To those who have installed a 15T, did your economy change?

[FrugalNinja250]

I'm doing an informal survey to see if installing a 15T front sprocket had an effect on fuel mileage, and if so, in what direction. If a documented change was noticed, how much was it?

[kkim]

Originally Posted by FrugalNinja250

I'm doing an informal survey to see if installing a 15T front sprocket had an effect on fuel mileage, and if so, in what direction.

you might also want to add... "and by how much?"

also, is this only for pregens? if you want everyone's response, perhaps the "general" forum for a better cross section?

[CynicalC]

Don't forget "how did you calculate and document the change?" and "have your riding habits changed?"

[dubojr1]

Originally Posted by CynicalC

Don't forget "how did you calculate and document the change?" and "have your riding habits changed?"

This is what would make it so hard to understand everyone's input. Personally I did not notice much of a change. Down a little if anything but is it from the sprocket change or grabbing a little more throttle due to the new found pep...IDK

To be real technical, we would also need information on whether most of the riding was done on the highway, city, stuck in traffic, climbing mountains, track, etc.... The list goes on and on....

[speedgsx98]

I have (2) 250 ninjas. In 3 tanks on the one, I got 62,64,63mpg with a 15t. On the other bike, with the 14t and correcting for the speedo dif between the two bikes, I got 64mpg.

I use the bikes for commuting on to work going 70-75mpg for 22miles and through city streets with stoplights for 3 miles. 25 mile each way commute.

Problem is that when running a 15t, that even though your rpms are lower, you need higher throttle input to get the same thrust. SO, it sort of cancels itself out. Only reason to go 15t then is to get the bike in the proper rev range for the type of driving you do.

I think I'll be sticking with the 14t on the one bike, but will be leaving the 15t on the other.

[Live2ride]

No matter how easy I rode with my 14t sprocket I couldn't get above 50-50.5 mpg. I rode rather cautiously on my first tank with my 15t and got 57.5 mpg. I expect the mpg change to be minimal after several tanks with the 15t. I love the higher gearing though; which is much more important .

[road_rascal]

I got back today from a trip 'up north' to WI and got 67mpg. I was going about 65-75mph on the highway and some back roads. Love this little bike!

[Yasko]

15t is the best mod by far for the pre-gen...

[Jinx250]

MPG jumped from mid/highs 40's to mid 50's. Zero change in my riding style other than adjusting for the difference in the way the bike runs. Each gear is taller now, so I can do "more" before shifting. Other than the adjustment to the gearing, I still ride it like it's a rental - no mercy.

[Donnyd21]

Just got mt 15T installed today, best mod ever, no more searching for "7th" gear. Lowered my rpms by 500.

[Live2ride]

My first two tanks after the 15t were 57.5mpg riding easy and 54.5mpg riding her hard with a lot of wot and high rpm. I got around 48mpg average with the stock gearing so it did increase gas mileage but not by a huge amount. I honestly expected better mpg when I bought the bike so this was definitely a plus. I like the taller gearing and the comfortability it gives me more so than the extra mileage.

[FrugalNinja250]

My mileage dropped to 48 on a tank last Friday. However, I had full saddlebags and was doing 80 (actual) into a steady 15-18 mph head wind, giving me an effective airspeed of nearly 100 mph. Not surprised my mileage dropped. Coming back with the tail wind and still at 80+ my mileage rose to 59.

[Donnyd21]

I am nearing the 200 mile mark on my 15T, I plan on filling up on thursday and will post back my MPG results.

[Buffalony]

Sprocket changes do not affect fuel economy.
Still takes the same amount of energy to go just as fast.

[FrugalNinja250]

Originally Posted by Buffalony

Sprocket changes do not affect fuel economy.
Still takes the same amount of energy to go just as fast.

Yes, from the external point of view it does take exactly the same amount of energy to go a given distance, all considerations of wind and terrain being equal.

However, the input energy never equals the output energy, and what you're referring to is the output energy. The input energy is in the carbon-hydrogen bonds of the gasoline used as fuel. The motorcycle's systems converts this input energy into the output energy with varying degrees of efficiency. It's in the conversion where you gain or lose fuel mileage. The higher the efficiency, the less fuel is consumed to go a given distance, right?

Enter the BSFC map:


This is a way of visualizing the relationships between power output, RPM, and fuel consumption in an engine. You can see that fuel consumed for a given power output decreases as RPMs rise, then at a certain RPM range the fuel consumption stabilizes, then actually increases as the RPMs continue to climb.

Why is this? Well, there are many, many factors at play, most related to variations in engine design. Intake and exhaust resonant tuning, for instance, greatly affects the RPM band where BSFC numbers are the lowest. Internal engine friction, both mechanical (cams, bearings, piston ring friction, pumping oil, etc.) and that due to pumping losses (it consumes energy to suck air past a throttle plate), all have significant effects on the amount of output energy can be extracted from the input energy.

