ok, to start I already have the anti det device, and have been using it for 4 months now. Getting it or not is not the point to this thread so please don't make it into that.



We all know by now that this device eliminates the trailing ignition in the combustion cycle.



Would it be worth my while to us the trailing ignition signal and the trailing coils firing the leading plugs, instead of having the stock leading coil which provides a wasted spark.



I got this idea from the microtech LT8-X which runs 4 separate coils. The advantage I could see with this is that it would allow for each coil to fire only when needed thus allowing for a better charge in the coil (especially in the higher rpms) and less chance of preignition if using something like an MSD or AEM C2DI with 20degrees of spark duration.



I also realize that I would have to modify my ignition maps significantly to account for the split which currently exists. This bring up another question...with the PFC should I just copy my leading ignition map and put that in as my trailing map or should it be slightly different because the crank angle sensor for the trailing is not in the same spot as the leadings sensor is.



Bob

hmm very good idea my friend, very good indeed, i shall use you to do this to my car after i get the PFC , free of charge of course, so we can both test out your idea and then eventually sell it to others https://www.nopistons.com/forums/pub...IR#>/smile.png





btw, your right about the dildo thread thing





btw2, house and kwrib both exist in the thread now

hahaha, yep, you noticed that too, can't really sell it though, it's just a tuning issue/possibility.

you can always sell tuning bro, how do you think steve kan makes all his mula ?

Sure would like an HKS twin power for the RIGHT price.... https://www.nopistons.com/forums/pub...#>/biggrin.png https://www.nopistons.com/forums/pub...#>/biggrin.png https://www.nopistons.com/forums/pub...#>/biggrin.png

whats wrong with wasted spark?

not 100% sure, have heard that it wastes the coils charge as well as can cause preignition if to retarded (such as a 20 degree spark discharge could cause).



Anybody else...come on!



sorry dude it's sold

Nah, not a problem. Actually anyone running a plain vanilla MSD 6A (part # 6200) is really getting 40 degrees, not 20. The 6200 thinks you have an 8 cyl, so you get multisparking up to 6000 RPM and for 40 degrees.

The MSD spark actually doesn't last 20(40) degrees...it restrikes every millisecond within a 20(40) degree window. The actual duration of each spark it determined by coil characteristics. 200-300 uS might be reasonable (I'm guessing here).



Exercise for the reader: If you run a MSD 6A one each _trailing_ coil, how many degrees is the firing window?



Also anytime you are firing two plugs with 1 coil, remember that the plugs are in series. In a way you have a positive plug and a negative one, connected together through the engine (engine/chassis ground is not part of this equation). Both plugs will see the same current, and the current will be approximately the same as if the coil was firing only one plug. It takes maybe a couple thousand volts more to fire the extra gap (not under much pressure), and once the arc has been established this drops to something negligible.



The only thing that bothers me is having the current run through 2 spark plug resistors (about 5000 ohms each) instead of only 1, but I haven't nailed down yet whether this is really a problem.

https://www.nopistons.com/forums/pub...1047683561.gif

tried reading this a couple times so I wouldn't sound like an idiot, but a few things there sounded odd to me still.



Why does it think we have a v8? I thought the fire pattern was more similar to a v6.

So why does it fire for 40 degrees?



For my homework exercise I got an answer of 20 degree, is that right? Or would it now think we have even more cylinders (silly msd) and fire for like 80?



OK, so the leading coil is slightly different from the trailing correct? Where it's capacitor plates with the negative charge is attached to one plug wire and the capacitor plates with the positive charge are attached to the other? Versus the trailing which have it + plates hooked to the plug wire and it's - plates attached to the engine...well so to speak.

Interesting



Another thought is that the FD leading coils are notoriously wimpy, with bad breakup in high boost and high RPM applications. As well as plenty of stories of the leading coils failing or burning out ( yes I understand this is usually due to ignition amps). Thus the fact that each coils fires only half as many times now should add longevity and reliability to the ignition system.



Let me know if I am getting what you are saying.



Bob

A V8 fires 4 times per revolution. A 4 cyl fires 2 times per rev. So at say

6000 RPM, (100 revs per sec) a V8 fires 400 times per second, where a 4 cyl

fires 200. This is important because this is the only information the MSD

has about RPM.

The leading coil fires just like a 4 cyl - twice per revolution. If you were

to connect an 8 cyl tach to a rotary, it would only read half of actual RPM

because an 8 cyl engine fires the coil twice as often (again, 4 times per rev

vs 2 times per rec).

