Quote:
Originally Posted by redyaris
I have been meaning to ask you some questions about how you get the FE you get with such a large engine. Although BMW's have always got better than average fuel economy, than other bikes.
1. What is the bore size of your carb. or fuel injector?
At 80km/hr the GS500 is turning at 3000rpm in 6th gear, I find I have to gear down to 5th gear if I want to accelerate smoothly. I do suspect that I may be running rich but I will only make changes after installing a O2 sensor and readout. At 110km/hr I use less than 20% throatle, which is just off idle, at 4200rpm. The GS500 has 2, 34mm mikuni carbs, which may be way to big for good fuel economy. The Kawasaki Ninja 250 has 30mm carbs 22% smaller. I may look into getting smaller carbs maybe as low as 28mm, if mikuni makes ones that will fit in the place of the stock carbs. I do agree that there is room for impruvement, although I dought that at 110km/hr I will get better than 70 -80 mpg. I will keep going to see at what level it ends... 
If you look at the 82.5mpg I got at Lacey averaging 40mph, between 30mph and 55mph, it is clear that under the conditions you face I to would get much better than the 68mpg I get now. |
1. I must admit that after an hour of googling I don't have the faintest idea about the injector diameter. I can tell you the cylinder bore*stroke (100*83mm), the compression ratio (11.5), I even found the Bosch part number for the injector, but nothing about the intake size
Rpms: it's 2800 at 70km/h and that's about the bottom of 5th with Teresa. Of course acceleration is quite weak here, but it doesn't hurt anything when I'm cruising. At ~3500rpm it's much better, but if you have power for a brisk acceleration the engine is too strong to work efficiently
I try to keep the engine at somewhat higher rpms on inclines, especially with a passenger. And I usually glide the declines. It's not rare that I P&G on flat either (with 90-110km/h pulses then glides down to 70).
In 4th the bottom is ~2500rpm, though she likes ~2700-2800 better. It seems the most efficient gear to me, even a bit better than 5th, given that I really use it at <3000rpm (~60km/h) - I think aero drag kicks in at the speeds where I can shift to 5th. I cruised pretty much in 4th in the winter, I was simply cold in 5th and didn't feel lively enough to P&G
In lower gears I practically always P&G (except for steep inclines), and if I have at least ~500-600m to glide I like to FAS.
Redline is at 7000rpm anyway. I never see it, I shift as soon as possible.