Attachment 941431
This is what we ran with stock torque converter, stock engine, stock exhaust manifolds, and catalysts.
Video here:
https://youtu.be/bdJz6CJALtU
I don't think that this car would have gone any faster with a converter, the stock converter is pretty well suited to the 8 speed trans with a PD at this level. In the video you can hear the tires at their limit through first gear and in reality pulling a bit of timing at launch might have resulted in a slightly better pass.
We have gone as fast as 9.1@ 153 with the stock converter and 8 speed trans, but launching 1st gear at that level requires a well prepped track. I have just got home from Power Tour and none of the tracks could support a 1st gear launch with the really low first gear of the A8. (no real prep and lots of street tires running on the track)
With that in mind - the solution was to launch in second
which resulted in:
Attachment 941432
Our 60' increased from a "prepped track" value of 1.39 to 1.52, but still a pretty respectable ET and MPH. Unfortunately after about 8-9 passes we began to notice some transmission problems, I think the transmission is still OK, but I believe that we have failed the lockup function in the stock converter. At least that is what the data looks like.
At this point I have no plans to continue to run the A8, we will be switching to a TH400 with a higher stall converter which I believe will ultimately be a faster solution in this car. Once the A8 is at this power level I don't think there is a good answer - it is near it's limit and shifts to much costing you precious time with every shift. Each shift requires 0.25 sec with ignition timing at about 0 - that's over a full second of a low 9 sec pass with heavily reduces power. The TH400 will happily shift under full power.
SO - with a PD you're in good shape with the stock converter up to the point that the transmission can't handle it anymore. I'm not saying that you won't be slightly faster with a higher stall, but as the car get faster it's less necessary.
The centri gets benefit from the converter, higher RPM at the line will allow it to get higher boost and further into is power range for better 60's.
Not sure if this exactly answers your question, but it summarizes my A8 learning to date...
