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Old 02-01-2010, 10:49 PM   #1
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Default Low impedance damage

Hey,

So I made the mistake of running megasquirt Hi-res code on my friends 5.0 mustang without knowing that he had low impedence injectors. I began tuning it and was having sparatic issues over 3000 rpms and couldnt get it tuned right. I originally thought it was weak spark but it turns out this was probably it.


Could running low impedence injectors without in line resistors have harmed the board permanently? Do I need to put 10 ohm 10 watt resistors in line with each injector or can i use an equivalent and just put it on the actual injector channel from megasquirt?

Thanks!
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Old 02-01-2010, 11:11 PM   #2
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Do the resistors, and hopefully you didn't fry anything.
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Old 02-02-2010, 09:44 AM   #3
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probably didn't harm anything (but im not positive) 10watt 10ohm resistor on each injector's 12v signal.

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Old 02-02-2010, 09:48 AM   #4
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yeah i was reading on MSextra.com forums. looks like the current limiting circuit was protecting it from any damage.

I have 4 injectors per channel (Channel 1 inj 1,4,6,7 ... channel 2 inj 2,3,5,8)

They are obviously in parallel. I could do the math and find an equivilant resister to put on each channels 12v supply instead of each individual injector right? I can do the math to find the resistance, i just dont know about the watts.
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Old 02-02-2010, 09:51 AM   #5
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yeah, beyond any thinking/researching I want to do this morning
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Old 02-02-2010, 09:55 AM   #6
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haha im sitting in senior mechanical engineering vibrations at 8am right now... my mind is somewhat going. Ill do the equivilance circuit. I believe 4 10 ohm resistors in parallel is equal to 1 2.5 ohm in series. I just dont know the watt ratings that I would need for that.
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Old 02-02-2010, 10:14 AM   #7
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probably play it safe and go with a 50-100watt resistor with a built in heat sink.
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