Ballast, Blaster II, ohms, current, friggin volts!

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Rice Nuker

Rice Nuker

Let the Coal Roll!
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Well, I could not get a msd ballast at the local napa or orilleys so I just got a .5. Now trying to calculate the actual voltage at the coil (at idle I reckon).

Since I have been sipping on some knob creek and playing with my engine test stand all day, I suck even more at figuring out the process of determining voltage at coil out of the resistor based on the load of the coil (I have no idea how many amps the blaster II draws at idle or any other time. I assume it is 4 amps at idle and 7 - 10 at 6k). One thing, it is a USA coil rather than made in the south east end of Srilanka, so that might be a good thing.

It appears we have some sharp folks here and I was wondering if someone would chime in on how to figure the voltage out of my circuit after the .5 ohm ballast given a specific amp load. Secondly what is the predicted amp draw of the blaster II at idle and at at 6K so I can be happy about my wiring choices. Oh yea I am building an engine test stand for this slant that was chucked out the back 40 for 2 years.

Much appreciated. GBA.
 

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Found this:

http://www.msdignition.com/Products...03_-_Blaster_2_Coil_w/Ballast___Hardware.aspx

a partial quote:


"Most late model vehicles with electronic ignitions do not require a ballast resistor, check your ignition and manufacturers specifications to determine if a ballast is required in your application.The Blaster 2 Coils are supplied with a 0.8 ohm ballast resistor"

I'm gonna go out on a limb here and say, "run it."
 
Thanks 67, yea I can "run it" but half the fun for me is figuring out and learning more. I reckon I can test the ballast when cold to get its actual ohms (if my 150 dollar meter is near accurate), test volts at distribution block at idle then at coil at idle then both at 4K to get some figures. I was hoping for someone to give me a basic rundown application of ohm's law to my project.
 
It goes beyond Ohms law, I will explain why. It is a long but true story. An ignition coil is an inductor and has resistance. I have a blaster coil and a good Ohm meter the DC resistance measured at 1 Ohm. I the 0.5V is added in there is 1.5 Ohms. There is other resistance to in the wiring from the battery .. ignition switch to ballast and ignition module. As a guess, it is likely below 0.5 Ohms so the total is now 2 Ohms. If the battery voltage is 12V the current would be I = V/R, or 6 Amps. By now it seems like a long story, but it is just starting. The 6A would be with coil powered and engine stopped, and the switch being points or electronic driver on. The engine being stopped, is not part of the original question, and the original question about the coil voltage has not been answered. I will get to that. First the electronics in an ignition system has a voltage drop, called saturation voltage. It is typically below 2V for a Darlington transistor and perhaps a 1V for an IGBT. The voltage at the + side of the coil, engine stopped could be 7V, by assuming a 2V saturation, and have the remaining supply voltage is split between coil, and ballast plus car wiring, each with 5V.

Now the story gets longer. We only considered the DC, or direct current measurements. The coil inductance changes all that. When an inductor is first powered, it opposes a change in current. The current starts at zero and increases with time, limited circuit resistance or other factors. The increases with an exponential formula with the time constant of inductance divided by resistance. I will not go into detail, but the point is, the current varies with time. It starts low, builds, when ignition happens the energy stored in the coil is used to fire the plug, and it starts all over again. It is an varying signal.

Some electronic ignitions control the coil charge time, and time that activity such the the coil is just in time for the ignition event. Some build current limiting in the solidstate switch. Those ignitions do not require a ballast. Ignitions including OEM mopar, Pertonix, Mallory unilite, and others need a ballast!

If you desire to measure the ignition current, use the meter on AC volts and measure the voltage across the ballast with engine running. For the 0.5 Ohm ballast, the current will be twice the measured voltage. The is because I=V/R. For systems without a ballast a 0.1 Ohm power resistor may be inserted in series with coil and AC voltage measured and multiplied by 10. Or better yet use scope and measure peak current. It is what matters.
 
KitCarlson said:
It goes beyond Ohms law,...................... It is a long but true story............................. An ignition coil is an inductor......................... We only considered the DC,................... The coil inductance changes all that. ...........................
Some electronic ignitions control the coil charge time,............................. .
Click to expand...


Well put.

And if all that isn't enough, "we" have to deal with the tricks of the Mopar voltage drop in the harness--and changes in battery voltage, which ALSO affects the outcome.

Probably the best "backyard garage" answer is to monitor coil temp over a period of time.
 
Excellent answers above. What ignition module are you using? I can't make it out in your photo, but looks like maybe a GM 4-pin HEI. If so, you don't want a ballast resistor. As 67Dart273 says, the main purpose of the ballast is to keep the coil from getting too hot, which happens with older ignition systems - points or original Mopar box. Later ignitions - HEI, Mopar spark computer, Ford TFI manage the dwell time so the coil doesn't overheat with the full ~13.4 V voltage.

