slideshow86 Posted March 11, 2008 Share Posted March 11, 2008 Ok I have an 84 4wd brat. It has a nippon-denso distributer( I know from a 2wd ). I know its ok to swap the whole nippon denso system out for the hitachi system as long as the coil goes with. My question is, how do I identify what type of coil it is? It is in the stock bracket and is black. The only thing written on it is "external resistor required" and the #12. The P.O. did the swap and I dont know what is what. Is it supposed to be labeled? This one isnt. Pretty much the car runs, ok but has low power. How do you test a coil? I just want to make sure everything is right and rule it out as a possibility. Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted March 11, 2008 Author Share Posted March 11, 2008 -Double Post- Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 11, 2008 Share Posted March 11, 2008 Coil's are tested by checking the resistance of the primary and secondary windings. Per book specifications: ND coil: Primary: 1.13 - 1.38 Ohms Secondary: 10,795 - 14,605 Ohms Hitachi coil: Primary: 1.04 - 1.27 Ohms Secondary: 7,360 - 11,040 Ohms GD Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted March 11, 2008 Author Share Posted March 11, 2008 Thanks GD Now Im off to search what a primary and secondary winding is and how to test it. Now at least I know how to tell the difference. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 11, 2008 Share Posted March 11, 2008 Just a matter of using your ohmmeter on the terminals of the coil. You know the coil works, so it should be obvious from putting the leads across a few of the terminals which is which. A good, accurate Digital Multimeter (DMM) is essential to any automotive toolkit IMO. And not a cheap one either - those are good for paper weights. You need at least something with a range function - it greatly improves the usability of the DMM's - you can tell the meter what you are interested in and it will be able to disregard small changes that will confuse the readings on cheaper meters. GD Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted March 11, 2008 Author Share Posted March 11, 2008 ok so I just didnt know what to set the settings on my MM. I have, Primarys 1.4 secondary 9.58? (thats the heighest reading of my mm) would this be 9,580 ohms? If this were correct, my coil would be bad. All I have is a bunch of 4wd coils. Time to search what msd it takes...... Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 11, 2008 Share Posted March 11, 2008 Time to search what msd it takes...... MSD coils are crap - made in mexico along with Accel. Get an OEM ND coil. Try rockauto.com or thepartsbin.com GD Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted March 11, 2008 Author Share Posted March 11, 2008 Coil's are tested by checking the resistance of the primary and secondary windings. Per book specifications: ND coil: Primary: 1.13 - 1.38 Ohms Secondary: 10,795 - 14,605 Ohms Hitachi coil: Primary: 1.04 - 1.27 Ohms Secondary: 7,360 - 11,040 Ohms GD I know there bad but I can have one now to see if it fixes my problem and carry an extra when I get one. Here are the spec's of the blaster coil BLASTER 2 AND 3 SPECIFICATIONS Output Voltage: 45,000 Volts Maximum Operating Voltage: 12VDC Primary Resistance: 0.7 Ohms Secondary Resistance: 4.7K Ohms Turns Ratio: 100:1 ACCEL SUPER STOCK UNIVERSAL IGNITION COIL Primary Resist 1.2 Ohms Secondary 8.9 k Ohms Turn Ratio 100:1 Max Voltage 42000V Yellow If the primary and seconary doesnt match my oem coil. How could this be the right coil? Will it hurt anything? Even the specs for the accel's dont match. Those ohm readings are lower than what I have now. Im confused. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 11, 2008 Share Posted March 11, 2008 If the primary and seconary doesnt match my oem coil. How could this be the right coil? Will it hurt anything? Even the specs for the accel's dont match. Im confused. It can hurt, yes. The resistance of the MSD/Accel are lower in order to facilitate a larger, hotter spark. While this may be good/useful for ignition (which is still debatable, and highly depends on application, mixture, ect), it is causing more voltage to reach the ignition module inside the distributor. This will degrade the module faster - often pushing an older module over the edge. Nothing lasts forever, but as with all electronics, the hotter you run them, the shorter their lifespan. So there is always risk involved. Just as there is with running a ND distributor on a Hitachi coil - same situation if you reference the above specs I gave. The ND module was not designed to trigger the larger voltage that the Hitachi coil runs. GD Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted March 11, 