I was thinking a bit about this after my last ride: what would be the optimal shift RPM for different goals? Obviously, the optimal shift RPM for max acceleration would be a bit after peak torque, which IIRC would put your "optimal performance" shift around 9Kish since peak torque is like 8.3K or something like that. But, what would be the optimal shift RPM for best fuel mileage? I would imagine that this is much lower in the rev range, but I have no idea how to "calculate" it so to speak. I guess a better question is: at what point in the rev range is the motor using the least fuel per revolution?

I usually shift a bit sooner than 9K if I'm just cruising (I'll try to shift for optimal acceleration if I'm doing a "spirited" ride lol), keeping my cruising RPMs at like 5-6K, shifting around 8Kish if I'm trying to go faster for longer than just a second. I don't know if that's "optimal" but it "feels" right if you know what I mean. Anyway, at what point do YOU upshift, and why?

Quote from: qcbaker on February 22, 2017, 11:13:18 AM
But, what would be the optimal shift RPM for best fuel mileage? I would imagine that this is much lower in the rev range, but I have no idea how to "calculate" it so to speak. I guess a better question is: at what point in the rev range is the motor using the least fuel per revolution?

It uses the least fuel per unit distance traveled (which is what you care about for fuel mileage) at the lowest RPM that can sustain the desired speed, with all else being equal. But all else is not possibly equal because throttle position is an important factor.

If the fuel delivery were linear with respect to throttle position (and it's not, this is needle profile and other issues like turbulence in the intake and exhaust and vacuum and valve overlap etc.) then 4K rpm at WOT would be the same fuel consumption as 8K at 1/2 throttle. But the problem here is that WOT is usually a bit more rich than mid-throttle, especially if you are in the gap between pilot and main, and of course air movement meets greater restrictions at high rpms than at lower rpms but probably negligible difference if you are only at 1/2 throttle.

The theory should be that the engine is most efficient at the torque peak. But the truth is lower rpms will almost always result in better fuel economy so if you really want to get best fuel economy the old fashioned circa 1970s fuel crisis rule of highest-gear possible, lowest rpms possible, and never ever use WOT will apply. So in other words if you can cruise along in 6th at 40mph and 3500 rpm then do it, unless the load (hill, etc.) requires you to open the throttle more than about 1/2, in which case you are better off downshifting and running at 1/2 throttle and 40mph in 5th at 4k rpm.

I know this is not the technical answer you are looking for There are just way too many variables. I didn't even get in to wind resistance which is why fuel economy drops with speed after a certain point. Basically it requires very little hp to sustain highway speeds, but the amount of hp increases exponentially as either the frontal area increases or the speed increases. Finding a speed low in the curve results in best fuel economy pretty much regardless of gear/rpm/etc because it simply requires the least power. For most cars this winds up being like 45-50 mph. Below that speed you cannot utilize the higher gears because the car doesn't make enough torque in top gear to sustain that speed (like my Jeep at 35mph in 6th... it would stall). So speed is far more of a factor than gear selection or rpms, it's just that ordinarily it is vehicle speed that dictates gear selection and engine rpm for most of us.

BTW in my ordinary riding, no hurry and just routine and not trying to be fast at all, I tend to shift before 5-6K rpm and cruise at 3-4K. I only really rev over 6K rpm if I have to get out ahead of traffic quickly, like making a right turn into traffic or merging on the highway. If I was riding a 650-class twin like an SV650/ER6n/FZ-07 I'd probably never have to rev over 6K. And even with my very sedate riding habits I routinely leave my dad in the dust on his Shadow 750, even not trying. I bet he shifts under 4K every time and never uses more than 1/2 throttle.

Quote from: mr72 on February 22, 2017, 11:31:54 AM
...
I know this is not the technical answer you are looking for There are just way too many variables....

Well being that I doubt there is one perfect "answer" to my questions, what you posted is great. Very informative. 


Also, isn't the Shadow 750 like 200 pounds heaver than the GS? I would imagine that has more to do with you outpacing him than your riding style.

