MicroSquirt.com read only forum (Jan.15,2018)

Here's the basics. 56 chevy truck, 350 sbc, GM crossfire tbi injection (2- 2.5 ohm 65 lb injectors), HEI (7 wire), wide band, high pressure pump in a surge tank, going to use a microsquirt version 3 that has not been purchased yet. I will probably have a lot of questions before I finish this, so let's start with the injectors. Current injectors are 2.5 ohm each. One on each bank of the mS.
Ohms law says 14 volts/2.5ohm injectors=5.6 amps. 5.6amps x 14 volts= 78 watts. Way over the 5 amp maximum. I've read up on using resistors to raise the impedance of the injectors, but no one is really in agreement of by how much. I know they have used the Micro on the TPI successfully. Those injectors are 18.2 ohms each (4 per bank) which is a connected load of 4.55 ohms. These put a load of 3.076 amps (43.064 watts) on the drivers. Should I resistor(2.0 ohm 50watt) my 2.5 ohm injectors to match the 4.55 ohm load of the TPI? Some say to add 8 ohms or so but reduce it if it wont run. I would like to only do this once if possible. I've read the injectors operate more accurately at the lower ohm loads at idle and WOT. Will the Microsquirt live a long and happy life at 3 amps of load on the drivers, or would it be better at a lesser amperage? I know it's long winded for a simple answer, but I would like to know the whys and hows of this too.

3 amps ought to be OK. From other customers' reports, 3 to 5 ohms of inline resistance tend to work fairly well with TBI injectors. You'll want to make the resistors oversized; 25 to 50 watt power rating would be a good idea as you don't want to run them at their maximum power rating.

OK. Getting back on track again. Finally. Was getting set to purchase the mS V3 but need to confirm, am I on the right track? Would a Megasquirt 1 or 2 be better suited than the Micro? I know the Micro and MS1 cannot run the IAC motors,and the mS cannot be altered like the MS ecus and thats OK. I dont see the need for the extra future expansion of the MS2 for my application and I like the compactness of the mS. There's not a lot of room under my dash. This is going to be a very basic injection system, nothing fancy. Basic HEI and 2 injectors. So what do yall think? Will the mS leave me wanting more?

MS2 can driver the stepper IAC and its injector drivers have considerably higher current capacity, which is very useful with TBI injectors. I'd use an MS2 over a MicroSquirt for this application.