Ignition question involving use of ballast resistor

Yes, but the thing is that the coil inductance and the distributed inductance of the coil are so enormous that the cable doesn't contribute a whole lot. The cable impedance is pretty heavily swamped.

Someone mentioned spiral-wound cables for RF suppression... I have never used such a thing, but they could have enough series inductance to change things. The most important part of that is that they will be a low pass filter.

It is, but the coil resonance itself is so substantial that the cable shouldn't change it TOO much.

It would be fun to measure it with a scope, though, and see how changing the cable length alters the waveform. It bet it doesn't do much, but it would be fun to see.

--scott

Reply to
Scott Dorsey
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I will find out soon what the emissions are. I just got back from a freeway run and some stop and go driving and the only problem was a sag when I floored it at about 25 to 35 mph, like the accelerator pump was out of adjustment or the power valve was not opening. I tweaked the pump linkage a bit but it wasn't out that much. I checked timing and it is at spec. Checking the power valve will involve tearing into the carb, which I will save for another day. It could be that the main jets are a tad too small, but before I do anything else I will take it to a smog shop for a dry run to see what the emissions are. At least the ignition system seems to be performing okay and that was my main worry.

Reply to
Jack

2 ppm HC is easy. Retard the timing 2 degrees and it will drop right down... Just to cover the bases... Is the Cat OK? a temp gun should show a hotter outlet than inlet. Does it run hot enough? No 160 TStat? Absolutely no misfires? A dollar bill held up to the exhaust should not vibrate. HTH, Ben
Reply to
ben91932

Thanks, Ben, I'll definitely keep that in mind when the time comes.

5 BTDC shouldn't look that much different from 7 BTDC.

There has been an annoying misfire at idle for quite some time, although with the current ignition system that I described elsewhere on the thread, the idle seems to have smoothed out considerably. But the smog test I have to take doesn't cover idle. It covers 15 and 25 mph on a dynamometer. Sometime in the next week or two I am going to get a dry run at the smog shop to see what it's reading.

Reply to
Jack

The modern equipment would be the Snap On Modis or the Snap On Vantage Pro.

Reply to
Steve Austin

Jack,

from readin gall the above posts, my GUESS is that the combination taht casues the stumble is for some reason casuing a WEAK spark. As one poster said, it is hardest to develop spark during acceleration when compression is the highest, so I guess there is some interaction in the electronics and the coil such that you have a poor spark at that time. Somehow the 1 Ohm ballast cures the interaction. I would leave the 1 Ohm in the circuit and be happy, but if you want to analyze this further I agree with another postr, you will need a scope or ignition analyzer to look at the SECONDARY waveforms and see just what is going on with and without the ballast.

also as far as I know, the purpose of resistance plug wires is to reduce radio interference. They don't really lower or raise the voltage of the spark AT THE PLUG.

You are doing a great job at narrowing in on this.. but I think you need a scope to get to the next step.

Mark

Reply to
makolber

Thanks, Mark for the encouragement. I am *more* than happy with the ballast resistor. After I got things working right by putting one in the system, I googled "ballast" at the msdigntion.com/forum site:

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and came up with a whole slew of posts regarding using a ballast resistor to compensate for the low primary resistance of the MSD coil when used on a mechanical distributor ignition that uses a magnetic or Hall effect pickup and electronics to fire the coil. The primary of the MSD coil is .7 ohms and the replacement stock coil that I had been using was 1.7 ohms measured with a digital meter.

MSD mentions nothing in their instruction sheet for the coil or ignition about using a ballast resistor except when points are involved. Neither is this info on any of the pages of their website except buried in the forums in answer to questions of people who are trying to install their units. So, according to the advice of the MSD techs, I did the correct thing, but it sure would have been a helluva lot less time and nerve consuming had they discussed the need for a ballast resistor in a non-points distributor in their instructions.

In all the advice to people asking about this the techs would invariably state that *NOT* using a ballast resistor could result in the failure of the electronics that fires the coil in non-points systems. You would think that a company like MSD would be more thorough in explaining in their installation instructions the correct way to wire up their units without causing damage to your vehicles electronics, but here we are.

I'm glad I held off buying low resistance wires. It didn't make sense to me that they would correct the problem I was having.

Reply to
Jack

Jack

Read Dans' reply more closely.

I would suspect that too much primary current just supersaturates the coil and it doesn't discharge properly, inhibiting the next charge/ discharge cycle.

Dan

Your post centered aound the ballast resistor selections. And Dans post says it all. Perhaps things would be improved by a RF coil or choke with a resistance of the same ohmage as the ballast resistor you have determined to work well.

The secondary voltage is not really effected by the plug and or wire resistance. Perhaps by their construction. The signal at the plugs is really a complex Radio Frequency waveform that without a good scope can not be interpreted. The usual monitor scope found in the garage is not up to this.

And finally the manufacturer of your ignition should probably not be in businees at all. They know little if anything about ignition systems. You vehicle manufacturer should be relied on. Contact their high performance folks for advice and guidance. Undoubly the manufacturer maximized the performance of your original ignition.

Bob AZ

Reply to
Bob AZ

The vehicle manufacturer, Chrysler, is the one that stuck me with an electronic feedback carburetor for which I cannot buy a replacement mixture control solenoid.

Do you really think they would grace me with advice and guidance?

Get real.