On an otherwise stock bike, I went to #20 pilots and #132.5 mains along with going +1 on the CSS, once I got 69.8 Mpg riding on the open road literaly going from gas station to gas station, shifting between 5-6K. It's the right hand Shenanigans that lowers your mileage 

EDIT: up to #20 pilots, not #17.5 (#17.5 is stock)

Once again mr72 comes through with hard scientific reason and leaves little room for additional comments.   

I've noticed when I am in a mood to ride aggressively I tend to stay down a gear, that leaves me a few K RPMs higher than I need to be, and closer to that powerband.  Aside from me letting the RPMs climb before shifting, just cruising at a higher RPM also sucks the fuel down.

Interestingly enough, me trying to be conservative on my Buell equates to about the same gas mileage as me going all out on the GS.
At the same time, me going all out on the Buell doesn't result in that much less fuel economy.  It's not working as hard as the GS to crank out the HP, and it redlines about 5k less...

Quote from: Watcher on February 22, 2017, 12:43:55 PM
Interestingly enough, me trying to be conservative on my Buell equates to about the same gas mileage as me going all out on the GS.
At the same time, me going all out on the Buell doesn't result in that much less fuel economy.  It's not working as hard as the GS to crank out the HP, and it redlines about 5k less...

That's because the weight, frontal area, rolling resistance, your vehicle speed, etc. are all very much the same between the two bikes, so the power requirement is the same and the fuel requirement is the same (ish).

It's just like why my Miata gas mileage was not significantly different than a Corvette. 3x the displacement makes little difference, both cars have similar frontal area (and total wind resistance) and therefore going 60mph requires the same amount of power for either car which consumes the same amount of fuel. Everyone thinks "bigger engine, worse fuel economy" but that only really applies if bigger engine means bigger vehicle (more wind resistance) or bigger engine means go faster.

Never gave much thought to economy riding but copied this from an old post of mine on my thoughts about shift points for spirited riding:

Don't know about others but my stock GS500 power band was 7000-9000 rpm.  Max stock hp is at 8500 and nothing is gained going more than 10% over max hp since the power drops off rapidly after 8500.  Shifting the GS down one at 9k if your still accelerating results in a drop to approx 7k rpm putting you right on top of the torque curve where you want to be.

Doesn't mean much on the city streets but running in the mountain twisties with bigger bikes it matters.  I remember running 7-9k rpm for hours in the mountains back 10 years ago when I was a kid of 70.

I've often wondered about this, both on my bike and in my cars. Great response, mr72.

I tend to ride down a gear when riding aggressively, as watcher says. It not only gives me better throttle response, but the engine braking is more effective. Plus if I'm riding with my more experienced friends, I have to stay at those higher RPMs to even think about keeping up. On a commute or casual ride, I probably shift the GS around 6500 or maybe a little higher, but i don't cruise below about 4500. That's just what feels right to me. On the other hand, when driving my truck I typically go for higher gear, low throttle unless I need more. I don't care so much about fuel mileage in the bike - I know I'm doing better than I would be in the Ranger.

Quote from: rscottlow on February 22, 2017, 01:27:21 PM
I don't care so much about fuel mileage in the bike - I know I'm doing better than I would be in the Ranger.

Isn't that the truth.  Even at our worst we still beat almost every 4 wheeled vehicle on the road.

What's that?  0-60 like a Corvette but MPG like a Prius?   

Quote from: Watcher on February 22, 2017, 03:02:38 PM
What's that?  0-60 like a Corvette but MPG like a Prius?   

Well, and the utility of a Formula Ford and the all-weather worthiness of a bicycle... and let's not talk about range, please

Upsides, downsides.

I don't mind the weather, but it does suck to not be able to go proper grocery shopping...

Quote from: Watcher on February 22, 2017, 04:05:17 PM
I don't mind the weather, but it does suck to not be able to go proper grocery shopping...

How much room do you need for a 6 pak, loaf bread, and bologna

Quote from: Watcher on February 22, 2017, 04:05:17 PM
I don't mind the weather, but it does suck to not be able to go proper grocery shopping...

102 Mpg...and Costco Compatible 

Quote from: richamor on February 22, 2017, 05:54:27 PM

Quote from: Watcher on February 22, 2017, 04:05:17 PM
I don't mind the weather, but it does suck to not be able to go proper grocery shopping...

