I built my megasquirt on Saturday and spent the last couple of days getting familiar with it, in anticipation of installing it in the next couple of weeks. My setup is I have a GSL-SE engine with an S5 N/A intake and fuel system and ignition system. I anticipate that almost everything in the settings will be the same as for a second gen. I know there are going to be differences, but they will be minor.

I am planning on controlling the BAC. I have a megasquirt I with the v3.0 board. My intention is to shave 2 teeth from the CAS and use the built in VR circuit. I understand that to control the BAC I have to replace a resistor and a transistor, according to the FAQ. Maybe I should not control the BAC? My friend who knows a lot about FI says that it's good to have because then you can use it to perform "tricks" with your tune such as help out with decel enleanment and so forth. This stuff is very new to me but it seems reasonable.

with the new firmware 029n, the menus in megatune are very different from the screenshots in the FAQ. I was able to find most of the settings in the new firmware, but there are some differences I couldn't figure out.

1. Accel / Decel Enrichment screen
2. Outputs screens ( all of them are very different now)
3. I couldn't find the screen where MuayThai said to do this: "Here is where the EGO correction step counter is changed from the default to milliseconds."
4. Injector staging screen

Other questions:

What is the purpose of the 4.7k pull-up resistors? I found lots of references to needing them, but nothing that explains WHY they are needed.

There is mention of changing the bias resistor for the IAT sensor. I am using the stock IAT from my S5 intake, so I am sure that I want to do this. But I remember from constructing my v3 board that there are TWO IAT bias resistors on the board... which one do I change out? or both? If I change bias resistors, do I still have to use EasyTherm and calibrate it?

I'm sure I'll think of other stuff. Thanks.

 

they are in there. just surf through all the menus.

Other questions:
to tell the coils to fire. if they arent there, te coils have nothing to tell them to fire.

you replace R4 on botrh boards ONLY.

heres is an easy to grasp setup on how to use easy therm. load easy therm, and from the file menue, click on rx7. then on the bottom options, click on com 1o r whatever one ms is connected to, and then on the right hand side it will ask yo which map you wana use or something. choose custome, and it will ask you for a file. this file is loacated in the zip files from which you got your firmware. load this up and proceed to burn it to the megasquirt. i had to have my boot pins unjumpered and i had to have the firmware upgraded for it to go smoothly. sometimes i simply reflash my firmware where i screw something up this way.

 

the only thing that has changed from the FAQ is the menus, the dialogs are almost all still the same.

The pullup resistors basically allow you to get a +5v signal to the ignitors whenever the LED's are off... so basically they allow you to use the LED's to control the ignitors. without these, there would be no +5v square wave to the ignitors, and therefore no ignition.

R4 should be the only bias resistor you change. The other bias resistor is for the coolant temperature sensor.