Reply to
Jack

Jack

All things considered I do believe the manufacturer is a good source. I have contacted Chrysler myself and received good advice. And after a long evening conversation with a Ford Ignition Systems Engineer I am more aware of the choices that the manufactures make.

Remember I advised to contact the manufacturers Performance folks. They have a periodic magazine that is available by subscription. I read all the issues at the dealer while getting my car and truck serviced.

Chrysler, Ford and GM do make decisions as to whether parts ar available and for how long. I did own a 87 Chrysler 5th avenue for a number of years and I would expect to be able to locate whatever I would need for it. Might take some time but if the demand is there the parts are usually available.

In another instance just this past year I needed a fan blade for a 64 Dodge PU and the Chrysler dealer bent over backwards to locate one for me. Took a few days but they called when they had the blade and there was no charge.

Bob AZ

Reply to
Bob AZ

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Shouldn't you be using figure 4 for your truck, unless you have switched to a points distributor ? Have you tried wiring it using figure 4 to see if it would run any better ?

Reply to
Mike

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That's what I thought when I first got the unit over a year and half ago and that's the way that I first wired it up. Didn't start that way. I got nothing but cranking when I turned the key to start. Again, MSD is totally remiss in their instructions about wiring up a *Hall effect* pickup as opposed to a *magnetic* pickup. One has to dig into their forums to discover that a Hall effect pickup is wired the same as a points system and not as a magnetic pickup system.

Notice that a Hall effect pickup is not mentioned in the wiring instructions. However, preceding the Figure 2 diagram is a key to the colored wires of the 5900 unit. Notice that the white wire is for "Points or *electronic ignition trigger*". On my truck, 87 Dak with 3.9L engine, the Hall effect signal from the distributor is sent to the spark control computer where it is processed and amplified and then sent to the coil. This is the same signal that a points system sends directly to the coil and, after much frustration and finally an email to MSD, I realized is the "electronic ignition trigger" referred to in the instructions. Both are to be connected to the white wire.

I can only assume from the wiring setup in Figure 4 that the signal from the *magnetic pickup* is already processed with spark advance information inside the distributer, as there is no provision for it once the wiring harness from the distributor is disconnected. The 5900 has no timing processing, just firing from a signal fed to it. This puzzled me at the time that I tried to use that wiring scheme, but it seemed like the one to use at the time.

The following from an MSD tech spells out how to wire up a Hall effect pickup to an MSD ignition. The unit is different from the 5900, but the principal is the same:

"If this is a Hall Effect Pick up, then you can use the white wire of the MSD Unit. The white wire is an input that can be triggered through a point or amplified style pick up, such as a hall effect. The other method is a magnetic pick up. Thanks, msdtech2"

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Reply to
Jack

Bob, you'll have to excuse me for being a jaded. I bought this truck new and have taken very good care of it. That fact that I cannot buy a $60 replacement part that is crucial to running the truck has caused me seemingly unending problems.

How would one find these "Performance folks" on the net?

Reply to
Jack

If I remember correctly I called them from a number I got at the dealer who had their magazine in the waiting room. I would go to the Dodge site to locate an internet address for the Dodge Performance people. Or ask at the service counter.

Bob AZ

Reply to
Bob AZ

You might also try these guys.

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Reply to
NapalmHeart

And suppresses "ringing" in the circuit.

And given the fact that the electronics that drive the coil are basically analog amplifiers, it changes their output current profile directly too.

Reply to
Steve

Well, they can't keep EVERYETHING in production forever. I rather doubt that I could go to a Chrysler dealer and buy a carburetor for my 1949 Plymouth Club Coupe, either ;-) Everything becomes obsolete eventually, and you have to come up with acceptable replacements.

Chrysler's performance aftermarket segment (Mopar Peformance) can be found at

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But frankly, they're not nearly as helpful for the old-school carbureted guys as they used to be. They're too busy selling crate versions of the new Hemis for people to retrofit into their muscle cars (not a bad idea, but its gotten too dominant for my tastes). And on top of that, you're looking for parts for an 80s 2-bbl v6, not a 1969 440 Magnum.

I'd take a look at places like:

Manciniracing.com Edelbrock.com Summitracing.com Jegs.com

Just off the top of my ol' noggin ;-)

Reply to
Steve

Reminds me about the old joke about the man talking about his axe: "Yep

- I've had this axe for years - best axe I've ever owned. All I've ever had to do to it was replace the handle twice and the head once."

Reply to
Bill Putney

Thanks Steve, but I got the damn thing figured out.

I can understand the Mopar guys wanting to go where the money is.

These electronic feedback carbs must have gone on a gazillion cars and trucks and those who bought them are left holding the bag.

But I got the non-feedback version of the Holley 6280, which is a 2280, and finally got the MSD setup working right with the addition of a 1 ohm ballast resistor to bring the MSD primary on the coil up to 1.7 ohms, same as the stock coil, which seems to have made everything okay. The damn thing runs better than new. I'm pretty sure it will pass smog, with a little denatured alcohol and 2 degrees retarded timing.

Now that I have it running perfect, I want a new one, or at least something with fuel injection.

Reply to
Jack

time was when chrysler was famous for keeping replacement parts for everything forever (more or less) but they had to dump this policy after the near bankruptcy in 1980 or thereabouts. too bad.

Reply to
z

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