Crane xr-1 point to electronic module

[richie49]

My question about this conversion has to do with the coil. I have the module and the car runs and the spark isnt the strongest.The coil is supposed to be the recommended coil a PS 20? Not sure if it is because its not marked with anything.What Id like to know is if anyone has used the hei coils used with the small cap hei's I have several of the coils but dont want to try them without knowing if using them might burn out the module. I have reset the module as to the instructions. I have a chevy hei distributer and it works great BUT the distributer is too tall and hit hood.The point style distributer is short enough to work without hitting thus the conversion.

Richard ( richie49 )

[Tuner]

As per Crane instructions "The XR-i requires ballast resistance to limit coil current"

http://www.cranecams.com/uploads/instru ... 1700c_.pdf

You will need to measure the resistance of the combined coil and ballast resistor(s) to be sure it is at least 3 OHM. The HEI type coils have low primary resistance, usually about .4 (four tenths) OHM, so you may need a regular 1.5 OHM points ballast resistor PLUS an additional .8 OHM resistor like the MSD 8214.

https://www.msdperformance.com/products ... parts/8214

[richie49]

Tuner
I have hooked up the round canister coil with a ceramic resister with a 1.8 ohm resistance . The coil doesnt have a spark that will jump a hei spark tester so that was why I wanted to change coils. So the small cap HEI external coil should be ok with just the ceramic resister then. Thanks Ill test it out later.

Richard

[Tuner]

You need to know the combined resistance of the coil and ballast resistor(s) is at least 3 OHM. If your resistor is 1.8 OHM the coil must be at least 1.2 OHM ………… 1.8 + 1.2 = 3 …… or the smoke will leak out of the XR-1 thingy. It may be invisible smoke, but just the same, without the smoke, no spark. In that case, you can put the points back in and burn them up too. …….. so …… 3 OHM total.

[richie49]

Tuner
Thanks I was going to check both the coil and the resister but I usually need a reminder.Ill measure the coil and resister and see if I have to get a bigger resisterLooks like I wont be able to test anything till Monday anyway( you know Honey do this or that ) Gotta keep the missus happy.

Richard richie49

[novadude]

So with 3 ohm primary resistance and the same coil as a points system, the crane module is nothing more than "electronic points", no? With high primary resistance and the same turns ratio, it likely not doing anything that points won't do, right?

[Geoff2]

Nooooooooooo, you cannot a HEI coil with two ballast resistors. Typical HEI coil is 0.5 ohm, designed to take the full 12v. If you have two ballast resistors that are in series & add up to 3.5 ohms [ total cct resistance is now 4 ohms, not 0.5 ], then the HEI coil only gets 1.5 volts, not 12!!!

Use whatever coil &/or resistor that Crane recommends.

[Tuner]

Nooooooooooo, you cannot a HEI coil with two ballast resistors. Typical HEI coil is 0.5 ohm, designed to take the full 12v. If you have two ballast resistors that are in series & add up to 3.5 ohms [ total cct resistance is now 4 ohms, not 0.5 ], then the HEI coil only gets 1.5 volts, not 12!!!

Use whatever coil &/or resistor that Crane recommends.

N00000000000000000, you cannot mutilate OHM's Law that way.

This MSD resistor https://www.msdperformance.com/products ... parts/8214 is for use with low-resistance primary coils to limit current in induction system applications that do not limit current electronically. In the case of a .4 or .5 OHM coil, adding the .8 OHM resistor with 1.7 OHM regular ballast resistor results in 3 OHM total resistance. .5 + .8 + 1.7 = 3

[novadude]

Nooooooooooo, you cannot a HEI coil with two ballast resistors. Typical HEI coil is 0.5 ohm, designed to take the full 12v. If you have two ballast resistors that are in series & add up to 3.5 ohms [ total cct resistance is now 4 ohms, not 0.5 ], then the HEI coil only gets 1.5 volts, not 12!!!

Use whatever coil &/or resistor that Crane recommends.

N00000000000000000, you cannot mutilate OHM's Law that way.

This MSD resistor https://www.msdperformance.com/products ... parts/8214 is for use with low-resistance primary coils to limit current in induction system applications that do not limit current electronically. In the case of a .4 or .5 OHM coil, adding the .8 OHM resistor with 1.7 OHM regular ballast resistor results in 3 OHM total resistance. .5 + .8 + 1.7 = 3

The whole reason for primary circuit resistance is to limit CURRENT to the module (or points), right? What Tuner is saying should work fine.

