Just wondering

[KarlS]

On a RT with the engine reving at 3500 would the gas mileage be better in 3rd gear (obviously going slow) or in 6th gear (going a bit faster).

 

Karl

[Mister Tee]

Generally, riding (or driving) in the highest gear at the lowest speed without lugging the engine will yield the best mileage. It may be a tossup between 5th and 6th gear as to which is more efficient, but certainly not between 3rd and 6th. I have not personally tested different speed/mileage combinations so I can't say for certain what the most efficient speed is on these bikes.

[Survived-til-now]

+ 1

 

But I have always stuck to the rule of thumb that says you operate at 50% of the red line i.e. I aim for 4000+ rpm when cruising. I seldom let the bike go below 4000 rpm and although it will pull at 3500rpm the engine feels sluggish to me.

 

So if I were at 3500 rpm in 6th I'd change to 5th......

[Lineareagle]

Rode 8500 km recently on the R1200GSA averaged 44 mpg. Just as mentioned ran at 4000 rpm and changed gears to maintain that.

 

 

[Highway41]

Your gas mileage would be about half as you would cover only about half the distance.

Bill

[upflying]

You can try some of these hypermiling techniques..pushing is especially easy on a bike.

[EddyQ]

On a RT with the engine reving at 3500 would the gas mileage be better in 3rd gear (obviously going slow) or in 6th gear (going a bit faster).

 

I'd guess 3500rpm in 3rd (maybe 40-45mph) would result in slightly better gas mileage than 3500rpm in 6th (perhaps 60mph). The air friction is higher at the higher speed and so the engine has more strain and uses more gas. But it is a guess. At 60mph your mileage goes up quicker and may overcome the higher gas usage. Once, I did let the BC compute mpg for a slow, off highway route where speeds were 30-45mph. The mileage was up around 50mpg.

 

For those folks that ALWAYS ride above 4000rpm. Cruising at 40mph on my RT just isn't pleasant at above 4000rpm. The engine has so little throttle that the engine response is jerky. Sure, when I am in twisties or the slightest bit agressive, above 4-5Krpm is where it is at. But almost never much above 4000rpm when cruising below 45mph.

[ShovelStrokeEd]

Fuel consumption is primarily about the following, more or less in order.

 

Aerodynamic drag

Acceleration vs mass of bike

Engine efficiency (mostly BMEP but other factors as well)

Terrain

Rider habits (throttle transitions and braking)

 

My R1100S delivered its best fuel economy ever one day on the BRP while trying to average 50 without ever going over 60. As I recall, it was around 52 mpg on a bike that cruising at 80 would barely get 40 mpg.

 

My Triumph Sprint's best mpg was about 56 while trying to terrorize I70 from Grand Junction to Littleton, CO. Rarely under 90 mph until I ran into some snow/rain just before the tunnel. Most of the time, on the gas but, those of you who know, realize that I was at some really high elevations at that point and it doesn't take that much power to move through the air. ECU leaned the mixture to compensate for air density as well.

[Quinn]

My best gas mileage is when I fill up with the bike on the side stand.

 

I also get better mileage when using one particular pump at an Exxon station near my house.

 

---

[Joe Frickin' Friday]

Fuel consumption is primarily about the following, more or less in order.

 

Aerodynamic drag

Acceleration vs mass of bike

Engine efficiency (mostly BMEP but other factors as well)

Terrain

Rider habits (throttle transitions and braking)

 

If we reduce the situation to steady-state cruising, then the two factors to consider are aero/tire/driveline drag and engine efficiency.

 

Going faster induces more drag, and so requires more mechanical energy per mile.

 

If the engine is operated at a constant 3500 RPM despite the faster forward speed of the bike, then the engine must be operated at higher load; this usually results in better engine efficiency, i.e. burning a fixed quantity of fuel results in a great amount of mechanical energy delivered to the flywheel.

 

OK, so we have two offsetting factors. Which one wins out as you move to higher (or lower) forward speed with constant engine RPM? Hard to say. Generally speaking, cars get their best fuel economy somewhere between 35-55 MPH. Maybe the same is true of bikes? 3500 RPM in third gear would put you below 35 MPH, but 3500 RPM in sixth gear would get you toward the top end of that sweet range.

