midnight mechanic

I got that you substitute the GM dr100 (or the 7 pin one, which or more findable), for the frail j109 ignitor, but what about the coil? Can I use OEM. How important is it to get exactly the right parts?

I don't want to re engineer DFIS, I want something that someone else has made work.

yeti

iTrader: (1)

I'm using the following:

2 x LX301 ignitors
2 x MSD 8222 (for leading)
1 x ACC 8140 (for trailing)
a bunch of wire and connectors
an aluminum heatsink
thermal paste
FC plug cables (since the SA/FB ones were not long enough.)
and moved the trailing cables to the leading posts on the distributor.
FE Leading plugs and either FC or FB trailing plugs. (I don't recall which probably FB plugs though.)

I think that's about it.

midnight mechanic

from Summit Racing's website, they list a very wide range of cars that these will work on.

Hence, I could choose any ignitor HEI module and coil, and it should work? Or do I assume to much?

yeti

iTrader: (1)

I would assume any HEI module and coil would work but there could be some matching required for best results. The only thing I can think of is that the coils don't like laying on their side but the model I listed don't mind and apparently even the oil filled coils can lay sideways or Mazda would have designed stock differently, hopefully. I think you are right though.

midnight mechanic

>>>coils don't like laying on their side......sideways or Mazda would have designed stock differently, hopefully.<<<

OEM coils have been lying on their side for decades.

didyou put the new coils where the OEM ones went?

Toruki

Here are some photos of how I did mine per @t_g_farrell method in his signature

Two new coils mounted on a bracket and using existing bolts on the strut tower, 2 HEI's on the heatsink aluminum plate, thermal paste underneath them


Connection at the distributor, used shielded audio cable


Looking the other direction, labeled components

Benjamin4456

Some coils genuinely do not like laying on their side. This is because oil filled coils can either leak when in this orientation and/or the oil no longer sufficiently submerges the internals and cooling is affected negatively. The OEM canister coils are oil filled as far as I know but work fine on their side, although I've had some aftermarket ones that do not like it. Normal MSD blaster coils explicitly state to not install them in any orientation other than upright.

That said, some coils are epoxy potted and couldn't care less if they are on their side or not. This is the case with the MSD High-Vibration Blaster coils, which I am running in my car on leading. I have these paired with some generic GM HEI modules from AutoZone (PN: DR100). There are certainly more options out there though, but I haven't felt a need to go with fancier ones as of yet. Main thing is to stick with the four pin modules.

Moving beyond the coils, I'd really suggest running better plugs on the leading side. I use BUR7EQP's (stock FC and FD leading plugs) as the later design works better with DFI and the platinum helps them last longer. You'll burn through the stock FB copper plugs really fast with DFI. Leave trailing plugs stock if the trailing ignition is stock, which most DLIDFIS setups are.

A heatsink is also a must, although it doesn't have to be an explicit heat sink. I just use a big aluminum mounting plate, some people mount them on the strut tower, others repurpose computer heatsinks, and some use the heatsinks specifically designed for these igniters. Whichever you do, make sure to use thermal compound. Most igniters will come with some that is generally sufficient.

Best of luck on the project! It's certainly a worthwhile mod on these cars.

midnight mechanic

Toruki, that's "DFIS For Dummies" ! ! I have several of their books.

Joekaistoe

I recommend against using 7-pin GM modules, they have a built in timing curve that will likely cause your timing to get unpredictable when it combines with your mechanical and vacuum advances. I did a little write-up about igniter/module choice here: https://www.rx7club.com/1st-generati...arned-1144543/

As for what coil, I used Ford TFI coils. They're epoxy-filled coils, plentiful in the junkyard and should have favourable specifications for our application.

In terms of what to look for in a coil, that's a whole big thing. Aftermarket companies advertise high voltages, but that's one of the least important factors in selecting a coil for most applications. As long as the voltage is high enough to jump the gap, anything higher than that is pointless.

