LS2 coil bench testing

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LS2 coil bench testing

Postby turbo_manx_maniac » Fri Aug 13, 2010 3:55 pm

I have a new MS1 V3.0 board running the extra code, I added the 5 volt pull up circuits (2) to run 4 LS2 coils in wasted spark config.

I have verified that the 5 volt pull up circuit is working via LED's. Jstim V1.5 is running the 36:1 wheel code connected to the MS unit.

I have a small harness wired up to test 1 coil, problem is that the MS resets like crazy the spark is very erratic.

I have the spark output inverted and about 5ms dwell. Any ideas how to get this working properly, or is this too much of a stretch to test on a bench?
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Re: LS2 coil bench testing

Postby racingmini_mtl » Fri Aug 13, 2010 4:07 pm

How did you connect the coil for your test and how are you powering it? If you're trying to power the coil from the JimStim or from a wallwart then you're simply overwheling the power supply. Neither the JimStim nor a wall wart will be able to provide the 10A+ that the coil requires when charging.

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Re: LS2 coil bench testing

Postby turbo_manx_maniac » Fri Aug 13, 2010 5:36 pm

Power and ground for the coil are fed from my power supply, it's a PC ATX type with a 15A 12V output.
I ran the coil signal ground to the ground header on the Jstim, and then the coil trigger wire to Inj1 which is one of the outputs from the 5V mod to the MS board.

The coil is getting power from the PS, and only the trigger signal from the MS through Jstim.

I have the power supply going into the Jstim terminal, I also power the coil at that point, and also have connected the spark plug return to the ground there. Seems the coil is sending a transient through the power supply that resets MS. I've tried adding filter caps across the PS terminals with no change.

It does spark some while the MS resets, but seemingly at a much higher frequency than the IGN frequency.


Thinking about building a PWM trigger circuit from a 555 and eliminating MS to make sure I have the basics good.
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Re: LS2 coil bench testing

Postby turbo_manx_maniac » Fri Aug 13, 2010 7:05 pm

More data.

I decided to try using 2 separate power supplies, their only connection was the ground on the Jstim. This made no difference, surprisingly.

I then decided to just trigger the coil by itself, that worked fine.

Then I noticed if I ran the MS by itself, not connected to anything, the noise from the coil would reset it. To be clear, the MS was running on jus tthe stim and a separate power supply, no serial cable or anything. The closer the coil and spark plug are the worse the resets. I then made a 4' cable to run the trigger signals and it works much better, however still resets allot.


Next was to run MS from a 9V battery. No real change, it still resets! Seems like the MS is exceptionally susceptible to the coil noise. Another thing I noticed is that the faster the RPMs the more it seems to cut out, but it's not a linear thing.

ANy suggestions or ideas?


Next, the coil gets pretty hot, pretty quickly. I've tried inverted and non, and until I reduce the dwell to ~1.5ms, the spark intensity doesn't change much.

Obviously don't want to bolt this on the car until I understand what's happening.

Looks like there is better support for this in MS2, and obviously MS3. Now thinking MS2 upgrade may give better control on the dwell, but might just be confusing things... :| :? :? :?
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Re: LS2 coil bench testing

Postby turbo_manx_maniac » Fri Aug 13, 2010 9:20 pm

Well mostly talking to myself, but further testing has made some improvements. Looks like most of the noise is from not using a resistor plug or wire, swapped to a resistor plug and things got allot better, I don't have a resistor wire but will pick some up tomorrow.

Main issue now is the heat from the coil, but i suspect it's from not running a resistor wire.
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Re: LS2 coil bench testing

Postby W113 » Fri Aug 13, 2010 10:43 pm

Hi.

Resstor wires/plugs helps the noise issue a lot. But it will not change you coil temp very much. High increase in coil temp is most often due to overdwelling.
And I hope you have earthed the spark plug threads to the common +-0V supply point.
To further resetproof your install you can try som minor board mods( MS1 specific) sOLDER IN 0,1µf/ 10v mylar caps as follows on the underside at the CPU socket pins. Leads must be real short.
#1 Pin 6 to pin 2
#2 Pin 2 to pin 2
#3 Pin 20 to pin 19.

Good luck

W113
If not understood , it will not work
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Re: LS2 coil bench testing

Postby turbo_manx_maniac » Mon Aug 16, 2010 1:21 pm

Thx W111.

The resistor wires fix all my issues. I no longer reset no matter how close I bring MS to the coil/sparkplug (within reason of course).

The wires along with the dwell setting fixed the coil temp issue, it runs at almost ambient temp.


I've been running a V2.2 board with MSnS for the past 6-7 years, spark and fuel. I run Taylor wires (non resistor) and non resistor plugs and have had no issues, that's why I was so suprised to see the difference that the resistor wires made. Live and learn.
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