Quick question regarding MAP sensor plug.

I am running the hemi 6 box and Carb wire harness 04 to 08 I am also running my Fast EFI system in place of the carb.

Do I use the MAP for the msd box or do I use the MAP for the Fast system?

My gut tells me to use the map for the Fast System and just get a dummy plug for the msd harness. let me know if I am on the right track

thank you all

I don't know for sure but you might need to run both map sensors. The MSD uses the map sensor to determine engine load and where on the map to look up timing for that scenario. The FAST also uses a map sensor to determine engine load.

You might see if there is a way to let the FAST control the timing. You would want to ask Mopar Rich on here for details like that.

Hence the issue. I have the Fast 1.0 ez-efi it does not control the timing. But what would be done if you ran a true carb no efi. there is no map sensor on a carburetor?

I agree, you need 2 map signals, 1 for each of your systems to work properly. Using 2 sensors is probably the easiest.

A carb uses the vacuum created by the venturis in order to 'know' what to do for fueling.

The folks at MSD suggested I tie into the Fast harness in the wires and then they both will read the same. I sure don't feel like cutting up these harnesses only to find out you cant cut the wires. this is really got me lost.
his second suggestion is to zero out the values in the MSD box and save them that way. I am a few days away from trying to start this thing so I can still do some research on this. I am just not sure about cutting the harness wires for anything like this.

Any guidance is appreciated.

If you could get the correct type connectors and make an adapter harness vs cutting the wires,that way the job is reversible and no erratic readings from soldered connections.

I have a Hemi-6 carb system that I had trouble getting spark until I plugged a MAP sensor into the harness, even though the instructions say you don't need one. I had planned to run fixed timing in a drag race application. I pulled the MAP out of my '03 Dodge 5.7 and it plugged right in and had spark. I have a Drag-Pak intake that has provision for a MAP on the back of the intake. Found a Standard Motor Prod. MAP that bolts to intake. Don't remember the number, but could get it for you. Thoughts were, if you were to use this type of MAP, you could maybe drill and tap a 1" carb spacer for this type to run your MSD ignition and use the one in your FAST system for the injection, you could save from splicing harnesses. Depending on what type of intake you have...Just a thought...