2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

CDI, Jacobs box, maybe make my own?

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Old Jan 31, 2016 | 08:34 PM
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CDI, Jacobs box, maybe make my own?

I have been really eyeballing the jacobs 1000 CDI box for a while and I got to thinking, "What the hell makes me unable to make this myself?".

Now I know the Jacobs box raises the capacitor input voltage to 500v or whatever coming from the igniter and dumps that to the ignition coil, but I dont see why we couldn't add a small capacitor between the ignition coil and the igniter to just boost ignition current a little bit.

From what I can tell, the igniter keeps the ignition primary wires energized, spark needs to happen so it turns off. Basic transformer theory really.

I am thinking of putting a small capacitor between the igniter and coil.

Or I might just buy the jacobs box.

...Or I might just put on my $27 alternator belt, that I havent had time to do, even though the jacobs box will be quicker.
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Old Feb 1, 2016 | 12:09 AM
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JJ..since you got the juices flowin..heh.

I thought about getting one of those Electric Hand dryers that they use in garage restrooms and using it for a Turbo..run it off a 12V Dc to 120 Ac Converter..hit a switch and get BOOST..
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Old Feb 1, 2016 | 12:21 AM
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Originally Posted by misterstyx69
JJ..since you got the juices flowin..heh.

I thought about getting one of those Electric Hand dryers that they use in garage restrooms and using it for a Turbo..run it off a 12V Dc to 120 Ac Converter..hit a switch and get BOOST..
That'd be no different than hooking up a leaf blower to your intake......which i've seen a video of someone doing that at a dyno, it did work, maybe 30 horse
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Old Feb 1, 2016 | 12:42 AM
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Originally Posted by jjwalker
I have been really eyeballing the jacobs 1000 CDI box for a while and I got to thinking, "What the hell makes me unable to make this myself?".
The very definition of "the American Spirit".
I had a similar inspiration as I began developing an ignition based on Babbage's Difference Engine #2 (#1 being too antiquated, obvs).
After you feed in the appropriate data, my analog ECU calculates and prints out the optimal spark timing, which you initiate manually.
With a strategically placed red button.

The prototype batch fires all four plugs simultaneously which- Top Tip!- is probably not the right way to do it. V.2 will incorporate discrete rotor firing, I'm going with the controversial Top>Bottom firing order rather than rotor1 and rotor2.
Grading on the site has begun and we should be laying concrete next week, so this piggyback ECU should be online soon.

An unexpected problem was maintaining a fast and steady ignition button push rate...much more difficult than I was prepared for.
As configured, the ticker tape unspools from the dash, I rip it off and read the instruction ("PUSH BUTTON") and execute the command. Lather, rinse, repeat.

Spark is strong and appropriately lethal but my achieved rate of 15 firing events per minute will not sustain idle and the emissions are off the charts.


The point is, your Radio Shack Racing mod project may run into a few snags (in my case, underlying tenets of the physical world) but do not be discouraged.

You'll get that fan belt installed someday.
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Old Feb 1, 2016 | 07:34 AM
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LOL! It was just a half *** thought!

I guess I'll just get the jacobs box.

It's my birthday in a few days and wanted to buy myself some car goodies. Turning the ole three zero so I figured I'd get myself some demister grills, an idiot light panel and something else for the car and kind of paused at the jacobs ignition box. Got to be worth just a couple of unicorns right?
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Old Feb 1, 2016 | 11:50 AM
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i turned 30 on the 24thh! congrats
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Old Feb 1, 2016 | 06:38 PM
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Thirty?...
I can't remember back that far!
(It was the 90's..and it snowed heavily..lol!)
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Old Feb 2, 2016 | 05:54 PM
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ive wanted to do it myself also. but its a bit more complicated than just a cap. you need a 12V to 500+V converter, the actual CDI circuit (consisting of SCR diode, normal diodes, caps, and resistors, etc), and a microcontroller to decide how many re strikes per RPM. obviously you wouldnt want it to fire just once, duration would be way too short, and you dont want it to fire constantly and cause preignition

im still a big fan of inductive ignition.. nothing beats constant spark duration an inductive coil can generate
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Old Feb 5, 2016 | 08:12 PM
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So, I am probably going to to buy this tomorrow or Sunday depending on the responses.

Worth the $200 or not?

I saw a dyno sheet showing a 10hp increase (here on the forum) and $200 for 10hp isn't bad. Torque went down slightly but I would attribute that to the engine being heated after the first 2 dyno pulls without real world cooling going on.

I can easily drop the $200 for the box and can have it wired in 15-30 mins also taking into account easily moving it back to stock in the event the box fails. I just don't want to spend $200, be dissatisfied, and be stuck with an ignition box I am not going to use.

Yay, or Nay?

Last edited by jjwalker; Feb 5, 2016 at 08:23 PM.
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Old Feb 6, 2016 | 12:18 AM
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$200 bucks?..meh.
Shop around JJ..they go around 75-150 tops...used.
Also a MSD 6AL is just as good,.(or 6A)
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Old Feb 6, 2016 | 06:58 AM
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Thanks styx, what about this?

