msd ignition question
09-03-04, 11:21 PM
#1
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msd ignition question
i have a 79 and i think i might go this route... my question is do i need to get a different distributor to work with this or will it work with the 79 points system i am a bit confused about that...
Mike
Mike
09-04-04, 02:36 AM
#2
Ah, I see you read your other thread and posted.
Just for anyone else who may be interested, yes the MSD can be triggered by points. Use the white wire. Your leading points assembly will last almost forever since it takes a lot less current to trigger an MSD box than it does to trigger the stock ignition.
It's also a good idea to get a 2nd gen leading coil and run both leading plugs in direct fire mode. Forget about hooking the MSD to two coils as the MSD's CD output isn't as 'grand' when it must split apart to power two coils' primaries (the MSD's output is finite afterall).
You'll also want to get a set of 2nd gen leading spark plugs to take advantage of the greater spark potential. Look for two NGK BUR7EQ. Leave the trailing plugs stock since they're still running through the cap and rotor, but be sure to move them to the leading part of the cap to take advantage of the carbon button and one less gap tp jump.
Just for anyone else who may be interested, yes the MSD can be triggered by points. Use the white wire. Your leading points assembly will last almost forever since it takes a lot less current to trigger an MSD box than it does to trigger the stock ignition.
It's also a good idea to get a 2nd gen leading coil and run both leading plugs in direct fire mode. Forget about hooking the MSD to two coils as the MSD's CD output isn't as 'grand' when it must split apart to power two coils' primaries (the MSD's output is finite afterall).
You'll also want to get a set of 2nd gen leading spark plugs to take advantage of the greater spark potential. Look for two NGK BUR7EQ. Leave the trailing plugs stock since they're still running through the cap and rotor, but be sure to move them to the leading part of the cap to take advantage of the carbon button and one less gap tp jump.
09-04-04, 03:06 AM
#3
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okay i am new to this exactly how am i supposed to connect the 2 spark plugs to one coil? or am i missing a step? and would this work as good as changing the dizzy or should i just go with your method? in my area i could possibly get away cheaper with just the msd. but if it is really that much better i would do the dlfi thingy
09-04-04, 04:52 AM
#4
The 2nd gen leading coil I mentioned earlier actually has two outputs on it. This is how a single coil can spark two plugs at the same time. 
There are pros and cons with any setup. There isn't one perfect solution yet, although DLIDFIS comes pretty close.
Without getting into too many details, the MSD is good on a 2nd gen leading coil due to the nature of the CD output working better with the single primary winding in this coil than if it were hooked to two seperate coils, as mentioned here. http://www.mazspeed.com/msd.htm
The above info is for an electronic distributor, but all you'd need to do is substitute the MSD's green and purple wires for the single white wire, and substitute the two coils for a 2nd gen leading coil.
I have tried the MSD hooked to two coils as was not impressed. Then I went to DLIDFIS and I could actually tell that the sparks had longer duration just in the way that it sounded (it sounded better). It also completely stopped backfiring. In my opinion, back then, the MSD sucked majorly in a cost vs performance aspect, and I simply couldn't recommend it to others. Then a little more recently, I picked up a 2nd gen leading coil (for free) and hooked it to the MSD (which had been collecting dust since '01, the $200 paper weight). It actually showed some promise. So much so that I'm keeping it around to install on my '73 12A with an '83-'85 rotating assembly.
Would I ever get another MSD? I seriously doubt it. Especially when GM HEI ignitors can be purchased for as little as $15.99, and are very common at any auto parts store. Anyway, since I already had this MSD sitting here, and I was interested in possibly trying 2GCDFIS (it was gaining popularity at the time), I picked up a 2nd gen leading coil. Then on a whim, I hooked the MSD up to it and liked what I saw. Besides, 2GCDFIS is supposed to be the easier cheaper alternative to DLIDFIS. LOL, I can wire up DLIDFIS in my sleep so the only motivation I had for even wanting to try 2GCDFIS was that the coil was free.
I guess I got lucky. I hope it works out in the end.
There are pros and cons with any setup. There isn't one perfect solution yet, although DLIDFIS comes pretty close.