How much room do you need for a 6 pak, loaf bread, and bologna

For me?  I do fine with a 2-liter, some OJ, bread, cold-cuts, cheese, and maybe a frozen pizza.  Plenty enough for my backpack.
But as soon as I need a pack of TP or paper towels or want a case of pop it turns into multiple trips, or I just borrow a car.
Luckily I don't live alone so grocery shopping is usually a household affair and we take the Cherokee.

This is getting quite off topic, though.

if I can strap a kayak to my GS. you can find a way to carry two, two liters.  I've even used my little GS to pull out a baby cow stuck in some mud...

TBH. I get annoyed with my GS having so many issues, then Its times like this, I remember all the stupid things I've done with it. I mean, how many people can admit to have ridden their GS with street tires, through water so deep, your mid thighs are under water sitting on the seat..

though I will not recommend you do that with your GS.. I am a professional....  and my GS is about worth scrap money at this point. wish someone would buy the rear plastics, and the F front light fairing mount bracket. so I can rid of the stuff I know i'll never need... lol

Honestly with the way the Buell tail is configured it's crap for luggage.  Even the factory Buell saddlebags I had never seemed to fit properly.
So all I can do is the tank bag, a backpack, and MAYBE a small tail bag if it doesn't get in the way of the backpack too much.
Honestly, using a cargo net to strap stuff to the under side of the tail would probably work better, so long as I don't ride through dirt or compress the shock enough to have the tire contact anything.
Or I custom fabricate some saddlebags to grab directly onto the subframe instead of grab each other under the seat...

If I still had a GS I would be more than willing to take that guy shopping and load it up, at least it has room behind the rider.

Quote from: Watcher on February 22, 2017, 09:09:24 PM
Honestly with the way the Buell tail is configured it's crap for luggage.  Even the factory Buell saddlebags I had never seemed to fit properly.
So all I can do is the tank bag, a backpack, and MAYBE a small tail bag if it doesn't get in the way of the backpack too much.
Honestly, using a cargo net to strap stuff to the under side of the tail would probably work better, so long as I don't ride through dirt or compress the shock enough to have the tire contact anything.
Or I custom fabricate some saddlebags to grab directly onto the subframe instead of grab each other under the seat...

If I still had a GS I would be more than willing to take that guy shopping and load it up, at least it has room behind the rider.

I know what you mean.. I like my bikes to have lots of extra room for "supplies" I care less about cosmetics and more about utility of my motorcycles. ONE day ill get a motorcycle with a side cart! ONE DAY!

Quote from: Suzuki Stevo on February 22, 2017, 06:41:36 PM
102 Mpg...and Costco Compatible 

That brings us back to the mpg point. It's not so much about displacement or even RPM. The scooter is tuned to operate in its most efficient range at nearly the speed where wind resistance becomes a big deal. And a 2 cycle makes more power per RPM. Brut anyway it won't go faster than maybe 45 or 50 and the transmission puts it at the optimum rpm for the power needed.

To go 60 mph takes about 1.8x as much power as going 45, which requires 1.8x as much fuel, so that scooter would get 56 mpg going 60 mph if all else were equal (and if it had enough power to go 60). Not being precise, just making an example. Your GS gets close to 56 mpg going 60 mph. If all it could operate optimally at 45 mph (it can't) it too would get 100 mpg at that speed.

Quote from: Suzuki Stevo on February 22, 2017, 06:41:36 PM

Quote from: Watcher on February 22, 2017, 04:05:17 PM
I don't mind the weather, but it does suck to not be able to go proper grocery shopping...

102 Mpg...and Costco Compatible 

I'll never understand why every motorcyclist doesn't also have a scooter. They're just so damn convenient. And they pay for themselves. And they're fun as hell.

Quote from: Jim Moore on February 23, 2017, 12:27:21 PMI'll never understand why every motorcyclist doesn't also have a scooter. They're just so damn convenient. And they pay for themselves. And they're fun as hell.

I still have my Burgman 400, it goes a little over 100 Mph indicated (an honest 95 Mph for arguments sake) and gets 65+ Mpg all day long, it's also my go to bike when it rains, Tupperware is easy to clean...I hope the Internet Police can handle a little off topic

Real Men ride scooters, I have nothing to prove to anybody