Forget about measuring resistance of your ballast and coil. For <1 ohm, you need to use the "4-wire method" with "Kelvin connections", which usually requires a special scientific multimeter. Best you can do is subtract your lead resistance, but even then it is hard to get a good connection at the probe tips. Even then, as the ballast and coil heat up, their resistance greatly increases.
 
Awesome. The three people I wanted to hear from. Thanks very much!

I can grasp the generalities of the behaviour but havent had any education in theory or applied theory so it quickly gets beyond me. I did think the ballast would behave differently as it go hotter so the testing of resistance would be difficult and yield varying numbers (maybe there is more than that reason). This project is a complete waste of time in order to test a radiator I bought used. I thought I would try some citric acid in mild solution to clean the radiator by running it on an engine.

The icu is hei 4 pin, mid grade Napa. Was going to power it with a relay activated by a run switch.

Saturday I decided to just get my 360 running that was sitting in the back 40 for 2 years as the flywheel I had for the /6 did not fit (center hole too small in flywheel) maybe not even a /6 flywheel. Built about half the mobile test stand so far. Going to transfer the electrical panel over to the new stand.

Ignitions are very interesting to me and so are electromagnetic fields, so thanks much for the responses. I need to re-read them and look up some stuff and hopefully learn something.

I wasn't sure if 4 pin hei had dwell control and or limiting. I reckon it would since the mopar unit used the ballast as a current / voltage limiter. Still not fully clear on current limiting, seems that would be voltage limiting. I think dwell control is duration for coil saturation but seems it would be at full voltage. Maybe there are derivations which combine both.

What control behaviors do 4 pin hei and 8 pin hei have regarding dwell and current limiting features? Is current limiting implemented by voltage limiting from ecu to coil?

I guess I am doing away with the ballast if 4 pin hei can handle the dwell and current to the coil.
 

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The GM HEI modules have an analog dwell control. It is a form of prediction to set the dwell period based on the the frequency of ignition pulses. It works with resistors and capacitors, comparators and other circuity. It also tweeks for extended dwell at lower RPM. It may also have a current limit. It is a late 70's technology. The IC that Motorola made for these features has been obsoleted for general sales.

The 8 pin module is similar but has hooks to use with a micro control to provide a digital timing reference. It has an input for the the micro to control the ignition driver. When the 8 min module is used without an ECU it is in the limp home mode. It is designed to function on a GM car and defaults to limp home mode for starting, then under ECU control for normal driving. The GM application has a locked distributor ... no mechanical advance. The ECU provides the timing control. If used with mechanical advance distributor and no ECU it works too, and many seem satisfied. Some think adding an ECU to a mechanical advance distributor is the way to go. I think it would be similar to standing in the back of a truck, shooting prairie dogs in a plowed field, while the truck is moving. Or running on top of a train to maintain a certain velocity or position with respect to a ground location. I have never tried any, so do not know for sure.
 
Well, that is great and thanks for the summation and pontification :).

I think distributors tied to camshafts associated to the crank via timing chains which signal anything with a gadget on its shaft is asking for all sorts of errors. Couple that with phasing issues on vacuum advance and antiquated analog circuits managing a single coil and the entire process is a nice crude harmony of inaccuracy of ignition. It friggin works but so does a 1 cylinder john deer tractor.

cop is obviously the way to go and second to that is wasted spark. Crank monitoring with high resolution coupled with cam position is the other facet, excluding the ignition system.

I just dont understand the obsession with distributors considering the price of going to crank triggerd wasted spark system. I am really surprised there is not a kit with a hand held gadget tuner. Maybe it is just not worth the money but custom tailoring a map based on variables which are precisely repeatable and accurate seem like a good way to make more horse power and all the above.

I am striving for edis and a mega derivation box myself as I am not savvy like you guys with programming and hardware. I think it will be an applicable way to start understanding more.

Does the 8 pin vs the 4 pin have better dwell management or current management or is it just negligible. I understand the 8 pin will run in limp mode which is fine if you have a mechanical / vacuum dist but it may be a pointless upgrade on such vs. the 4 pin.

Thanks for the great responses guys!
 
I think it's pretty simple, really. Most of us want vacuum advance, so by the time you get crank triggered ignition set up with both RPM and vacuum (MAP) sensors, you might just as well use EFI. So if you use something like even my current Holley Commander, or maybe, Megasquirt, that's already built in. I'm actually using a conventional distributor at this time, but plan to change that, as I'm contemplating going from TBI to port injection, and also thinking of going from the Commander to Megasquirt. A crank triggered set up would be easy.

