Please understand that when I said Blow Hards, I MEANT IT 100%. I said it not as a knock on anyone in particular, but more as a compliment to Henry Schmidt. Henry is the complete opposite of a Blow Hard. When he talks actual knowledge comes out that more often than not is of real benefit to anyone interested in 911's. That's why I am here, real world knowledge that relates to Porsche 911's. Keep in mind, this is simply my experience and my opinion. Have a great weekend.
Bryan

Still not sure of your Blow Hards definition. I agree Henry is a hell of guy due respect.

Here is my blow hard:
http://media.putfile.com/Revs-91

I notice you edited your comment. "seem"

You ask about mindless banter, this whole statement is unnecessary and only fans flames of a non-existent fire.

Your electrical contribution is welcome and valued but personal inputs like this are valueless.

Now for the rest of your tirade, to paraphrase Shakespeare:
"Me thinks thou protest too much "

By editing and removing inflammatory posts can you limit the fallout. Good job.
http://forums.pelicanparts.com/uploa...1171130914.gif

Listen clearly, It is not an attack on Henry. It did not usewords like "mindless banter" or "meaniless" "tirade"or "BS and it did not offer a challenge, Mr. Turbo_pro. I clearly gave you some concessions today as a gentleman. Although, it was not deserved by you.

I made an observation that you can't deal with. Not intelligent enough to let by gones be by gones?


I don't care what you think. My analogy, "sorry not Shakespear" Don't let your bull dog mouth get your tiny little A$$ trouble.

BTW, Mr.Turbo. I edited my reply as a means of offering a hand shake, men do that. First, I don't expect any fallout and there were non, if that makes a difference. I can't imagine anyone expecting me to take (quote me) "your trash talk". If so, so be it..

People should be able to have opinions and disagreements. I stand by my first comment! As I said before, it is clearly not any attack and not meant as one. If anyone can twist that reply as one of an attack, give me a break.

Now back to you Mr. Turbo. Yours was a direct attack, and for what? Let's say I was in error. Hey, I have a history of disagreements with Loren. Doesn't mean that I don't respect him and vise-versa. And, we did get over it. So OMG, I said' lets get over it" the horror the horror I'm amazed.

You have no credentials to tell me what is welcome here. Go look in the mirror and say " are you talking to me" Yes I am!

Faning the flames? Yes you are. As a matter of fact, my neighbor had a field fire today. It was rather serious and threatened my property and house as well. I ran over and together we were able to put at the fire before the fire department got there. Your analogy was rather timely.

"With respect to triggering two MSD Blaster II coils with one MSD 6AL cd box, the MSD technicians say that there are no problems what so ever."

So! The statement from MSD most likely implies that their unit will work and
not be damaged by using two coils. But I really doubt that they have fully
tested this setup for twin plugs on a Porsche under ALL conditions; e.g. engine
loads, temps, compression ratios, & etc. The use of twin plugs is to lessen the
likelihood of detonation. And without PROPER spark voltage and energy levels
to BOTH plugs, there's no guarantee that one will have an adequate true twin
plug operation.

Just because something appears to work, DOESN'T imply that it's working
properly based on the design goals or system requirements. The same analogy
can be applied to using aftermarket fuel injectors. Just because the engine
"seems" to run O.K., doesn't imply that the fuel charge is proper nor does
it imply that the ECM can adequately drive that injector and NOT sustain long
term damage.

As mentioned before, Porsche could have used a simple 2 coil & single CDI system,
i.e. It would've been cheaper, but they used two inductive discharge ignition
systems. That type of twin plug system ALWAYS assures that each plug receives
adequate spark and energy under ALL conditions.

Bottom line: It's rather naive to assume from a supplier, i.e. a MSD, that its
product is being used properly for a given application without an explicit technical
writeup which has fully tested the product in the final application.

I understand now "Positively" the issue here. I have read plenty. Do a search on username "Henry Schmidt" and read. Notice the cronies "you'll know who they are."

If cronies equals fans, then you'll find there are more fans than you can count.

Do a search on Supertec and Henry Schmidt and you'll get actuate information from one of the best engine builders around.

I do those very searches and unfortunately Henry has chosen not to post as often because mindless post about personality rather than quality Porsche information.

Read again boy, you are little defensive concerning Henry which I have clearly said is due respect. He is a great engine builder. What more do you want? My issue is with with those interpreting and disrespecting others posts.

I just wanted to expose you so thank you for the confirmation. It didn't have to be this way. It was your decision. Henry can defend himself, which is apparent.

Time to unsubscribe from this thread as it is no longer relevant to the topic.