As you can see from the BSFC map above, you get your best efficiency at lower RPMs with higher percentage of available power consumed at that RPM.

Horsepower is a function of RPM, as can be illustrated by the horsepower formula: Torque x RPM divided by 5252. The same torque at higher RPMs produced more horsepower. However, at higher RPMs more power is lost due to pumping losses and internal friction, losses that stay the same regardless of whether you're putting out 10 horsepower or 30. If you're only using 10 horsepower at an RPM where 30 is available the losses are higher per horsepower than they would be if you were putting out 10 HP lower in the RPM band where only 15 horsepower was available. The net effect is that you generally want your given power output and RPM to be in the part of the BSFC map where fuel consumption is the lowest, and that's usually lower in the RPM range where power used is a greater proportion of power available.

So yes, the amount of output power it takes to go a given speed is the same at any RPM, but the amount of fuel energy consumed to produce that power can vary pretty significantly, and thus significantly affect fuel mileage.

The Ninja 250 relies on RPM to get it's maximum power rating, and fuel efficiency is secondary to that. I theorized that moving my cruise RPM lower in the RPM band that I would end up using a higher percentage of available power at cruise to maintain the same speed (available power being lower because of lower RPMs), and thus would move into a more favorable portion of the BSFC map. The reduction in friction and pumping losses helps here as well. The results were conclusive to me, a definite increase in fuel mileage as proven by dozens of measurements before and after the change.

Wiki on BSFC (fairly short, it's ok but not great):

http://en.wikipedia.org/wiki/Brake_s...el_consumption

Sample BSFC maps:

http://ecomodder.com/wiki/index.php/...28BSFC%29_Maps


Then again, maybe all those tens of thousands of engineers and a century of scientific observation and experimentation are wrong...

[Alex]

Originally Posted by FrugalNinja250

Then again, maybe all those tens of thousands of engineers and a century of scientific observation and experimentation are wrong...

That's a bit harsh. I think the most correct way to think about this is somewhere in between your position on one side, and on the other position stating that there is zero effect. In other words, you are provably correct that lowering revs will have lowered pumping losses, and therefore should have better fuel economy if all other conditions are kept equal and measured very precisely. But I believe you are over-estimating the gains, and are unable to attribute any gains or losses due to this one change alone.

Pumping losses just aren't that different from an engine turning 9000 rpm making X hp and an engine turning 8500 rpm and making the same X hp. A few percent of rev changes are a fraction of a percent of economy differences.

The analogy would be someone deciding to substitute one diet can of soda per month for a normal can. It can be scientifically proven beyond a shadow of a doubt that the individual is taking in X fewer calories per month due to that change. But everything else they eat and/or every bit of exercise they choose to partake in that month will have a much more significant effect on their ultimate weight gain/loss.

Sprocket changes aren't a panacea for economy gains. They can be a very small part of it. Riding conditions and riding styles will always have a much, much larger effect.

[dubojr1]

oh now you've done it.... Information overload...

[Buffalony]

Originally Posted by Buffalony

Sprocket changes do not affect fuel economy.
Still takes the same amount of energy to go just as fast.

I knew what I was doing when I posted this Alex. lol

Great response Frugal.

[FrugalNinja250]

Originally Posted by Alex

But I believe you are over-estimating the gains, and are unable to attribute any gains or losses due to this one change alone.

I didn't estimate the gains. I measured them. In real numbers. Over a ten month period of time, before and after. Kept records. Averaged. Analyzed. Many, many samples. My mileage went up, significantly enough to measure, and the only change was the sprocket. Riding habits the same. Mostly the same commute every day, day in and day out, month after month after month. I got the bike with 2K, it now has 31K. From 2K to 18K was with the 14T, from 18K to 31K is the 15T. 16K miles pre, 13K post.

If you don't want to believe it, then don't, but please don't try and foster the opinion that I'm imagining things or am incapable of real empirical observations and statistical analysis. I actually took this stuff in college...

[Buffalony]

Originally Posted by FrugalNinja250

I didn't estimate the gains. I measured them. In real numbers. Over a ten month period of time, before and after. Kept records. Averaged. Analyzed. Many, many samples. My mileage went up, significantly enough to measure, and the only change was the sprocket. Riding habits the same. Mostly the same commute every day, day in and day out, month after month after month. I got the bike with 2K, it now has 31K. From 2K to 18K was with the 14T, from 18K to 31K is the 15T. 16K miles pre, 13K post.

If you don't want to believe it, then don't, but please don't try and foster the opinion that I'm imagining things or am incapable of real empirical observations and statistical analysis. I actually took this stuff in college...

Why didnt you just say this and post the data for us to view instead of starting a poll?
I dont mean to sound rude. The question came up after reading this post.

