Any cars running an MFI engine with a 6-pin CDI box?

[911SCfanatic]

Seems like there's not a lot on this topic. I see where people have swapped 3.0L engines into an early car. What I don't see is where someone has run a 3.0L ignition on an MFI engine. Trying to figure out how to retain the speed switch stuff when using an SC distributor, which uses a hall effect sensor for the tach signal. Is this signal usable by the speed switch for the MFI controls?

[john walker's workshop]

you could try tapping into the purple/black tach wire in the plug. may work, may not, never tried it.

[911SCfanatic]

That's what I was thinking, but I was hoping someone else already did the experiment.

[304065]

Bill,

As Loren pointed out today, the TD output from a six-pin is a six-volt square wave with about 10mA of current. As such, that will probably not be suitable to trigger the MFI speed switch, which is driven by the same circuit that drives the 3-pin CDI, an 11-volt square wave through the points to ground.

Have you considered an MSD "RPM activated switch?" These may trigger off the tacho output. The other alternative is to roll your own speed switch with an LM2917.

Good luck!

[Henry Schmidt]

Use the tach signal from a single 6 pin CD.
The speed swith is not an issue.
Just remove it.
Your system will function without it. All of it.

11-speed switch?
12-cold start solenoid
13-shut off solenoid?
15-micro switch?
52-auxiliary start relay? ( the thermo-time switch and the speed switch)

[911SCfanatic]

Henry, you know I'm with you, brother. Never doubted you and still don't. Picture this though...

For the 20th hour in two weeks, I pore over my '72's entire wiring harness laid out before me on a 4x8 sheet of plywood in my dimly lit basement. Behind me are blown up color wiring diagrams taped on the wall with annotations scribbled everywhere. I work through the wiring harness with my multimeter performing countless continuity tests. Painstakingly I repair misdeed after horendous misdeed committed by all the POs that came before me. I curse their very existence. Finally, I make it to the end of the harness that mates with the engine harness. Before I rip out the wires and mysterious unnecessary black boxes, I think "what if I am about do the very unspeakable act of which the POs before me are guilty?"

I have to understand what this stuff does before becoming comfortable enough to eliminate it forever, otherwise I won't be able to sleep at night...You have a business to run and I don't expect you to indulge my psychological frailities. But if I lose one more night of sleep over this, I am going to call you.

[Henry Schmidt]

What ?
Let me see if I understand what you're saying. You're worried about the wiring to an equalizer when your car has no stereo.

[911SCfanatic]

NOW you understand!

[jstgermaine]

Originally posted by 911SCfanatic
You have a business to run and I don't expect you to indulge my psychological frailities.

Why does Henry get better treatment than me?!

Hurry up and get done with this stage already...I have my rats nest to send you.

[911SCfanatic]

Now, you--I expect you to indulge my "issues." I thought we were in the same support group?