EFI University

[C. Ludwig]

This copied from another board:

"I know there are a few of us using these coils,
http://www.diyautotune.com/catalog/i...oil-p-394.html
http://www.034motorsport.com/product...roducts_id=277

Ive always seen the charge time gets recommended at 2.5ms-3ms. we checked them with a scope today and output kept climbing up to almost 9ms charge time, the output was roughly 3x what it was at 3ms charge time. We settled on using 7.5ms charge time as it was close to 90% of the peak output.

Time will tell if the coils will last with such long charge time, I was/am a little hesitant with it as it seems odd to be so far off the "recommended" settings."

Full thread here: http://www.rx7club.com/showthread.php?t=900063

Issue of input voltage was brought up and voltage was logged at:

cold idle 13.6v
hot idle 12.2v
hot 1500rpm 12.9v

I've been told a charge time of between 3.0 and 4.0 ms is appropriate and have had good success with those values on rotary engines that have seen up to 25 psi of boost. What is the actual safe limit in both ms and duty for charging these coils? Thanks!
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Haltech, AEM, Apexi PFC Sales, Installation, Tuning
Custom Harness Solutions
www.ludwigmotorsports.com

[RootesRacer]

The reason you can put the dwell so high and continue to get progressively more powerful spark is because the coil itself is very powerful, and has a special magnetic circuit (yes I said circuit) that prevents core saturation to very high field strengths.

Typical dwell figures of 3ms is fine for light loads, dwells beyond 6ms will continue to build spark energy, but of course with extra heat generated and life reduction of the coil.

Ideally, the ECU used will have a dwell mapping strategy to allow the coil so run cool at light loads, and increase the dwell time under load, so that at max cyl pressure, the the spark does not go out.

Hope this helps a bit.

[Buzzard]

Max 88% duty cycle. For coil per cylinder on a four stroke I have run 12ms at idle. At 6000rpm over 16ms can be used. With a distributed setup the dwell will need to be calculated.

Chris

[RootesRacer]

[John at J&S]

Do those coils have active current limiting?

[Pantera EFI]

I can add this, the IGN-1A coil charging can be seen as a "bucket" filling with water (electrons).

When the "bucket" is full, wasted water (overfilled) will be lost.

That loss heats the coil reducing efficiency.

Now, that "charge line" can be seen with a scope, when the line slope starts to level, the coil is full.

Lance

[John at J&S]

ok, that means it has active current limiting.

An internal circuit starts robbing the drive signal from the gate of the IGBT, holding the coil current at a fixed level.

Basically, it turns the IGBT into a ballast resistor when the current goes above a pre-determined point.

[jalai]

No, there is not active current limiter inside of coil.
All coils limit current to some level (depend on voltage and primary resistance).

[John at J&S]

Does anyone know who created this diagram:

http://www.mazdamaniac.com/images/rx8/electronics/ls2/ls2_coil_schematic.jpg

It looks like a current sense resistor in the IGBT drain. Can't tell what the box is on the gate.

What's the inflection point at 5msec in your #28 pic? Doesn't that mean the coil is fully charged and the current starts to run away?

[RootesRacer]

[jalai]

LS2 coil is current limited by electronically (an some other coils too). This coil "curves" is picture #40. (primary current stop just to when limit start)

I think this 5ms change of curve is when coil iron core magnetic flux goes to nonlinear area. (is this understandable cluse?)

And I know that IGN-1 is not the same as IGN-1A but there is one more measurement in my IGN-1 picture.
AND coils "works" similar (IGN-1A = next picture #29).
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Sorry My language...

[Pantera EFI]

Hi Jalai, again "fine work" your are very thorough.

I would ask for you to do your test of the IGN-1 with a 25 AMP supply AND
a 50pf load on the secondary.

We use a 36 AMP@105c IGBT to drive the IGN-1 coil.

Lance