[almost40]

ok, so YES a 15T or 3 off the rear will result in better fuel economy an average.

[Buffalony]

Originally Posted by almost40

ok, so YES a 15T or 3 off the rear will result in better fuel economy an average.

Yes. According to the data.

[Fly'in Ninja]

I did the sprockets change: 15f - 42r on my '09 250r

90% freeway = 68mpg @ 60-65mph (up from 62mpg)

[Buffalony]

one for mythbusters? I think if two riders in the salt flats decided to test this doing exactly the same speed, then yes I could understand a 15T doing a little better. Throw in all the real senarios of driving and I think the difference will be neglegible.

[Alex]

Originally Posted by FrugalNinja250

If you don't want to believe it, then don't, but please don't try and foster the opinion that I'm imagining things or am incapable of real empirical observations and statistical analysis. I actually took this stuff in college...

The last time you posted up numbers, you said it used to get something like 59 mpg on average, and with the sprocket change it gets something like 62 on average, right? BTW - both of those are great mileage numbers, so the bike appears to be in good tune and your riding environment/commute seems to be mileage friendly.

If you have all of that data, post the variation in tanks across both timescales, and it will be much easier for you and everyone else to judge the effectiveness of the sprocket on improving fuel economy. Heck, didn't you mention you got 48 mpg on just the last tank?

The only thing I learned in 5 semesters of college stats is that with enough time and effort, you can get them to mean anything.

[Johnnyscoots]

OK. Did not touch the front sprocket but went down to 41 tooth on the rear. Have averaged the higher range (65-67mpg) vs. the 45 tooth (61-64mpg) dependent upon where/how I drive. I have had a reading of 69mpg, but that was probably an anomaly as my girlfriend's brother had the bike for a week so I'm not sure about his fill up technique, so my estimates for fuel economy would be suspect. The primary reason for the sprocket change was to increase fuel economy, and I primarily use it for work/minor shopping trips/visit the girlfriend. Quite happy with it!

Johnny

[almost40]

Originally Posted by Johnnyscoots

OK. Did not touch the front sprocket but went down to 41 tooth on the rear. Have averaged the higher range (65-67mpg) vs. the 45 tooth (61-64mpg) dependent upon where/how I drive. I have had a reading of 69mpg, but that was probably an anomaly as my girlfriend's brother had the bike for a week so I'm not sure about his fill up technique, so my estimates for fuel economy would be suspect. The primary reason for the sprocket change was to increase fuel economy, and I primarily use it for work/minor shopping trips/visit the girlfriend. Quite happy with it!

Johnny

I run mine cause it gave me the best times in the quarte mile. Plus it seems perfect for my weight and engine power output..........PLUS I get the mileage when Im a good boy.

Best thing about the 41 rear is 7000rpm-60mph
8000-70mph
9000-80mph
Not exactly but real close. but theres plenty left in the motor at 80mph at 9000rpm

[Johnnyscoots]

Almost40:

On the RARE occasions I try to see what it can do, the tach shows 10K rpm's at 95 indicated. What kind of quarter mile ET's you getting? I've seen people (Racer X, I think) get under 15, but only after doing a wee bit of work to it. Still impressive for a 250!

Johnny

[FrugalNinja250]

Originally Posted by Alex

Heck, didn't you mention you got 48 mpg on just the last tank?

You got me, Alex, you've caught me in The Lie.

(Though, you forgot to mention the context, namely, the circumstances where I explained why I got 48 on that tank. Color me surprised...)

It's obvious to me that you Believe that changing sprockets can have no effect on gas mileage. You have utter Faith that you are correct in your Belief. If there's one thing I've learned in my many decades of life, it's that True Believers will Believe what they Believe, regardless of *any* information that contradicts those Beliefs. I could post my data, take up a whole page of the forum, but honestly, I know you won't believe it.

And the whole question arises, why do I have to prove this to you in the first place? A thousand other claims get posted on this forum and yet this is the only one that prompts you to demand the data to support the conclusion. A rather trivial conclusion, at that.

I'm already noting innuendo and sarcastic personal attacks by other members against me, stuff like "FrugleBugle" and "...more time calculating your mileage", etc, just because I have apparently committed heresy by claiming a sprocket change increased my gas mileage. This is evidently the kind of forum where behavior like this is expected and tolerated. That's too bad, Life's too short to put up with crap, it honestly is.

I've found that when the sarcasm and snide comments start (especially from a moderator!) and the trolling starts (Buffalony) then it's time to depart.

Later...

[Alex]

Frugal - I'm sorry you feel that way. I'm not trying to be snide. Though I do employ sarcasm at times (OK, alot!), it's very rarely mean-spirited, and it certainly wasn't here. I've got an engineering background just like many others here, and data trumps blind belief just about anywhere.

