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Index > Engine/Drivetrain > Thread: Rotary ignition systems
Thread: Rotary ignition systems [' This thread is 5 pages long: (1) 2 3 4 5 ']
Jeff20B


Moderator
Posts: 661
posted August 28, 2001 09:04 AM

Rotary ignition systems

Before I begin, I must preface this whole ignition debate with a little background info.

A few years ago, a really smart guy named Paul Yaw studied the ignition system of his REPU (after he installed the famed '81-'85 electronic distributor from an RX-7) and figured out a way to get a wasted (double or dual) Leading spark to both Leading plugs at the same time which is similar to the 2nd gen's Leading ignition system, but without the supposedly weak spark at high RPM that the 2nd gen's coil seems to suffer from (due to a shared secondary winding).

He figured that a common V8 points aftermarket ignition system upgrade called "MSD" was the answer. After hooking it up he couldn't believe the extra power all throughout the RPM range etc. But what he failed to realize was that the MSD box should not be hooked to two coils in parallel because it employs a CD spark which, by nature, has low amps but high voltage. Hooking it up in parallel ends up cutting the available amps in half (I'm not sure if series is better because it cuts the volts in half, and for a non-kettering system like the MSD, this can be a bad thing). Secondly, the mutlisparks supposedly cut down to one single spark after 3000RPM (however, the MSD box doesn't know when you've reached 3000RPM because it only counts pickup pulses per minute, not the amount of cylinders/rotors). Thirdly, The CD spark is too short in duration for a rotary. Mazda never used a CD spark (switched by points or otherwise) on the rotary even though other auto manufacturers were already doing this at the time. Instead, they stuck with points all the way up to 1980 when they finaly had an electronicly switched long duration ignition system. Fourthly, he didn't even mention that the Trailing coil and plug wires could be moved to the Leading part of the cap.

Well, regardless of how botched the MSD runs on a rotary, many people who would never have come up with this on their own have tried it and felt the power gains.

I however, have gotten even greater power gains on my REPU by using parts that have been available to us since 1981. It uses dual leading ignitors and fires the same amount of times per eccentric shaft rotation as the 2nd gen coil (but does not share the secondary windings), has full duration, uses seperate coils and allows a full 12V (or 13.8-14V) to each coil, and costs less than purchasing an MSD box.

I call it Dual Leading Ignitor Direct Fire Ignition System (DLIDFIS for short). Myself and many others have tested it, and they all have liked it. Especialy me!

This is the forum to post info like this in. Anybody interested? I'm not sure how many people actually visit this site on a regular basis, but we all either have an REPU, or would like to get one in the near future because we know something special when we see it. This ignition system is the same way. It boggels my mind that not more people(than myself) have figured it out yet. The REPU is THE best mini truck from the 70s period. DLIDFIS (so far) is THE best rotary ignition system period.

Still interested? I only ask because I need to incorporate the answers to your questions into my article. The more fully written it is, the more it will benefit people in the future (kinda like that R&T article about the REPU).

Thanks for your consideration.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Jeff20B


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Posts: 661
posted August 28, 2001 07:19 PM
Edited By: Jeff20B on 28 Aug 2001 19:22

Hey, thanks for the positive feedback!

About the preripheral port: Some people who tried the MSD direct fire ignition system (MSD DFIS for short) actually noticed a decrease in power above 8000RPM (I mention the 8000RPM bug in my article). They went back to single Leading spark (through the cap) and they had power up past 9000RPM again. Well, DLIDFIS uses the same exact parts that the stock system uses, and it's been proven to run to 9200 or something by a racer who missed a shift (hehe), but there hasn't been any testing on a peripheral engine yet.

The point is that if the stock system can run reliably up to 10,000RPM, then so can DLIDFIS.

About the Leading/Trailing split set 0 degrees apart: It will work just fine because there is no drift in timing between the Leading and Trailing. Like mine, yours will remain rock-solid at all RPMs.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Jeff20B


Moderator
Posts: 661
posted August 28, 2001 07:28 PM
Edited By: Jeff20B on 4 Jun 2002 01:42

Here is the most recently revised article.

http://www.geocities.com/cd23c/dlidfis.html
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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rotarynews


Moderator
Too Many Rotary Websites
Posts: 206
posted August 28, 2001 07:29 PM

Interest...