Assuming the goal of your ignition is to transfer the maximum amount of energy to the spark, you need a coil that can charge to maximum energy (or close to it) at high rpm and discharge all that energy. Luckily for us, this isn't a very difficult task for our engines, seeing as they only fire twice per revolution. This means a coil from a distributor-equipped V8 has twice as long to charge on our engines than they're used to. Ever heard of the rumor that GM HEI modules run out of steam at 4000 rpm? That translates to 8000 rpm on our engines, plenty for an un-ported engine.

So now you know you want a coil that charges fast and holds a lot of energy. How do you figure out which provides that? The 2 numbers you're looking for are primary resistance and primary inductance. I'm not going to make this a huge write-up, so the cliff notes are:

1. High primary resistance only slows down the coil charging, you want that as low as possible on an electronically controlled ignition (higher resistance is required on points ignitions).
2. A higher primary inductance coil will charge slower, but hold more energy at a given amperage. A lower primary inductance coil will charge faster, but hold less energy at the same amperage. You are looking for a Goldilocks coil that charges fully to nearly max rpm (or at least peak power), but holds plenty of energy to give you a long duration, hot spark.

Unfortunately, specifications for factory coils are not easy to find, but best I could gather was that Ford TFI coils have a primary resistance of ~0.6ohms, and a primary reluctance of ~6.9mH. At the 4-pin HEI module's 5.5A max charging current, this means it has time to fully charge up to 6000rpm (if your 'W' terminal is left open and its wire is grounded), and it still has 82% energy at 7000 rpm and 60% at 8000 rpm.

If you go with a performance ignition module that charges the coils to a higher amperage, you will want to go with a coil that has a lower primary inductance, since the Ford TFI coil will charge too slow in that case.

midnight mechanic

the 2 leading coils plug in to what on the distributor ?

t_g_farrell

iTrader: (1)

If you are using a powerful enough ignition you can run the RX8 plugs. They cost $$$ but should last a lot longer. Thats what I run and have been running for a few years now.

Great info added in here.

Toruki

When you remove the J109 OEM ignitor from the dizzy, there are two terminals that can accept small spade connectors (which is what I did above). Those two wires go to the W and G on the HEIs.

This diagram is from this thread https://www.rx7club.com/1st-generati.../#post11180836 here on the forum. It shows the leading and trailing, but as it says, you can just leave the trailing as factory.

speedracer_not

sorry, I don't get it! what do the two leads from the the two leading coils plug into on the distributor, when OEM has just one lead coming from the one leading coil plugging into the distributor?

and I was going to ask about that relay, that's the black white wire (it is fuzzy on my monitor) that goes to 86 ?

Toruki

Terminal 86 energizes the relay o power the whole setup from battery. It's an ignition position +12V

In the modified setup, the Leading signal simultaneously goes to both new HEI ignitors and triggers front and rear coils at the same time in a "wasted spark" setup. So if the front rotor needs a spark at the end of compression, the rear rotor gets one too but that rear spark is irrelevant because it occurs during exhaust. Wrap your brain around the craziness in the firing diagram below. :P

So why one Leading coil for OEM? Because it runs through the weird *** rotor/distributor cap circuit that points the spark at the correct rotor at the correct time. One downside is all of the extra resistance and carbon buildup in the cap/rotor resulting in less powerful sparks.

Edit: Wasted spark does not work for Trailing and from what I've read here, it would pre-detonate and damage the engine. I'm not sure of the mechanism though, it makes my head hurt. If you upgrade the coil for Trailing, you can get a stronger spark, but it has to go through the distributor cap. One minor tweak is to use the Leading distributor cap connections for the F/R Trailing as the internal circuit is a bit more direct.

midnight mechanic

but what do the 2 leads from the 2 leading coils plug into on the distributor ?

Toruki

For the output, Coil #1 one high voltage connection goes directly to the the leading front spark plug, Coil #2 to the leading rear spark plug. That's the "direct" in DFI = Direct Fire Ignition. It's like coil on plug in that way.

The leading are the lower set of plugs.

j_tso

iTrader: (2)

To answer why wasted spark doesn't work on trailing, reference the image quoted.
The rear rotor has its ignition triggered. Looking at the position of the front rotor the leading plug won't have an effect on anything because it's facing exhaust gas.
However, the trailing plug has compression coming towards it. If it were fired while the rotor is coming forwards the mixture will ignite and try to push the rotor back.

