MS2 ECU - Jetta VR6 running, keep blowing 15amp Coil Fuse

[kingtal0n]

I have not seen any manufacturer release a schematic to their coil packs inner workings. You can be sure however that a logic triggered coil pack contains an internal driver.
All coils will have a 12v connection for the coil primary, excluding ballast resistor coil primaries which run on about 9v but start on 12v.
Sounds like Paul who is a VW guy knows all about your coils.
Any potential delay can be compensated for by setting the ignition setting Tooth No1 angle and spark hardware latency settings with a timing light.

thanks for helping me learn, I just need to know about ignition in general,

Can we tell just by looking if this is a CDI or standard inductive type of coil? How do you know just by looking whether it will work "going high" or "going low". If I found a coil in a junkyard, how could I identify the ones that need to go low to fire? Arn't there some coils with internal drivers that use "going high" also? And if so, couldn't I add a inverter buffer to make it work with the opposite setting (to use it in an application that normally "goes high" and visca versa if I couldn't just flip the control box in the ecu software, like with an OEM computer, to run a different coil )

[slow_hemi6]

In most cases a decent multimeter, oscilloscope and factory wiring diagrams are pretty much all I need to sort out ignition. Most people have their favorites for one reason or another. Those are also the ones that tend to have the most information on them. Going to a wreckers and just grabbing some unknown coil is a fairly bad idea. The megasquirt manuals are a great resource on ignition systems and how to set them up and configure.

[prof315]

I have not seen any manufacturer release a schematic to their coil packs inner workings. You can be sure however that a logic triggered coil pack contains an internal driver.
All coils will have a 12v connection for the coil primary, excluding ballast resistor coil primaries which run on about 9v but start on 12v.
Sounds like Paul who is a VW guy knows all about your coils.
Any potential delay can be compensated for by setting the ignition setting Tooth No1 angle and spark hardware latency settings with a timing light.

thanks for helping me learn, I just need to know about ignition in general,

Can we tell just by looking if this is a CDI or standard inductive type of coil? How do you know just by looking whether it will work "going high" or "going low". If I found a coil in a junkyard, how could I identify the ones that need to go low to fire? Arn't there some coils with internal drivers that use "going high" also? And if so, couldn't I add a inverter buffer to make it work with the opposite setting (to use it in an application that normally "goes high" and visca versa if I couldn't just flip the control box in the ecu software, like with an OEM computer, to run a different coil )

Most stock Automobile coils are inductive type whereas many Motorcycle coils are CDI but there is no way to tell just by looking. There are also logic coils and dumb coils. Logic coils have the ignitor built in and require a low voltage/low current "logic" trigger. Dumb coils require an ignitor of some sort be it external to the ECU like the 4 channel Bosch unit on early VW 1.8Ts or internal like a BIP373. You misunderstand the whole "going high" "going low" thing. It has nothing to do with the coils but rather the ECU hardware. The hardware you are using in your ECU is a logic driver that works "going low"

[kingtal0n]

You misunderstand the whole "going high" "going low" thing. It has nothing to do with the coils but rather the ECU hardware. The hardware you are using in your ECU is a logic driver that works "going low"

This is what I am reading:
"Many ignition modules (aka. "igniters") and some coils with built in igniters require a 'logic level' signal. Generally this means a 0 or 5 Volt signal that changes from one of these levels to the other at appropriate times (generally to initiate dwell and spark). "
http://www.useasydocs.com/details/logic_level_spark.htm

ex
"The Bosch 211 fires the coil when the ignition signal from the MegaSquirt-II/MicroSquirt® controller goes from high to low. In TunerStudio, you would set:"
http://www.useasydocs.com/Bosch_211.htm

These pages indicate that the "high" and "low" is used for dwell and spark, and that it must match the hardware of the COIL you are using, not the ECU hardware as you seem to be saying, can you explain in more detail?

[slow_hemi6]

If you consider what I have discussed so far, you have the going high and going low settings describing the processors output.
Your ECU has a single transistor buffer/driver connected to the processor output which causes an inversion.
So Going Low setting on your ECU actually produces a going high output from your ecu output, due to the inversion. Going High setting will there for produce a going low output from your ecu output.
You have to know whether that logic level output will drive your coil hardware and which setting will produce the type of output that coil hardware requires.