Right here, I'm interested... Even though I have a psudo 83 Ignition, I think there is much that could be done to improve the system.
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rotarynews


Moderator
Too Many Rotary Websites
Posts: 206
posted August 28, 2001 07:45 PM

No time limit...

This silly BBS system doens't allow html, only UBB... I've been searching the code, trying to locate where it strips out the HTML...

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Jeff20B


Moderator
Posts: 661
posted August 28, 2001 09:05 PM

I'll be taking pics tomorrow. Then I hope to get them developed and scanned with a negative scanner. No girly man photo scanner for me. Scanned photos never look all that great anyway. Scanned negatives are the only way to go to get decent quality.

Where are you rigger? I can't drive anywhere at the moment anyway because I need to rewire my electric radiator fan. I did get to install a fuel pressure regulator and "dead head" my pump today though. It should help with my fuel delivery probs.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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risc


1st Gear
Posts: 23
posted September 05, 2001 05:14 PM

What type of signals do these 1st gen igniters need? Rising or falling edge, constant charge or constant duty? Do you have a sugested charge time?

I'm asking because I've got a haltech in my 3rd gen and I want to improve the ignition system. I'm running kinda rich and sparkplugs foul quickly. I was going to install a MSD box on the leading but what you said about CDI makes sense. Do you think DLIDFIS would be an improvement on the 3rd gen ignition? Matt the HITMAN recomends the TII coils, but you mentioned that they suffer from shared secondary windings. I happen to have a set.

What about using 2 TII trailing coils and igniters for the leading?

To keep this on topic I intend to try out DLIDFIS on my REPU after I rebuild the motor. Which should be comming out this weekend.

-Dom

       
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Jeff20B


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Posts: 661
posted September 05, 2001 09:02 PM
Edited By: Jeff20B on 9 Sep 2001 00:38

> What type of signals do these 1st gen igniters need? Rising or falling edge, constant charge or constant duty? Do you have a sugested charge time? <

I'm not exactly sure about what 1st gen ignitors actually need. All I know is that it works on the falling edge. The reluctor has a slow rise time, then it drops off rather quickly. This also has the effect of producing lopsided AC. The pickups are little alternators. But the output wave form is not a nice normal looking sine wave. It is infact some sort of saw tooth formation with more on one side of the 0 volt line than the other.

The voltage output does increase with RPM, but I was able to measure 3-5 volts from simply spinning the shaft by hand. The meter I used has an LCD so it might have faster response time than an analogue meter type. Somebody (possibly myself) needs to hook up an osciliscope to the output of the pickup. I have access to an osciliscope so I'll go ahead and undo the Trailing ignition (it'll still run fine with DLIDFIS hahaha). I'll test the voltage and wave form at different RPMs.

Oh, another thing about the pickups producing lopsided AC; I hooked up an LED to the plastic pickup connector and spun the shaft. It caused the LED to flash when spun. LEDs only allow current to go one direction. that is why it flashed when exposed to AC. It only flashed in one direction, then I flipped the LED and it flashed only when the shaft was spun in the other direction, however it was a bit dimmer. This proved the pickup had less than a perfect AC sine wave.

So that's what the ignitors want. I hope I was able to answer your first paragraph correctly.

> I'm asking because I've got a haltech in my 3rd gen and I want to improve the ignition system. I'm running kinda rich and sparkplugs foul quickly. I was going to install a MSD box on the leading but what you said about CDI makes sense. Do you think DLIDFIS would be an improvement on the 3rd gen ignition? Matt the HITMAN recomends the TII coils, but you mentioned that they suffer from shared secondary windings. I happen to have a set. <

Hmm, I also seemed to be running rich with my MSD. My plugs and tailpipe tips were covered with carbon. Then I took off my high performance foam air filter which was not really dirty and went back to the old blue canister style. I did some more driving. The plugs were still getting carbonated! I also had a bad run-on problem after I shut off the key.

I got sick of it and pulled it all off and hooked up DLIDFIS and cleaned my plugs. Then I drove a similar amount of miles with DLIDFIS as I did with the MSD, and checked my plugs. I noticed that my plugs looked text book perfect and there was no new carbon in my exhaust tips! Yes, around 20 miles on each ignition setup and DLIDFIS was the winner by far! No highway miles, only stop and go (always floored) city type miles during both tests. I really couldn't believe it at first!

