Turbomark7

My blue Jacobs ignition box was driving two Crane LX91 coils in lieu of the weaker stock lead coil. This worked fine for quite some time until the ignition box burned up. Turns out that it should be one ignition box per coil please; the Jacobs was quite over-worked. So, sandwiched in the same limited space in front of the SMIC are two Jacobs FC1000 boxes each firing one coil.



On another note, the Bosch race plugs I've tried are too cold, but I like the design. I may not get hotter plugs in time for my 1900 mi. round-trip trek for R.R. so for now I'll soldier on with NGK 10's.

Jims5543

i USED TO RUN 10'S ACTUALLY 10'S WILL BE GOOD FOR YOUR HIGHWAY TRIP THEY LIKE HOTTER ENGINE TEMPS.





I Have a set of NGK Racing 10's that I might throw in on sunday for the open track day. Right now I am running OEM 9's all 4 holes.





Someday I might upgrade my ignintion I just have not had any issues to justify messing with mine yet.

Turbomark7

I understand some run 9's on the lead and 10 - 10.5's on the trail; this with single turbo and associated mods. How safe is that?

Turbomark7

I now run two Jacobs FC1000 boxes driving two LX91 coils on lead that spark NGK 9's at low- and mid- boost settings with good results. While my stock coil wasn't cutting it (Jacob's Rotary Pack kept burning them down), perhaps a TwinPower box on stock L coil may have been sufficient. I have abandoned the Bosch race plugs which are too cold for the street and track and will use NGK 10s for the occasional drag run.



It turns out that an ignition box driving two coil simultaneously will fail at some point; mine did and therefore the changes.

83turbo

Depends alot on the box and the coils. An MSD 6A driving even one really hot coil will likely fail (by "really hot coil" I mean MSD Propower, Mallory 28880, etc). The same box will drive a pair of Blasters forever. The thing to look for is inductance. Hot coils are less then 1 mH. I measured 4 mH for a Blaster (I think MSD claims 7 mH - note that inductors are very "sloppy", and tend to give different readings on different meters). FC coils are also about 4 mH. Don't know about FD coils - I haven't heard anything nice about them yet. Two Blasters in parallel would be 2 mH.

Primary resistance in ohms really doesn't matter. Higher resistance here can be bad for the coil because it will generate more heat. Having said that, most really low resistance voils tend to be low inductance as well.

The FC lead coil is only 0.25 ohms - the lowest I've seen for any "normal" coil (as opposed to Propower, etc). The next best would be a Blaster SS at 0.355 ohms.



I have know idea what the limitations are on a Jacobs box (apparently less than 2 LX-91's )

Turbomark7

What do you think is an ideal combo of box and coil?

83turbo

I've been kind of partial to the C2DI that AEM makes - I haven't actually used one but the specs look good, it's compact, and was designed to fire both lead and trail with the same box. Just remember that although it is a 4 channel, you would wind up using 3 of them (unless you've got a standalone with separate outputs for L1 and L2).

The stock FC ignition is quite strong, but it looks (on the scope) like changing to an MSD (or similar CDI) makes about 4 times the current.

The Crane Hi-6 has a stronger coil driver, but this only helps if you have a "hot" coil. If you are running stock coils it doesn't buy you anything over the MSD. (Also the analog vs digital thing only applies to the control electronics and doesn't have any real impact on the spark).

As for coils - if you are running an MSD-6A or a Jacobs, you want to use coils which are compatible with an inductive ignition system. Even though those boxes are CD (and not inductive), you want a coil that has enough inductance that it doesn't blow the coil driver. The MSD will drive 2 such coils in parallel, whereas from what TurboMark says, the Jacobs will not.

I don't think there is a real problem with using a single lead coil (2 post style) for both lead plugs vs using 2 separate lead coils. The current is not getting divided - remember that with that setup, the plugs are in series. The "wasted" spark isn't costing much in terms of voltage either, as it is not under much pressure.

Of course there are many more coil choices available for single post coils compared to twin post coils. Nology sells some really little coils, but I haven't tried them - the only ones I see on ebay are the higher resistance ones.

You want a low primary resistance. Now I have heard that an MSD 6A needs a certain minimum primary resistance - I will point out that this really isn't true. The real requirement is a certain minimum _inductance_ (ie "resistance to change in current flow"). The resistance doesn't come into play until "steady state" is achieved, which never happens.

All of this could probably fill a book. Basically you can run whatever box you want, as long as you don't overload it with the wrong coil(s).

I'm not a particular fan of the HKS Twinpower. I'm sure some people have had good success with them, but because it is a "piggyback" type, the output is severely limited by virtue of not wanting to fry the OEM ignition. For alot less $$$ you can get the AEM box.

Sorry for the long post - I hope it is clear.

l8t apex

man I think it great you can speak that. 83TURBO can be the Judge ITO of spark and some of your points shopuld be pinned. You have helped me a little(PM) but there is something to a reply you gave me about allowing the spark on the DIS-4 system

to last a little more. The coils are hot but with short duration.

Thanks for the help.

Turbomark7

My set up - meet the new boss (Jacobs), hopefully not the same as the old boss.

Turbomark7

The other FC1000 (a bad-*** name indeed) is mounted underneath the one you see and you can see the coils mounted on the battery case in a brilliant move by Freddie.