By: ThailandPCX (offline)  Friday, 24 July 2015 @ 10:04 PM ICT (Read 675 times)  

Hello... I am wanting to understand How to Tune a Variator... I see variators come with different weights for fine tuning your variator... I.E. 8 gr... 10 gr... and 12 gr... But, I do not know is what to do... what are the different weight variations for... and what the different weights do for the variator...

I do understand centrifugal force causes the weights in variator plate to move outward causing the plate to move inward; causing the plated to come closer together; causing the belt to ride higher OK you go faster...

But, what I don't understand is the different weights, their uses and their reaction... heavier weight moves for slower to centrifugal force smoother shifting... lighter weights move more quickly causing faster acceleration.. I do not know

Can someone educate me on the different weights, what they do, there reaction in the variator and how to properly use them..




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By: Flying Squirrel (offline)  Saturday, 25 July 2015 @ 12:11 PM ICT  

CVT weights Explained

It is all to do with the forces generated. If you fit lighter weights, for instance, the engine has to rev a bit higher before the system changes gear. So you can equate this to revving a manual transmission car more before you change gear. If you fit heavier weights the engine "short" shifts and changes into a higher gear sooner. Manufacturers strike a balance between performance and fuel economy. Another thing manufacturers have to do is take into account the weight of the rider. This is why the old non ESP Honda PCX 125 had different weights in Asian than it did in the EU/US.

So fitting lighter weights can give you better acceleration because the engine is allowed to make more power as the system moves through the "gears"

Numerically the top speed is limited by the dimensions of the pulleys and by the horsepower the engine develops or is allowed to develop to overcome aerodynamic drag.

That being said it is a balancing act. The rotating forces generated by the weights have to overcome a counter spring in the rear. So it you fit lighter weights the engine has to rev higher to change the ratios. The most common misconception is that lighter weights give less top speed. Depending how light you go as long as you have enough force to completely overcome the force of the counter spring then the top speed will not change.
In a few cases, mostly 2-stroke scooters, installing lighter weights will actually increase top speed.

If you fit very light weights the engine will rev high all the time as the force applied to the system is less. As witnessed by the scooters one sometimes sees, or rather hears, which are ridden up and down sois as it the throttle were a switch. Roar-coast, roar-coast, etc.

Weights are not the only factor. The shape of the ramp along which the weights travel is also important. You can equate this to having gears that are close together as in a sports car or further apart as in a family car. Yet another manufacturer's compromise. Steeper angles require more roller weight than the less steep ramps.

Dimensions/diameter of the weights can also be altered. Dimensions of the pulley angle in variators can also be different. It is not unusual to see unused sections of variator pulleys . Most often at the top of the speed range but also sometime at the bottom. Some variators are machined to give a lower "!st" gear as well as a higher top gear.Sometimes spacers can be fitted to separate the pulleys to give better lower gearing but care has ti be taken not to compromise the top speed.

If the system is designed correctly you can achieve a balance close to ideal where you get better acceleration and hill climbing ability together with a comfortable cruising speed. But increased performance is not free as the engine has to burn more fuel to make the extra power.

Crass commercialism: J.Costa has a variator for the PCX . It is optimized for sporty, everyday riding. They do, however, have units optimized for racing.



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