I did not touch any adjustment screws or anything on my carb. at first I thought the foam filter was clogged or something. But that didn't make sense since I swapped that out before I stopped using my MSD. My Trailing plugs looked very similar from MSD to DLIDFIS so it wasn't an air filter problem. I really did have more power as well!

If that's not enough to sell anybody on the DLIDFIS concept, I don't know what is. Well, I guess you'd need to read my article, but you know what I mean.

Woops, got a little carried away there hehe!

To try to answer your question about 3rd gen coils... firstly, the 2nd gen Leading coils share a primary winding, and I think the secondary winding has a Y adapter for dual outputs. You can test this by hooking an ohm meter to each output. If it's a short, then it's a simple Y adaptor. Either way, it's still shared!!! With DLIDFIS, each plug gets it's own personal coil. No sharing here!

Hmm, I don't know how a 3rd gen coil works, but I would assume it's similar to the 2nd gen style.

> What about using 2 TII trailing coils and igniters for the leading? <

As far as using dual TII Trailing coils, you probably could. At least they would be seperate and not have to share their bussiness ends. It would be the same as DLIDFIS with 1st gen Diamond coils (but there is an ohm discrepenacy with 2nd gen coils using 1st gen ignitors). Hmm, I can tell you that a guy hooked up a 1st gen ignitor to a 2nd gen Leading coil to take the place of the 2ng gen ignitor and fried the 1st gen ignitor! The ohms of the coil were too low for the 1st gen ignitor. I have no idea what the Trailing coils' ohms are, but I'm pretty sure it is similar. In other words, you probably can't use them.

So to answer your question based on my belief that the 3rd gen Leading coil is similar to a 2nd gen Leading coil (shared parts and all), yes, DLIDFIS would be better to use (but get some good hi performance coils that will replace the 1st gen Diamond coils with similar ohms readings, or just do what I did and use 3 diamond coils).

> To keep this on topic I intend to try out DLIDFIS on my REPU after I rebuild the motor. Which should be comming out this weekend. <

I have been wholey impressed with DLIDFIS. It offers more low end power than the MSD, which offered more low end power than stock single fire through the cap. So each ignition mod I've done has been an improvement over the last. Oh yeah, it's a truck! More low end power is really helpful! For high end power, how does 9k+ RPM grab you?

Got a little carried away again, or did I?
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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risc


1st Gear
Posts: 23
posted September 17, 2001 12:25 PM

Whats a fair price to pay for igniters?

How much would you pay for the J109 ignitors?

Thanks
-Dom

       
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Jeff20B


Moderator
Posts: 661
posted September 17, 2001 06:03 PM

No more than $50 for a used one.
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'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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repuguru


Redlining
Posts: 319
posted October 05, 2001 09:35 AM

I am going to build me one

Ok Jeff I am dropping in my new engine next week and when I finish dialing in my YawPower street carb the ignition is the next item of attention. Paul Yaw suggest using the coil set up from a Buick Grand National because it has 2 places on the one coil for the high voltage lines. Sounds sano. He did talk about the MSD ,but really didn't dwell there. No pun intended. Bang for the buck he thinks the Buick coil is the choice. I guess there would be no problem in matching them if I go this route. What do you think?

       
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Jeff20B


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Posts: 661
posted October 06, 2001 11:04 PM
Edited By: Jeff20B on 6 Oct 2001 23:11

I think the dual output DIS style Buick coil has shared windings. Bang for the buck? How much does a Buick coil cost? How much does an extra Diamond coil cost? So you want to run a single Leading ignitor on a Buick (DIS) coil setup, similar the standard poorman's ignition, and you're hoping that it'll work good for you.

Heh, bang for the buck, to me, means DLIDFIS. The next step up from there would be the crank triggered setup on the '93 13BREW engine (which would suck to try to work on. We stripped one of those engines today and we don't plan on using any of those parts).

The Buick coil will work for you if the primary ohms are similar to a single Diamond coil. Otherwise you'll burn out your ignitor. And besides, the Buick coil shares the primary and/or secondary windings with two plugs. You gotta remember that this was meant for a stock piston engine, not a rotary. The bean counters control how much cool stuff goes into cars.

