Nice Crack!!!!!

[Vintage911Racer]

HELP!!!

I have been chasing this problem for about the past year now. I have never really given it any thought until now. Here is the deal.

I keep cracking or blowing up my rotors in the dizzy!!! WHY. The car ran fine for the first 3 years without this problem. Have not changed a thing. Had the Dizzy rebuilt, changed wires, changed plugs, changed coil and it is still doing it. What I had to do was grind out the resistor in the rotor, place wire from contact to contact, solder it in, thus making a new rotor just by passing the resistor inside of it.

Now I do have a little background for you.

For the first 3 years the car had no problems. Changed to Hot wires for about 9 months no problems. Then I changed to the HOT Wire coil, with the hot wires, and BANG. The problem started.

SO I switched everything back, but now it is still doing it.
Why does this continue to happen. And it happens right away, within the first 5 minutes of running the car. I am tired of custom making Rotors.

Does anyone have some ideas????

Thanks guys

[Zeke]

Too much heat when you solder? Can you epoxy the jumper wire in?

[snowman]

What the hell is a dizzy???

Why remove the resistor, it doesen't hurt anything. As to power, it dosen't add power to remove the resistor or increase the spark energy. The only thing a hot spark does is to help prevent fowling at startup and low speed, and then only if you are using it as a daily driver. If you are then you should invest in a good cap discharge ignition system. SPARKS ONLY START THE BANG, they DO NOT MAKE POWER in an engine.

[feelyx]

You are probably getting a voltage spike to the coil for some reason. I would start with the charging system to make sure everything is up to par there before moving on to the ignition module.

Tim in Sac

[Zeke]

Originally posted by snowman
What the hell is a dizzy???

Uhh..distributor?

Why remove the resistor, it doesen't hurt anything

Aftermarket ignition systems like I had on my 914 race car blow out the resistors. They TELL you to get a solid rotor and if NA, jump it.

[snowman]

Sorry, dude, just picking on your slang.

As to the resistor, there is no reason for the ignition to "blow out" the resistor. The resistor does exactly NOTHING until after the spark has happened. then it just limits the current to a finite value, which is generally helpful. Again the extra ZAP enegy only helps burn off a fowled plug, not doing a thing to help power. This huge power spark plug thing only helps an engine that is running overly rich and keeps fowling because of it. Any modern engine should be running close enough to the proper air/ fuel ratio that extreem zapping of the plugs should not be required. If it is fix the fuel system, not the ignition system.

[Vintage911Racer]

ZEKE,

Since I have jumped the resistor, I have not had the problem. I just keep a few extra rotors with me in case one goes bad. I just made some new ones last night as spares.

I was just curious as to why the aftermarket ignition systems are causing the resistor to explode?

"to much heat when you sloder"

How can you tell??? I am going to solder some back ups I made last night, what do I have to look for when I am soldering to make sure I am not getting too much heat. I have not done this since Jr. High School.

[Zeke]

Originally posted by snowman
Sorry, dude, just picking on your slang.

As to the resistor, there is no reason for the ignition to "blow out" the resistor. The resistor does exactly NOTHING until after the spark has happened. then it just limits the current to a finite value, which is generally helpful. Again the extra ZAP enegy only helps burn off a fowled plug, not doing a thing to help power. This huge power spark plug thing only helps an engine that is running overly rich and keeps fowling because of it. Any modern engine should be running close enough to the proper air/ fuel ratio that extreem zapping of the plugs should not be required. If it is fix the fuel system, not the ignition system.

I'd like to see someone else chime in on this. I don't know where your info comes from, but I've never heard this before. I'm going by what I have heard, though. BTW, MFI engines tend to be tough to tune and seem to favor the rich side to run nicely. And the S cams I have tend not to help.

I have no idea why the resistor was designed in the first place and you don't offer that either. But, my guess is that the ignition systems some of us use, i.e., MSD with a hot coil, weren't around then. So maybe a resistor rotor is not needed anyway. I know a rev limiter rotor is not needed with an electronic ignition, and the simple ones are a hell of a lot cheaper.

[Vintage911Racer]

Milt,

Where can you get an Rotor without the resistor in it???? Do they make them.

[klatinn]

Hi,

Here my $0.02 worth:

The resistor in the rotor is there for 2 reasons:

1. Reduces radio interference
2. Lengthens the spark duration

When an ignition fires, the high voltage is required only to jump the spark gap. Once the spark burns, the voltage over the plug is only a few hundred volts, not thousands. The ignition system stores a finite spark energy in the coil (conventional ignition) or a capacitor (CD ignition). The less resistance there is in the spark current path, the faster that energy discharges. You can get the spark duration so short that it does not ignite the mixture reliably. This is a problem specially with CD ignitions that have a very short spark duration (<50usec) in the first place.

