let's play 'name that part'--keyed to an early car wiring diagram
 

What are these in layman's terms and where are they located? BTW, my car is a '72 MFI and I'm prepping for an SC 6-pin CDI box ignition but keeping MFI.

11-speed switch? (appears to provide tach signal and is connected to dizzy)
12-cold start solenoid (I think this is the device on MFI fuel console)
13-shut off solenoid? (wire running to micro switch)
14-thermo-time switch? (wires running to the starter and auxiliary staring relay)
15-micro switch? (wire running to speed switch)
52-auxiliary start relay? (it has wires running between it and the thermo-time switch and the speed switch)

I've spent about 3 or so hours searching threads and making little progress.

I will be running an SC dizzy with a 6-pin box (actually two 6-pin boxes for a twin plug dizzy). What do these do and what can I get rid of? Can I ditch the speed switch and use the tack signal from the 6-pin boxes and keep my '72 tach gauge? Any guidance would be a HUGE help.

If you keep the MFI you will need all of it. These items are for the MFI. Speed switch(or RPM Transducer) activates above 1500 Rpm, when microswitch is depressed it activates the shut off solenoid through the microswitch until RPM is below about 1300RPM. In other words when you are driving at 4000 RPM and lift your foot off the gas pedal to stop at a light, the throttle linkage pushes the microswitch, the stop solenoid is activated and the fuel flow to the injectors are stopped so that the MFI pump does not put fuel for 4000 rpm performance when the throttle is closed. The other items help cold start performance. Now the question-are you getting the MFI recalibrated. I do not believe a stock 2.4 T MFI will provide the fuel for a 3.0L without major changes. You may even have to change the injectors to a bigger size. The MFI pumps are calibrated for the volumetric efficiency of each engine. Talk to Gus at Pacific Fuel Injection. He will tell you what is possible. Good Luck.

Is the micro-switch the switch mounted on the stacks?

I am building a 2.8L MFI engine. The MFI pump was already rebuilt and calibrated by Henry at Supertec. What it really comes down to is that I'm incorporating a twin plug ignition based off of an SC distributor using two 6-pin CDI boxes. (I am not using an SC engine--it's built off of a '74 mag case with all of the controls from either the '72 or '74).

The speed switch uses a tach signal from the distributor. I now have an SC distributor, which sends its tach signal to the 6-pin CDI boxes. I assumed that all of the MFI electronics went away, but perhaps I was wrong...

Started this thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/310212-any-cars-running-mfi-engine-6-pin-cdi-box.html

Hi Bill
Call me.
Most all that junk should be eliminated. 11,12,13, 14, 15 are now obsolete items.

11-speed switch? (appears to provide tach signal and is connected to dizzy)
12-cold start solenoid (I think this is the device on MFI fuel console)
13-shut off solenoid? (wire running to micro switch)
14-thermo-time switch? (wires running to the starter and auxiliary staring relay)
15-micro switch? (wire running to speed switch)
52-auxiliary start relay? (it has wires running between it and the thermo-time switch and the speed switch)

Run a tach wire straight from one CD to the violet and black wire that goes to the tach. Depending on the tach, it may work. If it does not, send it to North Hollywood Speedo. They can convert the tach, add the appropriate red line and if you want they can add a 10K RPM face.

Interesting. I'd like to see a thread on that and how that is accomplished. I'm sure John Cramer and a few others will be all over that info as well. Just for instance, how does one disconnect the fuel shut off and not suffer fuel passage to the clyinders and consequent backfiring when decelerating? Inquiring minds want to know.

Bill
Post a picture of your pump.

Well, I think one thing Henry is referencing is the fact that I will be using his cold start enrichment device. But I don't think that addresses the shut off feature when taking your foot off the accelerator. Maybe the answer is that you live with occasional backfiring. I couldn't find any threads addressing how 11-15 & 52 work with one another. That's why I wanted to know where each of these devices are located so I could try and figure out how these component operate as a system.

(I haven't talked to Henry about it because I like understanding and working through the issue myself as much as possible first. I'm getting close to throwing in the towel though.)

It would be cool to come up with a way to have the two systems talk to one another...especially since it appears it hasn't been done before.

o.k....here is the before (we'll after it was rebuilt, but before it was modified):
http://forums.pelicanparts.com/uploa...1161129389.jpg

and here is the after:
http://forums.pelicanparts.com/uploa...1161129434.jpg

(notice the beautiful Supertec craftsmanship :) )

http://forums.pelicanparts.com/uploa...1161129569.jpg

So, the device that was eliminated from the MFI pump--which component is that? IIRC, it is the cold start solenoid that uses the little expanding washers. We eliminated that in favor of the mechanical enrichment device that Henry makes. From all of the threads, it seemed like there where more MFI cold start problems than I cared to deal with (forgive me MFI purists).

And, what is the little jobbie at the top of the MFI fuel console--is that necessary any more?

For those inquiring minds:

Notice that the pump was built without the decell solenoid.
That makes the micro switch and relay pretty useless.
A properly built performance pump does not need a decell relay.

Now note that the pump has a Supertec enrichment devise.
With this hand operated cold start system, the cold start injector also becomes obsolete, as does thermo time switch and the relay.
It has long been my conjecture that the cold start injectors cause most of the throttle shaft wear.

As for the tach and speed relay issue:
We build the twin plug units to function just like a stock SC distributor. The signal from the CD (6 pin) go directly to the tach (sans relay). This will drive some early tachs. When there is a problem, the early tach can easily be converted to work off this signal. The cost is reasonable and sending the tach out allows the tach to be calibrated for the engine it's now working with. ( red line, 10K or just freshen the dial.
A new speed relay could easily cost more than this simple modification.

No extra crap and no problems.

http://forums.pelicanparts.com/uploa...1161130888.jpg

I just read scfanatics other thread about the speed switch and tach signal. SC, you have bought a completely engineered system from Supertec. As Henry says none of those electronics will work now. Way do you need a tach signal to the speed switch? Supertec has removed the stop solenoid so all the electronics to control it are useless. Since the warmup thermostat is also gone in favor of a manual cold start system, all the cold start stuff is also useless. The speed switch is not needed to get a speed signal to your tach. The tach signal on the original MFI came from the distributor. According to the electrical diagram this bl/pu wire goes to the speed switch but also tees off to go to the tach. The distributor sends the rpm to both the tach and speed switch. The speed switch uses the tach signal from the distributor for its output to operate the,now extinct,stop solenoid. The speed switch does not send a signal to your tach. Hook it up like Henry says. He knows.