Hi all. I'm thinking of doing some very long highway miles and a friend (not an FJ guy but an old cyclist) recommended switching out both sprockets to get lower RPMs on the interstate and therefore better gas mileage.
Has anyone experimented with this? What kind of gas mileage do you get with different sprockets? Will I need a new chain? Is there any advantage at all?
Seems to me if I ride from NYC to LA and Back the gas saved might not even pay for the new parts.
Any thoughts?
Thanks!
I am running 18 front, 38 rear and getting 46to 48 MPG... And that is with SupperTrapp slip-on pipes, UNI pods and the jetting. NOT TOO BAD EH?
Dave,
I am running a 18t front and a 38t rear. When I rode to Colorado in July, When I was doing highway riding I got 53mpg.
Mathematically that is 307 miles to a tank. :pardon: :pardon:
I did put a new chain on when I did the swap. I got a 110 link chain and removed one link.
Fred
Quote from: FJmonkey on October 06, 2013, 04:09:40 PM
I am running 18 front, 38 rear and getting 46to 48 MPG... And that is with SupperTrapp slip-on pipes, UNI pods and the jetting. NOT TOO BAD EH?
So what's low speed acceleration and starting out like? I mean like when you're driving at low speeds in town.
Quote from: aviationfred on October 06, 2013, 04:10:49 PM
Dave,
I am running a 18t front and a 38t rear. When I rode to Colorado in July, When I was doing highway riding I got 53mpg.
Mathematically that is 307 miles to a tank. :pardon: :pardon:
I did put a new chain on when I did the swap. I got a 110 link chain and removed one link.
Fred
So what's low speed acceleration and starting out like? I mean like when you're driving at low speeds in town.
I have never changed the gearing on my motorcycle, but have some thoughts on this.
I have a car that gets 70MPG on long trips and often think about mileage and how I can improve it. Mostly as a way of keeping my mind occupied on said long trips. :biggrin:
* You'll notice a far greater fuel mileage increase just by changing your throttle, shifting, coasting and braking habits.
* Changing to a taller gearset will force a change in the above habits, likely to the detriment of fuel mileage.
* As it stands, you can cruise along all day in 5th gear. With a taller setup, you may find yourself downshifting more often.
* I rode LA to Nova Scotia and back (17,286 miles) with Givi hardcases (extra 120 lbs + wind drag) and averaged 46MPG with stock gearing.
* Let's dream you could up the mileage by 5MPG and get 51MPG??? In a 6000 mile trip from NYC to LA and back, you'd save $48 in fuel.
* If fuel mileage was your *only* goal in a specific driving window (freeways), it might be worth doing, but you'll likely negatively effect drivability as well as fuel mileage in the real world.
Cap'n Ron. . .
Good points capt
I went from stock to 18/38 this spring. As far as I can tell, I get the same MPG now as before the change. I find the way I drive and a good carb sync has more effect on mpg than the gearing does.
I get the best gas milage (45+mpg) when riding 2-up and loaded, following the speed limit, accelerating moderately, and slowing down well ahead of the next stop sign.
Quote from: Bminder on October 06, 2013, 04:14:28 PM
So what's low speed acceleration and starting out like? I mean like when you're driving at low speeds in town.
It makes for a taller 1st gear which I like especially when turning onto streets. Probably a tad more clutch is needed when starting but it isn't a problem.
Quote from: markmartin on October 06, 2013, 07:52:55 PM
I went from stock to 18/38 this spring. As far as I can tell, I get the same MPG now as before the change. I find the way I drive and a good carb sync has more effect on mpg than the gearing does.
I get the best gas milage (45+mpg) when riding 2-up and loaded, following the speed limit, accelerating moderately, and slowing down well ahead of the next stop sign.
Could not have said it better myself.
I've been on 18/38 since the Yahoo group days (around 100,000 Kms now). Still on the original clutch with no slip encountered so far. The bike does not accelerate has hard (obviously) but on 5000Km trips makes for more relaxed cruising in the 100 - 120 KPH range (ie hovering around the 4000rpm area). In 5th the torque there is perfect for passing without having to change down and I am still motoring (not pushing) with fuel to spare at 350kms.
I think if you are more of a canyon blaster maybe its too much gearing, but for me its just about perfect.
Horses for Courses.
