1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Can the J-109s be done away with?

Old 01-09-10, 08:38 PM
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Can the J-109s be done away with?

I've done some searching on the forum and all I can find seems to be either expensive MSD systems, and/or second gen ignition control modules running the leading spark plugs, while the stock distributor and trailing J-109 is still employed to run the trailing system.

Is there a way to install a 2GDFIS (2nd gen Direct Fire Ignition System) in a way that completely replaces the J-109 ignitors in a first gen car? (An '83 12A is the motor in question).
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Old 01-09-10, 10:10 PM
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I'm short on time but yes, they can. Well, actually, they can be replaced with GM HEI ignitors used on some other vehicles. Search for that term and you should find some threads.

There are some other, more expensive options too, like MSD and the like.

Good luck....


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Old 01-10-10, 12:19 AM
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the ignitors trigger the coils. if u want to do away with them, u need to come with another way to trigger the coils. u dislike them that much? the engine will actually run without trailing so u could do the 2g setup and not run trailing. if u insist on doing away with the uniqueness of the engine.
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Old 01-10-10, 02:58 AM
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Originally Posted by anotherfire View Post
I've done some searching on the forum and all I can find seems to be either expensive MSD systems, and/or second gen ignition control modules running the leading spark plugs, while the stock distributor and trailing J-109 is still employed to run the trailing system.

Is there a way to install a 2GDFIS (2nd gen Direct Fire Ignition System) in a way that completely replaces the J-109 ignitors in a first gen car? (An '83 12A is the motor in question).
This link covers it for DLIDFIS, but you can do the other ignition mods as well, you just remove the J-109's and replace them with the HEI modules.
https://www.rx7club.com/forum/showth...hlight=dlidfis
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Old 01-11-10, 06:40 PM
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Originally Posted by rxtasy3 View Post
the ignitors trigger the coils. if u want to do away with them, u need to come with another way to trigger the coils. u dislike them that much? the engine will actually run without trailing so u could do the 2g setup and not run trailing. if u insist on doing away with the uniqueness of the engine.
I guess I was hopeing to find a way to remove the distributer aswell as the ignitors. the 2G systems seem to bypass the dizzy and the leading ignitor for the leading system, so I wanted to know if the same thing could be done for the secondary, thereby rendering the dizzy, and both J-109s removeable. I think this would be a nice mod for simplicity, and maybe reliability? and maybe a little extra power?

The uniqueness you refer to is the secondary spark that is supposed to burn up a little extra fuel, but generates little, if any power? I started a thread to find out if there was any possible advantage to disableing/removing the secondary circuit.
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Old 01-11-10, 07:16 PM
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You can't run the trailing ignition like the wasted spark second gen leading. If you look closely at the second gens, they use a crank angle sensor in place of the dizzy. This sends a signal to the ecu. Then the ecu sends a signal to the coils telling them when to fire. The third gens use a hall effect system with a trigger wheel and sensor at the front crank pulley. This signal is sent to the ecu just like the second gens.

So basically what I am trying to say is, you will have to have something to trigger the coils. Either a dizzy, or something to trigger an ignition ecu. Like others have said. You can just run the second gen gen leading coil, and just do away with the trailing.

Eithor or.
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Old 01-12-10, 07:52 AM
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Originally Posted by anotherfire View Post
I guess I was hopeing to find a way to remove the distributer aswell as the ignitors. the 2G systems seem to bypass the dizzy and the leading ignitor for the leading system, so I wanted to know if the same thing could be done for the secondary, thereby rendering the dizzy, and both J-109s removeable. I think this would be a nice mod for simplicity, and maybe reliability? and maybe a little extra power?

The uniqueness you refer to is the secondary spark that is supposed to burn up a little extra fuel, but generates little, if any power? I started a thread to find out if there was any possible advantage to disableing/removing the secondary circuit.
The distributor is still used on 1G Rx7s even when the 2G coil is used.
Theres no way around that. You need to have something that indexes the
crank as it rotates. On 1G Rx7s thats the distributor and on later Rx7 its the
crank angle sensor (sits in the same spot on the engine). As mentioned you
can get rid of the J109 by replacing with the GM HEI.

So no theres no way you can remove the distributor unless you install some
other mechanism to detect the crank angle.
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Old 01-12-10, 10:11 AM
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You could always try to work up a one-coil-per-plug system as used with modern engines... but if you don't have ignitors you still need something to do the job of amplifying the trigger signal into something that can handle the current required to trigger the coils into field collapse & make spark.

Any ignition system has to do certain things:

1) Detect crank angle to determine firing time
2) Advance that firing time proportionally to engine speed in order to compensate for burn time
3) Generate a firing signal
4) Amplify that signal sufficiently to arc the plug
5) Get the firing current to the right plug

The distributor/points/coil system lasted as many years as it did because it was inexpensive, acceptably reliable, and did the job with adequate precision for the times.

Electronic detection and amplification replaced points (in 1980 on the RX-7) when it became more reliable and cost-effective - - and proved to be easier to interface to the move to electronic control systems dictated by the emissions laws. But a distributor system with one (or two, for us) coils stayed cheaper for a long time.

Fast, reliable computer control and stricter fuel economy standards, and the drop in the cost of onboard processing power, were what finally did in the distributor. It simply became more cost-effective & simpler for the manufacturer to handle ignition control through a computer, even though the electronic controls cost the consumer a lot more in the purchase price. The manufacturer had other goals besides price-point that went into their calculation - - mainly, meeting mandated emissions performance and reliability standards.

But on a straight parts cost standard, nothing has gotten cheaper than the original dizzy/points/coil system that date back to Tesla - - 19th-century high technology.

Here's a funny thought: Raw replacement parts cost for the complete ignition system in a RX-8 (ECU on down to plugs) probably exceeds half the original MSRP for an entire 1st gen RX-7.
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