I was using the gear speed calculator that Cody mentioned on Zilvia and thought something seemed off on the calculations. I was using the gear ratios mentioned in the US S13 FSM at first. What was odd is that at 3K rpm in 5th gear I am seeing 63mph (verified by GPS) and this didn't jive with the calculator. So I did a little digging and found out that the S13 SR20DE tranny gear ratios are different... dope! And from further discussion they match up with the S14 DET I guess.
I ran speed calculation for the 4.08, 4.36, and 4.63 rear ends I was looking at, 4.36 and 4.63, and ended up with a 4.63. The 255/40/17 tire size is pretty common for most HPDE guys including myself so choose that for the calculator.

I have a DET tranny in the garage, so have the option to switch to this tranny at a later date if I feel like it, if I need more top speed. With the reconfiguration of our local track it won't have any long straights anymore so I might be ok with this setup as is.
Anyways, thought it was interesting and wanted to share my findings. Any input or questions are welcome.
**UPDATED the graph***
I ran speed calculation for the 4.08, 4.36, and 4.63 rear ends I was looking at, 4.36 and 4.63, and ended up with a 4.63. The 255/40/17 tire size is pretty common for most HPDE guys including myself so choose that for the calculator.

I have a DET tranny in the garage, so have the option to switch to this tranny at a later date if I feel like it, if I need more top speed. With the reconfiguration of our local track it won't have any long straights anymore so I might be ok with this setup as is.
Anyways, thought it was interesting and wanted to share my findings. Any input or questions are welcome.
**UPDATED the graph***
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