Without getting into too many details, the MSD is good on a 2nd gen leading coil due to the nature of the CD output working better with the single primary winding in this coil than if it were hooked to two seperate coils, as mentioned here. http://www.mazspeed.com/msd.htm
The above info is for an electronic distributor, but all you'd need to do is substitute the MSD's green and purple wires for the single white wire, and substitute the two coils for a 2nd gen leading coil.
I have tried the MSD hooked to two coils as was not impressed. Then I went to DLIDFIS and I could actually tell that the sparks had longer duration just in the way that it sounded (it sounded better). It also completely stopped backfiring. In my opinion, back then, the MSD sucked majorly in a cost vs performance aspect, and I simply couldn't recommend it to others. Then a little more recently, I picked up a 2nd gen leading coil (for free) and hooked it to the MSD (which had been collecting dust since '01, the $200 paper weight). It actually showed some promise. So much so that I'm keeping it around to install on my '73 12A with an '83-'85 rotating assembly.
Would I ever get another MSD? I seriously doubt it. Especially when GM HEI ignitors can be purchased for as little as $15.99, and are very common at any auto parts store. Anyway, since I already had this MSD sitting here, and I was interested in possibly trying 2GCDFIS (it was gaining popularity at the time), I picked up a 2nd gen leading coil. Then on a whim, I hooked the MSD up to it and liked what I saw. Besides, 2GCDFIS is supposed to be the easier cheaper alternative to DLIDFIS. LOL, I can wire up DLIDFIS in my sleep so the only motivation I had for even wanting to try 2GCDFIS was that the coil was free.
I guess I got lucky. I hope it works out in the end.
09-04-04, 01:34 PM
#5
This thread has a few pictures of a some 2GCDFIS installs. You'll be able to see what a 2nd gen leading coil looks like. https://www.rx7club.com/showthread.p...hreadid=243350
09-04-04, 05:53 PM
#6
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sweet man thanks.. i wonder how much i could get one of those 2nd gen coils for.. i will have to search that one out. thanks for all your info... my only other question is in your opinion should i do this with my points system or switch it out for a new dizzy.. i might try it with the points first then later switch it to the other dizzy.
09-05-04, 02:38 AM
#7
If you're going to use an MSD, it doesn't really matter. You could eventually get yourself an '81-'85 dizzy, but it's not urgent. The trailing side of the ignition system would be improved a bit with an electronic dizzy (no more changing or adjusting points), but it would still be fired through a cap and rotor, so you probably won't feel a difference in the butt dyno. A chassis dyno would probably show an increase of maybe 2HP.
You know that leading does 99% of the work, right? That's stock. If you've got a direct fire ignition system which fires both leading plugs at the same time, well, leading takes over trailing's job as well.
If you've ever seen inside a rotor housing, you'll have noticed that the leading hole is normal in size but the trailing hole is quite small. So even if you upgrade the trailing spark from points to electronic, it's still not going to net you very much extra power. The hole is small to try to prevent burning air/fuel gasses from venting into the next incoming rotor face. Of course some does blow by and there is a bolt kit available that is machined to plug up that hole and thread in like a normal spark plug (trailing ignition obviously no longer functions), but that's for another thread.
Now consider having that second spark per rotor face. It's a late-leading spark from the rotor's perspective. It sparks exactly 180º after the regular leading spark, and it looks something like this. http://www.rotaryengineillustrated.c...es/an-WCA.html
Notice how it sparks right before the exhaust port opens? Pretty cool, huh?
You know that leading does 99% of the work, right? That's stock. If you've got a direct fire ignition system which fires both leading plugs at the same time, well, leading takes over trailing's job as well.
If you've ever seen inside a rotor housing, you'll have noticed that the leading hole is normal in size but the trailing hole is quite small. So even if you upgrade the trailing spark from points to electronic, it's still not going to net you very much extra power. The hole is small to try to prevent burning air/fuel gasses from venting into the next incoming rotor face. Of course some does blow by and there is a bolt kit available that is machined to plug up that hole and thread in like a normal spark plug (trailing ignition obviously no longer functions), but that's for another thread.
Now consider having that second spark per rotor face. It's a late-leading spark from the rotor's perspective. It sparks exactly 180º after the regular leading spark, and it looks something like this. http://www.rotaryengineillustrated.c...es/an-WCA.html
Notice how it sparks right before the exhaust port opens? Pretty cool, huh?
