LS2 Coil Specs / Weak Spark

[William Roth]

Hi,

After looking at the LS2 coil video I decided to do some testing on the LS2 "Yukon" coil
to possibly use it with my system. Before doing the board mods, I built a signal generator
box similar to the one in the video for the purpose of testing coils. I purchased
a C1251 Wells ( Autozone) coil for testing.

With the box set to 5 Hz and 5ms of dwell (using a scope) I get a spark, but the spark seems weak and not loud like in the video. With a .1 ohm current sense resistor in the primary path line I see a nice. nearly linear current rise on the primary from 0 to about 7 amps over the 5 ms of dwell time.

I measured the inductance of the secondary with a good BK Inductance Meter set to 1Khz
and read 12.4 Henries. It reads 13.1 henries at 100 hz. I was expecting a much higher
value .. in the range of 25 - 40 Henries. However I can find no posted specs for this.

The secondary resistance measures 5.2K ohms referenced to Pin A.

Question: Are these numbers in the correct range ?

I also measured the resistance from Pin A ( ground) to the heatsink and the
mounting bracket. I get 3.2K ohms.

Question: Is the coil bracket normally grounded to the engine in a vehicle or is it isolated ?
I was expecting to have close to zero ohms between the coil bracket /case and Pin A.

Thanks,

Bill Roth

[8974Ollie]

The brackets are bolted directly to the valve cover.

[jumpinjan]

I built a signal generator
box similar to the one in the video for the purpose of testing coils.

Bill,
In reference to your spark generator box, did you use a circuit based on the 556 chip and very similar to an RC servo bench tester? I have built one for my RC model work, and it seems like a perfect design to fire coils on the bench too.
Jan

[William Roth]

I made my signal generator using the VCO section of a 74HC4046 PLL IC for the frequency generator, where the center frequency is set to 90 hz and no offset. This gives me precise linear control of the frequency from 0 RPM to 10,000 rpm ( 0 hz to o 180 hz). This output goes to a 74HC221 Monostable Multivibrator configured to allow adjustment of the dwell from 0 ms to 10 ms (full range). Changing frequency has absolutely no effect upon dwell. It is very precise and stable with no jitter.

I try to stay away from 555/556 ICs because they can only be triggered on a trailing edge without extra components, and because the trigger signal must be shorter than the output unless even more components are added. Besides, I had plenty of these IC's already laying around.

Now All I can do is hope that someone somewhere is kind enough to give me the correct secondary inductance and resistance specs for The D585 LS2 Coil.

My measured secondary inductance of 13 H seems too low.