NoPistons -Mazda Rx7 & Rx8 Rotary Forum

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-   -   How Do Cdi's Work? (https://www.nopistons.com/2nd-generation-specific-17/how-do-cdis-work-12636/)

sunshine 02-20-2003 06:14 PM

Ok guys...how do these little magic boxes work? I have a 1991 N/A, and from what I heard, a CDI box would help performance a bit, increase mileage, and smooth out revving. I want to install One (1) CDI box, either MSD 6A or Crane Hi-6. I know the box would connect to the (+) and (-) terminals on the leading coil assembly, but what does it do then? How does it work?



Is one box enough for a strretported n/a? I know Vosko has 3 of them...I dont think I need that many!

Thanks...please be as detailed as possible.

pengaru 02-20-2003 06:20 PM

i beleive the quantity of boxes is just needed because of the way ignition works on a rotary. I think it's one per rotor on trailing then the third handles leading for both rotors.

vosko 02-20-2003 06:25 PM

pengaru is correct

pengaru 02-20-2003 06:30 PM

thanks vosko https://www.nopistons.com/forums/pub...IR#>/smile.png



now... why do you think you need these? The stock ignition on the 7 is quite good and you're running an NA, I'm sure there are plenty of things you could do with the money that would make more of a difference.

sunshine 02-20-2003 06:39 PM

Well...your point is well taken. I would like to put a box on because 1) I'm getting hesitation/hiccuing about 7k. I dont know if its spark/fuel/air of Slipping clutch related. 2) beacuse I really want a smooth idle, and better gas mileage.



I recently put in a rebuild engine. So fairly new plugs/wires, new fuel filter, clean injectors, new ACT s/s clutch w/HD PP. So, I am raking my brain as to why its hesitating at 7k!



So...can I use only one CDI box for leading, and leave trailing alone?

Apex13B 02-20-2003 06:41 PM

one on the leading coil will be more than sufficient on an all-motor application

rxpower 02-20-2003 06:45 PM

Malory ignitions are the funk

its what we are using at the shop now

and they are cheaper than MSD's

only about 118. :bigok:

vosko 02-20-2003 06:45 PM

what plugs are you using ?

pengaru 02-20-2003 06:50 PM


Originally Posted by sunshine' date='Feb 21 2003, 12:39 AM
Well...your point is well taken. I would like to put a box on because 1) I'm getting hesitation/hiccuing about 7k. I dont know if its spark/fuel/air of Slipping clutch related. 2) beacuse I really want a smooth idle, and better gas mileage.



I recently put in a rebuild engine. So fairly new plugs/wires, new fuel filter, clean injectors, new ACT s/s clutch w/HD PP. So, I am raking my brain as to why its hesitating at 7k!



So...can I use only one CDI box for leading, and leave trailing alone?

you really don't care about leading, it's not that significant. The trailing is what is really important for power and correct operation.



Your problems i'm 99.99999999999% sure are not your ignition system being a limitation.



You likely installed your street port motor? right?



there are so many variables on the stock ECU it's not even funny, what do you have left on it? rats nest eliminated?



did you replace the vacuum lines when you installed the motor? You could be running out of fuel, but... I doubt thats the case on an NA, even street ported. Have you confirmed your timing is correct, and that everything is connected properly?



A common mistake for people to do is replace the vacuum line on the boost sensor, with a normal line, and forget the orifice which goes in the line. Without it you will have the problems you are describing.

sunshine 02-20-2003 06:55 PM


Originally Posted by pengaru' date='Feb 20 2003, 07:50 PM
A common mistake for people to do is replace the vacuum line on the boost sensor, with a normal line, and forget the orifice which goes in the line. Without it you will have the problems you are describing.

You may have just hit it on the nose. I DID replace all lines with silicone - even the boost sensor one. I was not aware of an orifice in there! DO TELL ME more.


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