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09-05-04, 02:59 AM
#8
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sweet i would just like to say that you are wonderful for spending your time teaching a newbie like me about all this rotary stuff.. i appreciate it. from all the studying i have done i believe i am going with the 2nd gen coil system.. i found one from someone on here that would send it to me for $15 including shipping. so i will go that route.. so let me once again see if i understand it all.. i am going to do the 2gcdfis and will be able to keep my stock dizzy at least for now and then switch to an electronic dizzy later. am i correct on this?
i have other questions about other things for you but i will ask at a later time. i am confused about the gxl-se swap for the suspension.. i dont know if you know about that or not but i am assuming with your vast knowledge you are the best one to ask. but that is going to be my winter project. that and an intake and some porting...
anyways.. thanks again for your help.
i have other questions about other things for you but i will ask at a later time. i am confused about the gxl-se swap for the suspension.. i dont know if you know about that or not but i am assuming with your vast knowledge you are the best one to ask. but that is going to be my winter project. that and an intake and some porting...
anyways.. thanks again for your help.
09-05-04, 03:57 AM
#9
Hey thanks! I appreciate positive feedback from a receptive audience. I find it difficult to teach others who haven't got a clue how ignition systems work in general, or know nothing about rotary-specific stuff. It's easier for me to communicate with people who already have a basic understanding of the concept/subject I'm discussing. You showed promise so I decided to add a little extra to my posts directed toward you.
That sounds like a good deal for a coil.
Hooking a 2nd gen leading coil to a J-109 or other ignitor is called 2GCDFIS. This means if you wanted to run 2GCDFIS, you would need an electronic dizzy. No MSD would be required.
Ask hornbm. He transfered some GSL-SE suspension parts to a non-sunroof '85.
That sounds like a good deal for a coil.
Hooking a 2nd gen leading coil to a J-109 or other ignitor is called 2GCDFIS. This means if you wanted to run 2GCDFIS, you would need an electronic dizzy. No MSD would be required.
Ask hornbm. He transfered some GSL-SE suspension parts to a non-sunroof '85.
09-06-04, 01:18 AM
#11
Bimmer *****
Originally Posted by evil_motors
sweet i would just like to say that you are wonderful for spending your time teaching a newbie like me about all this rotary stuff.. i appreciate it. from all the studying i have done i believe i am going with the 2nd gen coil system.. i found one from someone on here that would send it to me for $15 including shipping. so i will go that route.. so let me once again see if i understand it all.. i am going to do the 2gcdfis and will be able to keep my stock dizzy at least for now and then switch to an electronic dizzy later. am i correct on this?
i have other questions about other things for you but i will ask at a later time. i am confused about the gxl-se swap for the suspension.. i dont know if you know about that or not but i am assuming with your vast knowledge you are the best one to ask. but that is going to be my winter project. that and an intake and some porting...
anyways.. thanks again for your help.
i have other questions about other things for you but i will ask at a later time. i am confused about the gxl-se swap for the suspension.. i dont know if you know about that or not but i am assuming with your vast knowledge you are the best one to ask. but that is going to be my winter project. that and an intake and some porting...
anyways.. thanks again for your help.
09-06-04, 04:04 AM
#12
Wow, thanks! I just like talking about ignition stuff and bouncing ideas off of others to test my own understanding of it. Again, it's the whole 'receptive audience' type thing.
Yeah, I was the last person to leave. Nobody got to hear the wonderful exhaust note of the REPU resonating through the trees (think Dan Atkins, lol
). Maybe next time?
Yeah, I was the last person to leave. Nobody got to hear the wonderful exhaust note of the REPU resonating through the trees (think Dan Atkins, lol
). Maybe next time?
09-06-04, 03:31 PM
#13
Bimmer *****
Originally Posted by Jeff20B
Wow, thanks! I just like talking about ignition stuff and bouncing ideas off of others to test my own understanding of it. Again, it's the whole 'receptive audience' type thing.
Yeah, I was the last person to leave. Nobody got to hear the wonderful exhaust note of the REPU resonating through the trees (think Dan Atkins, lol ). Maybe next time?
Yeah, I was the last person to leave. Nobody got to hear the wonderful exhaust note of the REPU resonating through the trees (think Dan Atkins, lol
). Maybe next time?
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