Fuel Economy and Vacuum Lines

I heard rumors that the position of the windscreen can affect MPG. I have found that is not true. I don't see any measurable difference whether the windscreen is up or down.
 
I can state from experience, towing a trailer reduces miles per gallon.

Are you shocked? I hope not.

I'm meticulous, if not OCD, about tracking my mileage on all my vehicles, and never add gas without filling the tank.

Hope I can get back out to Tucson to have Larry whisper to my 1300 before he retires, to see if he can really tune it to get that mythical 50mpg.

I'm not unhappy with 42 overall.
 
Temperature today from 25 to 29 degrees Celsius.

Riding at about 120kph I got about 43.5 US mpg.

Seems good, for sea level and humid.

My idle wanders a slight bit. (This is different than the idle dropping when the rad fans turn on...)

Is this slight bit of wander normal...??

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In Ireland I don't remember going anywhere without constantly slowing down and speeding up. Very much like here in the Yorkshire Dales. That will certainly affect your mpg.

I find that the best mpg is cruising at a constant 60mph in highest gear. I get about 10m/l average according to the display = which equates to 45 - 46 mpg.

On normal rides I am pleased if it is about 9.5 miles per litre average (43mpg).

Screen up definitely makes a difference on mine. (Mine is a repalcement screen with a flip up at the top - from BikeQuip) The instant fuel consumption display updates every 15 seconds, so if you can hold a constant speed on a level road for more than a mile, you can get two reading with screen down and 2 with the screen up. In headwind I have seen that drop from 9.5 to 8.5
Solo with a top box also reduces it. Fitting a pillion not only makes the ride smoother, it also improves mpg - no slipstream hitting the top box.

Balancing the starter valves certainly brings out the grins. When I first got it, the grage said they don't need doing, the computer ECM takes care of it all. That isn't true - it has to have a sound reference point. So smooth, so rapid. What you save in fuel is balanced by what you lose at the rear tyre. Fun though. Ignore the workshop manual instructions, Larry's method works much better.
 
Almost never used 5th gear unless I was on a freeway or doing 75mpg.
I don’t like lugging the engine, and making it work harder.
I see too many people shift up to 5th gear way too quick, and doing 40 mph in 5th.
I find better response, in the proper RPM range, and don’t have to down shift, then up shift to pass someone etc.
I find I get better MPG riding this way as well, at least for me.
 
I might suggest checking the air filter (when I bought mine it was unbelievably nasty) before digging into the fuel system. I can also post the troubleshooting guide from the shop manual if requested.
 
Regarding your question asking what affects fuel efficiency. Just about everything does, but below are some examples and ideas for you to mull over.

General state of tune, which includes spark plugs/wires, ignition system, engine valve gap, 5-way Tee, thermostat, etc., etc., etc..

How you ride- Twist the wrist, fuel consumption increases.
How you ride- Riding at an RPM that is to low for the current speed increases fuel consumption. The ST1300 likes to above 3,000 RPM. At highway speed it returns better fuel economy with an RPM closer to 4,000 than 3,000. Many of us tried to convince you of this in your previous fuel efficiency thread where you were adamant that the ST1300 is geared to high and that the engine RPM is always to high. At the time you were asking about a means to modify the transmission and/or the final drive to lower the engine RPM's. If you remain convinced of this and are constantly lugging the engine the fuel efficiency will be affected.
Where you ride- lots of stop and go, fuel consumption increases. Lots of elevation changes, fuel consumption increases.
Tire pressure- The lower the tire pressure the higher the fuel consumption.
Strong head-wind, fuel economy suffers.
Obstructed airflow to the induction system. This is not limited to the cleanliness of the air filter. An obstructed intake tract has the same effect. e.g. Mouse nest.
Dragging brakes.
Riding the brakes. Some people keep to much pressure on the brake lever in anticipation of an needing to perform an emergency stop instead of just covering it in preparation. They don't realize that they are activating the brakes ever so slightly.
Excessive resistance to wheel rotation other than brake dragging. e.g. Failing U-joint, failing wheel bearings, improperly installed wheel bearing/wheels.

For comparison purposes to give you some exact real-world numbers calculated by dividing the consumption in to the distance driven, not based on the results of the on-board computer, below is the fuel efficiency numbers for my 2009 ST1300.
Note to the number crunchers- If you do the math it might not work out exactly because I use Excel formulas that I have set to round up/down. It is more than close enough, I don't need precision to the 5th decimal place for calculating MPG. I generally ride between 100 and 120 KPH GPS reported speed when on the highway.

The average fuel efficiency of all miles ridden since the motorcycle was new, so a true average, is;
55.5 miles per imperial gallon, 19.7 Km/L, 5.1 L/100 Km, 46.2 miles per US gallon.

The last time that I went to Nova Scotia it was getting to/from the Cabot Trail and the surrounding area. It was probably a more sedate ride than what you might do because I was with someone older, so there was no knee dragging going on. The numbers will be a little higher because of that, but not enough to explain the difference between what I am reporting and what you report.
My average fuel efficiency on that trip was;
57.6 miles per imperial gallon, 20.4 Km/L, 4.9 L/100 Km, 47.9 miles per US gallon on that trip.
 
I agree Larry. I rarely use 5th and prefer the lower gears. It's just that I know that when I did the test some years ago, I did it in 5th gear.
 
