Another thread about chain and sprocket, this time for efficiency!

[Andrew's]

I have searched a lot to save reposting an old question, but I haven't come across much on changing sprocket sizes for economy.

So I ride my SV most days too and from work, I generally tickle it through the gears and spend 10 miles at motorway speeds. Would I see a reduction in consumption [improved econamy] if I fitted a 16 tooth front sprocket and stock rear due to lower revs at same speed?

This one? http://www.motorcycle-road-and-race.co.uk/catalog/product_info.php?cPath=182_183_188&products_id=403666

[speedplay]

Ask Ralph to post a yes/no poll for you....

[Andrew's]

Ask Ralph to post a yes/no poll for you....

This Ralph (http://forums.sv650.org/member.php?u=2405)?

[jambo]

Please God no...
We could try discussing the matter instead of just letting people blindly vote?

Here's the crux of it: If, in top gear, at cruising speed the rpm is higher than peak torque you might do well to raise the gearing.

But it will make the bike slightly less responsive at lower engine speeds

Jambo

[speedplay]

Please God no...




Sorry, the sarcasm was lost :(

[jambo]

Sorry, the sarcasm was lost :(
It's alright mate, I got it, but was worried the OP might not be used to it :D

[Stu]

I ran 16 so it can be done - hard to say if it improved economy. I thought it did so it kept me happy.

[yorkie_chris]

Quite possibly it will.
There's a guy with a curvy gets 80 odd mpg (the git!), I think he's done similar.

Also use a scottoiler or similar, a worn, dry chain robs a hell of a lot of power (hence petrol)

[graman]

I have used a 16t front for the last 25k miles and found it has improved economy and the engine is more relaxed when cruising. I have just changed now to a 17t front as I do a 70 mile round commute on dual carriageways and it is even more relaxed. It lowers engine speed and reduces friction but it still has to produce the same power at any given speed so the engine has work slightly harder. I have found a 3% improvement in economy for this last gearing change so you should get a similar improvement using a 16t. I don't know how it improved economy from standard to the 16t as I changed it when I first got the bike.

I certainly recommend using the 16t front for anyone who does larger mileages and motorway or dual carriage way work. If you use the bike for fun, sporty work or twisty roads it is not worth changing as you do loose a little acceleration.

[SVMAT]

Was thinkin about going 1 up at the front myself but decided against it as around town and anything under 45 my bike already labours in top gear. So id prob sacrifice economy in town having to drop into 5th, just to get it back on the mway. It all depends on the ratio of your mway miles to town i suppose. But the main reason i wont do it is it would make it alot harder to pick her up in second, so ill just fork out the extra couple of quid a tank.

[embee]

I too run a 16T on a curvey SVS. Th emain reason I went to it was because I always felt 6th was subjectively too low and I often looked for 7th (but this is a personal thing having been used to lower revving bigger twins).

It feels much more natural to me out on the open road and on motorways, and I can't ever remember searching for that elusive 7th gear since.

Economy? I reckon Graman's about spot on, 2 or 3% is the ballpark, whether you'd really notice that is debatable, it's maybe 1mpg, but it's likely to be in the right direction.

I'd say do it just for the more relaxed feel. I've often wondered what a 17T would feel like, unfortunately I'd need a longer chain to do it so haven't bothered, the 16T goes in with the stock chain length (curvey SVS).

[beabert]

Id like a more relaxed ride on the motorways too, but i dont think id be happy sacrificing my acceleration, i need two bikes lol.

[graman]

Embee is right about the standard gearing. It feels too revy when cruising. I have used a gearing spreadsheet to check the change in rpm at various speeds:-
The standard gearing 15t, = 14.1mph per 1000rpm
16t = 15 mph per 1000rpm
17t = 16 mph per 1000rpm

So at 70mph, standard 15t = 5000 rpm
16t = 4700 rpm
17t = 4400 rpm
You can see that it drops the rpm significantly. I run a NTV 650 as well which has 15mph / 1000rpm which is the same as the 16t gearing so I knew that the SV with more power, lighter and better aerodynamics than the NTV, it could pull a taller gear. It does and feels like a much larger engined bike with the engine spinning slowly.

This helps to get my economy to average at least 80mpg. (Not a misprint)

[MattCollins]

80mpg average is a tall ask... average I assume to be across every entry in a log book. I got pretty decent mileage out of the SV and even copped a little flack for it, but it was nowhere near an 80mpg average.

...............



For a bike that spends its days on motorways, a 16T counter shaft sprocket might be just the shot. However, if the bike spends the majority of its days running around at lower speeds in traffic then I'd suggest going the other way to better match load, rpm and road speed to the dominant conditions even to the point of gaining one full gear at those speeds. ie using 4-5 instead of 3-4 as the main cruising gear at lower speeds. Another benefit is that it is a lot easier on the clutch and oil plus it makes low speed manoeuvring a little easier.