Just doesn't seem logical to me to go to that much trouble on a carburetor fed engine. The lean burn boys tried that some time ago.
 
Yes, let me rephrase regarding distributors:
I very much understand that a nice MP or accurately phased tight dist, a good gear and tight timing chain can all be fairly efficient when set up with proper mecnanical and vacuum curves (but a fairly daunting task to alot of people) considering the cost of that vs a mega controller and edis / ecu installation. But alot of people spend big bucks on a distributor, coil and ecu system, and at that point it seems to make more sense to crank trigger / wasted spark / map-able ecu.
 
You are both on the right track. Ms3x is the way to go. Same with crank fire, EFI. EFI, and ignition share sensors and many related and interrelated calculations. My experience suggests only a few percent difference in performance of an engine management system vs well tuned carb and distributor ignition. There is better, economy, less emissions and smoother operation under all conditions.

About COP, might want to try coils on an early 273. I think coil near plug may be a better fit.

After all the work .... a 3rd gen Hemi not a bad idea, or a new Challenger is better for us older guys with painful body parts.
 
i just have 2 things to say. in an ac inductive circuit its impedance not resistance because it changes with frequency. the higher the rpms the more the empedence on the coil goes up causing voltage to go up and curent to go down with rpms. last important thing sumit has the rite resistor for that coil, the one you bought mite not be enough whats and consiquently burn out. i bought one for that coil and it was larger than the i have seen before meaning its higher wats
 
I prefer the 8-pin HEI to the older 4-pin because it is simpler, more rugged wiring. A factory cable runs from the module to the GM external coil, using sealed connectors, so grab all that and done there, plus you get a tach output wire. Snip off the GM connector for the pickup and you have a rugged connection to your Mopar distributor after you solder & heat shrink the wires (twist them and connect the right way - 50% chance). The "limp home" mode is not a problem, it just gives no advance unless a computer commands it (so ready for that). Your Mopar distributor can handle the advance as normal.

Re computer, the Holley Commander 950 can control the 8-pin module. There was a link posted by TrailBeast about a new, and maybe inexpensive, ignition-only controller called Rabid Gator, but maybe it never went production.

I don't think timing wander is a big problem if you have a good timing chain. I am more bothered by the clumsiness of jumping a spark thru air, even though it has worked since the 1800's. The easiest way to go distributor-less is using the Ford EDIS system, which many megasquirters use. I installed a 36-1 tooth wheel on my Dart's crank pulley for that and a pickup (not using yet). Normally it is a "wasted spark" system, but I am contemplating using a Magnum cam sensor (part of distributor) with a home-made logic circuit to trigger only on the compression stroke and fire a GM LS coil (1 per cyl). My day job keeps getting in the way of such fun.
 
I copied this from GMC BUBBA's post on jalpopyjournal. It appears someone took the time to monitor the hei ignitions behavior with different resistance coils and it very well may blow the whole "run a blaster II" out of water.

Based on this, I dont think it is a good idea to run a blaster II with or without a resistor on an HEI if a person wants optimum performance. It appears that .5 or slightly lower is the sweet spot based on some other info I got off the same site. It appears that GM Hei remote coil is .45 ohms.

The pictures are links to better pics on jalopyjournal

I reckon that is why most folks run the ford E core.

Here is BUBBA's into:

"The HEI came as a federal mandate to increase tune up mileage ( for clean emissions) and was a first from the Delco guys in regards to high energy ignition systems and was a home run from the first day forward.
The ignition offered high energy at 5.5 to 6.0 amps of primary current controlled by the module. Module also offered a varying dwell to prevent the igntion coil from overheating using low dwell at idle ( 15 degrees) and increasing with rpm to 30 up the rpm scale.
The orginal design was to use a .5 ohm untapped coil and isolated the primary and secondary windings ( caused some problems when left at high demand).
This discussion concerns the ignition coils used with the HEI.
I tested three coils this morning with the waveforms shown .
1- .5 ohm (oil filled) ignition coil. Unit ws single firing a 25,000 test plug and used as waveform shows 5.8 amps clipped with current limiting ( hence the flat spot at shut of of control) and used a preset time of 3.6 mili sec to get er done. This is a normal function of a properly working high energy ignition system. You can hear see and smell the energy ( and feel if your not careful)
2-1.5 ohm coil...... Unit still fires a 25 kv test plug but you can hear the difference in enegy, waveform shows a decrease in current to 3.0 amps . ( A new point ignition runs at this decreased level )
3-4.0 ohm coil, would no longer fire the test plug and using a standard plug spark was at 2,000 volts and 1.5 amps .....this one wouldnt owrk very well if at all!

Hope this clears up some mis conceptions in regards to HEI module control
The hamb is a great place for sure.........
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