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Coil Resistance

Moparfiend

Moparfiend

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Hi I hve a bew coil that I want ro use for my 318 stick ignition system. Does anyone know the stock resistance of the coil? I have a pertronix Flamethrower 1.5 Ohm coil and it just states for 8cyl.....

Thanks oh and after I getbit running I plan ti get rid of the points.....
 
There are several options. The classic points coil is 1.5 ohms on the primary and likely ~8mH inductance. The new "high output" are likely 0.600 ohms and 2.2uH inductance. If you do the math the difference is with "electronic" points you can ramp the lower inductance/resistance coil up to 4A fast enough get a full 40mJ or more of energy at 7000RPM. The 1.5 ohm/8mH coils are not able to run the current up to 4A or so before you have to fire the coil again at 7000 RPM, so less energy. The break point is around 5000 RPM. If you are not after all the performance you can get above 5000 RPM the coil you have is fine and can be used with points (you must use it with points actually) and can be used with electronic ignitions with the limitation that I mentioned above.
 
Thanks JimKueneman, for the information! I doubt I would ever go much more than 5,000 RPM on the LA motor. Not sure when I will convert to either a pertronix type of ignition or just a new pointless dizzy but I just need to try and get her running and had this new coil sitting on my bench. So it looks like its a replacement to the stock unit which means I can drop it in. I understand that I can not run it later with an electronic ignition so when I make that cut over I will need to make a complete change over to a new system......

Thanks again for the response!
 
Moparfeind said:
Thanks JimKueneman, for the information! I doubt I would ever go much more than 5,000 RPM on the LA motor. Not sure when I will convert to either a pertronix type of ignition or just a new pointless dizzy but I just need to try and get her running and had this new coil sitting on my bench. So it looks like its a replacement to the stock unit which means I can drop it in. I understand that I can not run it later with an electronic ignition so when I make that cut over I will need to make a complete change over to a new system......

Thanks again for the response!
Click to expand...

You don't have to change the coil depending on a number of things. They will claim they overheat but that is only if you remove the ballast resistor and use a system that mimics how points work (at low RPM the points are closed for a LONG LONG time between firings) and the I^2*R losses in the 1.5 can double the power in the coil. If the system is a smart system that calculates the ideal time to start charging the coil then it won't make any difference and actually be lower power dissipation than points at normal RPMs (at least that is what my simulations say).
 
JimKueneman said:
You don't have to change the coil depending on a number of things. They will claim they overheat but that is only if you remove the ballast resistor and use a system that mimics how points work (at low RPM the points are closed for a LONG LONG time between firings) and the I^2*R losses in the 1.5 can double the power in the coil. If the system is a smart system that calculates the ideal time to start charging the coil then it won't make any difference and actually be lower power dissipation than points at normal RPMs (at least that is what my simulations say).
Click to expand...
Hey Jim looks like your a EE and if not your obviously very knowledgeable with ignition systems. Do you have any recommendations for a replacement ignition system? I have not worked on ignition systems much and I don't know what the trade offs are. I just need hassle free operation and don't feel like getting my old dwell meter out anymore and futz with points. I see electronic distributors for $80 but not sure if I need something like an MSD box or what to go with it......
 
Moparfeind said:
Hey Jim looks like your a EE and if not your obviously very knowledgeable with ignition systems. Do you have any recommendations for a replacement ignition system? I have not worked on ignition systems much and I don't know what the trade offs are. I just need hassle free operation and don't feel like getting my old dwell meter out anymore and futz with points. I see electronic distributors for $80 but not sure if I need something like an MSD box or what to go with it......
Click to expand...

I am actually sitting here designing my own to fit in my points distributor for various reasons :). Yes I am an EE. I did not want the non stock look so I bought the Pertronix III but the double spark messes up the signal I use for the FiTech EFI. I did not like the version I and II since they are hall effect and you need to use their rotor. Other than that I would go for the Pertronix III if you don't use the "-" side of the coil for a Tach or EFI. Actually I will sell you mine at a discount. Run about 10 minutes total.
 
Hi Jim, Hum... I will want to run my old SupertachII any work around to use the Pertronix and my SupertachII??
 
JimKueneman said:
Yup they both work fine other than they are visible when installed which I did not want.

Jim
Click to expand...

One note it seems like it is crap shoot trying to get a reliable GM module these days from what I have been hearing at shows. Probably the FBO is the best bet. I have his lockout plate for the mechanical timing and love it. My design will have advance maps so I will just lock out the mechanical weights with his plate and program in the advance curve I want. I think his systems you can do the same thing.
 
Or give me a few months and you can beta test one of mine igniters since your just up the road :). I have it making 33kV spark on the lab bench right now. Will have my first circuit card for test at the end of next week if I can finish the layout before Friday.
 
Ooooooo..... '70 Sport Satellite...... Bring it down to Sonoita and I will getting it working.... I'll get it back to you in a few years :)
 
LOL, I might need your help! I have to digest the information you sent me to better understand all.
 
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