rdavidsrx7

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

nopistons94

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





btw, your right about the ***** thread thing





btw2, house and kwrib both exist in the thread now

rdavidsrx7

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

nopistons94

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

qwester007

Sure would like an HKS twin power for the RIGHT price....

j9fd3s

whats wrong with wasted spark?

rdavidsrx7

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

83turbo

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.

rdavidsrx7

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

83turbo

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.