No More IGNITORS
 

I have setup the Dual MSD conversion and my car is running smoother and accelerating fasster. The only problem now is hooking up the tach. I guess I could run a line to the MSD tach hook up and see if that works. If not I guess I will be calling MSD again.

The tach output terminal on the MSD works fine. It has the same square wave signal as the stock tach uses.

I assume your leading MSD is running through the cap and rotor. If so, shame on you for not having done a direct fire conversion yet. :)

I'll figure it out eventually. Don't you just run a jumper to another leading coil and then the coils directly to the plugs. Hey, could I get craZY AND RUN FOUR COILS. tWO LEADING AND two trailing or do I just have to settle with Two leading and one trailing through the cap. I've got three MSD coils right now as it is. Plenty of room for it. I'm using a three gauge pod right now. Bolted it to the shock tower and enlarged the holes a little bit, works great.

how much did it cost???

In my, and others' opinions, a DIS coil is actually better on leading with an MSD. The 2nd gen leading coil is a DIS coil for example. It has very low resistance and it's got two high tension outputs and will spark both leading plugs at the same time (0 and 180 degree sparks hehe) even if one has more resistance than the other. I just experimented with my MSD 6AL and a 2nd gen leading coil a couple days ago with all nearly every rotary plug ever made from '71 up to '92. It's what I'll use on my next rotary project with BUR7EQ plugs.

You could go ahead and use two MSD coils hooked in parallel to your leading MSD's orange and black wires, but I'll let you know that it will reduce the available amps by 50% (this is basic electrical stuff from elementary school). Two loads is prallel = same voltage, but half the amps. Two loads in series = same amperage, but half the volts. The MSD changes high amperage 12VDC into low amperage 400V capacitave discharge and causes the coils to become step-up transformers. It works somewhat ok on kettering style coils, such as the stock Diamond coils found on RX-7s, but it works better on coils designed with the MSD's CDI output in mind. Do you know if your MSD coils are meant for CDI, or for standard points or transistor ignition?

Also, you can't easily run two coils on trailing. In other words, you can't spark both trailing plugs at the same time and expect the engine to live very long. My engine bucked and snorted at anything above idle. I think peejay tried it once too. The trailing plug location on the rotor housings is the reason why (it ignited the incoming mixture way too early). Just run trailing with one coil through the cap, but move the plug wires over ot he leading terminals because there is only one gap to jump = hotter spark.

You are more than welcome to try to figure out a way to fire two trailing plugs at different times. I've never bothered with it because trailing doesn't reaslly add any power to the engine. The 2nd 180º spark on the leading plugs ignites the trailing edge of the AF mixture pretty well by itself. I once wired up a switch to turn trailing on and off while driving. It made no difference that I could feel during every driving condition I could think of, except I thought I felt a slight boost in power with it on once, but I think it was something in the road. I had my friend operate the switch too, and honestly, it was like chasing a rainbow or something. I had DLIDFIS, so the leading spark was adequate.

I've ran my car on leading only as well. I have a 1980 so the trailing is only on part of the time anyway. The only difference I could tell was the car smelled worse with it off but it felt like it had the same power. I believe trailing is only worth around 5% power anyway.

So your basic recommendation is to get a two tower coil from a 2nd Gen.

BLASTER 2 SPECIFICATIONS
Output Voltage: 45,000 Volts Maximum
Operating Voltage: 12VDC
Primary Resistance: 0.7 Ohms
Secondary Resistance: 4.7K Ohms
Turns Ratio: 100:1

These prices are new through Summit Racing

#MSD-6200 - MSD-6A Ignition Control $149.88
*You only need one, I just had another one
lying around the garage, same hook uip though.


#MSD-8202 - Blaster 2 Coil for MSD ignitions and OEM
electronic ignitions $28.95, 1-3 need
depending on if you get the two tower coil
from a 2nd Gen.

And about $25.00 for wire and connector

Yep. Several others have done it already and have had excellent results. The 2nd gen coils are also quite cheap. There may be more performance from an MSD brand DIS coil, but it's gonna cost you too. In all, it depends on your budget, really.

So would the 6A work on a 2nd gen DIS coil or do I need an MSD box for DIS ignition?


Thanks, Ed

What do you mean by MSD box? The MSD 6A is the box lol. It's a bulky red box that you've got to make room for under the hood.

The MSD 6A's orange and black (output) wires hook directly to the + and - of the 2nd gen leading coil. Disconnect the coil electrically from its base and hook the MSD to it. Easy as pi.

