Originally Posted by Richter12x2

Should be able to check out the megasquirt section of this forum to get a good baseline that'll run it, then use your wideband to finetune the tables. I have one that's sitting in a box here, it's been assembled but never tested or installed. I may break it out for fun and see if I can run the 3.8L v6 that's been sitting in the corner of the garage for the past year.

Originally Posted by muythaibxr

Official RX7 Megasquirt FAQ for MS1 (check here before you ask your question)
Alright, I'm going to post as much info as I can think of here having to do with the megasquirt on a rotary engine, each question in a post. Before asking a question in the megasquirt section, please check this thread to see if your question has already been answered.

First question, and the one that seems to be the most popular:

1) There are so many different options for megasquirt, what do I need?

Options:

There are currently 3 options available for the megasquirt board: v2.2, v3, and v3.57 (SMT)


The v3 board's advantages over the 2.2 board can be found here:

http://www.megamanual.com/ms2/pcb.htm

The v3.57 board is not DIY, but surface-mount instead, and requires less modification to use.

You can use any version of the board to run a rotary. I recommend the v3/v3.57 board if you have the money, but if not, you can get the 2.2 board, and it'll work just fine.


The next thing you need in each case is the ciruitry to handle conditioning the signal from the CAS. (2nd gen).

For the V2.2 board, you'll need a dual lm1815 circuit. For this, I recommend error*'s board, which also includes circuitry for several of the other features that msns-extra supports, such as EGT logging, table switching, water injection, launch control, nitrous control, boost control, and extra outputs (good for actuating VDI, aux ports, etc...)

For the V3/v3.57 board, you actually already have a single vr sensor conditioner, so you have 2 choices: cut two opposing teeth out of the CAS, and use only the single built-in vr sensor conditioner, or build a second vr sensor conditioner (lm1815 works)... you can do that in the v3 board's proto area, or you can just get error*'s, or jbperf's daughterboard, and only build/use one of the lm1815 circuits on there. It is recommended to use the second VR setup as that is less prone to noise.

For the v2.2 and v3 boards, you will need to install 1 4.7K pull-up resistor from the negative lead of each of the LED's to a +5v source:


If you plan on using the stock air temperature sensor, you'll also need to replace the bias resistor for air temperature with a resistor between 30k and 50k. On the v2.2 and v3 board you'll replace R4.

If you plan on controlling your BAC valve on a v2.2 board, you'll want to get a ztx688 or ztx689 transistor, and replace Q5 with it. Also, you'll want to get a 1/2 watt 510 ohm resistor, and replace R16 with it. You can also get a TIP12x transistor and wire that to the transistor through holes for the original Q5. The v3.57 board has a transistor built-in that can handle enough current, so no mods are necessary to use that.

I don't think anyone has done any testing on a v3 board to make it control a BAC valve, but I believe you'd want to change out Q4 with the ztx688 or ztx689, and change out R19 with a 1/2 watt 510 ohm resistor. You can also replace Q4 with a TIP12x transistor, which some have found is more robust than the ztx parts.

There are also 2 options for the megasquirt chip. There are the MS1 chip and the MS2 chip.

Finally, you'll need to wire the megasquirt up to your car. I'll post info on that in a later post.

EDIT, some false info updated. Pics will be re-added as I find or take some.
EDIT2: This FAQ covers items specific to MS1, I'll be adding another FAQ for MS2

Ken