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

 

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.

 

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

 

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.

 

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

 

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

 

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:

http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=ballast+site:msdignition.com/forum

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.

 

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

 

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.

 

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

 

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 ?

 

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"

https://www.msdignition.com/forum/showthread.php?t=653

 

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?

 

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

 

You might also try these guys.
http://www.manciniracing.com/

 

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.

 

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 http://www.mopar.com/performance/index.html

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 ;-)

 

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."

 

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.

 

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.