Regards,
Klaus

[john walker's workshop]

a vw bug rotor fits the smaller 911 distributors. the bosch rotor has a resistor, but some of the napa style repops may not have one.

[Vintage911Racer]

Klaus,

WHAT??? THis is a race car so radio interference is of no concern. I am running the Crane Hi-6 Ignition system with the Crane PS-91 Coil.

I have run the Rotor with the bypass on the resistor now for the past 2 seasons and have not had any problems. Car runs GREAT.

I put in a new rotor to run a test, and Bang it went. I have heard from several mechanics, that this is commom with aftermarket ignition systems.

Does BOSCH have a NON resistor Rotor, or does anyone have suggestions on what rotors to use, or do I need to perfect my Soldering skills?

[mskala]

Originally posted by snowman
...As to the resistor, there is no reason for the ignition to "blow out" the resistor.

Umm, excuse me, but there are RATINGS for power and
voltage on electronic parts, and if you run a 'hotter' system
with original rotor then yes, you will break things.

A few years back I had changed rotor on my Golf with a cheap
Autozone part. Wondered why a few weeks later the car
would barely start in the wet. Resistor was charcoal. (Probably
not up to OEM standards). Put back old OEM VW part and it
worked fine again.

Back on topic: I can't see why it would still happen once all the
OE stuff is back on the car. If you're running the Bosch CD, maybe
it was hurt by using the aftermarket hot coil. For my car I
remember people saying only use the OE coil, if you use the
cheaper bosch blue coil the CD is in jeopardy.

Mark S.
'70 914-6

[126coupe]

get me the part # on your dis I'll go to SSF and get you a non rev limiter rotor, and mail it too you

[Vintage911Racer]

Mark, I am or was using the Non rev limiter type. No matter what one I put in there, I blow up the resistor. So I just by pass them.

[snowman]

Klaus and Mark S. are correct. I am an electronics design engineer, consultant, with 30 years real world design experience, mostly military, but also commercial, communications, ham radio, GPS both receivers and space apps, missiles, munitions, radios, and misc applications, in the most severe environmental conditions possible, ie -55 deg C to Plus 120 degrees C operating, 100,s of G's operating, 1000,s of Gs inpulse, salt spray, humidity, rain dust, sand, ice and snow, scortching heat and worse. I also have a bsee and msee in electrical engineering. I would go to a modern ignition system, such as motec or electromotive if rules permit. Note the key word, SYSTEM. That means every component is designed to work togather. You can't just change one component and expect all the other components to survive or work porperly. The main benefit, of a state of the art ignition system, is more precise control of ignition curve, a good rev limiter, repeatable, high energy spark of the proper duration. All good for good low emmissions, but almost no impact on power. I personally think most of the other stuff out there, esp msd is just bs and marketing. The only real benefit of these ignition systems is to a street car, not a race car. Why? well they prevent fowling of the plugs due to all the bad things people do with their street cars, allow use of no octane junk gas without detonataing your engine and so forth, almost none of it applicable to a properly kept race car. A good set of points with a conventional ignition can make a race engine make exactly the same power as the most exotic system anywhere. Precise control of spark, knock detection and so forth are useful, but again mostly in a street car. Why? well you don't put pump gas in your race car do you? You put 110 octane or better (consequently not much worry about the knock detector) and so forth.

AN additonal comment, mostly pretains to Porsches, becaust they are air cooled and especially subject to detonation as a consequence of the higher cylinder temps. A lot of Porsche people run their engines un necessarily rich, why? because its safer. If you don't have a good handle on your air fuel ratio, the safest way is to run it rich, You loose a little power, but at least you don't burn it up. As a consequence many Porsches are subject to plug fowling. this in turn necissitates an overly hot ignition to keep the plugs clean. Proper way to fix it is to fix the AF ratio, but thats HARD to do, so the simple way is to do it, wrong, and compensate. So knowing that Porsche racers tend to need hot ignitions, whats the best, hot ignition? I would go with electromotive, with a coil per cylinder or motec with the same coil per cylinder. these ignitions produce a spark that will burn thru anything, and keep burning long enough to fire any gas that happend to be in the cylinder. NOTHING else can do what these systems can, esp MSD. As to those old folks who think a MAGnito is the way to go, thing again, those mags take a lot of hp to do what a modern system can with a lot less loss.