Similarly, an 8 cyl fires a plug every 90 degrees whereas a 4 cyl fires every

180 degrees. This is imprtant because the MSD will base its concept of 20 degrees

on a fraction of the time between trigger pulses. Since the MSD 6200 (standard

6A) is really an 8 cylinder box, it believe you are firing every 90 degrees. It

then figures the firing windows to be 2/9 of this time (which would be 20

degrees on an 8 cyl). Of course you were only firing every 180, so 2/9 of this

would be 40 degrees.

Not sure on the 6A, but the 7AL-2 comes in different varients for 4/6/8 cyl

applications to account for this. I don't know if snipping the config jumpers

on a 6AL would accomplish the same thing - I think those are just for the rev

limiter and not the "how many degrees per trigger" circuit.

As for the trailing - each trailing coil fires once per rev, just like a 2 cylinder

engine. So, you put an 8 cyl box on it and it fires away for 80 degrees (2/9 of

360 degrees). It isn't that the MSD thinks you have yet more cylinders - it

still thinks you have 8 (by design) even though you really only have 2 at this

point.

The coils don't actually have capacitor plates inside them - they are basically

transformers. But yes - that's the basic idea.

cool, thanks for the detailed explanation. How about the AEM? Do you know how that one works? Is it similar to the MSD?



Thanks

Bob

The AEM C2DI is slick - very powerful and will handle lead+trail with one

box. There is a switch to configure the unit for coil per plug or

waste spark. In coil per plug, each channel is basically a 1 cyl; in

waste spark each channel is a 2 cyl. For the rotary, it would be set

to waste spark mode so the trails channels would work fine. The lead is

going to get only 10 degrees of sparking though, because it is essentially

a 4 cyl coil.

AEM just emailed me the instructions today - I'll have to forward it to

my work address because my pdf viewer at home doesn't like the file

(won't let me see the pics, and now won't let me read the config switch

paragraph either).

With the AEM evryone says to leave all the switches off. So using this with the anti det device, where you are not concerned about the trailing, the switch should be set the other way to provide the 20 degrees of spark on the lead coil, correct?



Bob

83turbo i have the instructions scanned if you would like them.

Switch functions:

S1 - Multistrike. If this one is off, the ignition operates in single strike mode, so the whole firing window issue is moot.

S2 - Trigger edge - depends on whether you are triggering from the factory ignitor or straight from the ECU

S3 - Wasted Spark - "Off" causes the unit to assume an individual coil every 720 degrees (coil per plug). "On" assumes wasted spark with 2 cylinders per coil (360 degrees per event). The trail side on the rotary fires every 360; the single lead coil every 180. Assuming multistrike mode (S1 on), I would turn this switch ON - the trails would get 20 deg, and the lead 10 deg.

S1 OFF would yield 10 deg on the trail, 5 on the lead.



To get 20 degrees on the leading, you would need to set up a true coil per plug on the leading (ie each plug fires every 360 deg, like the trailing does). Some ECU's may support this directly. It could probably be done on an FC by wiring a spare trailing ignitor into the leading side, and sharing the "select" wire. I believe the FD ECU has discrete T1/T2 outputs so the same trick would work unless you are able to re-map the trail outputs to give timing appropriate to the lead plugs (maybe the PFC can do this?)







rfreeman27: I managed to print it out at work - thanks anyway

yep, pfc lets you independantly adjust the timing of the trailing so I basicly would just put my leading map over the traing essentially making it appear as though there was zero split. The only issue I forsee with this is possible Idle learning problems, but if I had to I could just manually tune the idle.



Bob

83,

I was just reading the instructions for the AEM, they say that swith 1 is the multifire disable, so if you turn that on it will disable the multistrike feature. So wouldn't you want it off then, to get the full use out of the box?

According to my instruction sheet, S1 off disables multistrike; s1 on enables multistrike.

maybe we have a different manual?

Mine says:

Switch 1 - Multi-Strike - S1 enables or disables multistrike plug firings. Disabling Multi-Strike (s1 - Off) makes engine timing much easier to check. Enabling Multi-strike (S1 - On - Default) makes the engine run smoother at low speeds.





I wonder if there are 2 different versions of the box to match the 2 different manuals?

Having spoken to a tech rep, it turns out that there was a misprint in the manual at some point. S1 OFF enables multistrike, S1 ON disables multistrike.

ahhhh, so you must have gotten the older manual.

Does seem odd to have a switch for multistrike, where off means on and vice versa though.



so back to my other question...if I were to hook up the trailing coils as I had talked about, would I want switch 3 to off to get the full 20 degrees? Or should it be on?



Damn now I am lost again https://www.nopistons.com/forums/pub..._DIR#>/sad.png

Why not split the signal to the leading and "Y" it to 2 seperate coils.

because everybody realized that using anti det was a retarted idea. Hey, lets make less power at similar boost levels so we can run 20lbs on the street!