walden

hello all..
the rear axle ratio for:
A8 is 2.91
S8 is 3.73

same gear ratios...
now lets do some educated guessing...
A8 0-60 is 6.7
S8 0-60 is 6.0

S8 is +50hp; +7torque

i personally think the S8 should be A LOT faster but its not.

now, is there an option to change the rear axle or the A8 to S8's 3.73? i bet that change alone would make knock 0.5 sec off the 0-60 for the A8...

any thoughts? it just doesn't seem there is much different in the A8 and S8...a few simple mods and the A8 is right there with a stock S8...

any thoughts?

ryoung

I doubt that many bought their A8/S8's for 0-60 times or street racing. Am I wrong?

On the track, my S8 would be better served with the taller A8 final drive. As is, you only use 1st gear to leave the pits. 2nd and 3rd are OK (but could be better), and then the revs fall off a cliff in 4th. With the A8's 2.901 final drive in an S8, 1st thru 3rd are reasonably well spaced and would be the only gears used at most tracks.

But then again, I doubt that many bought their A8/S8's for the track either.

KjellA

The S8 *is* a lot faster than the A8, I mean, from 6.7 to 6.0 is really a large gap.

And you know, as long as the engine is reving at a speed where it is on or close to the power peak, the final ratio is not very important for acceleration. Power to the ground is.

The A8 has about 70% of its maximum power at 3500 rpm. How long will you be under 3500 when accelerating from zero? Not long. Obviously, it would mean something to be able to rev higher at lower speed, but not a lot in this case.

What is interresting is that the S8 actualy has a very similar power curve to the A8, almost all the way up. It's just when they both pass 5000 rpm's the S8 will pull away with more power, and it will rev 1000 rpm's more than the A8.

With the A8's final ratio, it would be very difficult to get any advantage of the S8 engine's added power at low speed. You would simply not rev high enough to get the extra power. So they would be equally fast up to about 5000 rpm on 1. gear, and probably close to equal until the A8 had to shift at about 6300 rpm. (What speed would that be?). This is probably the reason for the S8's higher final drive ratio, it needs it to fully utilize the extra power, whichs is found at hight rpm's.

Let's say you put the S8 final drive on the A8. Yes, it would be a bit faster in 1st gear, at least to start with. But you would have to change to 2nd a lot earlier, thus loosing acceleration compared to the original ratio. And compared to the S8, whichs would shift about 1000 rpm's later.

On the other side, the A8 is geared to more than 200 MPH, so I guess it would be nice with a lower 5th, and closer ratios all the way.