Harvy
The gearing range most are using ( 17/18 - 38/41) isn't going to have much effect on economy, if any. It is more about the bike feeling relaxed at highway speeds with slightly lower revs. You will notice a bigger change in acceleration than you will in fuel consumption.
There are many, many things on the bike that will effect fuel economy more than gearing.
I have tried an few combinations over 2 bikes and settled on 18/41, it suits me, but I also avoid roads with constant cruising speed like the plague and would not want to trade off any more acceleration.
The FJ is for fun and it would a crime to nobble any part of that to save a few bucks at the bowser. Skip one coffee stop while on a ride and you have just saved more money than any gearing change will save you on fuel.
Someone here once said "Riding an FJ for economy is like going to a prostitute for a hug"
I agree.
Noel
Quote from: ribbert on October 06, 2013, 08:57:01 PM
"Riding an FJ for economy is like going to a prostitute for a hug"
Noel
But some of them are REALLY good huggers! :biggrin:
Cap'n Ron. . .
Quote from: Capn Ron on October 07, 2013, 12:11:58 AM
Quote from: ribbert on October 06, 2013, 08:57:01 PM
"Riding an FJ for economy is like going to a prostitute for a hug"
Noel
But some of them are REALLY good huggers! :biggrin:
Cap'n Ron. . .
Aside from the morals of it, the thing I don't get about it is why would any man... well to paraphrase name T. Kirk, boldly go where hundreds of men have gone before.
:bad:
Quote from: Bminder on October 07, 2013, 08:26:54 AM
Quote from: Capn Ron on October 07, 2013, 12:11:58 AM
Quote from: ribbert on October 06, 2013, 08:57:01 PM
"Riding an FJ for economy is like going to a prostitute for a hug"
Noel
But some of them are REALLY good huggers! :biggrin:
Cap'n Ron. . .
Aside from the morals of it, the thing I don't get about it is why would any man... well to paraphrase name T. Kirk, boldly go where hundreds of men have gone before.
:bad:
Hmmm, given the humour translation fails lately, I'll leave that one alone.
Quote from: Capn Ron on October 07, 2013, 12:11:58 AM
Quote from: ribbert on October 06, 2013, 08:57:01 PM
"Riding an FJ for economy is like going to a prostitute for a hug"
Noel
But some of them are REALLY good huggers! :biggrin:
Cap'n Ron. . .
Is that what Ron White called a "mouth hug"? :biggrin:
I totally agree that the single most moniating factor in fuel economy when riding a motorcyle is the style in which the rider applies the throttle and their average speed.
There are several factors that have an effect on fuel economy and their dominance can shuffle depending on where you are in the performance envelope.
Case in point, the interternal friction of the engine increases with the square of the RPM, but this loss is dwarfed by the cubic function of power required to overcome aerodynamic drag. (Power= 1/2*(rho)*(V^3)*A*Cd) Where Rho is the air density, V is how fast you're going, A is your cross sectional area, and Cd is your drag ceofficient.
Brisk acceleration from a stop uses more fuel as you are demanding more of the engine. From a pure efficiancy standpoint, you're maxium steady state fuel economy will generally be acheived if you are operating the engine at it's torgue peak. This is usually where your break specific fuel consumption is lowest with respect to the power produced. The trick, is gearing so that your typical cruising speed is in that range.
The real question becomes, if you do all of the figuring to gear for max economy, is it going to matter when over 70 or so the aero dynamic drag is the dominating factor?...
Quote from: AustinFJ on October 08, 2013, 12:16:01 PM
Quote from: Capn Ron on October 07, 2013, 12:11:58 AM
Quote from: ribbert on October 06, 2013, 08:57:01 PM
"Riding an FJ for economy is like going to a prostitute for a hug"
Noel
But some of them are REALLY good huggers! :biggrin:
Cap'n Ron. . .
Is that what Ron White called a "mouth hug"? :biggrin:
Ewwww...I'm with BMinder...wouldn't ever try that out with a pro! :nea:
Cap'n Ron. . .
Quote from: skymasteres on October 08, 2013, 01:00:51 PM
There are several factors that have an effect on fuel economy and their dominance can shuffle depending on where you are in the performance envelope.
(Power= 1/2*(rho)*(V^3)*A*Cd) Where Rho is the air density, V is how fast you're going, A is your cross sectional area, and Cd is your drag ceofficient.