Agreed,
As I also said, I recommender to the thread starter to go with piece of mind and go with twin MSD's(another twin-plug thread) because he wanted to extend his plug gaps. Last I heard from him, that was what he was going to do.

I haven't understood this thread since...

OK, everybody....


http://forums.pelicanparts.com/uploa...1171153153.jpg




group hug....

I have to add my two cents to this one. I'm not saying anyone is right or wrong or recommending anything I just want to see if you guys agree with my analysis.

This is how I think an MSD or CDI ignition works.

• A self resonant, switch mode powers supply boost converter charges a capacitor up to about 400 volts.
• When the trigger pulse comes in an SCR applies the capacitor voltage to the primary of the coil, which in this application is used as an auto-transformer with a 1:100 turns ratio.
• Energy is not stored in the coil as in a conventional ignition it just passes through it.

This is how I think the physics behind a spark works.

• You create a high intensity electric field between the spark plug electrodes by applying a high voltage ( >12,000 ).
• The strong electric field accelerates all the free electrons, knocks other electrons free from other atoms in the gap with an avalanch effect
• This forms an ionized gas in which the resistance is drastically reduced and relatively conductive.
• The voltage profile of the gap would be the initial high voltage before breakdown and then the resistance of the ionized gas times whatever the current flow is (much less voltage).

When you simultaneously apply the stored capacitor voltage to two coils (and two plugs) in parallel I could foresee several problems that would interfere with the goal of equally advancing and converging flame fronts in the cylinder.

I think you can model the coil (transformer) and spark gap as a variable resistor. You can also model two coils and CDI as a capacitor connected to two variable resistors in parallel.
The variable resistor has two states (with transition between them).[list=1][*]The initial high resistance of the insulator in the spark gap[*]The much lower resistance of the gap after energy is added and an ionized gas is formed in the gap.[/list=1] The problem I see with this setup is

• Unless everything is perfectly matched one of the gaps will breakdown first
• When one gap breaks down enough energy may be bled off the capacitor (voltage reduced) that the other gap may not have a chance to break down
  In the model above one resistor would be a high value and the other low
• If there is a large difference in the density of the insulator in the spark gap one plug could fire and the other not

If the capacitor in the CDI is big enough this setup could work fine but it is not intuitively obvious that it would. I don't know how you would test and prove this.

Don't make me close this thread guys...

That said, there's truth in what Loren and Henry say, even though they disagree. Yes, the system used by Henry works and has been proven. Yes, the MSD techs agree that it will work (although my experience with them personally has been less stellar). However, if you want to do it the 100% way, then the two boxes are the way to go. Sure, the shortcuts will work, but you may be sacrificing performance or reliability. Loren basically said that in his followup post, and he is correct on that account.

On the other hand, Henry is also correct in that it will work and it does seem to work for his applications, although it is indeed nearly impossible to tell if the spark is weaker, or if it's not firing properly on one of the plugs...

-Wayne

The question: Viable TWIN PLUG solutions???.
It is easy to get caught up in the minutia of perfection.
Perfect is often the enemy of the good.
Does one cd triggering two coils work? yes
Does it work well enough for most applications? yes
Are there better systems? yes
Do they cost more? generally
Will most of us see a performance enhancement? My dyno tests show no performance enhancements by simply adding a 2nd cd.

A story about perfection.
I had a chance to work with some group C and GTP Nissan race cars a few years ago. During this time, I had an occasion to disassemble the fuel cell on the R90C and much to my surprise I found three Bosch 962 fuel pumps installed in the tank. An engineer at NPTI had decided that loosing a race because of a faulty fuel pump was unacceptable and he decided 2 was better than 1 and 3 was better than 2. In all my research I have been unable to find one example of a race car loosing a race because both the primary and back-up fuel pump failed. It could be argued that the attention and energy spent on running three fuel pumps might be better spent elsewhere. It would be impossible to argue intelligently that a street car needs 3 fuel pumps. Then I remembered that NPTI had a $35 million a year budget so they could search for perfection.
My question to all of you "what's your budget?"

BTW: In the early 90s, Nissan racing took the best engineers they could find and designed a 3.5 lt. v12 group C engine. They drew diagrams, employed theories and came up with an engine that made 470 hp. That was 200 hp less than the competition. The engine never saw the track because 200 hp was too much of a deficit to make up in development. My point: sometimes engineers and their theories are just wrong.

What could be clearer.

I appreciate the real life examples [why not use 3 CDs per coil ?] :). Experience always counts.

Great post Rick!!!!!!

Your technical explanation was right on.