You apparently have the data to show that there has been a small uplift in mileage from changing your sprockets to a 7% taller final-drive ratio. The data you've posted so far shows about a 5% gain in economy. That seems very, very high to me. In a bike that cannot adjust its fuel mapping on the fly (stone-age carbs), the fuel usage across the rev range, and the throttle range is quite linear, so it cannot take advantage of any lean-burning or other tactics to lower fuel usage on lower revs and lower load. If I were a betting man (heck, I am a betting man!) I'd put it at a 3.5% expected gain due to 7% lower revs, and call it a day.

I guess in this thread, you're right, in that the question being asked isn't "how do you maximize your mileage on the ninjette?", and that's the question I keep answering, with someone choosing how hard to dial that right handlebar control being the prime factor in fuel mileage, either up or down. Your point is more targeted, that if one has already optimized everything else, going slightly taller on sprockets results in slightly better mileage. And as I said in the post above, and in this one as well, you're likely correct.

What the poll results do show (limited as they are), is that half of the people who do make the same sprocket change, aren't seeing any mileage benefit. And half of them are. I think that goes to the main point that I have been trying to make (evidently not without annoying you), is that this isn't a big deal in the overall scheme of how to improve the mileage on a ninjette. But to your point, it's not nothing, either.

[Buffalony]

Originally Posted by FrugalNinja250

It's obvious to me that you Believe that changing sprockets can have no effect on gas mileage. You have utter Faith that you are correct in your Belief. If there's one thing I've learned in my many decades of life, it's that True Believers will Believe what they Believe, regardless of *any* information that contradicts those Beliefs. I could post my data, take up a whole page of the forum, but honestly, I know you won't believe it.

A thousand other claims get posted on this forum and yet this is the only one that prompts you to demand the data to support the conclusion. A rather trivial conclusion, at that.

I've found that when the sarcasm and snide comments start (especially from a moderator!) and the trolling starts (Buffalony) then it's time to depart.

Later...

I'm truly sorry if you took it as trolling. It was not. This thread started out as a poll asking members if their economy benefitted from their sprocket change. Not as a thread providing good data showing that it actually does.

Sorry if you took our stance toward the topic as a personal attack, it was not intended as such. This subject has come up a few times over the past 2-3 years and no data was ever presented supporting the claim. So far I believe this topic is a two sided arguement.

I also believe this cant be proven correctly without the proper gadgets and gizmos such as those used on mythbusters. The episode that comes to mind with this is the pickup truck tailgate up or tailgate down. They determined a pickup with tailgate up actually had less drag. Anyhoo the flowmeters and such they used would suit this scenario quite well.

Post the data. I agree that it will be scrutinized. If it's valid and spot on cheers. Don't believe views can't change.

[Alex]

Originally Posted by Buffalony

I also believe this cant be proven correctly without the proper gadgets and gizmos such as those used on mythbusters. The episode that comes to mind with this is the pickup truck tailgate up or tailgate down. They determined a pickup with tailgate up actually had less drag.

I liked the one where they put golf-ball sized divots all over a Taurus to see if it would lower drag, and therefore improve economy. It did!

[almost40]

Originally Posted by Johnnyscoots

Almost40:

On the RARE occasions I try to see what it can do, the tach shows 10K rpm's at 95 indicated. What kind of quarter mile ET's you getting? I've seen people (Racer X, I think) get under 15, but only after doing a wee bit of work to it. Still impressive for a 250!

Johnny

I have run a 14.4 but 14.5 or so is the avg. Its all about. launch launch launch
Havent been to the dragstrip in a LONG time. Bought this bike, took it to the race track.....and thats all she wrote.

[Buffalony]

Originally Posted by Alex

I liked the one where they put golf-ball sized divots all over a Taurus to see if it would lower drag, and therefore improve economy. It did!

Really! I havent seen that one. Thats awesome. I'll have to add that one to the mod list jk

[Donnyd21]

Originally Posted by Donnyd21

I am nearing the 200 mile mark on my 15T, I plan on filling up on thursday and will post back my MPG results.

Filled up yesterday went 235 miles and put 4 gallons in exactly, got 63 MPG with LOTS of wot runs to 13k. Not bad, same MPG as with the 14T and same driving style.

[road_rascal]

Filled up again and this time I got 69.14 mpg (153 miles on 2.204 gallons). Not bad considering 80% is stop and go in town riding. Delicious .

[Bosgarage57]

Originally Posted by road_rascal

Filled up again and this time I got 69.14 mpg (153 miles on 2.204 gallons). Not bad considering 80% is stop and go in town riding. Delicious .

this is what I'm hoping for when I fill up mine.

[Buffalony]

I shimed the needles and pulled the snorkel. Now I'm getting 62mpg and it's a heck of alot more fun.