. I will soon test another camshaft with more overlap.


Quote:
Originally Posted by Chris Scott View Post
Even then, I've always thought an advantage of low comp for overlanding is an ability to run OK on low-octane fuel.
Yes, with low compression you can run low-octane fuel but the engine will not be efficient and it will use less fuel if you increase compression.
There is quite a few things you can do to keep compression up (and running lean) without getting problems. Newish bikes generally have higher compression then the old ones.
Increasing overlap will help you to run on low-octane fuel and it will also allow higher compression, nice!
A single-cylinder engine will suffer more then a multi-cylinder engine when it comes to low-octane.

Quote:
Originally Posted by Chris Scott View Post
That's assuming you can't electronically retard the ignition as you can on some bikes since many years. Is that what a low power mode will be on these latest bikes? Or is it lots of things in the system from throttle to exhaust?
Retarding the ignition will increase fuel-consumption. Best fuel-consumption (and power) is achieved when the ignition is a bit more retarded then where it's starts to knock. The way BMW has solved this is to install a knock-sensor, ignition is then adjusted based on the knock-sensor (and other parameters).
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Old 31 Aug 2010
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Hi Chris.

Do you mind me asking...What MPG did you get out of your Tenere XT660Z on your trip to Morocco.

Dazzer
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  #8  
Old 31 Aug 2010
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It's all here Daz, in excruciating detail:

XTZ660 Tenere review - fuel consumption data

A single-cylinder engine will suffer more then a multi-cylinder engine when it comes to low-octane.

I remember in the 1980s some singles ran terribly on Algerian fuel: my XT500 one time - and later a Honda XLM was much worse than 2nd gen. Teneres. I suspect fuel has got a bit better since then.

Chris
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Old 31 Aug 2010
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Thanks Chris

Nice to see that I'm not alone in logging the bike's fuel consumption on a trip.

Now don't set me off talking about Tyre wear


Dazzer
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Old 31 Aug 2010
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It's pretty impossible to factor in the most important variable though isnt it !!

Riding style !! You can get HUGE differences just on how smoothly you accelerate, if you have a heavy wrist, if you power through or roll the corners etc etc.

Back to the point Chriss, I think the manufactures promo brochures often have the average economies in the different modes. If you believe them that is !!
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