What are people modding with medium size bikes?

[redyaris]

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.

[theycallmeebryan]

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.

[alvaro84]

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 ) 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 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
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 ). 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 ).

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 ) and outright P&G when commuting.

[redyaris]

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. 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. My central focus is aerodynamics because motorcycle are poor aerodynamicaly. a good motorcycle has a drag coeficiant of 0.65 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.

[alvaro84]

Please keep that log updated

And especially note there anything you do to the fairing!

[redyaris]

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 .

[alvaro84]

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.

[redyaris]

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. 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.

[redyaris]

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.

[redyaris]

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,...]