Direct Fire Options for 1980 RX-7?
11-25-04, 11:05 PM
#1
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Direct Fire Options for 1980 RX-7?
So many options (I'm almost boggled from reading on this topic), just trying to learn which one might be best for me.
Goal:: Improve LEADING ignition on 1980 RX-7 (currently completely stock)
Note:: I will NOT modify the TRAILING ignition system. The information I seek is ONLY for the LEADING ignition system.
Option #1. Use 2nd Gen Leading Coil, triggered by a J-109 (using the 2nd Gen Ballast Resistor). This is documented (I believe) adequately that I can understand, obtain parts, and make it work (and lots of great experience on this board).
Option #2 Use GM-HEI Ignitor (Wells DR100, or Accel 35361) firing a GM HEI Dual Tower Coil (Standard DR39 or Accel 140017). This configuration has been implied in several threads, but has anyone actually implemented it successfully (this type coil without an MSD)? Is the wiring of the HEI Dual-Tower coil any different electrically than using the 2nd gen coil? Were there any problems (like adding a resistor so the tach works correctly)?
Option #3 Similar to Option #1, but add the 2nd Gen ignitor between the J-109 and the 2nd Gen coil (with the ballast resistor in the circuit). This configuration was implied in several threads, but has anyone actually done it successfully? What “extra” parts were needed (like a power transistor… what kind, and how is it wired). Is it better than Option #1 or #2 (why).
I favor Option 2, simply because parts (especially “High Performance” parts) are readily available.
I would really appreciate comments and suggestions from anyone who has an operational vehicle using option #2 or #3.
Thanks!!!
Goal:: Improve LEADING ignition on 1980 RX-7 (currently completely stock)
Note:: I will NOT modify the TRAILING ignition system. The information I seek is ONLY for the LEADING ignition system.
Option #1. Use 2nd Gen Leading Coil, triggered by a J-109 (using the 2nd Gen Ballast Resistor). This is documented (I believe) adequately that I can understand, obtain parts, and make it work (and lots of great experience on this board).
Option #2 Use GM-HEI Ignitor (Wells DR100, or Accel 35361) firing a GM HEI Dual Tower Coil (Standard DR39 or Accel 140017). This configuration has been implied in several threads, but has anyone actually implemented it successfully (this type coil without an MSD)? Is the wiring of the HEI Dual-Tower coil any different electrically than using the 2nd gen coil? Were there any problems (like adding a resistor so the tach works correctly)?
Option #3 Similar to Option #1, but add the 2nd Gen ignitor between the J-109 and the 2nd Gen coil (with the ballast resistor in the circuit). This configuration was implied in several threads, but has anyone actually done it successfully? What “extra” parts were needed (like a power transistor… what kind, and how is it wired). Is it better than Option #1 or #2 (why).
I favor Option 2, simply because parts (especially “High Performance” parts) are readily available.
I would really appreciate comments and suggestions from anyone who has an operational vehicle using option #2 or #3.
Thanks!!!
11-25-04, 11:08 PM
#2
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i thought i remember reading that a guy who did direct fire said it lead to now power increasements at all. I cant recall the forum, but hey alittle extra bells and whistles never hurts anything.
11-26-04, 01:02 AM
#3
Option 1 has been done by quite a few people and it works great.
Option 2 hasn't been done yet, but I suspect it shoudl work out to be quite similar to 2GCDFIS. I'm not sure about the wiring of a genuine GM DIS coil. I know the MSD DIS coil doesn't matter which wire goes where (+ or -) as long as they're both connected to the coil. I've never messed with a GM DIS coil so I can't comment on it from a personal perspective. Perhaps others here will know?
By the way, what do you mean by adding a resistor so the tach will work? Is it something GM cars require? Mazda tachs can handle a 12V square wave right off the negative terminal of the coil. I think they have internal protection diodes to resist inductive kickback and voltage spikes.
Option 3 hasn't been done yet. It was talked about by 83turbo and others (like myself) but it never got past that stage. It sounds like a great way to trigger a 2nd gen leading coil, but nobody's taken this challange on yet.
It would be great for you to go with option 2.
Seriously, you'd be the first to try this particular combination of components. All you need are the electrical hook-up instructions for the coil, I'm guessing. As for the ignitor, W goes to red and G goes to green on FB dizzies. Since the '80 dizzy reluctor is backwards (triggers on the other side of the pulse), you could try it both ways. If the VR sensor (pickup) wires are hooked to the ignitor backwards, it'll trigger at the wrong time. Easy fix. The other terminals, B and C, hook to the coil exactly the same way as the stock J-105 ignitor does. That is, if the GM DIS coil has an actual + and - anywhere on it. Have fun! 
