CraigH, I posted this back the last page.
Originally posted by InitialD
Something that makes interesting reading at the thread at the Electric forum which applies for gas powered cars also. Of particular interest is seaball's post which is in line with what the guys at Serpent are trying to drive at with regards to the low internal ratio of the 710 and the complaints that they have been receiving;
from a physics and theoretical standpoint, the lower ratio should increase overall accelleration based on the fact that the layshaft, in either case, will be rotating less due to the lower internal ratio to produce the same overal vehicle speed.
the importance here is that kinetic energy is a linear function of rotating mass, and a squared function of rotating speed. therefore, the intent with the lower ratio is to minimize the amount of kinetic energy required to accelerate the drivetrain to it's maximum speed.
another benefit of the lower ratio for belt cars comes with the increase in layshaft pulley size that is needed to acheive this lower ratio. this results in a more effecient drivetrain, since the belt won't have to form such a small radius through the wrapping of the layshaft pulley. additionally, the belt can be run even more loosely since it will have more teeth to contact it to prevent what is known as "ratcheting" or skipping of the belt under loads.
realistically, it may be insignificant, because the pulley mass increases due to its larger size, the spur usually needs to increase to get the external ratio high enough to maintain the same FDR.
there are always design compromises that will be made, but i do believe the intent of a low internal ratio is to gain a better spool up time through minimizing the KE required.
I believe on gas cars, it is even more paramount that the drive train rotates less times seeing how many parts rotate.