At least with my system, the spark ends up being hotter, and it was made for a rotary engine. That just makes sense to me in my world.

Not to diss Paul, but he once gave me advice on how to hook up Buick Grand national coils to a 20B. Hmm, that wasn't a diss. Uh... oh yeah, this is what I was going to say. I figured out an ignition system like DLIDFIS for a 20B and it won't be using Buick coils. That still wasn't a diss. Uh... I'm not going to diss Paul, he's cool. :)

I'll keep an eye on this BB for your questions.

Edit: Oh yeah, the part about the MSD. If you're talking bang for the buck, do not go out and purchase an MSD for your rotary. Use that money and purchase all the parts you'll need to run the Jeff20B style ignition! I'm telling you man, it runs better and costs less.
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'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Jeff20B


Moderator
Posts: 661
posted October 14, 2001 02:49 PM

I have reason to believe that Paul Yaw's timing settings give too much advance and can break Trailing plugs. It hasn't happend to me or anyone I know yet, but I've read stories of people who have gone to something like 20*BTDC Leading and 10*BTDC Trailing to be on the safe side.

Paul origionaly tried his settings for 13B engines on his REPU 13B where he was trying to get more torque out of it. The problem is that the advance is cranked up at a lower RPM to improve low end power at the expense of high end. Some peopl ehave complained not only of broken plugs, but also of weak or non existant secondaries using Yaw's settings.

My engine never goes above 6k RPM so I'm probably pretty safe. But for you out there who always get up to or past 8k RPM, be carefull!

One more thing, my secondaries feel very forcefull when they open. It makes me wonder if my decent low end power will diminish if I go to 20*L.
____________
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'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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rotarynews


Moderator
Too Many Rotary Websites
Posts: 206
posted October 14, 2001 11:50 PM

Online Source for J109's?

quote:
No more than $50 for a used one.

Non of the local junk yards I frequent had any J109's.. anyone know of a good online source?
____________
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*FD3s.net
*mazdarepu.com

The best way to predict the future is to invent it!
-- Tom Matano


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Jeff20B


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Posts: 661
posted October 22, 2001 10:37 AM

Do a search on Ebay or something. I've heard of somebody buying one that way once. I think it was less than $50 too.
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'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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repuguru


Redlining
Posts: 319
posted October 26, 2001 02:58 PM

po' boys ignition

Ok maybe bang for the buck is the wrong choice of words. I think what PY had in mind is the eqivalent of what you describe as the poor mans ignition and was thinking along the lines of a clean install of the GN double coil. I am sure you can do a clean install of another diamond coil but the double one sounded sano.
I now understand the difference in what you are describing between the two variations of ignition.
Can you later plugs when you add the Direct fire set up to your older motor? Would there be a advantage?

       
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Jeff20B


Moderator
Posts: 661
posted October 26, 2001 08:53 PM

Talk about clean, well, pics are coming of the engine bay of my truck. You can decide for yourself. I think I took some of my electric fan rewiring job... I might take a few more to be on the safe side.

Adding a 3rd Diamond coil to my REPU was child's play. It was much harder to add a 3rd coil to my Cosmo. It was also way easier to install an ignitor plate in my truck than the Cosmo. Infact, I'm still debating on the location of the ignitor plate for the Cosmo. I try to come up with a possibilty, then it turns out to be a bad one, then try again and again with more failure. That's how hard it's been. I'm about ready to try something radical. Come to think of it, installing the 3rd coil in my truck back in the day was QUITE radical. That's what I think I'll need; some more radical thought.

So in other words, using a dual output coil like the GM one or even a 2nd gen unit isn't the best option there is. What does sano mean?

I set my total advance to 20*L BTDC yesterday and also reset my Trailing back to a 10* split (this dizzy had been sitting for 10 years before I installed it in my truck and was a little stiff inside). So I now have 20* L and 10* T BTDC at or above 4000RPM.

I have been debating on rebuilding a GSL-SE dizzy which has what looks like a 25* curve in it. Hmmm...

