What are people modding with medium size bikes?
 

I have a Suzuki GS500 F which I have been modding for the last year or so. There are lots of threads on small bikes but not much on 400cc to 650cc bikes. What are people doing to improve fuel economy on medium size bikes and what are the results? So far I have got to 3.3L/100km [71mpg]... I hope to get to 2.5L/100km [94mpg]... click on Gray to see pics.

Wow! You have done some interesting aero mods to that bike. Did you test/measure the effects of those mods? I'd be interested to know how they influenced your fuel economy.

I see you already geared the bike up a little bit. Gearing seemed to help a lot on my bike. Other than that, most of my improvements have come from riding technique.

Do you ride mostly in a tucked position or casual? I used to ride tucked all the time until i experienced some lower back pain and didn't feel it was beneficial to keep tucking. I was able to hit 101.5mpg while tucking for an entire tank of gas. My best without tucking is 95mpg or so. I haven't really tucked since because lower back pain isn't worth 6mpg (5%) to me.

I top up Teresa's tire pressure to sidewall max instead of BMW recommended. It feels that it improves her coasting ability (and I'm so much used to the harder ride that I miss it if the pressure gets lower...). The same holds for tucking, though I only tuck for glides (only for glides) on my commute and seldom on my longer trips. It would really be tiring and (if it would be that comfortable I could have even bought a crotch rocket :D) I did not necessarily tuck for many of my best tanks (and clearly not in Austria, where I got very good ones lately).

I don't have any specific aero mods though, so I'm curious how much they could help. Teresa has only partial fairing, but equipped with a very small windshield that looks pretty aerodynamic :D wide handlebar is a different matter... but handles very well (NOT tucked). I was briefly experimenting with the windshied angle, but it wasn't a success. Anything I should do to aero shouldn't spoil her slim figure though :D :D :D
Electro mods: I replaced the back parking/brake, license plate and instrument panel lights with LEDs. Not much, but these are the most used ones (except the lowbeam, but I don't see any real LED alternative for a 55W halogene H3)

As for changing gear ratios: that's often a very efficient way to improve FE. We'll may do it with Ciliegia, may not (she's a bit offtopic here being a 250 :D). Teresa's toothed belt drive is another question, and the ratios are pretty good as they are already (can't even use 5th under 70km/h - the only place I'd need longer is the freeway, but we don't plan to use them too frequently anymore :D).

The most improvement I could get is through hypermiling, it was a blast to learn how coasting and Pulse&Glide works. I could reach several tanks around 2.6l/100km (~90mpgUS) this summer by trying to coast everywhere I had to slow down (and downhills!) on longer trips (works GREAT in Austria where there are thousands of villages and PSL changes in every km :D) and outright P&G when commuting.

What I have done to date, I have not tested regerusly because I am more interested in the long term outcome of better fuel economy. :thumbup:So my fuel log is my test, the trend is the mesure of my success. I have read enough aerodynamics to know what has worked in the past. The most noticable change came from the styrofoam "saddle bags" they are about 4.5" wide 16" tall, and 24 inches long. various shaped styro foam peaces have been glued on to fill up the space behind the legs in a way that does not interfear with stoping or riding the bike, it is a work in progress. I have begune to make my own plexyglass windshield extensions; heating them in my oven in a cemicycle shaped peace of sheet aluminium. Only screwed up a couple of times and have been learning... I rarley ride in the tucked position. I take the same view that Vetter and Janvos take... the fuel economy of normal riding is what matter to me. When I have got the real saddle bags made and installed I will post a DIY discription that others can copy. ;)I do not do much hyper miling on my bike, I do long costs to a stop, posted speed, gentle acceleration, nothing very radical. :oMy central focus is aerodynamics because motorcycle are poor aerodynamicaly. a good motorcycle has a drag coeficiant of 0.65 :eek:a good car has a 0.32 which is twice as good. I suspect that a aerodynamicaly well design conventional motorcycle can get to 0.45 even without going all the way to a "dustbin" fairing which is fully inclosed.

Please keep that log updated :)

And especially note there anything you do to the fairing!

alvaro84 when I look at your BMW F650CS the area I see that might help areo and not harm looks is saddle bags close behind the legs and not much wider than the legs but quit long, about 12cm wide 60cm long and 40cm tall. They would have to be on some form of rail so that they could be moved back to accomidate a pasanger. I don't know if you can find something like that in the EU but if you can they would help. For some reason BMW's have always been very good on fuel economy, and of all the manufacturers they have made the effort from time to time at providing areo bikes to the market. unfortunatly the market is driven more by fashion and style than good areodynamics :(.

Hm, I think I get it.
Thanks for the idea, I'll look for a way to try a 'saddlebag panel'. Removability is also a good idea, I do travel 2-up a lot.

alvaro84; good aerodynamics do not have to be unfashionalbe, good and fashionable graffics can cover what would otherwise be to strange for most peoples sence of style:cool:. The issue of good windshield aero is the exit angle of the edges of the windscreen, they should be as close as posible to paralell to the air stream, this is sometimes at odds with protecting the rider from the wind;). I have been out in the garage today doing more modds to my GS500, closing up usless "fashion" openings in the fairing and installing shrouds infront of the forks, the next 200km plus trip will tell if they really do something. I will post pic in the emggarage soon;).

The pic's are in EMgarage now.

