Mileage; and 5th gear may not be your friend

[pistolpete]

A lot of folks on the forums mention that they can get quite high fuel mileage from their Goldwing. On the other hand most could care less about efficiency and it is all about the ride.
Most of the time I am in the later group as I consider fueling up as at best a reduction of the fun I am having.

All of my running Wings are tuned pretty well and they make me smile broadly when I head out to some twisties somewhere. My favs are the Tail of the Dragon on US129 in Tennessee/North Carolina or Cherohala Skyway in NC/TN. So its either 2nd gear high rpm on 129 or a higher gear @ considerably higher speed on the Cherohala. My consideration for mileage during these times is a non factor.

I did a tune up on my Pennie Lee this AM and took her out for a spin to check her out. I wanted a little interstate run as well so I hopped on I-40 west and immediately was presented with a 9% up hill grade. Once I got to speed, I stabbed 5th gear and rolled on the throttle. Noticing that I had to keep the throttle on more in order to maintain the speed, I did as I normally do, I put her back in 4th. The thought hit me that 4th gear may be more efficient at maintaining this speed than 5th. Like most guys having a blast, mileage (efficiency) had usually not been an issue.

I stopped up the road just a little way and purchased a bottle of yellow fingernail polish. (Don't tell my wife) I then marked the throttle position at idle with a little tension on the grip and then marked it at WFO. I also marked three in the middle at 1/4, 1/2 and 3/4. Got on the interstate and headed east to the interchange where I got on earlier.

I entered the west bound side once more and accelerated to 70 mph then shifted to 5th gear. I held the throttle grip to the maintenance level of 70 and noticed the mark lined up at a about 2mm over the 1/4 mark. Shifting to 4th and maintaining 70, the mark lined up at 1/4 nearly right on.

Now I know that this is not an earth shattering revelation but it seemed to clearly point out that it all comes down to speed vs horsepower or better put, the maintenance of each.
I may try this again using a single vacuum gauge to show the results more clearly.

Another analogy might be fun vs wallet. I like fun better.

[Placerville]

Interesting analysis. My use of 5th gear has been restricted to flat freeway driving as any expectations of 'roll-on' power in in 5th doesn't produce much for me. Like you, hills take me into 4th. Now, second gear at 6K RPM, that's a different story.

[pistolpete]

So it would stand to reason that in this case, 4th gear would be more economic?

[Placerville]

Well, the faster the engine runs (in forth gear), the more fuel it uses so, the less economical it is. But, if your lugging it up a hill in 5th under 3K RPM, I imagine you're not doing the engine any favors. For me, I like keeping the needle above 3K RPM and to heck with my mileage.

[pistolpete]

Ok, lets explore that.
Going down a steep grade with the throttle shut off and the engine rpm is at 4k.
Am I using as much fuel at 4k going up hill?

[sunnbobb]

I found a cool little trick a few years back. I put some good earplugs in, and took my bike for a spin. With the earplugs in, I paid less attention to the exhaust noise and more attention to the "feel" of the engine. With the earplugs in, I consistently ran the bike at higher rpm (lower gears), and it seems my bike was much more responsive, and it seems, gas mileage improved, as I was lugging less, however slight.

[oldwings 78]

I think that on a bike the mpg is a non-issue. I also think that trying to "lug" power out of any internal combustion engine to save fuel is not practical. It is not good for main or rod bearings. (more stress less oil pressure at lower rpms) Let the engine pull in the power band and worry about mpg in your Suburban.
Terry

[rod willis]

These Bikes have a sweet spot of where the like to run and I have found that to be
between 3,000 and 5,000in most of the gear no matter what the load is on the bike
mileage for me dose not change much across the board I just run them where they like to run
Rod

[CYBORG]

i agree with the sweet spot idea. cyborg runs best between 2500 and 4000. 70 is 3800. there is little difference between 4th and 5th. a 1000 rpm or less. i have caught myself running at 70 in 4th, but notice that the bike runs hotter. shifting to 5th it cools down some. mileage is always 45-50, staying in the sweet spot, and not lugging

[pistolpete]

Wow! Thanks guys.