There is some guy on this forum, but can't remember who he is, who runs what sounds like silly gearing. It is not so silly around town because it enables the full use of the gearbox and possibly a better load/rpm/speed match across this range of road speeds... if he were inclined to settle down.

[Andrew's]

Thanks for the comments, it's defiantly sounds like it would work out for me, but I don't think it's worth changing my current set up prematurely.

[kaivalagi]

3% better efficiency increase on going up one tooth on the front doesn't sound worth the hassle for efficiency alone.

Why not just change your riding style a little and be more progressive with the throttle and take it easy?

Also, does changing the number of tooth affect the speedo? is it based on the front sprocket or wheel or what?

[yorkie_chris]

Speedo is driven on front wheel.

3% is not a lot but when you are doing what that guy above is doing and making lots of little changes and all of a sudden is getting 80mpg it is worth it.
That is no-sh*t DOUBLE the mileage I get.

I'm considering going completely back the other way with all my tuning mods. Milder cams, taller gearing.

[kaivalagi]

Speedo is driven on front wheel.
Good to know I can slap a 14tooth cog on there no worries, I don't need the top end and like has already been said going 4th-5th rather than 3rd-4th alot might actually be beneficial in some small way

3% is not a lot but when you are doing what that guy above is doing and making lots of little changes and all of a sudden is getting 80mpg it is worth it.
That is no-sh*t DOUBLE the mileage I get.
I get anything from 45 to 60mpg, higher for long runs, lower for evening/weekend blips...I just don't believe 80mpg, 70mpg maybe at a push but not 80mpg...surely not.
I've also been messing about with my riding style too and I reckon could get to 65mpg without mods if I could control myself all the time.

I'm considering going completely back the other way with all my tuning mods. Milder cams, taller gearing.
If you do please journal it so we have something from beginning to end to follow and whole heartily believe :thumbsup:

If 80mpg is totally genuine then I salute the poster, I just find it very hard to beleive...and need proof to go with it 100%

[graman]

To get a good mileage you need to record the amount of petrol you put in the tank and mileage and ideally put it into a spreadsheet so it can calculate the last average mpg and the total mpg. Now you have a base for checking data.

My runs are at consistent speeds on dual carriageways and do 30 miles with only one roundabout so there is hardly any accelerating or braking. Any vehicle is economical doing this as long as you do not go fast (over 60mph) as the aerodynamics rob the efficiency. (drag is proportional to the speed squared).

I have logged the fuel consumption for 25000 miles and always have achieved over 80mpg commuting. Before I used it for commuting I still got over 60mpg. I enclose a graph from the spreadsheet.

http://forums.sv650.org/attachment.php?attachmentid=8267&d=1291575586
Graman

[Stu]

30 miles without exceeding 60? Yup, cos that's going to happen.

[kaivalagi]

To get a good mileage you need to record the amount of petrol you put in the tank and mileage and ideally put it into a spreadsheet so it can calculate the last average mpg and the total mpg. Now you have a base for checking data.

Or just use http://www.fuelly.com/ and get a whole bunch of data incl' mpg

As Stu says though who consistently does 60mph or less on dual carriageways with one roundabout in a 30 mile journey? My speeds range from 40 to ~ the speed limit (maybe a few % over ;)) in parts on A (some dual carriage) and B roads, where I go slow for bendy bits I go faster for straight, safe and empty roads without junctions. I think anyone in these conditions getting 60-65mpg on an SV is doing well, and with one extra tooth on the front I would expect no more than 65-70mpg maximum for better road situations than that...

80mpg, if indeed possible, will not come from "real world" riding IMHO. Is your bike solely used to get to work and back? Do you ride for pleasure too?

[Andrew's]

I guess there lies the issue. I like most, would rather maintain the higher speed and cheat the revs :D

Awesome work with 80mpg though!

P.S In Derbyshire/South Yorkshire it is impossible to get really good mpg thanks to the hills. :(

[mikerj]

I get anything from 45 to 60mpg, higher for long runs, lower for evening/weekend blips...I just don't believe 80mpg, 70mpg maybe at a push but not 80mpg...surely not.
%

I can believe it if you aren't doing much start/stop riding. I regularly get over 65mpg even though I tend to cruise at 85ish, simply because for the majority of my commute the bike stays in sixth and it's a long enough trip (30 miles each way) that the engine gets properly warmed up.

An older guy at work gets a regular 75mpg from his pointy with a similar commute, though he's a very steady rider. With taller gearing and steady, long commutes that don't involve city centers etc. I think 80mpg is entirely feasible.