I had an MSD last 7 race weekends. The Bosch on my SC has lasted 34 years...

Okay, I'll play some more....

The MSD in a Porsche Cup Car comment is just plain ridiculous and self-serving. Why? Because Cup Cars have highly integrated electrical systems designed for the race track. Anyone with enough money to run a Cup Car is going to run the correct Porsche components. I doubt you could use an MSD ignition unit of any type even if you wanted to.

MSD ignition units just plain work. Go to any race track hosting a club race anywhere and you will see MSD ignition units installed in many cars with engines that cost anywhere from nothing to $50,000 or more.

I have no idea what your motive is here, but anecdotal evidence shows that MSD ignitions do what they are supposed to do and are reliable.

Scott

I'd venture a guess and say higher end racers use some variation of the coil-on-plug ignition technology.

There are a lot of older "higher end" engines out there not using coil-on-plug setups.

Scott

??

"I have no idea what your motive is here, but anecdotal evidence shows that MSD ignitions do what they are supposed to do and are reliable."

The technology has no merit! Where are the data? The MSD is just another CDI system
with less merit than the Bosch CDI. And just because the lemmings follow the naive,
doesn't lend credibility to a product. There're are a lot of automotive gimmick products
that sell and sponsor race teams, e.g. Bardahl, Slick 50, etc.

"Additionally, the spark pulse width of 40 microseconds is half of the Bosch CDI
which results in less time to fully facilitate complete fuel charge ignition resulting in
potential mis-fires and greater emissions."

"potential mis-fires"

And again, that's why all OEM ignitions now use inductive discharge ignitions which provide
longer ignition pulse durations than a CDI. If you use a MSD because of the multiple sparks,
then you must lend some credibility to a potential of an inadequate spark duration necessitating
an additional spark. But too bad the additional sparks of the MSD have little to no effect to
resolve the potential problem.

it is fine with me if you want to avoid my questions

you should also let people know that your work involves repairing Bosch units, so you are not exactly unbiased here

nonetheless, what you posted might indeed be correct - I would just want to see some actual data on misfiring and emissions ...

Both ignition systems work well, but for me they have different advantages. The Bosch is probably more reliable (although they are very old now). The Bosch works well for a stock street car and will allow longer life of components such as rotors. The MSD is cheaper, more available, can support a bigger spark plug gap (this will ignite more marginal mixtures and produce more power at a given advance). I like having a rev limiter I can set as well. I think most of us know all this and have chosen the ignition to suit our needs.

-Andy

Business must be slow... otherwise whats the point? Its all old news. As with most of these things we use them for a variety of reason and Loren shouldn't assume it has ANYTHING to with Company sponsored HYPE. For me, I had a bad permatune. Didn't have a Bosch Core. And didn't want to spend 2k, because I didn't have a core. Had nothing to do with company claims.

Comparative spark pulse signals using a MSD Blaster coil. The first image is the
MSD pulse followed by the Bosch. The vertical scale is the same for both but reduced
by about 45%.

http://forums.pelicanparts.com/uploa...1336449614.jpg
http://forums.pelicanparts.com/uploa...1336449634.jpg

You seem to forget, or neglect, the fact that firing a fouled or partially fouled spark plug is most often overcome by increasing the spark voltage risetime. And by pure chance(??) that is EXACTLY what results from the use of 450 volts sv 300 volts applied to the primary does. The "desired", target, primary current flow level, and thereby the magnetic field within the iron core, reaches the firing voltage level much FASTER.

"And by pure chance(??) that is EXACTLY what results from the use of 450 volts sv 300 volts applied to the primary does."

The key factor is the dv/dt of the spark pulse and not absolute voltage. 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. Now days with COP OEM
ignitions systems the max spark signal is about 300 to 350 and NOT the unnecessary 450+ volts
of the MSD. With coil turns ratios of 100 to 1, 20KV to 30KV is all that's necessary.

I don't understand....

The bottom display is as I would suspect, the primary voltage rises to the point wherein the plug fires and then the waveform drops to the level dictated by the coil secondary "fired" resistance (plug resistor, gap voltage drop, HV resistance wiring, ETC)of the secondary during the arc sustaining period.

The top display indicates the faster risetime, expected, but that following "flatline" is ratty enough to indicate an actual plug firing, TOO FLAT.

And WHAT was reduced by about 50%...?

Having build numerous versions of both, mostly for a '63 T-bird, I am well aware of the short-comings of a simple transistorized "switch" to replace the points vs an actual CDI. PNP transistors with the current handling capability required were pretty rare, expensive, and "fragile". If I remember correctly a 300 volt POWER zener was used to prevent the inductive kick of the primary from exceeding the breakdown voltage of the PNP. That 300 volt limit required a specially build ignition coil.

The biggest problem I had, remember, was finding the correct ohmage and power resistor to limit the current flow that was reliable enough in the long term.

Once I converted the system to CDI I built several for friends.

I actually turned the Ford distributor cam down on a lathe so I could make use of the magnetic trigger Chrysler introduced later on.

And the rise time of the PNP transistors were most certainly not any worse than the "condensor" used to limit the inductive kick risetime and prevent voltage flashover at the points as they opened.

Not being aware of the actual design of todays "coil on plug" inductive ignition I would still bet that they apply a fairly HIGH voltage, inverter supplied, to the primary but regulate the current flow level by lowering the applied voltage once the design current flow is attained.

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 dont know if the multi spark function is a gimmick or it actually has "some" advantages, maybe not all the time but just perhaps, there may be times when it helps.
but i do know everthing else you have said negative about MSD is highly skewed and biased and to say these things about a product that you have no other proof of being a bad product on a board for people that dont know any better is not right and personally i think is bad for your buisiness. i know i tend to shy away from someone that tells me how much another product sucks.



dont get me wrong, i am a VERY big fan of the bosch. if you had valid proof that the bosch was that much better, it would be different. for that matter, no one could even figure out which is more reliable because there are people that have had good luck with both and others have had bad luck with both.
if the bosch was perfect, you would not be repairing any bosch units and bosch CDs having been going bad since they have been putting them in cars. its not like they are just now starting to go bad.

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.:cool:) 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.

It is my belief that the purpose of the 450 volts vs 300 volts is to more rapidly overcome the inductive reactance of the coil, FAST buildup of coil internal magnetic field, and thereby have a much faster risetime at the plug gap.

Plus I suspect most any plug would have fired long before reaching the peak 45,000 volt output seemingly dictated by the input.

And...

Suppose the plug is fouled with gas or oil or a mixture of same...by the time you get to ignition pulse #8 the probability that the plug has now been "unfouled" would be pretty high, would it not...?

Since the ignition fires at roughly 28 degrees before TDC, the compression process is still under way. The mixture is moving and turbulent. The flame front can sometimes be slower than the mixture movement in the cylinder and head and multiple sparks help ignite the total mixture quicker.

I think that IS one of Loren's primary arguments as noted in his initial post.

I buy into this, especially with swirly top SC pistons and at lower rpms.