Hacked automatic transmission...possible?

[93sleeper]

How exactly are the shift points determined for the S13 automatic transmission? It all goes through the ECU, right? So what I'm wondering is if it's possible to hack the ecu to give you manual control of when it upshifts and downshifts, like a ghetto Tiptronic system. Maybe give false inputs to the speed/throttle sensors. I know it would still have the power losses of an automatic transmission, but it would be more fun to drive and less expensive than a 5-speed swap. Just a thought. Is this possible, and has someone tried it? Thanks.

[StockerThanStock]

What you're thinking of reminds me of the G35's transmission, you can shift when you want or let it just be an automatic.

[93sleeper]

Yeah, that's exactly it. There must be a way to modify our ECU's for that...

[180fan]

buddy club makes a air flow mod computer thing (like the s-afc) that also lets you change shift points based upon throttle percentages. You might want to look into that. Kinda pricey though. I saw it on takakaira if you want to know.

[Ghettokracker71]

You can unplug the fluid resistor plug and get harder,faster shifts....ask me how if you don't know:)

The auto trans ECU is the same as the manual one I thought on the S13 KA? I could easily be wrong but I thought the transmission had its own seperate control computer...You could proble remove the EPROM on that and put a daughter board on there? Maybe adjustable like the B&M **** for F-body autos,but I don't know if you could get tip tronic style or not? That'd be tricky,how would you tell it when to shift? You'd have to rig up switchs to control it somehow...As opposed to different shift settings. Like...**** I don't know. Stock,hot date,and race or something?

[180fan]

uh yeah, the auto and manual ecu's are slightly different with their programming. the resistor plug thing does make your shifts harder, not necessarily faster. I've yet to see or hear of anyone actually testing it on a strip to see if they've gotten a bump in performance with that "trick".

[93sleeper]

The shift points are determined by vehicle speed, throttle position, and engine speed, right? So there must be an easy way to fake those factors and trick the transmission into doing what you want. The car already has a switch on the accelerator pedal that makes it downshift at WOT...I could use that, right? The point of this project is to give manual control over the transmission for much cheaper than a swap would be.

[180fan]

Yeah I'm not too sure about the details on the buddy club system, but it's supposed to give you access to the shift points for the AT. I'm not exactly clear on how it achieves that but you can change the shift points.