Distributors and Ignition
 

Did some testing on distributor pickups and ignition configuration:
RX-7 first gen distributor tests at RX for your 7October 12, 2016
RX-7 first gen distributor testing
Key observations:
1.MSD recommends using Mazda OEM ignitors to trigger their units. This gives a nice square trigger pulse. When doing this:
a)Use MSD red to ignitor +
b)MSD white to ignitor -
2.When using Mazda magnetic pickups to trigger MSD boxes, need to use MSD polarity which is the reverse of Mazda factory polarity, thus:
a)MSD purple connects to Mazda green lead from pickup
b)MSG green connects to Mazda red lead from pickup
3.When using an oscilloscope to observe signals, check:
a) for electrical noise in test setup – on power supply to ignitors and on power supply to laptop/oscilloscope
b)Make sure the scope sampling rate is fast enough, need 5 millisec per division or faster

See attachment for full details

Nice writeup. Confirms some things I think.

Anyway, we know 80 reluctor is a poor design compared to the 81-85 design. I found this out the hard way way doing my TFIDFIS solution a few years ago.

Interesting stuff, great to see quantification of the signals from the pickups and the J109's themselves.

I gather you are going to use J109's to trigger MSD 6A/6AL boxes? I'd be curious to see the difference between the J109 overlayed with an MSD output.

I am looking at this test run:


https://cimg4.ibsrv.net/gimg/www.rx7...e4d69672e9.jpg

Like you said, the J109 looks like it outputs a decent enough square wave, getting to 0V in about 2 mSec. I wonder if the MSD box just gets there faster and if that's "better". But if MSD is using the J109 to trigger, I don't see how that would be possible, as the MSD would be dependent on the J109. Maybe at that point you have to mess with timing.

It would be cool to see oscope ch1 on the J109 and ch2 on the MSD.

It's interesting, also, that the J109's can go a bit negative (looks like about - 0.25V counting the divisions to 12V)

MSD configuration
 

Here is more info:
I am running dual MSD-6ALs triggered by J109 on my 12A bridgeport - I used this config because (1) MSD recommended it, and (2) I wanted minimal timing variation with RPM. This config for me runs clean to 9500 RPM. Some of the trace details may vary with quality of scope and scope sampling rate, this work was done with a PC-based scope. Wiring config and more pix of test setup attached.
Thanks and hope this is helpful

Nice!

If you still have the setup, it would be cool to see what this looks like, to quantify what the MSD box does compared to the J109's.


https://cimg2.ibsrv.net/gimg/www.rx7...f1b150d0fd.jpg

My basic assumption is that the faster the coil's magnetic field collapses, the stronger the spark is. Maybe that's just a small aspect in the face of much higher RPM's, dwell time, and coil charging.

Time to set the drill at 11 :)

Why trigger the MSD with the J109? Why not remove it and trigger the MSD with the reluctor signal directly? Since the MSD is basically an ignitor anyway.

Isn't it just the same reluctor, mounted upside down? :scratch:

Thats what I do. Gut the ignitor, connect the two inner tabs together, and the two outer tabs together, then use the stock ignitor plugs to run the MSD :)

Not exactly. See the pics in my TFIDFIS thread of both to see the difference.

Hi, test setup taken down, may be a while before I can get to this again. Will have to make sure MSD output does not fry the scope. J109 output is 12V max, MSD capacitive discharge I think is much higher

My reason for triggering with the J109 was (1) this is what MSD recommends, and (2) this setup should minimize timing shift with RPM, and (3) possibly more resistance to electrical noise affecting the trigger signal going to MSD. That said, I ran with straight magnetic trigger to MSD for years with no issue on the streetport version of this engine. Changed to this setup when I went bridgeport