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

Hello, ive been trying to plan the right MS setup for my car for a few months now. I will be purchasing a MS II kit soon, my main question is about injector firing.

I will be retrofitting the existing Edelbrock rpm air gap that is on it now to run a single throttle body with multiport injection. What are the benefits of batch firing the injectors? If the firing order of the engine is 1-8-4-3-6-5-7-2 would there be a notable difference or benefit if the injectors were wired 1-4-6-7 and 8-3-5-2 versus wiring them up 2-4-6-8 and 1-3-5-7? For that matter, would there be a reason to run simultaneous injection over batch?

If your curious or if the extra info will help, this will be going into a 1970 plymouth duster 4 speed with a 408 small block, aluminum heads, roller rockers/lifters, and about 10:1 compression. Thanks!

If the firing order of the engine is 1-8-4-3-6-5-7-2 would there be a notable difference or benefit if the injectors were wired 1-4-6-7 and 8-3-5-2 versus wiring them up 2-4-6-8 and 1-3-5-7?

This is the scheme I used on my first MS project (350 sbc w/ tpi) which worked very well. I tried other setups but this worked best for me.

Just one of many I am sure............
Ken

I have a Rover V-8 which has the same firing order as the Chevy and originally had Lucas injection which grouped the injectors 1357 and 2468. When I first fitted the MS I kept it the same, since I used a modified standard loom.

The next step was to fit EDIS, so since that needed some mods to the loom I decided to change it to the grouping Ken gives.

Conclusions? I think the idle may be smoother and low speed torque better - but wouldn't swear to it on oath. ;-)

However, it certainly isn't worse in any way so I see no reason not to. But I'd not rip apart an otherwise good loom just for this.

But I'd not rip apart an otherwise good loom just for this.

Dave makes a good point here. I wouldn't hack a good harness to accomplish this either. I made my own loom so it worked ok for me.

Ken

Thanks guys, I will be starting the wiring from scratch, so i dont have to worry about cutting apart a perfectly good loom either. I am still having some trouble visualizeing the benefits of batch firing over simultaneous. I see how they differ, but cannot see how these differances can make one more efficient than the other, just more confusing...Thanks again

The way I was told is firing only 1/2 of the injectors on a fuel rail at a time keeps down pressure variations that could occur by firing all 4 on one side at once.

Hey Dustbull –
Good to see another Mopar guy embracing lower-buck EFI!

If you’re looking for a cheap injector wiring harness, look at Cadillac Northstar and Olds Aurora 4.0 V8 around the mid-late 90s (give or take).

The harness contains only the injectors + 1 other sensor, it lays right on top of the intake with no other junk crossing over it, it has a big connector in it that you can use on your car if you want, and it's dog-gone cheap!

Ford 5.0 and 4.6, Magnum V8s and others I've looked at either require fuel rail removal, have injector banks split into 2 harnesses, and/or have a bunch of other sensors and junk in the way.

Steps (as I remember them):
1. remove the engine cover,
2. unclip each connector/injector (this takes a little practice on the metal push-clips),
3. follow the harness under the TB to the top of the transaxle and cut as far on the other side of the main connector as possible (but that's usually only a few inches before it blends into another harness).
4. pull the big connector under the TB, bending some small brackets, etc, to get clearance.

It'll take you about 15 min to get one out if you're slow. I've grabbed a few of these harnesses in the past and often the injectors are gone from these cars already, so there's 2 min saved on the injector clips.

Thanks a lot Fury Fan! That sounds like a great deal, and a good time saver; ill definatly have to look into that more. And DaytonaTurbo, i have heard that also, thats starting to seem to be the way to wire it them up when using a MS II. ...Of course im always looking for more information and opinions..Thanks for everything so far!