When I assembled my current 12A back in 2014, I put the crank pulley on 180 degrees off and it was doing just that. It was almost able to idle but it shook horribly.

midnight mechanic

LOL, I did that when I was doing a simple ATkins rebuilt engine swap. The directions made a big deal about marking the leading and lagging timing marks red and yellow when it is obvious which is which when using the timing light. Eventually I figured it out with only a leading sparkplug firing, there's just 3 other possibilities if you know that the pulley is in the wrong spot.

Isn't that some weird **** with the wasted spark firing into the exhaust gas? Mazda must of really rushed the design on that one, or the exhaust gas somehow fouls the plugs if they aren't sparked?

Joekaistoe

Wasted spark isn't a necessity, it's just a good pre-computer controlled ignition way to eliminate the added resistance of a distributor from an ignition system. It was used in some older sport bikes that have performance ignitions, and has since been superseded by coil packs and coil-on plugs that are computer controlled. There's an added benefit for wasted spark on rotaries that since it has a long combustion chamber, it has issues combusting all the gasoline in the combustion chamber; an extra spark in the power stroke may burn off a little bit extra gas and clean up the exhaust somewhat.

ray green

iTrader: (14)

The best, easiest and cheapest DR ignition to install is a second gen leading coil.

One screw hooks it to the strut tower and a couple male/female connectors will wire it right up to the stock wiring.

If you leave the stock coils in place and toss the extra plug wire in the storage bin, you can switch back and forth between 2GDR and stock in about 30 seconds.

Toruki

Thanks for that explanation, I can see it now in the diagram.

midnight mechanic

what is this DR and 2GR of which you tell me?

From the TFIDFIS diagram, I think the fuzzy reads ?
Parts:
Ford tfi coil: wells 5c1116 delpi gn10183 acdelco p581
coil pigtail: wells 1p1091 standardmotorproducts s539
4 pin HEI module: speedwaymotors 91012338 wells dr100 accel 35361
HEI module heatsink : acdelco 10474510
Notes:
3. best performance use a 30 amp relay
5. a switch can be added to 87 and ground for ignition kill switch

midnight mechanic

beating a dead horse, I searched for ignitions of late 80s or early 90s GM v8s.

On rockauto, Wells Vehicle Electronics was ubiquitous. Then googling them, all that came up was a bunch of watch me bend over and kiss my *** public relations crap. It would have me believe that Wells Vehicle Equipment made all the ignitions for everything since the beginning of time ? ? ?

Rockauto shows a huge variance of WVE ignitor and coil prices. What's the deal? Is Wells good? should I get the cheapest? is blowing more $$$ worth it?

Maybe I should just get the Accel 8140 and Accel 35361 (total = $175) that was mentioned in this thread?

And the problem with auto salvaging for late 80's early 90's ignitors and coils is that the parts have ~30 years old of service on them. And that's if I can find a car that old.

yeti

iTrader: (1)

I think you are getting a little too anxious over this. I was a little myself for many reasons but I just kept reading. I read/watched how ignition systems work, learned what each component does and why it's needed, and so on. Then I found a few different walkthroughs that I liked and started combined the best parts of each. Some used FC ignition parts but I read various back and forths about longevity and whatnot. I didn't feel comfortable with conflicting opinions especially when there were other accepted methods. Some use MSD boxes, I figured it wasn't economically the right move for me and didn't know where I'd mount it so scrapped it. Anyway, I landed on a list of parts and begin planning, then execution. Were there any surprises? Yeah, my plug wires where too short so I needed to solution for that. but the actual wiring everything up went basically as planned.

By far the most scariest thing for me was moving the trailing cables to the leading posts. I still don't understand how sends the signal at the right moment but it does.

midnight mechanic

I decided on :
ignitor = acdelco d1906 $29*2= $58.00 it goes on a CORVETTE ! ! and it's a 4 pin
coil = Nkg 49034 $28*2= $56.00 it's JAPANESE !