After installing some new mods I went on a 214 km test run in 10C air temp, windy, with some light rain,at speeds between 100km/hr and 120km/h, [62mph and 75mph] and got a disapointing 3.8L/100km [62mpg] :(I suspect that it had to do with the low teperature and the relativly high humidity both of which affect air density. I will have to make more test runs to see... and look into what relative humidity does to air density.:confused:

Air at 100% humidity is less dense than air at 10% humidity, so my engineering family tells me. I had emagined that it was the other way around. if I understand it right its because a molecule of H2O is less massive than a molecule of any of the other gases in air [N2, O2,...]:thumbup:

Hm, I don't know how humidity affects FE, but low temperature and wet roads hurt it (rolling resistance gets higher too). Wind is even worse. I can clearly see that I can't coast as long as I usually do (at the same places on my commute)!
Extra weight counts too - my last 100% 2-up tanks reached a disappointing 3.2l/100km (~73mpgUS).

interesting bike. i love the gs500. i had a 92 model about 10 years ago, but it was rough looking. anyways, cool mods, keep up the good work. one thing i might suggest, instead of those panels you put on the front forks around the fender, it would work alot better using a larger fender that actually covers most of the front of the tire. i am doing this myself this winter, just a suggestion.

Alvaro84 You are right about what happens when it rains, what I am saying is that until there is so much water in the volume of air that no more water can be absorbed the air gets less dense, as more water is added to the volume of air; beyonde its saturation point, and actual water droplets form, creating rain, fog, hail, snow sleet etc the density of a volume of air goes up. My daughter looked up the data and did some sample equations and even she was surprised at the outcome untill she thought about it for a minute because it seems so counter intuative. But once she thought about it and explaned it, it made sence, even with my more limited understanding of such things.

KawboyCafe What you see in the EMgarage pics is the quick and dirty version, not the proper solution that you suggest. I will keep this version on until I have run 3 [1200km, 750miles] or more tanks of fuel through it and then do what you suggest, probably next summer.

It seems I'll have a part gs500 soon too. At least the front rim. Potholes pretty much ate Teresa's front rim, to a point where she needed a guest rim just to pass our version of MOT - while we practically don't have flat enough roads to actually sense the dents in it... (Are most of our roads so dangerous? Then repair them, and leave me alone with this rim that got hurt by THESE roads, right...?)
OTOH, if BMW makes so soft rims (I'm not the only BMW owner one who got their front rims deformed because of bad roads, not at all...) I don't want to have another time bomb attached to the front fork. That rim is a piece of art, but a pretty time bomb is still a time bomb. I'd rather get something different. GS500 parts are easy to get, the tire size matches and brake disc size is close enough and it's on the same side...

Alvaro84 Do you know others who have done this conversion before? If not then I would caution you to take lots of mesureurment of all the parts. I have in the past modified wheel rims; both cast and spoked wheels and rims, to fit onto mini road race bikes [honda cr85 with suzuki cast wheel rims] and the amount of critical mesurements is amaising, to name just a few; axle and wheel bearing size, spacer size disc offset speedo cable, wheel to fork spacer and so on and on...

TTT I have a mechanic to take this measurements and give the nod if it's OK to do (and implant the new wheel too). I lack the knowledge and experience to make mods to such crucial parts. If an "alpha test" fairing piece fails it probably won't cause any serious trouble - unlike a failing front wheel :eek:

Alvaro84 Did you manage to find rims that are the same colour or will you have to paint them? As you can see my GS500F rims are black and I don't remember if they where any other colour.

It'll be a quest ;)
I've seen GS500 rims in natural metallic color (at least on the 'net), that must be becoming.

Red- What MPG were you getting before the aero mods?

I'm guessing the main reason I average 40mpg on my CBR600 is the gearing. I'm doing 5000rpm at slow highyway speeds.

Before the aero mods I could get as good as 67mpg at 53mph average speed and at 75mph average speed I would get 57mpg. after the aero mode I get 67mpg at 75mph and 71mpg at 63mph. At this stage I do not have a large enough sample size to be confident of my numbers. I am using the trend in my fuel log as my test, so until the number of entries gets to about 30 or so with a strong trend line I won't be sure. By some peoples standard this is not a very good test of aeromods, however my objective is fuel economy so this method works for my perposes.
On your cbr600 I would agree with you that a gearing change would help fuel economy. However you would have to accept a loss of acceleration and top speed in 6th gear. On my GS500F after the aeromods and gearing changes, one of the things I notice is I need less throatle to maintain speed on the highway at 75mph. The other thing I notice is that top gear acceleration is better than before the mods. These are subjective so a grain of salt is in order, until the sample size on my fuel log is large enough, and the average fuel consumption is better.

Your MPG increases sound substantial, and that is all I was wondering.

If there were a way to make only my 6th gear taller then that would be the optimal route. I don't use 6th gear on the track anyhow. It seems it's just too tall to be of any use on the track, and far too short for freeway cruising.

repoint5 one of the nice things about most sport bikes is the availability of sprockets; in your case you could have a front sprocket for the track and an other bigger one for the road, that way you could get better mileage on the road. Kieth Code [a twist of the wrist...] recomends a practice drill called no bracks, to held develop judgement of corner entry speed that could be transfered to riding on the street for better milage. By driving on the road without using bracks you also develope race craft, the accurate judgement of speed relative to the conditions at hand.

I have considered the sprocket change, but I really do like the acceleration that is available with the current gearing, with the exception of 6th gear. Why don't car manufacturers just make a very tall "cruising" gear anyhow?

As for my street habits, I do not use brakes unless I am stopping. Rarely do I encounter a corner that I need to slow down for, as a posted 25mph corner can be executed at 55mph+.

Track practice improved my riding ability and confidence more than anything else.

redpoint5 It sounds like the track you ride/race on has relatively short strats, so you can't get into 6th gear. You may still benifit on the track from a larger front sprocket if the track has slow corners on which you can't apply full throatle on the exit of a turn. You mit want to experament at the track with a bigger front sprocket to see how it affects your lap times. You could find that for some tracks the taller gearing reduces lap time...!;)