[modok]

Uses the points cam AND can only handle a 3 ohm coil?
What is the point of that? Worst of both worlds.

If the distributor is not worn out too bad, put points back in and use them as the trigger for a Ford TFI module, the tfi module it can run a HEI coil no problem.

A small diameter distributor cap will be fine as long as you keep the spark plug gap reasonably small and keep it inductive ignition.

[Circlotron]

Nooooooooooo, you cannot a HEI coil with two ballast resistors. Typical HEI coil is 0.5 ohm, designed to take the full 12v. If you have two ballast resistors that are in series & add up to 3.5 ohms [ total cct resistance is now 4 ohms, not 0.5 ], then the HEI coil only gets 1.5 volts, not 12!!!

Yes and no.
When the points close the coil will initially get the full 12 volts because no current has begun to flow. As the coil current runs up the voltage drop from the ballast resistors also increases, and when the coil current levels off, for sure there will be only 1.5 volts fed to the coil. But if this is enough to make the desired amount of amps flow after it has leveled off then fine. Better to have the heat from the voltage drop dissipated outside the coil in the resistors rather than inside in the coil primary winding resistance. Depending on the actual HEI coil though, if it is a low inductance one it will not store as much energy for the same amount of amps as a higher inductance one.

[modok]

Yes, I think that's right. It makes more sense to think in amps, rather than thinking in volts.

A coil designed to be charged up to 8 amps may not work as well at 4, as one designed to work at 4.

If you take a coil designed for 4 amps and run it on 6-8....probably will work great....but will it live? sometimes

[Geoff2]

Tuner,
Not a mutilation of ohms law at all. It is you that needs go back & study ohms law. The example I gave was 100000% correct, & is about as simple an example of Ohms law & Kirchoffs law [ look it up ] combined that you could get. I gave a simple example of how the voltage would be divided up. It does not matter what the current is because this is a series cct where the current is the same in each component. I did simplify the situation slightly because most modules, HEI included, have some type of current limiting device. Without current limiting, a 0.5 ohm coil would pass 24 amps using a 12v supply.

I will now use the exact numbers that used in your earlier post: 0.4 ohm HEI coil, 1.5 ohm res & 0.8 ohm added. I am assuming the resistors are connected in series so that resistors are 2.3 ohm total. The HEI gets 1.78 volts, the 1.5 ohm res gets 6.66v & the 0.8 ohm res gets 3.55v. Since the HEI coil is designed to work with 12v, it is not going to produce a spark on 1.78v.....

[Schurkey]

Tuner
I have hooked up the round canister coil with a ceramic resister with a 1.8 ohm resistance . The coil doesnt have a spark that will jump a hei spark tester so that was why I wanted to change coils. So the small cap HEI external coil should be ok with just the ceramic resister then. Thanks Ill test it out later.

Richard

I wouldn't expect any ballast-resisted coil to be able to fire an HEI spark tester. Not firing an HEI spark tester doesn't mean there's no spark, and it doesn't mean the engine shouldn't run. It means there isn't enough voltage available to jump the extra-large gap of the HEI spark tester.

Get a non-HEI spark tester, or an adjustable spark-gap spark tester.

[gruntguru]

Tuner,
Not a mutilation of ohms law at all. It is you that needs go back & study ohms law. The example I gave was 100000% correct, & is about as simple an example of Ohms law & Kirchoffs law [ look it up ] combined that you could get. I gave a simple example of how the voltage would be divided up. It does not matter what the current is because this is a series cct where the current is the same in each component. I did simplify the situation slightly because most modules, HEI included, have some type of current limiting device. Without current limiting, a 0.5 ohm coil would pass 24 amps using a 12v supply.

I will now use the exact numbers that used in your earlier post: 0.4 ohm HEI coil, 1.5 ohm res & 0.8 ohm added. I am assuming the resistors are connected in series so that resistors are 2.3 ohm total. The HEI gets 1.78 volts, the 1.5 ohm res gets 6.66v & the 0.8 ohm res gets 3.55v. Since the HEI coil is designed to work with 12v, it is not going to produce a spark on 1.78v.....

The HEI coil is only designed to see 12v while current is building. Once current reaches the maximum value - usually 7 amps or so, the HEI module becomes a "resistor" to limit current and the coil only sees a much lower voltage. (It usually does this by pwm. In some cases the dwell is limited sufficiently to completely avoid current limiting.)