 

Not clear which RT (1100/1150/1200) we're talking about, but the 1200's have cruise control and a built-in MPG readout. I don't trust it for absolute readings, but it could be useful for comparisons. It would be interesting to run (with cruise control) a couple of miles of straight/flat road at 3500 RPM in third gear, and then in sixth gear, and see what the display reads out in each case. You'd have to get up to speed, lock in the cruise, and then reset the MPG gauge at the beginning of each run.

[BailyD]

around town (45-50 mph County Roads) I found 5th gear regularly provides better mileage.

[MotorinLA]

+1 on drag factor. With crash bars and miscellaneous other less-than-aerodynamic objects hanging off the bike, the best I seem to be able to squeeze out of my R1200RT-P is 37-38 mpg. Interestingly enough, varying sustained speeds between 65-78 mph doesn't seem to affect the milage that much... go figure.

 

Sure beats the 25 mpgs I usually get around town while working... someone told me it has something to do with my lead wrist, I dunno.

[Mister Tee]

One of the reasons hybrids get such great mileage (in addition to being able to recover braking energy) is that their engines can run at closer to their optimal efficiency.

 

The most efficient throttle position for an engine is wide open. The most efficient RPM is somewhere near the peak torque torque point. The problem is that on a typical car or motorcycle, that's up near top speed. Ideally, you would run your engine in short bursts at full throttle and peak BMEP RPM and let the batteries do the rest. Hybrids don't go quite there but they can take advantage of more efficient engine settings than conventional cars can.

 

BailyD, if you ride on the highway, going 55-65 in sixth gear, how does that compare mileage wise to 50 mph in fifth? RT's are geared really high. I'd be in sixth at 50 mph on any other bike I've owned, but not the RT. I get up to 50 mpg cruising a steady 60-65 mph on the freeway, depending on the outside temperature and fuel I'm using.

 

I wish the RT had a "real time" MPG readout, so that the exercise that Joe F Friday suggests could be more easily performed.

[Joe Frickin' Friday]

Today I went out and did some tests to answer the OP's question. Test conditions:

 

-straight stretch of road, two miles long, running east/west.

 

-Winds were out of the south and the road was pretty flat, but just to try to eliminate any effects from wind or grade, I ran the bike in both directions and took an MPG reading from the on-board computer each way.

 

-I got the bike up to a stable speed with the tach at 3500 RPM, with the cruise control engaged, before reaching the start point. At the start point, I reset the on-board MPG computer and then let it accumulate an average over the two-mile run.

 

-For the entire two-mile run, I kept an upright posture and had the windscreen in the lowest position.

 

So here's what I got:

 

third gear, 3500 RPM

speed, 41 MPH

eastbound MPG: 54.7

westbound MPG 50.0

 

sixth gear, 3500 RPM

speed, 64 MPH

eastbound MPG: 54.0

westbound MPG: 50.0

 

At two miles, it was a pretty short stretch of road, and winds could have changed quite a bit between runs. I wouldn't be surprised to see those numbers vary plus-or-minus 2 if I were to repeat the test. But they're certainly in the same ballpark. It's fair to say that the increased per-mile energy requirement at higher speed is pretty much offset by the increased efficiency of the engine when operated at a larger throttle opening.

 

Point of amusement: there were a couple of bicyclists who must have wondered what the hell was up when they saw me pass them repeatedly, going back and forth on the same stretch of road five times (east/west in 6th, east/west in 3rd, then resume my original eastward journey).

 

 

 

[motoguy128]

Point of amusement: there were a couple of bicyclists who must have wondered what the hell was up when they saw me pass them repeatedly, going back and forth on the same stretch of road five times (east/west in 6th, east/west in 3rd, then resume my original eastward journey).

 

 

You should have pulled alongside and explained yourself... then offered to lead them out for a sprint to the next yellow sign up the road.

 

 

I would have liked to have also see 4th gear at 51mph and 5th gear at 58mph for additonal comparison.

 

For best mileage you'd probably have to try 50mph in 4th. Athough some feel that 3000RPM is too low.