Gas mileage king?

[garyahouse]

I was just doing some research about gas mileage online. On one of the websites I checked out (CLICKY), they were talking about the gas mileage of three bikes they were testing. it said that the new Goldwing was getting about 33 1/2 and the Beemer 1600 LT was getting about 35 mpg. Now I know that the Beemer is about 100 pounds more than the FJR, and the Goldwing is another 150 above the BMW. This would certainly account for SOME difference in gas mileage. But it seems a little odd to me. I routinely get 44 with my 05 FJR. I've read that some of you fellers are getting even more.

Here's what I don't understand. The FJR makes more horsepower than either of these two bikes, and is a decidedly more sport oriented power curve. Why is there such a difference in gas mileage? It's not too often that ya get to have your cake and eat it too. But it seems like we've got the best of both worlds: power and gas mileage. From all I've read about the two categories of performance and economy, this is a really pleasant surprise.

What's up with that?

Gary

darksider #44

 

[SkooterG]

Weight and primarily Air resistance.

 

[frankenfeejeer]

My momma used to say, "Never look a gift horse in the mouth."

Not really sure what the hell it means, but it seems to apply here!!

 

[Bungie]

Weight and primarily Air resistance.

Mostly the latter. Weight really only has affect of economy when constantly starting and stopping. On the hwy, it's actually a beneficial thing. Physics of inertia dont'cha know.

 

[odot]

garyahouse.....when are you going to come out and tell us that you are gay? We don't have a problem with it. Well, maybe porchekiller does....but the majority of us don't care.

 

[supertankerm60a3]

There is the loss of the internal friction created by the extra 2 cylinders. It takes more energy to spin the 6 and if the wing predates the 6 it also (probably) predates fuel injection. There is also the cross section to consider when figuring the aerodynamic co-efficient, ours is much smaller.

 

[TomInPA]

There is the loss of the internal friction created by the extra 2 cylinders. It takes more energy to spin the 6 and if the wing predates the 6 it also (probably) predates fuel injection. There is also the cross section to consider when figuring the aerodynamic co-efficient, ours is much smaller.

By "ours" you mean the bike? Cause I can tell you from the RTEs I've gone to, it's not the riders.

 

[garyahouse]

Just as a matter of clarification, I certainly understand that the FJR would get better gas mileage... being that it has less weight to haul, but my issue was how MUCH better. Just seemed like the two bikes I mentioned got awful mileage compared to the FJR.

While I'm at it, I'm going to have to disagree with you Bungie. Sorry bout that.You say that weight is a beneficial thing once yer up to speed due to inertia. To imply that weight doesn't affect gas mileage goes against the laws of physics. Consider for example, my Toyota Hybrid. It has a huge gas mileage meter right where most cars have a tachometer. It displays instantaneous gas mileage and is extremely accurate. At 60, for example, when I'm traveling alone, I get about 44 mpg on level ground with no prevailing wind. However, when i have a car full of adults, it will only get 38 or so. The only difference is weight. It takes more power to move more weight, plain and simple.

I would agree with Scoot's comments about weight and the drag coefficient, and when ya combine that with Tanker's comments about the extra losses due to 6 cylinders vs. 4, that might explain it. Come to think of it, In the automobile world, there's a reason that 4 cylinders get better mileage than 6 cylinders. However, the diff in a typical car that offers both engines might be 2 or 3 mpg. We all know this. Just seems like a huge difference between the Wing, the Beemer, and the FJR... to me.

Gary

darksider #44

 

[Fred W]

Weight effects the rolling resistance of the tires, even on the flat. It also requires much more power to haul weight up hills. Any inertial advantage if the down hill side is small in comparison. Increased weight is never an advantage in mpgs.

One big advantage the FJR has over the other two is that it has a smaller engine. Less displacement results in less pumping losses in the engine. It does make good horsepower at higher rpms, but when you are just cruising along can deliver better fuel economy than a larger, higher torque engine. FWIW, I have ridden my FJR and only got 32-33 mpgs. Let's just say that we weren't "just cruising along".

The FJR is hardly a mileage "king". If one were to look at fuel mileage alone, it would be hard to even justify riding one. Low to mid 40 mpg on a 650 lb., 2 person conveyance is hardly earthshaking. The way to achieve higher mpgs (without the use of electric power storage) is to use the smallest possible engine for the application, and gear it as high as possible, so the engine is running at its highest efficiency more of the time. But that is a recipe for a truly boring ride.