2008 Author Share Posted March 11, 2008 I thought I read some where that the nippon denso had the hotter spark? If that were the case its weird it also has more resistance across the coil windings? If I have 1.4 on my primarie and 9.58 secondary would this be a defective nippon denso or a hitachi? If it is running the correct primary but less resistance for the secondary, it would be hotter spark not less spark right? So it wouldnt cause loss in spark, it would actually be more spark. (Not really taking away from the over all power of the car, trying to figure out this loss of power here) Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 11, 2008 Share Posted March 11, 2008 All we are really concerned with for the ignition module is the primary resistance - that affects how much voltage the transistors in the module have to "switch" on and off. Lower resistance in the primary means more voltage to the module. Thus a Hitachi coil could harm an ND distributor, but it probably wouldn't cause damage the other way around (ND coil with Hitachi disty). Sadly, the "other way" isn't the one most people on here have gone. The 2WD advance myth has seen to that. The accell coil is better suited to the ND distributor than either the Hitachi or the MSD, but their quality of late is nothing short of ghastly. Others on here have been stranded due to failed accell coils. So while they won't hurt the module, they may leave you just as stranded. They moved their factory to Mexico a couple years ago and since then they have been crap. Same with the low end MSD's. The secondary coil resistance governs, to a large extent, how hot the spark will be. But it's a ratio of turns, not the resistance, that is the real specification that matters. Generally though, more turns equals higher resistance so if you don't have a ratio specification, then resistance is the next best thing. GD Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted March 11, 2008 Author Share Posted March 11, 2008 Ok I read a little about these resistors for coils and my search didnt come up with much. I know the coil in my car says "resistor required" I know when I was at autozone a half an hour ago, I looked at a few stock coils for these cars. The one that he pulled out for the nippon denso said "resistor required" stamped on it. I tested it just for the hell of it, It had the ohm readings that you (GD) gave me for the hitachi......Maybe he had the wrong coil in the box? It was the part number of what was on his computer? EDITOk I think Im understanding this. The primary winding controls the ignition module. Correct resistance is critical to make it last. The resistance of primary winding in the coil in my system is 1.13 - 1.38 Ohms (mine reading 1.4) Take that number add it to the ristance the stock resistor/ballast adds and thats what the ignition module needs to be at. I need to know what the resistance is of the stock resistor/ballast or the desired ohm reading of the ignition module, so I can find out the correct resistor/ballast to use w/ an msd. If I choose to use it (which I bought just incase) Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted March 11, 2008 Author Share Posted March 11, 2008 I couldn't wait for the email so I called support.The answer is I can use it if I put a 2.3 ohm ballast resistor to it, so as not to burnup the ignitor. Thank you GeneralDisorder! EZ I found this while searching. It is for an 86 spfi I think, Is this same affect working not to burn up our ignitors? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted March 11, 2008 Share Posted March 11, 2008 Subaru's don't use a ballast resistor in their hall-effect distributors. The module contains all the elements required for the electronics to function internally. A ballast resistor is needed on some older points/condensor style distributors because the coil is designed to operate at less than 12 volts, or EXACTLY 12 volts - as would be present durring cranking prior to the engine running (the resistor is bypassed for cranking). When the engine starts and the alternator pushes the system voltage higher than 12, the resistor keeps the voltage to the coil within it's operating range. So you neither have, nor require this device as the electronic ignition can operate at higher voltages, and thus spark power while cranking is not an issue. The coil is designed to handle a broader range of voltages. If the coil they are handing you claims it needs one then I wouldn't buy it. GD Quote Link to comment Share on other sites More sharing options...
slideshow86 Posted March 11, 2008 Author Share Posted March 11, 2008 Thanks again GD Quote Link to comment Share on other sites More sharing options...
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