transmission (for super mileage vehicle - urban concept... Nuvinci?)
 

Hello. I am a part of a team trying to build a super mileage vehicle(urban concept). We have decided to use the gy6 50cc engine and the vehicle weight is estimated to be around 100kg. What type of transmission should we go for?
Is nuvinci CVP a good option?

The gy6 engine already has a cvt transmission build in if I'm right. So I would use that and adjust the discs with weights. You could consider a 50cc Honda engine with a 4 speed, then you can get the rpm's you want whenever you want them.

The CVT has an advantage that it provides a broader range of ratioes for each driving condition, but the standard transmission of a Honda seems to be more reliable under harsh driving conditions and heavier loads.

nuvinci CVP is a traction device, thus has lower efficiency than a gear hub or chain drive. A dérailleur 10 speed cassette drive can have 98% efficiency and as a plus, it freewheels.

we considered using a CVP because it makes it really easy, giving the driver enough control, to run the engine at a rpm where it has min bsfc. Also the intake and exhaust systems can be tuned for the same rpm and it weighs less than a CVT.
will it be a significant compromise on fuel economy if we go for CVP?
can you please also suggest the attachments that would have to be made to use CVP with an IC engine.
thank you

I think the NuVinci is about 75% efficient? That is not good when efficiency is the goal.

Yes, definitely 75% isn't good. But wherever i read the efficiency was mentioned to be around 85%, and that could work given other advantages it has on other transmission systems. What do you think?

I seem to remember the 75% number, but I cannot find the source again, and I cannot find a definitive number, either. Even at 85%, that is more than 7X more loss than a cog set.

trans/mpg
 

Will the vehicle actually be operated on public roads,with all the attendant traffic,idling,acceleration,deceleration,yields,st ops,traffic lights,gridlock,curves,turns,parking,warm re-starts,cold re-starts,etc.?
Is 100 kg you all-up weight,including driver?
For all the transient loads,you'll need to keep the engine in it's peak BSFC island.12-speeds is equivalent to a CVT according to SAE research.
For a steady-state economy cruise you'd want a fully-locked,1:1 output(no overdrive)with a traction tire diameter which would yield the ideal 'gearing.'
Sprocket and chain drive has been used to good effect with some previous record cars.Very high mechanical efficiency.