IGN-1A Race Coils have a 19 amp IGBT ignitor is built in and can be driven with a 5 volt logic level output – an MS3X or MS3-Pro will run them directly (set spark output to going high), and we recommend a 270 to 330 ohm pullup if you’re building a MegaSquirt 1 or MegaSquirt 2
hallow, i using these race coils in a six cylinder wasted spark manner.
I put in 100ohm pullups and it rans good as far as i know but noticed the recommended size.
Should i put in a 330ohm??? What's the deal?
if 100ohm fires them then should i just leave or will this cause a problem later on?
That description was not on the diy site at that time either.
These coils work. I'm trying to narrow down a problem
and your 'just do it the right way bro' without reading my post is very counter productive.
i don't know why you would even post that.
if you can clearly tell me how a 100ohm resistor will damage the coils please tell me
you suggest they will in your earlier post.
Im 36 years old and i'm not trying to be snide with my question. They are actual questions because i do no know.
i'm not on facebook and i don't try to get into snobby internet forum fights.i hope we can move forward from here.
Well that was not my intent, and you kind of left off some details... Where exactly, did you list the problems in your post? You said it runs good??? You also left off that the supplier gave you directions initially. Maybe DIY has learned something over the years or the coill has changed a bit and requires different resistors now.
And to be clear I never said the coil *would* be damaged, I said why take a chance. Like I said I bought 8 myself, they're not exactly cheap.
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1995 Ford Lightning. Dart based 427 Windsor, Novi 2000, full sequential, E-85, etc. MS3X/v3.57 http://www.buildpics.org/
Well, I hesitate to jump into this but maybe I can help calm things down.
If it is working fine, and that's what Matt suggested, then I would leave it alone. That doc referenced is clearly out-of-date, and I have never seen a resistor designation like "4k7" before. Does that mean 4.7k or 47k? Or were they trying to say a more realistic 470? When you contacted Matt back then he probably recognized that you were having problems with not enough current drive to the coil input and suggested the 100 ohms as a value certain to get past that problem. (Matt, sorry if I'm "putting words in your mouth", I'm just trying to chill this thread)
So why would it be better to use the now-recommended 220-330? Because those values would put less current load on the drivers, yet still supply ample drive to the coils. It is always a good practice to keep currents as low as reasonable because it causes less heating of the transistor and that pull-up resistor; and it leaves the 5V supply less-loaded so it can handle additional sensors that may be added to it. Understand, the very little additional load you are adding to the supply is probably of no consequence. As to heating in the transistor/resistor, would only matter if you were running very high rpm so that the duty-cycle for that driver started getting significant. It's getting late and my math may be off, but I think 7500 rpm with wasted-spark and 3 msec/1 msec dwell/spark would be about 50% duty-cycle on those components; beyond that I would want to consider the wattage rating of the resistor, at least.
Another, perhaps more important, reason for keeping the current in that circuit lower is that the driver transistor can drive the signal closer to 0V, maybe giving more reliable operation of the coil with some types of (smart) coils. The other side of the coin, of course, is that too little current may not be able to drive the coil inputs close to 5V and cause similar problems. That as probably the condition that caused Matt to suggest the 100 ohm ones in the first place.
Got it? I would leave the 100s in there, but would use the 220-330 if doing it again. Yes, I agree that following the latest recommendations is the wise course as a general practice.
Alas, I did make a mistake when I posted last night. The math is still OK, I think, but some of the logic is wrong. Those 100-330 ohm resistors will draw the most current, and heat up the most, when the rpm is low, not high. Worst case would be "key-on engine-off", when a 100 ohm resistor would be drawing close to 1/4W. With heat-shrink on the resistor body to inhibit cooling a 1/4W resistor might be pushing its limits. But, how often do you sit for extended periods with KOEO? And, aren't common metal-film resistors rated for 300mW? I still say "leave the 100s in", but build to published recommendations in the future.
And do yourself a favor next time and build the going high TC4427 logic drivers. They are far superior to the going low "resistor" method.
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The 270 to 330 ohm pull up is the maximum value for the pull ups that we have found to give reliable operation. 100 ohm pull ups also work, particularly if you're doubling up the outputs.
Matt Cramer -1966 Dodge Dart slant six running on MS3X