Ford HEI Distributor

[Vantix]

Hey Gang,

Looking at wiring up a Megasquirt 2 for my 1967 Mustang with a 302. My current setup is on an Edelbrock Carb. As part of the setup, I have an HEI Distributor, similar to what you see here:

http://s196.photobucket.com/user/zombie ... f.gif.html

My megasquirt design will be based around using a Chevy TBI. I've purchased what I believe to be the necessary parts from DIYAutoTune, but I am having trouble figuring out how to connect the HEI distributor. The Dizzy has a 4 pin control module in it. My original thought was to connect the coil to the megasquirt in the same fashion listed here:

http://www.302w.com/images/megasquirt/img056.jpg

Will that work? Essentially, I'd run an additional line from the positive coil wire to the tach connector on my MS2 Relay Board (going relay board to simplify install). Then I'd run a line from the S5 on the relay board to the ground on the coil.

Additionally, I'll have to disconnect the vacuum advance and lock out the mechanical advance.

Any thoughts? Any advantage to swapping to a seven pin control module setup?

Thanks gang!

[Matt Cramer]

Are you trying to control spark, or just run fuel only?

[Vantix]

Both Fuel and Spark.

[rickb794]

TBI? Only marginally better than a carb.
There are much better solutions available.
Are you compromising due to hood clearance?

There is that wetted surface thing and fuel distribution issues.
Putting the MS between the pickup and the coil gives you full control. (throw away the module unless you are microsquirting)
You only need the module if you are using a v2.2 board or a uSquirt which have no ignition drivers.
An MS2 v3.0 or v3.57 has a native ignition driver
The modules that have more pins allow computer control but you give up some functionality.
Any distributor that is not locked will need to be fixed. (pay attention to rotor phasing)

Can you not find a Ford big cap distributor for your motor? The square framed Ford coil works great as well.
You don't need the HEI, it offers no benefits and does stuff that the MS will do on it's own.

[Vantix]

Hood clearance is definitely an issue. TBI seemed like an easy way of breaking into Megasquirt. Would love to hear your ideas on "next step" from here.

I was planning on connecting my system up like this:

http://psig.home.comcast.net/~psig/webp ... GM4pin.GIF

But you're saying ditch the 4 pin module altogether? Don't I need it to get the Tach info?

[rickb794]

Not if you use the VR input on the MS and use the native Q16 transistor to run the coil. If you need a special tach output you build one as needed (shown in the manual).

[rickb794]

Not if you use the VR input on the MS and use the native Q16 transistor to run the coil. If you need a special tach output you build one as needed (shown in the manual).

The HEI tach output is just a connection to the neg side of the coil.

[rickb794]

Which may not be compatible
With your tach.

[Vantix]

Interesting. I don't have a factory Tach, so that isn't an issue.

So if I wanted to run the VR direct to my relay board, where would I connect it to my relay board?

[rickb794]

It connects to the same tach input terminal. You ms will need to be re-jumpered to use the VR conditioner circuit if it is not set that way now.

[rickb794]

It is not recommend to use the relay board with low impedance injectors. Check your tbi injector resistance.

[rickb794]

You can use the HEI module to provide a high level (less susceptible to noise) by running the output to the MS tach input with a 12v pull up.

[Vantix]

Good Call on the low impedance. I'll make the adjustments. DUYAutotune confirms I already have the Flyback circuit, so I am good there. Will just need to adjust the PWM Settings.

[Sevindeess]

What did you end up doing? I have a similar set up. I used 4pin HEI but I have noise (spikes in my tach signal)


Thanks!

[rickb794]

Section 5.2.9 calls for a pull up resistor and refers back to 5.2.3 but that is for hall sensor and 5volts "Install a 1k resistor (any value 470R - 2k2 is likely ok)".

I'm not sure what size resistor should be used for 12v.

According to http://www.302w.com/images/megasquirt/img056.jpg the value is 1k probably 1/2 watt.

From http://s196.photobucket.com/user/zombie ... f.gif.html
Remove the connection from C to the coil neg.
Connect the resistor across the B & C terminals and connect the c terminal to pin 24 of the DB37, and use a basic trigger going high.

Connect pin 36 of the DB37 to the coil negative.
Typical settings
Spark Output = Going High
Dwell Type = Standard Dwell
Dwell ~ 3ms for a standard coil

Check rotor phasing see 6.2.2, dist will need to be locked.

The VR output from the dist can be used but the noise from your low impedance injectors compounded by your choice to use the relay board may not work well.

Using the higher voltage signal from the C terminal (with a pullup) will help overcome the noise. <<<<(this may not be bullet proof with the relay board)

[Rick Finsta]

You can also use a cap-to-ground noise filter on the 12V+ supply to the coil if you have noise issues with direct coil control.

[Vantix]

Sadly, I can't get get any kind of RPM reading while cranking...

I've got "C" run to my tach connector on the relay board. I've tried both with and without the resistor between "B" and "C". No reading.

Is the issue with the 4 pin module itself? Does it not provide a signal that the megasquirt can read?

Should I try connecting the VR directly to the megasquirt? If I go that route, do I still connect the spark output from the relay board to the negative on my coil?

[Vantix]

What did you end up doing? I have a similar set up. I used 4pin HEI but I have noise (spikes in my tach signal)


Thanks!

Can you tell me your wiring setup? I can't even get a signal to work at all!

[rickb794]

How is your main board jumpered?

[hybrid]

Should I try connecting the VR directly to the megasquirt? If I go that route, do I still connect the spark output from the relay board to the negative on my coil?

In my opinion, yes go direct.
No use introducing an extra part that you don't need.

Yes you can still use the same spark output - you just need to change your settings to suit your setup.
I'm using a MSD 8455 to run my windsor, which has a hall sensor built in. I connect the distributor to the Opto circuit, but you will connect yours to VR in if your dissy is VR (and it should be if it's paired with a bosch module).
I'm driving a MSD 6A box, which is very similar to driving a coil directly.

I would worry about one thing at a time. Get your RPM input working (which will in turn get your injectors pulsing), and then worry about your ignition output afterwards.

So if I were in your position I would get rid of the bosch module.

There is some good info on the VR conditioner here:
http://www.diyautotune.com/tech_article ... _index.htm

If you don't get a good signal, try reversing the polarity.

Once you have RPM input, you're on the downhill run.
By the way, you haven't mentioned which MS2 board version you are running.