Thanks for the MPG numbers on the bali,
it's about in line with what I got for the BMS TBX 260EFI.
I'm on a ramble right now, but feel like writing some of my thoughts down somewhere about MPG's and my (future)bike;
feel free to read it, or ignore it, as you please; but it helps me straighten things out mentally:
It seems that most scooters usually top out at 80MPG, regardless of engine size (50, 150, 250cc).
Larger engines, 500cc usually top at 75MPG, 600cc 70MPG, 650-700cc 60-65MPG, 750-800cc 50-55MPG, and so on...
Of course, smaller engines will most of the time be more fuel efficient, but not always, depends on the needs.
Does it need to face many uphill rides, lots of fast acceleration...?
I personally think it's a nice topic to debate; MPG; so allow me to speculate:
I'd state that from 50-250cc you got 80MPG avg; because,
while the 50cc's gain MPG, because they're small, and are used mainly in lower speed areas (less wind resistance to overcome), they are also more used for city riding (start-stop).
Meaning that they are topped out most of the ride (accelerating WOT to the next light, and so on; never really reaching max speed, always accelerating and braking), which works against their MPG numbers.
A well tuned 72-75cc BBK usually does not need to be maxed out to gain the street speed limits.
resulting me to come to a following conclusion:
For a 50cc at WOT the cylinder may be saturated, and normal compression/decompression(exhaust) strokes with a carburetor, may not get twice the performance from that same cylinder pumped with 25cc's of gas and air.
In other words, WOT riding is less efficient than regular riding, not only from wind resistance, and resistance from moving parts and oil, but also from optimal air/fuel content within a cylinder after the A/F valve closes, and before the compression stroke.
Riding style of a 50cc is expected to be city start stop traffic, but for a 150 as well as a 250 it's expected to do mainly suburban roads, and longer stretches of ride (eg: 5-10 minute rides)
The 250's are more made for even longer roads 10-20 minute rides, without too much start stop traffic.
Thus automatically, 150 and 250cc bikes have better roads to get good MPG results on.
When riding the longer rides (20-30 minute stretches) on a 50cc, MPG numbers really shine!
A 50cc can attain MPG numbers exceeding 105MPG (I've done it before).
The 150cc's is somewhat in a gray area, not too much info online about those...
I can only speculate they get somewhere between 90 and 95MPG, because the 250's top out somewhere around 82-84MPG; so I suspect the 150's will probably be in between.
I've said it before, but a 100-125cc engine would have the best of both worlds. Enough torque to keep up with traffic (without riding much WOT at all), enough speed to do short highways trips (55-60MPH), and high MPG numbers.
Some have even reported 125MPG numbers, for a Honda CBF125 motorcycle, (while more people get between 95 and 112MPG out of them; which is still better than a 50cc) and IMHO, it probably is the magical engine number that most scooters should strife to have.
Why magical? because it's strong enough to keep up with traffic, does not get ridden at WOT most of the time (Wot riding decreases MPG numbers considerably), is lighter than a 150cc for city riding, while at the same time it can keep up on highway speeds.
A fuel injected, manual geared, 125cc could be, very close to the perfect combo for a one person scooter.
Powerwise, most people seem to be happy about the performance of their BBK's (on 50ccs, eg: 72cc, 75cc, 80cc..).
So for a 4 stroke, anywhere from 72cc has sufficient power to keep up with traffic acceleration, but perhaps does not have sufficient speed nor cooling to maintain a speed of 60MPH.
For cooling reasons, as well as reliability reasons, I'm not too fond of BBK's; but would rather want to see a 150cc engine with a 125 'BBK', than a 50cc engine, with a 125cc BBK.
Another thing I've noticed in my car is,
When acceleration is about constant, but gears are increased (go up), MPG goes up.
As strange as it seems, just as long as the engine isn't drowning (used at max acceleration, or WOT for scoots).
If I only need 50% of the engine's acceleration, I might want to look how I can invest some of the remaining 50%; if I can put heavier sliders/rollers in resulting in me needing to use 25% more of the engine's potential, but also have a 25% faster speed, at wost it will be a draw in MPG numbers, at best I might get a lot better MPG; because engine RPMs go down.
Just as long as I'm not using WOT to accelerate, I believe there's room for improvement.
Engine RPM is very closely connected to MPG.
I understand what you're saying JR, by staying within the peak torque of the curve, but unlike on motorcycles, where an engine might have nearly as much torque at 2k RPM, as it has at 4k RPM (due to valve mods from the factory, and thus it could have a peak in the curve well below max RPM); on these scoots, the torque curve may show more torque at 6k rpm than at 2k rpm, but the torque curve is not linear;
Meaning it has more torque at 2k RPM, than 1/3rd of the torque at 6k RPM.
It's kind of like a curve like this:
(Power over RPM):
Eg:
If I only need 50% of the engine's acceleration at 2k RPM, (to make it easy for calculation) if at 6k RPM I have 100% of engine torque, and at 2k RPM I may have ~75% of engine torque, eventough I only need 50% of the engine's torque; then there's no need to keep RPM's as close to 6k as possible, as the MPG's used at 6k RPM are much lower.
Then it would make more sense to upgear the bike (or put heavier rollers in), so that I'd get more road speed per combustion cycle.
Dude, it's so complex to say in english, I'm not even sure I understand what I'm saying...
I wish I knew more technical terms in English to explain myself easier and better...
Changing gears on the Tao PX 150 (Powermax) it would make sense, as it's smaller, and generally for one person. The EVO is larger, and made to go with 2 people. So whenever an extra person is carried, I don't want to overpower the bike neither.
....blablablablablabl...blablabla....
So overall conclusion is, I'll wait until I get to ride the 150 with my wife, and see how much power I can 'trade' for MPG.