Looking at that equation... Although air density isn't anything you can control, I felt a marked increased in air drag in Death Valley!!! Steady-state speed is by far the biggest factor...slowing down a bit helps the mileage. You can't do much about A except duck your head behind the windscreen...which will likely lower your Cd.
My "road trip" car is a GEN 1 Honda Insight. It has (or had when it was last produced in 2006) the lowest Cd of any production car at .25 and I can regularly squeeze 75MPG tank averages out of it with some driving tricks....my best tank was 81MPG...I went from Los Angeles to Northern Utah without having to stop for fuel. Some owners of these cars have replaced the side-view mirrors with rear-looking bullet cams and an LCD screen in the dash to reduce drag even further!
This is all good "bench racing", but I don't ride the FJ for fuel mileage...at 45+ that's close enough for me!
Cap'n Ron. . .
I remember reading a few articles in the mags back in the '80s on motorcycle aerodynamics.
The things that stuck in my mind:
At 180mph, the fairing on the Yamaha Venture would have enough lift to pull the front end off the ground (I said it was an old article).
Motorcycles have the areodynamic coefficient of drag of a brick.
The rider and exposed wheels are the largest contributors to drag.
It only takes about 12 horsepower to drive the mechanicals (engine and drivetrain friction) of the motorcycle at a speed of 150mph.
It takes over 120 horsepower to push the motorcycle through the air at 150mph.
The Hooligan speaks the truth. I found this chart that was compiled from the specs out of old Car & Driver and Road & Track magazines.
Vehicle Drag Coefficient (cd)
Description Low Medium High
----------------------------------------
Experimental 0.17 0.21 0.23
Sports 0.27 0.31 0.38
Performance 0.32 0.34 0.38
60's Muscle 0.38 0.44 0.50
Sedan 0.34 0.39 0.50
Motorcycle 0.50 0.90 1.00
Truck 0.60 0.90 1.00
Tractor-Trailer 0.60 0.77 1.20
Motorcycles can have more Cd than a tractor trailer! Fortunately, we only have a fraction of the frontal area. In the case of my Insight, the FJ is about 1/2 the frontal area with about 2 - 3.6x the Cd...so the total drag on the FJ is about even to DOUBLE that of my car!
Cap'n Ron. . .
"operating the engine at it's torque peak"
This is why I think higher gearing doesn't really help the MPG deal. It sure helps with noise and comfort level though.
On an engine test stand (not real world) running at peak TQ is usually max fuel efficiency or "Brake specific fuel consumption (BSFC)". So that's running at 7500 to 8000 RPM....... ? What do I do with the rest of the gears..... :dash2:
George
Quote from: skymasteres on October 08, 2013, 01:00:51 PM
.......From a pure efficiancy standpoint, you're maxium steady state fuel economy will generally be acheived if you are operating the engine at it's torgue peak. This is usually where your break specific fuel consumption is lowest with respect to the power produced. The trick, is gearing so that your typical cruising speed is in that range. ......
I don't think this is a correct statement.
Operating a engine at its torque peak for the best 'mechanical' efficiency....yes, I can buy that.
But...
Operating a engine at its torque peak for the best 'fuel' efficiency?
Nope, I have a problem with that.
The best peak torque numbers on the FJ engine comes in at what....6800-7400 rpm?
My bike guzzles gas in the kookaloo zone.
Pat, the BSFC is almost always at the torque peak. I somehow doubt that you're cruising at your torque peak in a lower gear (thus running a rational cruising speed, as higher speeds would increase the drag quickly as described) for any length of time. I'd wager that you tend to be sitting near WOT when the needle takes a walk past the torque peak, in fact.....
Reducing frontal area noticably isn't that difficult. Lower the bike at both ends, remove the seat, and put your chin on the gas tank. If you're not gearing limited, your top speed will increase a surprising amount.
More importantly... Guys, c'mon. If you're that worried about mileage, let's worry about tire wear, chain wear, brakes, and so on. Gas isn't the only expense to think of here. But more importantly, why exactly are you using an inline 4 of well past a liter displacement? Sell the bike, buy a small diesel hatchback. Or trade down to an EX250. I mean, come on!
Quote from: andyb on October 09, 2013, 09:04:51 AM
Lower the bike at both ends, remove the seat, and put your chin on the gas tank.
This bloke's nailed the technique.
(http://upload.wikimedia.org/wikipedia/en/4/4a/Rollie_Free,_record_run.jpg)