MSD does have a DIS box, however a 6A box should work.

I'm going to find out soon if a 2nd gen trailing ignitor and trailing coil work better together than if it were hooked to the leading ignitor. Appearantly there is no dwell in the leading ignitor. That could lead to poor performance at high RPM.

Check this out.

Check what out. Theres nothing there

so what if i don't want to use an MSD box..

Couldn't i connect a 2nd gen two tower coil to stock J109 ignitors from an 81-85 RX-7?

yes...check the FAQ. I'm running it but with a 1980 and the stock ignitors.

Just use the ballast resistor and you're good.

Oops -- the file attachment function isn't working, so here's a link to the gallery, where you can see photos of my science project:

https://www.rx7club.com/photo/showga...p?ppuser=28650

I call it a Direct Fire Dissy. It just so happens there is enough space on the FB distributor shaft to install an additional trigger wheel. I ground two lobes off each of the wheels and installed them 90deg out of phase, so that one trigger wheel is for rotor 1, while the other is for rotor 2. I stacked magnetic pickups above the original two, so there is one for each spark plug. The two leading pickups (stacked above one another) are locked to the distributor body, while the two trailing pickups can be rotated with respect to the leading ones. They're adjustable from approx. 0 deg to 30 deg (eccentric shaft angle) delay from leading.

I checked for cross-talk with my multimeter, and it seems to be free from any.

The cap is just a shortened rotor cap, with an aluminum plate screwed and siliconed to the top.

I disabled the vacuum advance, but retained the centrifugal advance -- you can disable the centrifugal advance, too if you choose.

Alt. 1 (my plan): Run two MSD 6A boxes -- one off each of the leading pickups to direct fire the leading plugs. Run stock J109 ignitors for trailing. These would all fire MSD Blaster SS coils -- one per plug.

Alt. 2: A single MSD 6A box for both leading plugs. Run the leading pickup wires in series for a wasted spark setup. Run trailing as per above. Coils could be 4 or 3 with leading being a dual secondary coil, like an FC.

Alt. 3: Run 4 J109 ignitors and any coils you want. No CD or multiple spark -- but should still deliver a slight improvement over stock.

Alt. 4: Run an MSD DIS-4 box with Alt. 3. The box would plug in between the ignitors and the coils to deliver a CD multiple spark to all four plugs.

The last thing I need to figure out is how to trigger the tach. In Alts. 2 & 4, you could use the tach signal from the MSD box. In Alt. 1, I don't know if you can simply connect the tach outputs from both MSD 6A boxes together?? Alt. 3 -- no idea.

BTW -- The MSD tech reps say a ballast resistor should be used when running our ignitors with their Blaster SS coils because the primary resistance is so low it might cause an over-current condition in the ignitors.

I made something similar to that for my 20B. Three pickups at the bottom with three above on a rotatable base. No vacuum advance. Leading reluctor was stock (four tips). Trailing had two ground tips. Tach is standard 4 cylinder or rotary hooked to a leading coil (no adjustments!). J-109 ignitors and Diamond coils all around.

I junked trailing for now due to required space for three additional coils and money vs the amount of power it adds to the engine. Besides, two leading sparks per rotor face takes care of the trailing edge of the coil's unburned AF mixture quite well. Also, no other 20B, to my knowledge, is set up to run like this. I'll test fire it maybe in a week.

How well does your setup work with two pickups wired together into one MSD box?

I haven't tested any of these configurations yet.

After doing some research today on engine management systems, Alt. 4 is looking better. The reason is that I can set this up right now for my carbureted setup, and then some day when I go to EFI and I have an ECU that handles 4 channels of ignition, I can replace the DFD and ignitors with the output from the ECU. I think the MSD DIS-4 costs about the same as two 6AL boxes -- $400.

Will your leading plugs both fire at the same time?

These distributor modifications seem interesting. Can you show pictures of the insides.

If the oppourtunity presents itself, show it dismantled, including how you added the 2nd set of magnetic pickups.

I could do it either way -- wasted spark or not. If I combine the leading mag pickups in series and run them into a single leading ignitor, then run the output from that ignitor into both leading channels on the DIS-4, both leading plugs will fire at the same time (wasted spark). If I keep them separate, it'll run non wasted spark.

If I'm not concerned about emissions, and both leading and trailing systems are working properly, how much of a benefit is wasted spark? Do FDs run wasted spark like FCs?