Suzuki GS500 Fuel Economy

[beatr911]

Nice work redyaris! Do you have any photos to post that show your current configuration?

An update on my Chinese 200. Still getting about 79mpg US regularly. No P&G, EOC or any advanced techniques. Freeway speeds are just about 100km/h, anything faster and the consumption goes way up. Tucking down gets almost exactly 5mph faster with the same throttle setting. I really need better aerodynamics with only 12hp available. Took a trip to the other side of the Cascade range last week for work. The steep mountain roads and running WOT in 4th at rpm somewhere between maximum torque and horsepower took a toll on the consumption - about 66mpg US for that trip.

Thinking about doing a high-velocity intake port modification this winter to improve mid range and hopefully mileage. Maybe increase compression a bit while I'm in there. Also I may try to make the aftermarket exhaust a little quieter. I like how quiet the stock is now though but it kills power and I'm sure is eating a few MPG due to the restriction, I'm running at 80-100% all the time on the freeway.

This little bike just doesn't have a very efficient combustion chamber. Simple, yes. Just not efficient. The counter balancer adds friction as well, but the smoothness is really nice.

[redyaris]

beatr911
I have been finding out what works in terms of EOC on a motorcycle and it is that any time you can see a stop or slow down ahead you should pull and hold in the clutch and use the killswitch to turn off the engine, after 2 or 3 seconds put the killswitch back in the run position and EOC to the stop or bumpstart in top gear and switch to the appropriat gear and drive on... as you get the "habit" you will find more and more situations to use it.
The only changes to the GS500 not is the GARAGE pictures, is the behind the rear wheel boat tail, which seems to have had a larger impact than I had emagined it would.
With respect to your plans for your bike I suggest that you stick to aeromodds as more power means more fuel... as you know. the area that would provide max benifit is tapered and fitted cargo boxes on the sides behind the riders legs, and some kind of boatail behind the rear wheel, non of which will change the utillity or ergonomics of the bike [getting on and off...]. you might find that then you can have the extra 5mph with out tucking down, plus the same mpg at 5mph higher speed...?
Cleaning up the ports and matching surfaces may help a bit but they all mean more fuel use. Higher compresion could help FE?

[beatr911]

redyaris, my commute has three possible stops in 30 miles, and two are predictable so I back off early keeping an eye to not impede traffic too much. As a percentage, the EOC doesn't do too much over a cluch in coast, I do however shut off on coast down at the one light if I know I'll be there for at least 15 seconds or so - helps engine cooling.

Agreed on making the aero better on the trailing surfaces.

I'm debating on how far I want to go with aero. There are still efficiency gains to be had with engine optimization that will also provide additional power to the wheel. I'm looking to sell the bike in the spring (or sooner) and would like to keep the appearance pretty close to stock.

I think the real solution starts with a lower seat height to minimize frontal area. The Yamaha 250 Virago v-twin design has a really efficient little motor, a low seat height and combined with taller gearing is a real MPG winner. Adding aero to this bike should improve comfort, MPG and of course storage capacity, and possibly looks if done well.

The plan for the Yamaha Virago 250 (or chinese clone) is narrrow drag bars, a cut down and reshaped seat, a front fairing from a Hyabusa suitably modified, tapering side panels behind the riders legs, a rear cone and a fully enclosed land speed racer front fender fairing. I'd also like to extend the swingarm and middle of the frame about 4 - 6" to relocate the seat back farther and several inches lower. I'm thinking as much of an aerodynamic styling exercise as much as a practical aerodynamic exercise. It works in my mind and with gradeschool quality sketches, hopefully I can translate it into metal and plastic someday.

[redyaris]

The Yamaha project sound good, the "two bit" recomendation I do have is start at the rear and the cargo space then work your way to the front of the bike. When you do the longer swing arm be shure to incorperate mounting points for some rear wheel shraouding, I have a suspicion that the spinning rear wheel has a larger affect than most people think.

[redyaris]

Originally Posted by beatr911

I think the real solution starts with a lower seat height to minimize frontal area. The Yamaha 250 Virago v-twin design has a really efficient little motor, a low seat height and combined with taller gearing is a real MPG winner. Adding aero to this bike should improve comfort, MPG and of course storage capacity, and possibly looks if done well.

The plan for the Yamaha Virago 250 (or chinese clone) is narrrow drag bars, a cut down and reshaped seat, a front fairing from a Hyabusa suitably modified, tapering side panels behind the riders legs, a rear cone and a fully enclosed land speed racer front fender fairing. I'd also like to extend the swingarm and middle of the frame about 4 - 6" to relocate the seat back farther and several inches lower. I'm thinking as much of an aerodynamic styling exercise as much as a practical aerodynamic exercise. It works in my mind and with gradeschool quality sketches, hopefully I can translate it into metal and plastic someday.

I think the key to the viability of an effective aero motorcycle is a low seat height, because of the ergonomics of getting on and off the bike are changed by not being able to swing your leg over the rear seat unless you can come up with some simple/easy way of moving the cargo box for getting on and off. On the GS500 I can get on and off quit well even though I have a 30" inseam, but lower is always better, I do like your plan for the 250V-twin, although I have my doughts about the need for swing arm extension. I am toying with the Idea of a Vulcan 500 as a low seat height aeroproject but I will need more info for that.