I use the '81-'85 NGK BR8EQ-14 plugs in L and T. So can you. The advantage is that the plugs will be matched to the coils. Well, mostly. The Leading plugs are now pulling double duty, but the spark doesn't need to go through the cap either. If you trust me, then you should be able to do some cool mods to your truck.
____________
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'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Redlining
Posts: 319
posted October 29, 2001 10:31 AM

New Plugs

I have been running the BR8EQ14's with my stuff for years. When I buy a pre-80' rotary powered car or truck one of the first things I manage to do is to ditch the points ign.
What I was wondering is the possibility of using the 86' and later plugs. Myth has it the only reason we can't use them is because the 81-85 electronic ign doesn't have a strong enough spark to fire them properly. With the direct fire it sounds as if you could at least run them on the leading side? The advantage if anything perhaps would be plug life since they were made to work with the newer and stronger ignition the 2 gen RX7 came with. Have you had any problem with getting normal life from a set of the BR8EQ-14's with the direct fire?
Sano is slang for sanitary. As in a very clean install of the coil set up.

       
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Jeff20B


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Posts: 661
posted October 29, 2001 11:47 AM

Thats one of the first things I did on my Cosmo and truck was to swap in an el dizzy. The direct fire came later.

I've got a friend with an REPU with a GSL-SE engine in it and a carb on it. The carb is a nikki and is too small. He's going to be getting a supercharger soon. That should be interesting. Anyway, the engine still has a GSL-SE dizzy in it I think (I'll have to peak in to the advance weights and see if it has a 25* curve), and its using stock diamond coils with BUR7EQ and BUR9EQ. Those are 2nd gen plugs on a 1st gen engine. The plugs seem to run ok, but he's currently running a bit rich so we'll see how things go. He wants me to build him a DLIDFIS kit. (he was totaly impressed by the DLIDFIS on my other friend's REPU).

I haven't had any problems with running BR8EQ-14 plugs and direct fire yet. One thing that caught my attention a while back (like, last year or longer ago) was the fact that the Leading plugs were now going to be firing twice as often as before. This means more wear. But then I realized that in a stock ignition setup, the Leadings always wear faster than Trailing. Why? Because the Trailing plugs are sparking through a small hole while the Leading are fully exposed to the AF mixture. The spark electricity is not what is causing the metal to wear, its the burning (rather, exploding) AF mixture that does. The Trailing adds maybe 15% of the total power the engine produces. Probably less than 10% realistically (thats why Mazda put the tach on the Trailing coil, to show you if it ever dies on you - the tach would be dead). The point is that double fired Leading plugs will probably only wear 20% faster than before because that 180* spark is firing into AF mixtures that have already been mostly ignited by the Trailing plug. I could be wrong though. Maybe the plugs will wear 50% faster with direct fire. Tell you what, when I do a plug checkup I'll take them out and clean and inspect them. If the Leads look too far gone but the Trails are still ok looking, I'll only need to buy two new plugs hehe. Besides, these plugs were installed in my engine back in '95 and have something like 7000 miles on them. The last time I looked at them they were good enough to use again (I found them in a box after I put my truck's new plugs in my Cosmo for testing purposes. These old plugs looked so good I decided to use them in my truck again. I'm cheap! Hence the whole poor man's ignition movement started by me).

My friend also has a nice SA ('79 1st gen) with an '86 13B and dellorto. That engine had BR8EQ-14s in it and a couple had cracked porcelin. It didn't take an Einstien to realize this engine had the wrong plugs in it. We got two 7s and two 9s. Running problems solved. This engine has a 1st gen dizzy and single fire on the Leading plugs. I other words, the BUR7(9)EQ plugs are for the '86 and later engines, while the BR8EQ-14s are for '85 and older engines. But my friend's REPU has an '85 engine and '86 plugs, yet it seems to run ok, though a little rich. Hmmm...
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Jeff20B


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Posts: 661
posted March 22, 2002 01:55 AM

My friend's truck still has a funny misfire. It's probably caused by the 2nd gen plugs in a 1st gen engine. Swapping plugs is the only way to tell. Now to convince him...

My Cosmo ran great with two coils hooked to a single ignitor (I got it running a few weeks ago). I'm a little reluctant to go with dual Leading ignitors at this time because I also need to do something about the ignition in my MG. There is always the MSD option (eek!). At least I could, for now, have direct fire if I used the MSD. But where to mount it in that cramped engine bay? Ah screw it. Something'll turn up. If not a couple extra ignitors, then maybe a 20B or two.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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