[kingtal0n]

If you consider what I have discussed so far, you have the going high and going low settings describing the processors output.
Your ECU has a single transistor buffer/driver connected to the processor output which causes an inversion.
So Going Low setting on your ECU actually produces a going high output from your ecu output, due to the inversion. Going High setting will there for produce a going low output from your ecu output.
You have to know whether that logic level output will drive your coil hardware and which setting will produce the type of output that coil hardware requires.

wow so, the high or low setting seems very arbitrary; I understand it is simply processor output and that is not meant to drive anything besides a relay. What I am trying to learn is how this connected with ignition timing and dwell. I see that dwell is coil charging time, and the ecu sends a signal to fire (either high or low) the plug after some dwell period, but what I don't "see" the delay between the processor output and actual plug firing. How is this delay measured? Is it hard coded into the coil to account for? How is it that when RPM increases (or other conditions) this delay is accounted for.

And to be more specific, yes I see in the software there are variables to adjust in order to compensate for these delays; I do not want a user manual to tell me "how" to correct for the delay, I want to know how the computer itself is 'thinking' about the delay. If that makes any sense. Can we follow the sequence of events somehow?

1. trigger wheel denotes cylinder #1 is approaching
2. coil goes "low" to charge
3. trigger wheel denotes cylinder #1 time to fire by using rate of change calculations <---- ?????
4. coil goes "high" to fire plug
5. it takes 1.3ms for the processor output to affect the plug because of XXX devices within the coil <----- ????

So, what is missing from my imaginary situation above, whats wrong with steps 1-5, and how can we add steps to make this more complete?

[racingmini_mtl]

One foolproof method of knowing of you need to use low or high is to connect a test light in place of the coil. If the light is on and stays on when you turn on the MS, the polarity is wrong. With a high current coil, you can use a 12V light bulb; with a logic level coil, you can use a LED with an inline current limiting resistor.

In such a setup, the light would turn on for the dwell duration and then shut down when the spark is scheduled. The low or high setting is not arbitrary but is designed to allow you to set this for your system but which one you use does depend on which hardware you use.

And since there has been many different types of hardware setups throughout the Megasquirt history, it can be confusing for everyone in establishing which way to go. The test light method should provide a definitive answer (having said that, I think there are some rare cases of logic level coils which do not behave as explained above but I'm not 100% sure).

Jean

[kingtal0n]

One foolproof method of knowing of you need to use low or high is to connect a test light in place of the coil. If the light is on and stays on when you turn on the MS, the polarity is wrong. With a high current coil, you can use a 12V light bulb; with a logic level coil, you can use a LED with an inline current limiting resistor.

Great info, I see that the coil should not be charging while the ECU is just sitting on;

In such a setup, the light would turn on for the dwell duration and then shut down when the spark is scheduled. The low or high setting is not arbitrary but is designed to allow you to set this for your system but which one you use does depend on which hardware you use.

And since there has been many different types of hardware setups throughout the Megasquirt history, it can be confusing for everyone in establishing which way to go. The test light method should provide a definitive answer (having said that, I think there are some rare cases of logic level coils which do not behave as explained above but I'm not 100% sure).

Jean

Awesome thanks!

So Then, the "logic" in the coil decides how much current draw is available for spark, yes? And in a dumb coil, the "igniter" determines this instead? And when they say "coil logic" is that a processor or an integrated circuit that is performing the 'logic' or could it be both?

Also, what would happen if I tried to drive a "dumb coil" with a 555-timer circuit? lets say I push it through a transistor that can handle a few amps. How does dwell and charging time get factored into the pulse of a timer, it seems like when the timer goes high it charges the dumb coil, and when it goes low it (de-charges) collapses the magnetic field to give a spark. This makes sense from the inverter buffer point of view mentioned above (going high is really going low- to collapse the field in a dumb coil) If so, the MS ecu is acting like a "dwell timer" and has a configurable "dwell" setting for "dumb coils" I believe. Its all starting to make sense... (sorry if this seems like I am talking with my self I am trying to figure it all out )

[slow_hemi6]

1. trigger wheel denotes cylinder #1 is approaching
2. coil goes "low" to charge
3. trigger wheel denotes cylinder #1 time to fire by using rate of change calculations <---- ?????
4. coil goes "high" to fire plug
5. it takes 1.3ms for the processor output to affect the plug because of XXX devices within the coil <----- ????

So, what is missing from my imaginary situation above, whats wrong with steps 1-5, and how can we add steps to make this more complete?

That is kind of it in simple terms.
Please don't underestimate the speed of the processor, it usually gets it's entire main loop done in less than 1mS. An engine @ 6000rpm takes 10mS to turn the crank 360 degrees.
please also don't under estimate the hardware switching speed. Take the TC4427 for example, input to output has a delay of 30 nanoSeconds and a rise/fall time of 30nS. The setting to allow for hardware latency is in microSeconds... millionths of a second. Your 1.3 milliSeconds is way off the mark for switching speed in the electronics world.