(I already ordered it, send it back?)

http://www.summitracing.com/parts/MSD-6421
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Old Feb 6, 2016 | 08:40 AM
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sorry not sure about the operation of that one as it is a newer version.
I assume it would work fine since it is pretty well the 6AL but with built in limiter.
Just check it when it comes in and it you feel comfirtable with installing it then go ahead.
Re-Ted has a write up on the color coded wiring for the old style boxes on FC3S.org

Edit: the box is usually installed on just the leading coil and you need 2 more (one on each trailing) If you want to run trailing coils off the system.

Last edited by misterstyx69; Feb 6, 2016 at 08:56 AM.
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Old Feb 6, 2016 | 07:37 PM
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Yeah, just doing leading coil. It's my daily so using 3 CDI boxes is overkill. Hell one CDI approaches overkill territory.
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Old Feb 6, 2016 | 08:16 PM
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Is there any advantage to running 2 coils on leadings instead of just one? I know the impedance the MSD box sees will be cut in half if I wired them in parallel, but that also halves the spark duration (which is bad). It would be big monster spark plug exploding spark though.

If I ran two coils in series it would double the impedance seen by the MSD box and make spark duration twice as long, but halve the output power.

Running the MSD box to the single leading coil, with it split between rotors would be the middle of the two situations above.

Pick one of three.
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Old Feb 6, 2016 | 11:33 PM
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IDK, I just got 2 CDI boxes and 2 aftermarket coils for the Leading plugs.

That thing has stumble started on engine assembly lube fumes (had fuel pump fuse removed and injectors disabled).
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Old Feb 7, 2016 | 07:24 AM
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Just curious as to what setup you are running.
If you are N/A then all this stuff is really overkill.(stock coils will do a 450hp setup easily)
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Old Feb 7, 2016 | 07:56 AM
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Happy birthday to me today!

Styx, it's a street port on the primary intake and exhaust with no diffusers. The exhaust dual straight through magnaflows with a presilencer and no cat, but retained the stock manifold to hush it up. The engine is basically brand new, as I replaced all the housings with new. 2mm 2 peice seals, FD corners with springs. Very strong for an NA.

I know it's overkill and I have always prided myself by doing things to the car and keeping the engine bay showroom stock. I turned 30 today and I decided last week that I wanted a CDI box and to start yelling at kids to get off my lawn.
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Old Feb 7, 2016 | 08:10 AM
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weird. i turn 30 and decided i wanted a v8.







in my feiro.
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Old Feb 7, 2016 | 08:22 AM
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Originally Posted by lastphaseofthis
weird. i turn 30 and decided i wanted a v8.







in my feiro.
Haha, that would be awesome to have!

I never buy myself "oooh, shiney" things but I decided last week "I am turning thirty, I am going to find something and just buy it".

My 18th birthday I got a Tattoo at 12:03am and was at the gun store that same morning when they opened and bought a gun.

My 21st birthday, I had lost my car and had to wear an SCRAM ankle monitor (partied too hard!) and sat at home.

Got to make up for the crappy 21st birthday.
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Old Feb 7, 2016 | 11:43 AM
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RP advertises the Jacobs FC1000 for $179. Add shipping and I guess you're close to $200.
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Old Feb 7, 2016 | 06:46 PM
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Originally Posted by JerryLH3
RP advertises the Jacobs FC1000 for $179. Add shipping and I guess you're close to $200.
That was my first choice, it's unavailable, so I ordered this...

MSD 6AL-2 Ignition Boxes 6421 - Free Shipping on Orders Over $99 at Summit Racing

I couldn't find a brand new jacobs box anywhere to save my life so I said eff it and bought the MSD. Yes, I know it's overkill for an NA daily.
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Old Feb 8, 2016 | 07:11 AM
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The Jacobs ignition brand was purchased by Mr.Gasket/ACCEL/Mallory group back in Oct 2003. The Jacobs brand was promptly discontinued. The old obsolete analog ignition boxes were discontinued, the rest of the intellectual property and some of the remaining products were folded into the ACCEL & Mallory brands.

Then in Jan 2015 MSD purchased the Mr.Gasket/ACCEL/Mallory group then promptly discontinues the Mallory brand. The Mallory ignition boxes were discontinued and most of the remaining products were folded into the MSD or ACCEL product lines. The only ACCEL ignition boxes left are the ARCA trays for the last few carburetor engines in that series.

This was followed up in Sept 2015 when Holley purchased the MSD and now owns darn near everything.

Not too many options left anymore... FAST bought the old Crane ignition line and is trying to resurrect the products under the FAST brand. There are bit players too like; ICE, IFIS, Professional Products, Intellitronix and some private label brands like Summit Racing that have ignition control boxes, but MSD now basically owns the market.
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Old Feb 8, 2016 | 08:50 PM
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Coming in tomorrow at 10:00am so we will see.
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Old Feb 8, 2016 | 10:41 PM
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And what are we hoping/expecting to see?
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Old Feb 8, 2016 | 11:51 PM
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Originally Posted by clokker
And what are we hoping/expecting to see?
an Older guy with a CD ignition?..yelling get off my lawn?
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