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Old 08-05-2010, 07:43 PM   #1
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Default Megasquirt ignition control mods question

I've got a supercharged 1.8l that i need to megasquirt. I've run into a issue that I can't figure out.

I've read

https://www.miataturbo.net/useful-saved-posts-8/how-make-install-your-own-diy-megasquirt-13676/

Which is very helpful.

I'd like to avoid burning out coilpacks and needing to unplug when updating ECU's.

Joe Perez's post seems to fix the issue.

https://www.miataturbo.net/megasquirt-18/better-spark-out-circuit-33964/

My question. Does the the BIP373 mod do the same thing for driving stock coils?

The reason I believe this might be the case is both mods require you to mark spark out inverted = yes.

Last edited by heychris; 08-05-2010 at 08:50 PM.
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Old 08-05-2010, 08:23 PM   #2
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you dont fry coils if you dont do things that fry coils. follow joes method.

no, the bip373 drives coils without ignitors.
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Old 08-05-2010, 08:53 PM   #3
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Braineack.. I very much appreciate all your knowledge and posts..

I get that you have to be careful do all the things right.

I'm not sure what you mean by "the bip373 drives coils without ignitors"

do you have to modify the coil packs to use the bip373?

What I am most concerned about is unplugging the coils while updating. I can just see myself forgetting that step.

Does the BIP373 save you from having to unplug the coils?
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Old 08-05-2010, 09:02 PM   #4
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Quote:
Originally Posted by heychris View Post
I'm not sure what you mean by "the bip373 drives coils without ignitors"
Not all ignition coils have built-in igniters like the ones found on the '94 and later Miatas. You have to remember that the MS was initially designed to drive a V8 engine with a distributor and a single ignition coil, and the coils found on such engines almost never have on-board igniters.

(An "igniter", in our usual context, is just a logic circuit which switches the current to the coil primary on and off.)

Some computer-controlled engines, even those using wasted-spark or coil-per-plug ignition also separate the igniter from the ignition coil. The '90-'93 Miata is one such example, and there are many others as well. In such an application, you would have the option of either using the stock igniter or one BIP373 per coil. Generally speaking, it is usually advantageous to keep the factory igniter.


Quote:
do you have to modify the coil packs to use the bip373?
The stock '94 and later Miata coils cannot easily be so modified, and there would be no point in doing so.

Just get this whole BIP373 idea out of your head. It's not the answer.



Quote:
Does the BIP373 save you from having to unplug the coils?
What saves you from having to unplug the coils is the design of the ignition driver circuit. The "standard" MS design for driving logic-controlled coils (the one printed on the DIYAutoTune web page) is extremely stupid, as it inherently outputs a logic high whenever the CPU is not active, such as during a reflash. It's set up so that the CPU must actively force the outputs to turn off.


The circuit I did corrects this design fault, by inverting the signal such that it is off when the CPU is not operating, and requires the CPU to actively force it on. In engineering parlance, it fails in a safe condition.

Last edited by Joe Perez; 08-05-2010 at 09:22 PM.
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Old 08-05-2010, 09:10 PM   #5
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Thanks.. You guys rock!
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