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Old 04-30-2012, 05:37 PM
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msd 8975 retard activation wires

I just installed an 8975 digital retard with a 7AL2, I have the 1st activation wire run to the outlet side (+) of the relay for the nitrous as this is what I've read to be correct (sees ground thru coil until coil is activated), when I call msd tech, he said to connect the activation wire no more than 6 inches from the solenoid or it may not work correctly, now, does that mean that it won't see ground correctly and just stay retarded or does it mean that it won't retard properly? I would call back but I don't like waiting on the phone. Also, tech said that installing would retard current timing by 4-8 degrees, anyone install an 8975 and if so, how many degrees did it drop? This is a high rpm motor and doesn't like being below 4500 rpm and I don't want to advance it 8 degrees before I install it. This is only an issue because I'm by myself and if I just install it without adding some timing first, it's too hard to keep running while I reset the timing.

Any experienced replies would be great,

Also has anyone used an 8960 relay (DPDT) to power 1ea. nitrous and fuel solenoids on one side and break ground for an 8975 on the other (normally open on one side for nitrous and fuel and normally closed on the other side for breaking ground. as I looked at my relays, I couldn't see why this wouldn't work, there must be something wrong with the idea, it's much simpler than connecting to the positive lead at the solenoid. (no more than 6" away I'm told by msd tech)

Any thoughts,


Thanks, Robert

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Old 05-01-2012, 07:28 PM
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Quote:
Originally Posted by 9K-sbc
I just installed an 8975 digital retard with a 7AL2, I have the 1st activation wire run to the outlet side (+) of the relay for the nitrous as this is what I've read to be correct (sees ground thru coil until coil is activated), when I call msd tech, he said to connect the activation wire no more than 6 inches from the solenoid or it may not work correctly, now, does that mean that it won't see ground correctly and just stay retarded or does it mean that it won't retard properly? I would call back but I don't like waiting on the phone. Also, tech said that installing would retard current timing by 4-8 degrees, anyone install an 8975 and if so, how many degrees did it drop? This is a high rpm motor and doesn't like being below 4500 rpm and I don't want to advance it 8 degrees before I install it. This is only an issue because I'm by myself and if I just install it without adding some timing first, it's too hard to keep running while I reset the timing.

Any experienced replies would be great,

Also has anyone used an 8960 relay (DPDT) to power 1ea. nitrous and fuel solenoids on one side and break ground for an 8975 on the other (normally open on one side for nitrous and fuel and normally closed on the other side for breaking ground. as I looked at my relays, I couldn't see why this wouldn't work, there must be something wrong with the idea, it's much simpler than connecting to the positive lead at the solenoid. (no more than 6" away I'm told by msd tech)

Any thoughts,


Thanks, Robert
The MSD site has wiring diagrahm's on it I think.
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Old 05-02-2012, 06:52 PM
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They do now because they made one after I talked to one of the MSD techs. At first he said no then he said yes, I'm an mechanical engineer by trade and I know the 2 throws on the 8960 are not connected, so it's very easy to use 1 throw to break the ground on the 8975 stage and 1 throw to activate the nitrous solenoids. This is better for me because now I can start the engine without the fuel pump on. If I connect the retard stage to the solenoid + it wouldn't see ground through the coil with the fuel pump off because of a fuel safety switch that completes the solenoid grounds when it sees pressure. anyway, I wouldn't do it the way they drew the diagram because they show the retard stage connected to the "c" terminal instead of the "nc" terminal and the ground connected to the "nc". This limits the use of the relay, if the ground is hooked to the "c" terminal and the retard wire hooked to the "nc" you could still use the "no" terminal to complete a ground on another circuit when the nitrous hits.

Sorry for carrying on, but this is for other people who search for this subject as I did, and I couldn't find anything about using an 8960 to trigger nitrous and an 8975 retard from the same relay.

Robert
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