[Stromin'Nroman]

I'm talking here about a real 70mph (76 indicated) as opposed to a real 75mph (82 indicated) with stock gearing although I noticed no significant difference when trying a 16T front sprocket.

In states with a 70mph speed limit, which I do, my fuel consumption is in the 40s with a touring windshield and luggage. I got a low of 44mpg and a high of 49mpg coming through Iowa with its 70mph speed limit. Also, oil consumption is practically non existent. Illinois's 65mph speed limit is only slightly better.

In 75mph states in the same configuration, including flat Nebraska, I got a low of 35mpg and a high of 40mpg and enough oil mist made it through the breather to require topping off every 1000 miles or so. There is an out of proportion price to pay for that extra 5mph.

Around home with a sport windshield and mixed street and highway traffic and an Interstate speed limit of 55mph, where I usually do 60mph, I get about 60mpg. Pushing the air out of the way takes a toll in mileage.

Thanks for the info, I thought my mileage was high on a recent trip along rural secondary roads with long stretches of 60 mph or less (55-60 mpg). My wife's Harley did not similarly benefit from reduced speeds, it got 50 mpg no matter the speed.

 

[Malikenya]

I take it the other way...especially if I need to get somewhere. I don't see much difference between 75 and 85 mph. Maybe a few mpg's, but its still mid 30's. So that 15 mph difference makes it marginally worth it...I don't enjoy slab riding so the times I'm on the highway, I'm in a "hurry" to get somewhere or to get off an do the real riding.

Back of the envelope approximations follow:
15 mph (85 vs. 70 mph) over a 500 mile day is an hour and 15 minutes.
10 mpg (45 vs. 35 MPG) over a 500 mile day is 3.2 gallons @ $3.50 = $11.20 (and maybe an extra fuel stop so subtract 15 min)

So...is it worth $11 to shave an hour of slab riding?
Day 1: maybe not...
Day 3+: yes, especially if your mileage is more than 500.

Other variables not considered:fineprint:...traffic, time of day (i.e. heat, fatigue, etc.), tire wear at higher speeds, risk of tickets, etc.

 

[greywolf]

Thanks. So 70-75mph seems to be the conversion area. It may be where trail vortex forces start being established. It will be interesting to see how the different aerodynamics of the 2012 bike work.

 

[rjwinz]

Interesting point. I've always thought it was the revs. Above 6K the mileage starts to drop on the DL650. A lot of folks commented on this over the years. High speed traveling was one of the few reasons to consider the 1000. I don't need to travel over 70mph anymore.

 

[jokermtb]

Pushing the air out of the way takes a toll in mileage.

Especially, with something as non-slippery as a Strom.

 

[mark444]

.......with stock gearing although I noticed no significant difference when trying a 16T front sprocket.

Interesting..........also the $$$ vs. time analysis. So Grey, if I took a 1,000 mile trip, the 16T sprocket would not make an impact (revs = mental fatique, and fuel savings) enough to warrant the switch??? Just axing.........

 

[Improperly Torqued]

Back of the envelope approximations follow:
15 mph (85 vs. 70 mph) over a 500 mile day is an hour and 15 minutes.
10 mpg (45 vs. 35 MPG) over a 500 mile day is 3.2 gallons @ $3.50 = $11.20 (and maybe an extra fuel stop so subtract 15 min)

Great analysis! I love real data and hard numbers. Interesting to see the direct tradeoff of time against dollars.

To put a slightly different spin on it, using Pat's numbers, one could calculate exactly how much farther one could go if one need to stretch out a tank -- say, in central Montana on secondary roads -- by slowing down.

 

[greywolf]

Interesting..........also the $$$ vs. time analysis. So Grey, if I took a 1,000 mile trip, the 16T sprocket would not make an impact (revs = mental fatique, and fuel savings) enough to warrant the switch??? Just axing.........

It didn't for me but it's cheap enough to try it and see. I don't get all the talk about 5500rpm being smoother than 6000rpm. I could do 6000rpm all day, and have. I noticed no improvement in fuel economy which didn't surprise me because the Wee makes more horsepower at 6000rpm than at 5500rpm so uses less throttle to hold the same speed and others have posted no change in their travels. What I did notice was the lack of punch at city speeds and having to downshift an extra gear to pass in the country.

