One of the experienced and well equipped builders here could do an experiment- on engine, two ignitions, a dyno, and post results-couldn't they? Sure everyone's busy but it would be some valuable info to the group.

Id think the Co2 emissions could be different as well if there is less unburnt fuel? yes?

I'm not sure where this fits in the discussion, but, with emissions laws, manufacturers have more at stake than anyone in making sure everything gets burned before it escapes out the pipe.

It stands to reason then that more efficiency leads to not only cleaner, but more power per gallon.

On new cars, one coil per cylinder has become the norm hasn't it?

Like I said, I'm not sure where this fits into the MSD discussion other than new car manufacturers seeking to get a full burn.

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

Again, the key point is that next spark occurs too late!!!!!!!
It occurs .0015 seconds after the first which way too late
to have any effect. That's why the inductive discharge ignition, e.g. 911 3.2,
and used by ALL OEMs now yields better emissions.

Read here as calculations were done to show the ZERO effect of a 2nd & additional
sparks (post 48 & 59): http://forums.pelicanparts.com/porsche-911-technical-forum/657921-msd-benefits-3.html

Not sure what the point is. You have two choices in combustion without going into redesigns of the combustion chamber:
- Burnt
- Unburnt

There is no "kinda burnt". The variables involved that can effect efficiency of combustion are combustion chamber shape, point of ignition (multiple ignition points are one option), ignition timing, air/fuel mixture, charge pressure, charge pressure, and efficiency of atomization. Trying to light a fire after all the fuel in that spot is burnt doesn't make sense.
The only system where having 2 non concurrent sparks makes sense is a rotary where you have a leading and trailing spark in a really long chamber.
This points out well that if there was anything available in improvements from multiple spark it would have been jumped on by the manufactures.

The reason that the manufacturers all have gone to coil on plug is it is more reliable. It reduces the chain of parts that can degrade or fail. There isn't a problem getting an efficient burn but any time you can make the system more bomb proof the manufacturers will jump on board.

that may be one of the advantages of multi spark, which would be more noticable on a carbed engine where rich idle and hard cold starting could be a problem. i know on the 914-6 i built with carbs, fouling plugs at start up was always an issue, but i was learning about the webers with that car too.
with CIS you may never noticed if you have a bosch or MSD.

i have even had good custumer support from MSD. after my warranty for my unit was up, i suspected a problem with it. i sent it to them and they tested it for free.
problem was the coil, which may have been my original problem.

for someone to speak so negatively about a product that has not earned the reputation is not right. i dont know what motivatied this topic, but i am surprised it was by loren.

Loren is a troll. Look at this post:

http://forums.pelicanparts.com/6565817-post57.html

Scott

You do say in post 48, point #9 that the total burn time is 3.3-4.1 ms regardless of rpm and in post 1 here, the bulk of the pop is done in 1.5ms.

So the best that could happen is the second (1.5ms later) spark could ignite "something" (assuming something is there at the plug) but by the time the third spark occurs the party is over.

i talked with MSD. he said if you want to see the multi spark feature work, put the old system back on, run it and take a plug reading. then put the MSD on. he said the plugs will show a learner conditon because more of the fuel is being burned. i would think a gas analyser might show the same thing.

the higher voltage is there to keep the energy up. the MSD puts out about 100mjouls of energy per spark. that is the heat that ignites the fuel. i also have some paper work that states the output of energy.
electric fence chargers are the same way. they state their voltage but they also state the energy of their charger.

so it is like i said to wwest, the guys with carbs may see more of a difference than CIS, unless you have some oil fouling issues or other issues keeping it from running correctly.

Because of intake charge velocities, the movement of the charge is considerable within the combustion chamber. If it takes more than 3.0 ms for complete burn, why would a second spark at 1.5 ms after initial have no effect? The fuel is not completely burned yet and the charge is still moving in the chamber. To be precise you would need flame front speed as well as charge movement dynamics within the cylinder to say the second spark has no effect.

"Loren is a troll."

Here we go, like always! Now comes the personal attacks. Can't discuss the issue,
then attack the messenger, right? Sorry you wasted your money on a MSD, Scott!

"the higher voltage is there to keep the energy up. the MSD puts out about 100mjouls of energy per spark."

There's more than enough energy from the the Bosch CDI.
The Bosch CDI energy is: E = 1/2 C V^2 = 1/2 X 1.5 X 10-6 X 380^2 = 110 mj
The minimum energy required for ignition is 30mj.

You obviously missed my point.

If you take an equal car, put in a MSD and it burns cleaner with the MSD vs the Bosch with all other things equal, then you could argue that the MSD improves burn or the Bosch fails to burn.

Exactly. Measure Co2.

"If you take an equal car, put in a MSD and it burns cleaner with the MSD vs the Bosch with all other things equal, then you could argue that the MSD improves burn or the Bosch fails to burn."

OK, then do the test, i.e. everything equal - timing, AFR, spark gap, with multiple RPM points & loads.
The measurements are: HC - unburned fuel, CO - incomplete combustion.
The test needs to begin with Bosch CDI with all the variables set and unchanged other than replacing
the Bosch unit with the MSD once the initial test is performed.

Loren,

I have no dog in this fight. I use MSD. I am not switching to Bosch. If I had a Bosch core back when my permatune went out, I probably would use a bosch.

Rather than hypothesize based only on Labortory experiments where real world factors can not all be accounted for... why dont YOU link up with a professional with the tools needed (dyno, gas analyzer) and answer the question definitively. Its either yes or no. Otherwise, it looks like you are just trying to drum up business for yourself. I have no issues either way. Bosch makes great stuff. I have had no issues with my MSD.

This kind of wholistic testing will work better than a couple little graphs and statements that the technology is all crap or over hyped. Like i said earlier. Most of us dont use MSD due to to company claimed HYPE. i used it solely because I didnt have a Bosch core and needed something right away and MSD was basically the only choice. it has worked fine.

Thanks

In a twin plug engine running two coils and one MSD box, effectively cutting the current to the coils in half, a chassis dyno shows a 15 hp loss compared to the same set-up with two MSD boxes driving the coils at full current. There is a correlation between spark voltage and power produced. Mike Bruns has the details and the testing. Also, a wider gap means a bigger spark area which makes for a better fire starter. Unless the coil can produce enough voltage to jump that wider gap (Bosch cannot) gap will need to stay closer and smaller.

"There is a correlation between spark voltage and power produced. Mike Bruns has the details and the testing."

Don't think so! Sounds like smoke & mirrors put out to sell aftermarket ignition systems.
Let's see the data.

'Way out of line, TOO harsh.

Loren

How about being the first reply on this one; http://forums.pelicanparts.com/porsche-911-technical-forum/676515-oxygen-sensor.html

Part Number along with the Mambo Jumbo would be appreciated...

Maybe I can settle this...

Anyone dispute that 2 spark plugs for each cylinder provides an advantage?

Doesn't almost all, if not all, GA aircraft engines use twin spark plugs...??

If there is an advantage there then why not, given the induced swirling movement of the mixture, have 2 sequential sparks, or more, accomplish the same task? Ignite 2 areas of the mixture "simultaneously".

Hmmm...

Just realized...the I4 engine in my '93 Ford Ranger PU has dual plugs. Now why would Ford go to that effort absent a significant improvement..?