Posted by QKRTHNU (firstname.lastname@example.org) on May 08, 1998 at 12:57:27:
I have read up a bit on ignitions systems in the past. I realize that on a stock car or even one with basic bolt-ons and aftermarket ignition does'nt help out that much since there is'nt a need for a more powerful ignition system. But then once NOS or Forced Induction comes into play the Ignition system becomes critical.
My question is concerning the different designs for an ignition system. Most companies like MSD and Crane use Capacative Discharge setups. Then Jacobs Electronics uses Inductive Charging. I thought that the Inductive charging setup sounded pretty "Intelligent" compared to the real basic CD systems.
What are the advantages/disavantages of these two designs or do they both function equally as well?
Posted by T.O.O. on May 08, 1998 at 21:14:26:
In Reply to: T.O.O. - Ignition Theroy posted by body on May 08, 1998 at 12:57:27:
The ignition systems which come from the factory are very good these
days.....you must remember that the law requires cars to pass all emission
standards for 50,000 mi.
Most factory ignitions are of the inductive variety, and provide adequate voltage for an adequate period of time to do a reasonably good job of lighting the mixtures they run at "normal" cylinder pressures.
The capacitive discharge units provide a very quick rise time and the leading edge of the "spark" is almost vertical, as opposed to the curve from the inductive unit. CD's problems were always the fact that the duration of the spark was very short, which often cancelled the gains from the increased voltage.
Autotronic Controls Systems changed all that when they introduced the MSD-2 in 1973. Crazy street cars like my BOSS "494" Mustang were so radical that the normal procedure was: start the car and sit in it with the engine at 2500 rpm until you achieved operating temperature, ad only then would the car idle on it's own. I ran plugs that were 2 heat ranges hotter than the factory called for, and they needed changing every two weeks (fortunately they went through the center of the valve cover).
I went to El Paso to check out some of the "things" Autotronics was supposedly doing, and I brought back their "new" MSD-2. I removed the CD that ran best, and installed the MSD with stock coil. The first time I started the car it lit off immediately and was so smooth that, just for the hell of it, I let off the gas....and it idled soothly cold.....big change. After some "tuning", I went back to the cold plugs, and those things could be driven for 6 months before you'd get a misfire!....big change. The car also had an aluminum flywheel, and typically, I had to raise engine speed to 2500 rpm and slide the clutch to get moving smoothly or it'd bog and die. With the MSD, I could side-step the clutch at idle, and it'd pull away smoothly....big change.
The MSD provides a series of very intense "sparks" over a twenty degree period of crank rotation, and we quickly found that in the mileage/ emission programs we were involved in in the mid to late '70's, the MSD ignition was a critical component when running lean, and clean.
I have absolutely no affiliation with Autotronic Controls anymore (I won't go into that), but, as much as I'd like to, I can't find a commercially available ignition that's even worth considering. There will be some new "forms" of ignition you'll be seeing in another year or two, but until then, I hate to say it, but you're wasting money on anything else.
The other guys all have well packaged units and slick brochures, but if you study them, you'll find that the advantages they offer mean little in the real world, and they really don't compare apples with apples. All I can say is that the first one impressed the hell out of me, and, as I said, I can't find anything that works as well today either.