MSD 6AL2 Question. Kinda confused.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
MSD 6AL2 Question. Kinda confused.
Hey guys, I have a 1985 Corvette that I want to use an MSD 6AL2 ignition box with. I have the box and I mounted it and tomorrow I'm going to wire it up. But I'm a little confused. Judging by the instructions for where the wires go, it does not appear that the ignition box will have any input from the ECM. So this question is in regard to EST.
In the wiring diagram that I have attached, you can see that circuit 430 is the Distributor Reference Pulse, and circuit 423 is for the ECM's influence over timing advance.
Each time a pulse in induced to the Ignition module, current travels to Electronic Switch B, which is a magnet I suppose, and closes the switch to ground the primary coil. When the current is no longer induced in the Ignition Module, the primary coil circuit is opened again. When the ECM wants to take control of timing, it sends power through circuit 424 to Electronic Switch A, which switches the Electronic Switch B control from circuit 430 to circuit 423. At this point, a DRP is still going to the ECM, but the ECM now has control of when to send a pulse through circuit 423 to Electronic Switch B.
Now that we have that covered we can move onto how the ignition box is set up.
On page 4 at this link, you will see the instructions of where to wire up the ignition box. http://www.msdignition.com/instructi...pdf?terms=6421
If you notice, you have a main power and ground for the ignition box, a wire that runs to an ignition switched circuit, a wire that goes to the positive side of the coil, a wire that goes to the negative side of the coil, a trigger wire that receives DRP, a wire that goes to a switch to activate the 2 step rev limiter, and a wire that goes to the tach.
But if you notice, there is NO wire that goes to the box that comes from the ECM for Electronic Spark Timing.
So, how does the timing advance? I'm confused here. Maybe someone can help me.
Thanks!
In the wiring diagram that I have attached, you can see that circuit 430 is the Distributor Reference Pulse, and circuit 423 is for the ECM's influence over timing advance.
Each time a pulse in induced to the Ignition module, current travels to Electronic Switch B, which is a magnet I suppose, and closes the switch to ground the primary coil. When the current is no longer induced in the Ignition Module, the primary coil circuit is opened again. When the ECM wants to take control of timing, it sends power through circuit 424 to Electronic Switch A, which switches the Electronic Switch B control from circuit 430 to circuit 423. At this point, a DRP is still going to the ECM, but the ECM now has control of when to send a pulse through circuit 423 to Electronic Switch B.
Now that we have that covered we can move onto how the ignition box is set up.
On page 4 at this link, you will see the instructions of where to wire up the ignition box. http://www.msdignition.com/instructi...pdf?terms=6421
If you notice, you have a main power and ground for the ignition box, a wire that runs to an ignition switched circuit, a wire that goes to the positive side of the coil, a wire that goes to the negative side of the coil, a trigger wire that receives DRP, a wire that goes to a switch to activate the 2 step rev limiter, and a wire that goes to the tach.
But if you notice, there is NO wire that goes to the box that comes from the ECM for Electronic Spark Timing.
So, how does the timing advance? I'm confused here. Maybe someone can help me.
Thanks!
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Not yet. A lot of hot rodders that I talk to say I don't have sufficient flow, so I'm going to put a performance radiator in it. It should be here by the end of the week hopefully, and then I'll see if that fixes it. If it doesn't, they have a money back guarantee.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
As I mentioned before, I just installed an MSD6al on my computer controlled, hei distributor controlled bracket car. You are really making this harder than it needs to be. There are 4 wires you need to run the MSD unit; Hot at all times from the battery, Ground, Ignition hot, Tach signal (on my car brown from distributor). Hook these up, set your 2 step control high rpm dials and go racing. I forgot if you are going to use the 2 step, you'll need to supply 12 volts to the blue wire when you want the 2 step to be activated.
