5thgenmaxima

iTrader: (1)

http://www.cardomain.com/ride/2195944/3

What you are looking at is a scope of the primary side of the igntion coils.
(A scope meter connected to an ampmeter around the wires going to the coil.)

I originally confirmed two bad coils and decided to replace all six and had the opportunity to scope them before replacing.

You can see the upwards curve is creating a magnetic field (The line on the graph is going upwards), You can also see the coil will reach maximum saturation (peak out) at around 700 mv on the graph. I had the ampmeter set to 10/1 so this is showing a maximum saturation (peak point) of about 70 amps, (The graph shows it as MV, but the ampmeter actually reads amps and convers it itno volts for the graph)

You can see that coils #1 and #2 seem to "appear" fine while at idle, but when snapping the throttle you can see the coil failure pretty well.

You can also see that during throttle snaps coils #3 and #6 reach full saturation just before the coil collapses.
Electromagnetic induction is when the coil collapses from one magnetic field into another. When it collapses the energy is transferred from the primary coil then induced into the secondary coil. This happens because when the primary coil is collapsed the energy created inside the coil looks for a place to go and since the secondary coil is the past of least resistence so the energy is transferred there. During this process the energy gets converted from a high current, low voltage into a low current, high voltage energy for the secondary ignition system. In the case of coil-on plug design - directly into the spark plug.
This is necessary because energy can not be created, it can only be changed from one form into another. Modern day spark plugs require 40,000 + volts to the plug in a 12 volt system.
Electromarnetic induction in this case changes the energy from low voltage to high from collapsing the field from roughly 200, 20 gauge windings and inducing it into 20,000, 40 gauge windings.

Upon closer investigation you can see how long each coil takes to reach full satuartion.(APX. 700-750 MV)
1=4.2ms
2=4.7 ms
3=3.9 ms
4=3.2 ms
5=3.6 ms
6=3.8 ms
(MS=millisconds)
When you speed up the rpm's you obviously demand the plugs fire more times per second, thus the ecu collapses the coil at shorter intervals to send the power to the plugs.

You can see on coil #1 during the throttle snap that the ecu collapses the coil apx. 3.1 milliseconds after it begins creating the field. Since the coil hasn't climbed to maximum saturation it causes a weak spark across the plug, causing a weak/or mis fire and unburned fuel. That gives a high voltage (low oxygen content) reading in the 02 sensors which in turn leans out your fuel to adjust your A/F ratio to 14.7..
After you replace your coils you have a cleaner spark, which in turn richens your fuel trim. This explains why people seem to have a reduction in fuel economy after replacing their coils.

You can see above that #'s 1 and 2 take the longest amount of time to reach maximum saturation. #'s 4 and 5 are still in good condition.

Looking at the graph during throttle snaps you can see that coils #3 and #6 are getting close to reaching maximum saturation near the collapsing point, which is a good indication they will fail soon. Under a heavier load/higher rpms #3 and 6 may mis fire slightly as well, just not enought to notice.

In conclusion, #'s 1 and 2 are bad (The coil callapses before they reach maximum saturation.) #'s 3 and 6 are going bad.(They reach maximum saturation at around the time the coil collapses during mid-level rpms) and #'s 4 and 5 are still in good condition, with coil # 4 showing the lease amount of aging. (They reach maximum saturation 1-2 milliseconds before the coils collapse.)

irish44j

iTrader: (38)

very nice....more science to the art of finding bad coils. We're getting close...Nissan had better watch out!

DrKlop

iTrader: (3)

That's pretty interesting. I was ganna check my coil this weekend with the DMM, I gess I'll try your method as well.

But where can I get the oscilloscope... Steal it from my EE lab? j/k

5thgenmaxima

iTrader: (1)

I realize not everyone has access to a scope, my primary reason for testing the coils is to compare the true condition of each coil (I.E. scope) to Resistance measurements, so members can find a true measurement of what would be considered good or bad by just measuring resistence of the coils..

Besides, I always enjoy when someone can teach me something new, time to return the favor.

DrKlop

iTrader: (3)

seriousy, you gave me a great idea and right on time. I'll find the dam scope and test it your way as well.

Thanks for the idea!

Maxima-Ness

stupid question....how do you know if you have bad coils? I mean, whats the initial tip off?

5thgenmaxima

iTrader: (1)

mis-fire and/or p0130.
I have also been running lean lately.