Gosh, given the level of response I've gotten from my quiz in post #25 (exactly zero), I'm getting the distinct impression that ignition quizzes aren't particularly interesting.


Oh well, perhaps I should have made a thermostat quiz instead.

 

If you have points in the distributor and the dwell jumps around can that be a sign that the bearings are worn? If that is true would the dwell also jump around with a pertronix? PG.

 

Question #1
Answer 4 volts

Question #2
Answer 8 volts

PG.

 

No, but I respect your guts and willingness to try to tackle this engineering quiz.

If I may ask, how did you arrive at these numbers? (No criticism, just interested in how you were dissecting the circuit.)

 

Thanks for the reply, I used this formula:
E=IxR
E=voltage
I=amperage
R=resistance

Voltage divides across a restance. This resistance is in equal parts. Youmust find a common denominator (12 volts ./. 3=4 So one would be the common denominator. 1 ohm would have 4 volts across it, 2 ohms would have 8 volts across it.
12 volts impressed across a 3 ohm resistance ( 2 ohm ballast resistance + 1 ohm winding resistance) 12 /3 = 4

Ballast resistance:
8 = (12 / 3) X 2 ohms

Where did I go wrong?
I'm just trying to figure this out.
PG.

 

Now that would be fun

 

Your math and formulas above are correct for a series resistive circuit. I applaud your logic and detail.
Unfortunately, a points ignition system is a series circuit with, not two resistors, but a resistor and an inductor (which has some resistance internal to itself due to all the wire length in the windings). This inductance greatly complicates the math (and the current waveform).
My question was what are the voltages at the start of dwell. You have, however, correctly identified the voltages at the end of dwell. Due to the inductive qualities of the coil, the start and end voltages (and currents) are very different. This quiz is a simple attempt to explain why measuring the ignition system (with a voltmeter) while the engine is running will not give you an accurate reading of the voltages in the system, nor will the voltmeter reading explain the physics of the system.
I'll (temporarily) stop here at this point in the description so as to allow others to chime in with their thoughts on the quiz.

 

Hi Mike, no problem about criticism, I looked up a formula and took a shot at it. What do I know about a inductance in a coil? I am convinced that a resistance wire lowers the current and not the voltage and I think that was the point that you were trying to get across. We had some fun now lets move on.

Anyone have an answer to post # 42?
PG.

 

Without knowing what RPM the poster is talking about, inductive resistance is pretty DA*N hard to calculate in my book but, I guess that is because I'm a product of the California Public School system Your problem is missing a little VITAL information.

 

No, the RPM is irrelevant for this quiz. The voltages are the same at the start of dwell regardless if the engine is idling or at redline, and are only affected if the dwell time/burntime requirements overlap at high RPMs. It is the end of dwell voltages and current that are substantially different, depending on the coil risetime characteristics and the allowed dwell time at a particular RPM. I purposely phrased the problem in such a way that an answer could be derived by logic, and would not require a long mathematical formula (such as asking for the current and voltages at 12 degrees into the dwell period at 3700 RPM ). I'm trying to tailor this discussion for car enthusiasts, not engineers. (There's a bunch of additional "secondary" ignition issues that we could throw in to complicate the quiz, and I'm happy to discuss them, but it generally just puts the rest of the forum to sleep.)

 

Well, yes and no. We both agree that a resistor restricts/limits the current through a circuit. A side effect of this current restriction is a voltage drop across the resistor, proportional to current. This variable voltage drop is distinctly different in function and waveform from another type circuit that provides a lower voltage for other parts to operate in. This second circuit item, properly called a voltage regulator, provides for a constant voltage regulated output regardless of the current that is passing through it. Hence my frequent disagreements with some other posters that the ballast resistance regulates the voltage that the coil sees. The instantaneous voltage at and across the coil is changing continuously, up to the point where maximum current is reached.
(Please pardon the lengthy paragraph. I ended up typing more than I had planned, and the extra info is just for anyone who may be interested in the additional technical trivia. )
I appreciate your interest and willingness to discuss this topic.

 

Hi

If you have points in the distributor and the dwell jumps around can that be a sign that the bearings are worn? If that is true would the dwell also jump around with a pertronix?

This could be caused by a worn cam chain, by worn cam to distributor gear or even by a badly shimmed distributor lower end.
No, Pertronix will not fix this problems.

Rgds. Günther

Edit says: Thanks 69427 that your explanation shows a touch of Voltage info .

 

Here is my take. The pertronix will not fix a worn out distributor however in many cases installing the old original pertonix will make the engine run better. If the cause of the engine running bad was the points bouncing the pertronix unit is much more forgiving and will still fire accurately. I believe the directions use to state the distance between the module and the magnetic ring could vary up to .100 without causing a problem.
Installing the pertronix to correct for a bad distributor is just masking the problem and with the the money spent you could have just fixed your distributor.

How about Mikes Quiz ? I find this pretty interesting and of course don't have any idea how to arrive at the answer but can't wait to see what some of you come up with as answers.

 

Whats a good price for a PERTRONICS II module and distributor??

Thanks

Bill

 

JC Whitney used to have Pertronix pretty cheap but if they are the "LOBE" type I would not buy one.
Ecklers sell the lobe type.

 

On 11-11-03 I installed Pertronix IGN1181, bought it from The Paddock, paid $69.95.
With the points set the dwell was steady at 31* from idle to red line.
With The Pertronix the dwell became 34*, still steady from idle to red line.
35,000 miles later it's still good.
Did I get better mileage? No!
Does the car go faster? No!
Did I break even yet? Maybe!
Another excuse to take a long test ride? Definitely! PG.

 

too bad this thread went off topic...

Back to the original posters issue....

I have a 1971 Camaro 350 (engine most likely very similar if not the same as the 350 in a 1971 Corvette.)

I too was having Idle problems when I installed the Ignitor III unit and its Flame Thrower III Coil. It would run fine with the old coil, points and condensor, but no idle with the pertronix units.

I traced the + wire from the coil... It has "Resistance Wire" written on it. I routed a new pure 12v wire to the Flame Thrower III coil and to the Ignitor III module. I also installed the Pertronix FlameThrower III Dual Core stranded spark plug wires.

It idled better but still wanted to die. I backed out the 2 idle fuel/air mixture screws on the Quadra-Jet 2 whole turns.. Idles pretty good now. Not 100% satisfied with the Idle, but love the performance out on the road.

I think it needs more fuel at the idle because it has a hotter spark and the fuel in the cylinders are burning too fast to drive the piston. The additional fuel give it a longer burn time?

I have the timing set to 10 degrees. Idle at 630 in drive.

1971 Camaro 350
Quadra-Jet 4bbl
Crane Economizer Cam
Autolite type 26 plugs (.040 gap)
Pertronix Ignitor III
Pertronix FlameThrower II Coil
Pertronix FlameThrower Magx2 Plug Wires
(rest of the engine is stock)

Hope this helps. (sorry, I am not a Corvette owner)

 

Hello
Yes ther are c;earance requirements- go to mid america corvette and get the technical bulletion on the pertronix- I just put one in on my 68.