Quote:
Originally Posted by Lorenfb
. . .
And again, that's why all OEM ignitions now use inductive discharge ignitions which provide
longer ignition pulse durations than a CDI.
. . .[/B]
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Quote:
Originally Posted by Lorenfb
". . .[/B]
Do a little research into why a CDI was used versus an inductive discharge is the late '60s, i.e. because the rise time
(key for firing fouled plugs) of transistors back then were limited.
. . .[/B]
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Quote:
Originally Posted by wwest
Again, having enough time, virtually limitless time in comparison, to precharge each "coil on plug" inductor, removes the previous limiting factor for inductive ignitions.
WHOA...!!
Are you of the mind that these new COP ignition systems are NOT inductive ignitions..?
http://www.wellsve.com/sft503/counterp_v4_i3_2000.pdf
You should also be aware that with an inductive ignition system the coil turns ratio has nothing to with the level that the secondary voltage will rise to unless/until limited via an arc being initiated. 100K volts would not be unusual for an internally well insulated coil. |
I think it is pretty clear that Loren knows that they are inductive devices and has stated so. He is simply educating people on why
once upon a time CDI made a viable choice because of limitations in the available transistors.
I have found a lot of this really educational and the point that the second pulse comes so late is fascinating but I have have a much simpler argument why MSD is totally unnecessary and it applies to a much wider range of what people do with the ignition system on a car.
Here is the big defining reason in a nutshell:
You can't get more burnt then burnt.
A fun quote from a guy I used to build race cars with: "
If more is better then too much is just right!". It encapsulated a lot of things like why we were awake at 3 AM still working on the car, but it also had something to say about how to analyze the cars that we were racing against. A lot of them had WAY more resources but a lot of that was used on things that didn't make a difference. If we could keep them dumping time and money on useless stuff then it gave us more chances to level the playing field.
(
We put more then one fake device on a car so they could waste time "playing catch up".)
One key area that people waste money on is ignition. The description of the ignitions job is pretty simple:
Start the fire at the correct time.
If you have a good quality triggering system, an adequate spark, a good pathway for the spark to follow, and a reliable spark gap then you have the problem solved. Solving a problem that is already solved isn't that smart. The MSD markets itself to solve a problem that doesn't exist if the previously list of necessary items are handled.
Back to
You can't get more burnt then burnt...
People buy items to fix things that aren't a problem and the fixes are very often worse then the original and often less reliable. The key attribute of these type of devices is that they are "
cash flow devices. (
Quote happily stolen from Jerry Woods.
) They are designed with the basic rules of patent medicine applied which is: can I make something about it
sound interesting, new, and plausible so I can get someone's wallet to open itself.
Ignitions are a great place for this kind of junk. Split Fire plugs, Nology plug wires, MSD ignitions... All of these devices are claiming that they are basically capable of getting the air/fuel mixture to be more burnt then burnt. If the fire was already lit then why are you needing to light it again? If it didn't light the first time then why would you try to light it again instead of just fixing the basic ignition system components that caused the failure?
I do see a use for some MSD products and it was partly listed here: Rev limiting and boost retard. The MSD can allow the hobbyist to add these features to a car for reasonable money. There may be better ways to accomplish these tasks but I've never looked into it and these would be on the table. I would still expect an after market system to be less reliable. But it would be a trade off to get a feature that might not be available a simpler way. There isn't any aftermarket company that can afford to do a fraction of the R&D that any car manufacturer does. Factory stuff may be boring but it has more thought behind it then people realize.