Glen, I think the guy you're talking about is fellow forumite kettleman. His setup is the only one I've ever been aware of that didn't improve at least one aspect of the engine. The only other DLIDFIS setup that didn't add any power was on my friend's '77 REPU with excessive blowby of the apex, side and oil seals (exhaust literally flows from the breather on the oil fill tube!). It's got an Atkins supercharger, which I'm sure isn't helping the blowby situation. He's got an S5 T2 nearly ready to swap into the truck soon. Anyway, it has an air/fuel mixture guage that used to be all over the place on the rich side of stoich. After DLIDFIS with two GM HEI ignitors and one more stock coil, the AF guage is rock-solid one LED to the rich side of stoich (perfect for most of us). Before the conversion, he thought his stock FB ignition system, that was transplanted into the truck from a GSL-SE, was all that. He believed in the power of stock, lol! Heh, when he saw the steady guage, he thought I had accidentally unplugged the O2 sensor! It may not have improved the power noticeably, but at least the engine is experiencing more complete combustion now. I'm sure after the engine swap, the more complete combustion can be used to accelerate the truck instead of just leaking past all the seals.
You know, I honestly think the supercharger is the only thing keeping that engine running. It doesn't idle, and he's tried all his Holley trick on it. He even changed carbs to one that Atkins was sure would work. My thought is at idle speeds, the boost is so low that the engine just doesn't want to run. It actually runs decently above 2-3k, though down on power (it's a little more powerful than my REPU with a stock carb). Sorry to get off topic.
Option 2 hasn't been done yet, but I suspect it shoudl work out to be quite similar to 2GCDFIS. I'm not sure about the wiring of a genuine GM DIS coil. I know the MSD DIS coil doesn't matter which wire goes where (+ or -) as long as they're both connected to the coil. I've never messed with a GM DIS coil so I can't comment on it from a personal perspective. Perhaps others here will know?
By the way, what do you mean by adding a resistor so the tach will work? Is it something GM cars require? Mazda tachs can handle a 12V square wave right off the negative terminal of the coil. I think they have internal protection diodes to resist inductive kickback and voltage spikes.
Option 3 hasn't been done yet. It was talked about by 83turbo and others (like myself) but it never got past that stage. It sounds like a great way to trigger a 2nd gen leading coil, but nobody's taken this challange on yet.
It would be great for you to go with option 2.
Seriously, you'd be the first to try this particular combination of components. All you need are the electrical hook-up instructions for the coil, I'm guessing. As for the ignitor, W goes to red and G goes to green on FB dizzies. Since the '80 dizzy reluctor is backwards (triggers on the other side of the pulse), you could try it both ways. If the VR sensor (pickup) wires are hooked to the ignitor backwards, it'll trigger at the wrong time. Easy fix. The other terminals, B and C, hook to the coil exactly the same way as the stock J-105 ignitor does. That is, if the GM DIS coil has an actual + and - anywhere on it. Have fun! Glen, I think the guy you're talking about is fellow forumite kettleman. His setup is the only one I've ever been aware of that didn't improve at least one aspect of the engine. The only other DLIDFIS setup that didn't add any power was on my friend's '77 REPU with excessive blowby of the apex, side and oil seals (exhaust literally flows from the breather on the oil fill tube!). It's got an Atkins supercharger, which I'm sure isn't helping the blowby situation. He's got an S5 T2 nearly ready to swap into the truck soon. Anyway, it has an air/fuel mixture guage that used to be all over the place on the rich side of stoich. After DLIDFIS with two GM HEI ignitors and one more stock coil, the AF guage is rock-solid one LED to the rich side of stoich (perfect for most of us). Before the conversion, he thought his stock FB ignition system, that was transplanted into the truck from a GSL-SE, was all that. He believed in the power of stock, lol! Heh, when he saw the steady guage, he thought I had accidentally unplugged the O2 sensor! It may not have improved the power noticeably, but at least the engine is experiencing more complete combustion now. I'm sure after the engine swap, the more complete combustion can be used to accelerate the truck instead of just leaking past all the seals.
You know, I honestly think the supercharger is the only thing keeping that engine running. It doesn't idle, and he's tried all his Holley trick on it. He even changed carbs to one that Atkins was sure would work. My thought is at idle speeds, the boost is so low that the engine just doesn't want to run. It actually runs decently above 2-3k, though down on power (it's a little more powerful than my REPU with a stock carb). Sorry to get off topic.
11-26-04, 02:31 AM
#4
BEST THREAD EVER----> https://www.rx7club.com/1st-generation-specific-1979-1985-18/m-s-d-l-i-d-f-i-s-365484/
There is my thread aboot my ignition. I run the MSD direct fire, but youse a MSD GMstyle Dual tower DIS coil. We have chosed to call this the MSD-DIS setup. And frankly its fu(king amazing. Running just the msd was nice, but this is awesome. And I highly suggest it.
There is my thread aboot my ignition. I run the MSD direct fire, but youse a MSD GMstyle Dual tower DIS coil. We have chosed to call this the MSD-DIS setup. And frankly its fu(king amazing. Running just the msd was nice, but this is awesome. And I highly suggest it.