 

[OydnaR]

Pushing the air out of the way takes a toll in mileage.

High speed traveling was one of the few reasons to consider the 1000.

my lil nekid SV650 got milage very consistent with Greywolf's experience with the wee, most of the time in the mid to upper 40's, but I could get 60 if I really wanted too, worse was steady high speed highway, as low as 32 in cold weather

cause I wanted my replacement to be oriented for long distance highway to get to a destination quickly then explore and take my time, maybe slab it back home too.

best milage I ever get with my Vee is about 45, but worse(except for a couple tanks during breakin) is only 41, maintaining a 80mph (gps) pace

 

[greywolf]

Yep. Really get on some speed and the Vee mileage is as good as the Wee.

 

[p38arover]

I'm talking here about a real 70mph (76 indicated) as opposed to a real 75mph (82 indicated) with stock gearing although I noticed no significant difference when trying a 16T front sprocket.

In states with a 70mph speed limit, which I do, my fuel consumption is in the 40s with a touring windshield and luggage. I got a low of 44mpg and a high of 49mpg coming through Iowa with its 70mph speed limit. Also, oil consumption is practically non existent. Illinois's 65mph speed limit is only slightly better.

In 75mph states in the same configuration, including flat Nebraska, I got a low of 35mpg and a high of 40mpg and enough oil mist made it through the breather to require topping off every 1000 miles or so. There is an out of proportion price to pay for that extra 5mph.

Around home with a sport windshield and mixed street and highway traffic and an Interstate speed limit of 55mph, where I usually do 60mph, I get about 60mpg. Pushing the air out of the way takes a toll in mileage.

Converting that into Rest of World figures
60mph ~ 60mpg ---- 96km/h ~ 3.92 l/100km
70mph ~ 44-49mpg ---- 112 km/h ~ 5.35 - 4.8 l/100km
75mph ~ 30-45mpg ---- 120 k/h ~ 7.84 - 5.23 l/100km

My last long distance trip (800km) I averaged 4.5 l/100km but that included highway and secondary roads and bush tracks.

 

[dancer]

So, GW, going through Iowa you showed about a 10% variation in fuel economy. What accounted for it, do you think? Hills are not really a problem there. Drafting? Wind? Big lunch? :mrgreen:

 

[Improperly Torqued]

I don't get all the talk about 5500rpm being smoother than 6000rpm. I could do 6000rpm all day, and have.

+1. I truly do not understand some people's fixation with sprocket teeth. This is a small engine that loves to spin and, while plenty strong enough at high RPM, is most definitely lacking in low-end torque. I simply cannot imagine why you'd want cripple it further at low RPM.

Like you, I've spent entire days in the open west at 6k RPM, and both I and the bike liked it just fine.

 

[greywolf]

So, GW, going through Iowa you showed about a 10% variation in fuel economy. What accounted for it, do you think? Hills are not really a problem there. Drafting? Wind? Big lunch? :mrgreen:

There were a lot of sections near major cities and in construction areas with lower speed limits. Also, one gas stop in Iowa had some mileage done in Nebraska.

 

[Spartan]

I'm doing this from the top of my head so don't beat me if I'm wrong.....

Theoretically, one should have lower pumping losses and reduced friction at lower rpm. That is true more on paper then in the field. More often then not, it's so small that it can be eaten up by aerodynamic variables.

As for the difference in consumption between 70 and 75, frankly, the Strom is a aerodynamic brick. Since air resistance (drag) increases as the square of velocity, a 5 mph increase can have large effect...on a brick. In an average car, there is about a 6% difference in consumption between 70 and 75mph BUT the car is far more aerodynamic then a bike. A car may have a drag coefficient of .35 and a bike probably more like 1. Given triple the drag, it could be as much as 18%.

Graywolfs 44 to 49mpg can easily turn into 36 to 40 mpg.

How can we get it back? Wear tighter underwear or remove one's head to reduce the frontal area.

That's it, I used up all my smarts for the week.



P.S. Please don't confuse frontal area with drag coefficient. We are comparing a car change of consumption based on it's drag coefficient by it's frontal area and ditto for a bike.

 

[sd2ftl]

single plug / dual plug

Excellent information regarding how speed affects mpg. I noticed many responders are riding 2007 & newer models.

