Quote:
Originally Posted by ghostlt1
So the 2.77 gear ratio from the factory is the optimal setting for the A10?
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Almost, just think the engineers spent years thinking about this and with todays tech, It's getting hard to make anything better. Either because is already maximized, or its locked by complex software so anything you do will decrease overall performance.
The main difference is dictated by how manual and autos work internally, design and etc...
The A10 has planetary gears that are concentric and has 6 clutches, which engages 2 or 3 at the same time to produce this 10 different gear ratios.
The manual transmission has the limitation of the H pattern you need to manually shift and it reduces or multiplies speed by transfering movement from primary to secondary shaft back to output shaft.
Reducing speed too much with a high ratio, like 4.7 to 1 of the A10, means that one gear will be too big and the other too small. Small gears can't take much torque, and making everything larger will render the transmission too big and heavy.
So the different ratios 2.77 and 3.73 are based on design constrains and physics that have more to do with transmission design than anything else.
Rule of thumb and history tells us that that to launch a car you need a 10:1 final 1st gear in approx and reach Vmax in a 1:1 ratio @ rpm of max power.
The A10 does this, and the M6 too with Vmax in 5th gear @ 0.74:1, not ideal but having less power losses than the auto makes for it.
A10: 7th @6000 rpm = 181mph
M6: 5th @6000 rpm = 179mph
Sorry if the answer is overkill, but It is an interesting topic.