Andrew Shadow said:
Riding at an RPM that is to low for the current speed increases fuel consumption. The ST1300 likes to above 3,000 RPM. At highway speed it returns better fuel economy with an RPM closer to 4,000 than 3,000.
Click to expand...
This is so much of it.

The bike doesn't want to be in low RPMs. Mine makes an actual grumble when it's at anything lower than about 2,000, is extremely loud through 3,000, and starts to get quiet at 3,000. It's not any louder or more strained up through about 4,300 RPM. What that leans to is that the bike is burning about the same fuel per second at both 3,000 and 4,000 RPM. More rotations for the same amount of fuel means more distance traveled for the same amount of fuel.

Long story short, RPM bands sit on a bell curve, and peak efficiency is found by finding the highest RPM-value closest to the plateau of the curve.
 
What an interesting discussion! I'm also a bit of a fuel consumption watcher across all of my vehicles. My MT-10 is definitely at it's most economical running at 5-6K (over 70mph) and gets progressively worse if I run much slower than that; this is important to know because the low fuel light comes on after about 13L use.

On my ST I have a tendency to run the lowest possible rpm that the bike is comfortable at, but maybe I should be keeping the revs closer to 4k to get better economy? Seems like a good experiment. I generally head out on rides through the same terrain to the south and it is a repeating cycle of slow-speed ridges and valleys for the first 50km, and that does not produce low fuel usage on any vehicle. My best mileage is open twisty roads where the brakes are rarely needed and speed is managed by rolling on/off the throttle.
 
10% variability in reported fuel mileage could easily be explained by regional blends of gasoline, or the weather, the road conditions, the temperature conditions, the rider weight and cargo. With Honda’s programmed fuel injection, it would not be expected to have any variation in the richness of the fuel mixture that wasn’t compensated for by one of two sensors, the most important one being the coolant temperature. If the thermostat is operating properly and the engine is running at the correct temperature there’s no point in trying to lean the mixture with a throttle body synchronization. That procedure only affects the idle and the immediately off idle fuel mixture and has nothing to do with the mixture in the mid range and higher range. That's handled by the ECU based on the airflow data sensor at the air box and O2 data from the exhaust stream.

Personally, I think that there should be at least a few tanks of gasoline run through any bike with the mpg calculation based on corrected distance mileage and fuel burn, not from any onboard mpg readings not corroborated against distance/fuel burn calculations, or a "ringer" mpg like my 59.4 mpg tank. That was held steady <55 mph, flat road, 100 mile loop with no stops right back to the same gas pump.

I didn’t see it specifically used in the thread, but wouldn’t put too much credence in the instant mpg per gallon read out on the dash. Over 1,100,000+ miles of reported rider information the ST1300 delivers 38 to 46 miles per gallon in the middle of the bell curve distribution.
 

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dduelin said:
I didn’t see it specifically used in the thread, but wouldn’t put too much credence in the instant mpg per gallon read out on the dash.
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Because I kept my mouth shut and my meat hooks off the keyboard, but I agree.
I've stated before, I use the onboard fuel "calculator" as an entertainment device, because it makes me laugh.
Meanwhile, recording the odometer and resetting the trip meter at every fillup will tell the truth.
I'm consistently returning 42mpg, but usually ride in a more sporting manner, but not excessive speed, just 70 - 80mph, mostly closer to the middle of those speeds.
(If you want to be technical, and mention the inaccuracies of the odometer, or variance due to tire wear, or the atmospheric pressure last Wednesday or the alignment of the planets, I don't do all that. Just a calculator, and consistent recordings.)
 
The Dark Shadow said:
Temperature today from 25 to 29 degrees Celsius.

Riding at about 120kph I got about 43.5 US mpg.

Seems good, for sea level and humid.

My idle wanders a slight bit. (This is different than the idle dropping when the rad fans turn on...)

Is this slight bit of wander normal...??

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Click to expand...

I think that is very good milage I live at about 23 feet above sea level temperature here usually between 45 degrees F in winter and 90+ degrees F in summer. Average speed of riding is between 60 to 80 mph my mileage is usually between 38 and 42. season seems to have little effect.
 
In my opinion, you are getting pretty normal. I commute about 5 miles each way - yes, I spend as much time warming the bike up as riding. On 10% ethanol I get about 32 US mpg, consistently.

On a recent 1000 mile trip, running ethanol free (mostly 87 octane) I averaged 42.5mpg over the entire trip, and this was through Oklahoma/Arkansas scenic routes (lots of turns and elevation changes). Best tank I had was on ethanol free 91 octane and got 45.2 mpg.

I am not doubting that a well tuned bike and a well tuned rider can accomplish the higher 50s as stated, but I suspect the majority of owners see closer to that 38-42mpg as Dave mentioned in his post.

Ryan
 
Igofar said:
Almost never used 5th gear unless I was on a freeway or doing 75mpg.
I don’t like lugging the engine, and making it work harder.
I see too many people shift up to 5th gear way too quick, and doing 40 mph in 5th.
I find better response, in the proper RPM range, and don’t have to down shift, then up shift to pass someone etc.
I find I get better MPG riding this way as well, at least for me.
Click to expand...
Do you remember the recommended shift points in the Honda users manual...? 5th gear by 50kph... lol
 
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