Though now defunct (thanks to GM) the SAAB auto engineers had a pretty good idea, building small, relatively low compression 4 cylinder engines (most were only 2 liters, not much bigger than an Old Wing's) and then using forced induction (turbochargers) to effectively increase displacement and boost engine torque only when required. We own several of the later model "sport sedans" in our family. With the higher pressure turbos they are a fun car to drive, with 221 ft.lbs torque at full boost. They were relatively low rpm engines so the horsepower was a fairly mundane 210, but take my word for it, torque is where the fun is. And with merely a reprogrammed ECU boost control, and higher octane fuel, you could increase the torque even higher, at the risk of reducing the engine longevity. Even with a curb weight of over a ton and a half, and multiple passengers onboard, those cars routinely deliver 33-34 mpgs if driven with a light foot.

 

[Bungie]

Every time I make that statement about weight...

I'm not saying weight enhances gas mileage, I'm saying it's not as detrimental as most people think. At least as not near as bad as poor aerodynamics.

Case in point since were spitting out examples.

My FJR typically gets 19km/l (by the way, measuring consumption this way is considerably more accurate than mpg. Just don't get my started on L/100km shit!)

My CBR250R typically gets 28km/l.

Both real world taken over the past 18 months.

My FJR weighs close to double the CBR and has over 6 times the horsepower. Yet manages a very respectable showing in the comparison. If I doubled the weight of the CBR, yes, consumption would drop in steady state cruising but not by much. Conversely, if I filled my FJR tires with helium and cut the weight in half (LOL!) consumption would decrease somewhat, but not substantially under the same conditions.

Stay with me here...

Now, leave the weight as they are. Bikes are aerodynamic slugs. If I 'tuck' on the CBR, my consumption goes way down up to 33km/L (over 100mpg!). The point is aerodynamics is a MUCH bigger factor than weight is.

Now all that being said, if you modify your driving/riding techniques, you can make that weight work for you. Especially if you live in hilly country. Read up and Pulse & Glide. Weight dramatically increases glide potential. If I'm going along at 65mph and pull the clutch in on the FJR, and let it coast down to 55mph, the distance it uses is MUCH longer than the same experiment on the CBR. The difference is weight (inertia). If I do the same in my car (which has FAR better aero's than a bike) and weighs 5 or 6 times the FJR does, it will glide under the same conditions 2x farther then the bikes will.

Their is a reason the hyper-mile competiters like Craig Vetters guys don't go nuts trying to lower weight, no, they spend all their efforts on aerodynamics and minimizing other frictional losses.

Weight only has a huge affect during speed changes. Not steady state cruising.

 

[Fred W]

My FJR typically gets 19km/l (by the way, measuring consumption this way is considerably more accurate than mpg.

Wait, what's that? How is 19 km/l any more accurate than 44.7 mpg? Not understanding that one.

Technically since 1 km/l is equal to more than 2 mpg (2.35215 to be exact) the mpg scale would seem to be a finer one.

As for the inertia thing, yes you will be able to glide further, but the expense of getting that weight up the hill to begin with overrides and savings on the glide. That is the point. Plus there is the increased frictional losses of having to hold that weight up against gravity.

Also, aerodynamics is huge, as you say, especially more so as speed increases. The wind resistance increments at a log rate. OTOH, if you only wanted to travel at walking speed, guess how important those aerodynamics are.

 

[Bungie]

'Pissing match' over. I'm sick of every forum (not just this one) turning every convo into some sort of dick swinging contest.

See ya in the spring!

 

[Redfish Hunter]

(Avoiding the pissing match!)

On our little bike trip this fall we had almost a full day of riding the Natchez Trace at 50-54 mph. Our #'s were:

Harley 110 inch w/trailer 38 mpg

Goldwing 1800 44 mpg

FJR w/PC-V 50 mpg

ST1300 (stock) 51.9 mpg

These are all calculated, not going by the bike computer readouts. The FJR and the ST are normally much closer in mpg. In fact when we are in the mountains the FJR usually gets very slightly better than my ST. At 55 mph the FJR and the ST turn exactly the same RPMs. The FJR, the ST and the GoldWing all dropped 1-2 mpg in the mountains.