I should clarify why I shifted to 4th gear. I too let the bike tell me where she likes to run the best and even though I was going up a grade in 5th she wasn't lugging and I had fair throttle up response. I too could not care about mileage but it is a reasonable way to "check" each time you make an adjustment or tune the engine like I did.
Like Cyborg and Sunnbobb, I feel that when the engine is even at a higher rpm under less load, it runs more efficiently.
This test was to help those that ask "What should my mileage be on average?" as I have seen before on this forum. It is a legitimate question for those who recently bought a wing and/or is just asking.

Pete

[BruteSquad]

This is semi-related, I think, just bear with me. I bought a Dodge Durango 5 or 6 years ago. It was the smaller V8 (nope, it's not a hemi) and got horrendous gas mileage. When I first got it I would try to wring every last ounce of gas out of it. Pull away gently, try to keep RPMs low, creep up to lights so as not to come to a complete stop, etc, etc. I wasn't getting very good gas mileage. Probably 12-13 mpg. I decided one day it just didn't matter and this thing was thirsty and started driving my normal style. I'm not flooring it everywhere, but am definitely more on the aggressive side. I got better gas mileage and averaged over 14 mpg on almost every tank. The only time I could get that mileage when I was babying it was when I had long highway stretches. I think it was the same kind of thing, that engine just didn't like lugging along. It needed to be in the sweet spot.

[salukispeed]

Seems to me that the sweet spot will fall right where the max torque rpm is. The engine combination ( Cam, Timing, jetting, port design and runner length and general tune ) is the MOST EFFICIENT and most productive at max torque. Therefore it makes sense that the best use of the fuel mixture comes at the same rpm. Many engines seem to have max torque somewhere around 1/2 the max Horse power rpm or slightly less. So too low rpm is no good either if it takes a lot of throttle to run there. Lots of fuel/air going in but not the best use of it. Low rpm can sometimes work to help mileage but only if it can be at very light throttle like with the wind or slightly down hill or even a lower gear.
Just thoughts!

[pistolpete]

Salukispeed,
Excellent input thank you.

[millerdog]

I can never seem to get more than 35mpg out of mine. I am in to the throttle pretty heavily most of the time. I think the factory brand new mpg specs were somewhere in the 30 to 35mpg mark. I could be wrong on this.

[Whiskerfish]

Everything below is all on my dressed 78. The 75 is my toy so I do not track economy on it. So long as I make it close to 100 miles before switching to reserve on the 75 I consider that a good day, and one I have smiled a lot during!!

On the dresser I track my Mileage quite a bit, more or less every tank. I have seen 50 (twice out of hundreds of tanks) and I have seen the low 30's out of the same bike in the same state of tune. Most of my riding is a mix of slab and country roads and on average I see high 30's to low 40's. Max Fuel efficiency is 45mph in 5th gear on a level country road with few stops and no traffic. Minimal acceleration and minimal braking. The worst for me is either a high speed run (80 plus) on the Slab or a hard push in the twisties. Either can result in the low 30's.

As for the sweet spot, most of these engines come "alive" about 4500. For me that is where the fuel economy heads south. A Slab run at 4,000 rpm in 5th may result in a 42/43 mpg reading and a slab run at 5,000 rpm will result in a 36/37 MPG reading. As you increase the rpm above 5 grand the fuel economy will continue to decrease.

Pete IRT the original observation I can not believe that Throttle setting is directly reflective of fuel economy. I think that is only part of the equation. Physics would require that steady state RPM has to be directly related to air flow and in these setups that has to correspond to fuel flow as well right? So more rpm at a steady load/ acceleration state would require more air flow and as a by product more fuel???