My 2006 (single plug per cyl.) wee never achieved such high mileage as previously mentioned. A steady 70-75 (indicated) mph-gets me around 52 mpg @ best, with a pair of pelicans & a topcase.

 

[Midnullarbor]

.
Shame, Spartan !
Surely you meant the air resistance (drag) increases with the "square" of velocity - in other words, the fuel burn per mile increases with the "square" of the speed.

All other things being equal, the fuel consumption would rise 15% for for the 70 up to 75 mph increase.
But, as you say, they aren't quite equal : it's a whisker under the square for the drag ; and the transmission & tyre frictional losses are closer to linear in their increase ; pumping losses a bit more than linear ; and though I haven't seen the "specific" fuel efficiency curves for the 650 engine, I'd be willing to bet that the engine cruising at 70 is still in the section of "rising thermodynamic efficiency" as you open the throttle a bit more (for holding 75 mph) - which will partly compensate for the higher friction/drag effects.

The new Glee-Strom may well have a slightly narrower and more aerodynamic frontal section, but it will still have the same old stubby turbulence-causing rear where the majority of wind-drag is generated [just as occurs in all motorbikes not born for the salt flats]. And the same stubby turbulence-causing rider, like me. (And I, for one, don't intend to abate that effect by stripping down to a bathing-costume and "planking" on my Suzuki 650, a la the Vincent 1000.)

That's why I am rather incredulous about the claim of 10% better fuel economy for the new Glee-Strom. By the time you subtract the same friction in transmission & wheels (since those factors are unchanged for the new model), and allow for much-the-same (since the combined rider-and-bike gives similar frontal area and non-laminar-flow sides & rear) air drag, then the result would require an engine thermodynamic efficiency gain in the region of 12 - 15%. For general riding usage, that's a helluva lot, for an engine that was already pretty good before the "upgrade".

Most likely, Suzuki has found a particular circumstance [say, cruising at 43 mph] where the 10% improvement is demonstrably true - and has let the Advertizing people run with that, to imply a more general benefit.
Regardless, even any smaller "real world" improvements are good, especially as (if the published power curve is indisputable) Suzuki has achieved the excellent result of improving the 650's torque at low revs [say below 5000] AND at high revs [say above 8000].
.

 

[Malikenya]

Interesting point. I've always thought it was the revs. Above 6K the mileage starts to drop on the DL650. A lot of folks commented on this over the years. High speed traveling was one of the few reasons to consider the 1000. I don't need to travel over 70mph anymore.

I think its more about power loading:fineprint:...or as often measured/indicated in a carb context, manifold pressure.

Bottom line is that for a given situation (speed, wind, hills, etc.) there is a specific power required. At all speeds below max, that is a percentage of power available. Power available (to the ground) varies only with RPM (which varies with gearing). Best fuel efficiency is theoretically reached when the power loading is the lowest. Which is often simplified to be the point of maximum excess power (i.e. when Pavail - Preq is largest). Initially this appears to be at the higher rpm, since it is capable of making more power (> Pavail) and Preq is held constant. But...:headbang:

As already pointed out, pumping losses go up with RPM too so the efficiency of creating that power goes down rapidly once the flow starts compressing (it is said to be "choked" at the point where the local air speeds approach the speed of sound). I don't think you'll see much difference in pumping losses between 5500 and 6000 rpm since it is still a long way from is designed red line and well below peak HP, but there is a cost to that 500 rpm. How much? You would have to measure/calculate the fuel burn at a given rpm as a function of HP to nail it. At zero load (neutral) 6000 rpms will burn more than 5500. At whatever HP the power curve says is the max made at 5500, 6000 will be more efficient (lower power loading). The curves cross at some point, the question is where. The real question is which burns more at the 25-30HP (WAG) loading required to maintain 70mph.

All that to say: Could go either way and probably isn't a huge difference...:beatnik: :green_lol: :biggrinjester:

So, GW, going through Iowa you showed about a 10% variation in fuel economy. What accounted for it, do you think? Hills are not really a problem there. Drafting? Wind? Big lunch? :mrgreen:

Fuel quality from one fill up to the next can vary that much too.

 

[greywolf]

Another variable in mileage calculation is how much the tank is filled. Filling to exactly the same amount just doesn't happen.