Greetings, all.

I realize there are a handful of threads on this and I'm not really trying to create another one as much as I'm looking for understanding of how the car interprets and utilizes what I assume to be the two speed inputs (SP1 and SP2) it takes from the transmission for purposes of limited the cars top speed. Furthermore, many of the links and documentation from prior threads simply does not exist anymore, unfortunately.

I'm currently running a Haltech Elite ECU pin a piggy-back form to the Aristo ECU which still controls a few functions like the auto transmission, body controls, drive-by-wire, idle, etc. However, I'm plagued by the pesky JDM speed limiter built into this Aristo ECU. So I'm turning to the masses for some help. The car is a mostly-stock 2JZ-GTE vvti with the accompanying Aristo 4 speed auto.

I understand there are 2 speed sensors that share speed to the Aristo ECU. My understanding is they basically do the same thing for purposes of redundancy (right?). So my thought / hope is to intercept these signals and monitor them for voltage changes and at/near the speed cutoff, mimic the voltage through the Haltech ECU on over to the Aristo ecu in hopes that I can fool the car into not realizing it's over the limit.

I realize there are 2 aftermarket solutions. It seems the HKS SLC 2 is the one I have read about people having success with in attaching to the Aristo swaps, particularly with auto transmissions. There's also a Greddy which I have read in the Supra forums works, but I'm a bit suspicious that it's only effective for the manual transmission version JDM ECUs. Can anyone confirm or deny this?

Furthermore - does anyone have any diagrams or PDFs of the installation instructions for either of these above signal manipulators? There might be some really good information therein that I could use to attempt to pattern after for my efforts with the Haltech.

Finally - The other concern that comes to mind for me is that from what I gather, these 2 speed sensors mentioned earlier also are interpreted and used by the transmission. Whenever I hit the speed limiter, the car is still in 3rd gear, having not shifted to 4th. For those who have defeated the speed limiter using the Aristo 4 speed, what is the behavior of the transmission above the ~115mph speed limiter? Does it behave as expected and shift on into 4th gear above that point as expected or is there any erratic behavior?