Megasquirt-related questions

I found a ad on the rx7club for a 1986 Mazda RX-7 with a JDM S5 Turbo II swap and a ton of go-fast goodies. The OP mentions something I'm confused by. The car is running in "open loop" mode because it has an FD3S upper intake manifold and TPS, and the FD TPS doesn't talk to the S5 ECU. What do "open loop" and "closed loop" mean for EFI?

Also, he mentioned that he was going to Megasquirt it before he decided to sell it, which is probably the route I would take were I to buy the car. Would Megasquirt 2 or 3 "learn" the TPS's outputs, or would I have to know the range beforehand?

Closed loop means that it will trim the fuel by looking at the O2 sensor.

Rotaries don't really like running closed-loop, I look at the O2 for tuning but I have never allowed it to think for itself. (This being on Megasquirt already, i've never played with the factory electronics)

MS has a fully calibrate-able TPS input. I just needs to be somewhere between 0-5v sweep. You can leave it out and do everything with MAP but it's harder to do decel and tip in enrichments.