With the PC-V installed but the O2 sensor still connected, the FJR and the ST are within a couple hundredths of a mpg down in Flatlandistan.

Here is my take, and I think we are all partially correct. The weight issue has greater effect in stop and go traffic and climbing hills. The aerodynamics play a greater role at higher speed. The # of cylinders has less of an effect than the efficiency of the engine. If less cylinders were the answer, the Harley would be more efficient. It never has been even without its trailer.

 

[Fred W]

Hmmm, I guess that was directed at me. I didn't realize we were having a "pissing match", just thought it was just a discussion.

 

[MCRIDER007]

There was a big discussion in one of my bike magazines several years ago and the author was claiming that rolling resistance (tires, bearings, engine friction) had a linear increase in resistance as the speed increased but air resistance increased at a rate equal to the square of the speed (4 times the resistance at twice the speed). He claimed that at 10 mph it only took 10 percent of the HP (required to maintain that speed) to overcome air resistance but at 60 mph it took 90 percent of the HP to overcome air resistance. If these numbers are anywhere close to being accurate than weight plays a big factor at very slow speeds but a very small factor at highway speeds.....which I think everyone generally agrees with, the only question is how much.

 

[Bounce]

1998 GL1500SE (carbs where the back venturi open up above about 60mph)... worst was 17mpg (solo riding).

 

[garyahouse]

Hallelujah. That was seriously productive, and true to our usual forum bantering, there's always a dogpile looming on the fringes of any conversation we get into.

Bounce (Edit) Bungie, I appreciate this statement that you made:

"I'm not saying weight enhances gas mileage, I'm saying it's not as detrimental as most people think. At least as not near as bad as poor aerodynamics." Add to that Fred W's and Mcrider's comments about aerodynamics and it all begins to make sense. I recall reading in the past how drag coefficient from air resistance is not linear. That is, the faster you go, the more of a factor it becomes. I forget the exact numbers, but going 200 takes a lot more power than going 150... as compared to how much more power it takes to go 60 than it does only 10... though the diff is 50 mph in both cases.

Bungie, you spoke of pulse and glide. I've read a good amount of that, and utilize it on a regular basis -- as I AM INDEED a hybrid owner. It's amazing how well this works. However, as Fred wisely pointed out, getting the weight up to speed takes horsepower and there ain't no free lunch in that department. I can pulse and glide all day with a carload of people and I won't get near the mileage I will in an empty car. The weight makes a difference. But DO NOTE that your words were appreciated, Bungie.

Redfish:

Looking at your real world numbers, the difference between the FJR and the Goldwing seem a little more like what I'd expect. It was interesting to see what a bike can get at those speeds. I've noticed in my hybrid that above 55 mileage starts to degrade in a hurry, so it only stands to reason that it would do so on any vehicle, 2 wheeled or 4.

Love this forum

Gary

darksider #44

 

[Bounce]

?

I think you confused me with someone else. All I did was post real-world numbers for a GL1500. I typically got about 30 to 32 mpg with one tank through higher elevations at interesting speeds... (17mpg).

A bugati veyron is pushing against air that pushes back like syrup as it breaks 200 mph. That's in spite of it having a better drag coefficient than most any typical production bike.

 

[Redfish Hunter]

FWIW those MPG figures are a little better than what we normally get but the speed limit on the Natchez Trace is 50 mph and we were staying pretty close to that. 51.9 mpg is much better than I ever got with my ST1300. I am certain that disconnecting the O2 sensor so the Power Commander could function properly knocked about 1 to 1.5 mpg off the FJR's mpg figures. A fair trade-off though. I freely admit that Dad and I don't push our bikes very hard most of the time so our mpg figures are usually pretty fair.

I never got a chance to calculate mpg figures for my cousin's GoldWing again on that trip but we always fueled up together. It was usually a tossup between my ST and Dad's FJR as to who took the most fuel but we were never more than about a tenth of a gallon apart over a 200ish mile run. The GoldWing always took more but I think that the mountains affected him more than us. My ST outweighs the FJR and it has more frontal area. I have no idea which is the more aerodynamic but I would have to guess the FJR. The 'Wing has lots more weight and lots more frontal area, climbing the North Carolina mountains definitely affected it.

As "The Total Package" the FJR is pretty darn hard to beat.