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

Hello everyone! I have been researching MS for the last few years and recently decided to take the plunge. I have a '74 Jeep Cherokee with an AMC 401 V8 that is going to be converted.

I will be running MS-1 with the v2.2 mainboard (no flyback board), and using a TBI unit from a GM 454 engine. The resistance on these injectors measured at 1.5ohms. However, the manual does not specifically say what to do with only two injectors at 1.5ohms.

The table states that with more than three (less than 2.4, and greater than 1.2ohm) to use resistors or the flyback board, but what about with only two? Will I be okay using PWM alone, or should I buy and use two resistors rated at only a few ohms (2-3) to lessen the load? I don't want to burn up my flyback circuit.

Thanks for any help you can give!

Are you looking at a 2.2 I based on cost? Or do you already have one? What are your future plans for this engine? The 3.0 boards have the flyback stuff on the board (or at least a place for it). I looked at starting with 2.2 but started looking at all the other stuff I could do with a 3.0+ and MS2 (Idle Air control and more ignition options are features that comes to mind) and even though I have not had time to implement those options I plan to as soon as I get my car out of winter storage. If you do much reading here you will see that at first many people think they want the most basic system and want to keep a 'backup' system in place, before long after some reading or a few miles on the project they want to have more options and control. I didnt think I would ever want to do spark control but after seeing what you can do with fuel I cant wait to play with spark.

Hmm, I tested them today with a new multimeter and they are now reading 2.0ohms. Still, the question remains.

I actually bought and built the MS-1 v2.2 kit a few years ago when it was more popular, so I figured I might as well make the most of what I already have. I plan to upgrade it to MS-II (for timing, since I already have a HEI dizzy) in the future, but that's not important right now.

The engine will rarely see a redline of 4,300-4,500rpm; it's mostly a low-end torque monster and is used from idle to 3,000rpm.

If I have to, I'll buy the flyback board - but I would just like to know if it is actually required for these two injectors. I've spent hours looking for any info, and I have only found one tidbit of information on a Scout forum saying the flyback board was required. However, no explanation was given and the manual suggests I'll be fine with pwm alone.

All of my bases are covered except for this nagging question. Do we need to use resistors or a flyback board for GM TBI, and specifically the 454 injectors?

You do need something because those are low impedance injectors but exactly what I dont know. I started out with with 3.0 so I didnt have to figure all that out.

Just a little below where this link will take you is a table with injector resistances and requirements.

http://www.megamanual.com/v22manual/minj.htm#pwm