Spark voltage is not the principle benefit of the MSD ignitions. The primary benefit is multiple spark discharge (spark duration).

In our tests, using solid core wires (not suggested by MSD) we saw no performance benefit (up to 7400 RPM) using a second MSD unit. This is the functional red line on a 2.4/2.7 (70.4) crank so testing beyond that point was meaningless.

Quick side note from MSD tech assistance: "There is no voltage drop across the second coil. Even with two coils each coil receives 450 volts at all RPMs within the limit of the box."

Other reputable engine builders have made posts suggesting that in some configurations they have tested, there was a measurable difference in output between the one box/dual coil approach and two boxes/dual coil approach. These were apparently dyno tests. Of course, none of these tests are published with all of the pertinent details. But I believe that there can be a difference, depending on the variables. So sorry to suggest a contradiction to your experiences Henry.

My engine builder is at the top of the food chain, with decades of experience, and my application is racing. He has a lot of "area under the curve."

He uses the dual box/dual coil set up for projects like mine. I don't think the small financial benefit of a single box/dual coil set up for my project is in any way justified, based on what I have learned thus far.

And as far as "safety," I think I have a really simple wiring approach that can provide at least some warning if one of the two boxes has a failure. How this compares to the "built-in" safety one gets with a single box/dual coil set up is really something only MSD could answer based on statistical analysis of field failures.

In my experience, the boxes have been reliable.

And to me, a description of the benefits of MSD should include words like reliable, cheap and ubiquitous.

Sorry to hijack this tread.

But i am looking for the left side heater ducting, that Will fit with the twin ignition distributor. Engine 2.3 1971.

Where can i buy it.?.

Thx. Olsen

What your looking for comes on the turbo cars.

930 106 321 01

Da.. You guys are fast....:)

Thanks, Will this also clear the convert 2.4 distributor with Jag. cover.?

Thx. Olsen

I have a custom piece that will work.

PM me with your email for pics and price.

Hello Tom.

Thanks, I have Sent PM.

Thx. Olsen

Has anyone tried the new 6AL-2 Digital System?

Will this unit still operate 2 x coils as the instructions aren't very clear.

4 years after the question was asked by Chris, I have the same concern: can 1 msd 6AL-2 trigger 2 coils for a dual plug application?
Thanks!

This is so debated. I bought one 6 Al digital, but I recently saw some data of actual testing and it showed that 2 was the way to go.

2 or 1 box
 

I have been following this for a bit.I have an experience is 1975 with a Factory 3.0 RSR ENGINE that one CD box failed & the motor ran but was not as sharp for power.I have used 2 MSD Boxes for 40 years & never had a failure.MSD 6A.I have put SC magnetic pickups in at least 50 964 twin plug setup set ups with no problems because in 30 plus years my shop never had to replace a SC magnetic pick up for a non run situation.I had a few Electramotive failures with one bank failing & the performance was less than two working.I drive a G-320 TWIN PLUG Mercedes here in Costa Rica and I have a relay every now & then that only fires 6 instead of 12 & it is noticed because the truck weighs 6400 lbs.& makes only 168 H.P & IT FEELS FLAT.CIAO Fred Bottom line is 2 is better than one.

Oh yes. :)

Yes, so it has always puzzled me why MSD units don't multispark beyond 3400 RPM despite their name. For me the fun is just getting started at 3400 RPM in a 911!

That's why we designed our units to dual spark (with adjustable gap) up to 10000 RPM.

This is the sort of results we are getting. Motor is bone stock 69S, setup by Loren Beggs using one of our CDI+ units.

Thin green and blue is Bosch CDI
Thick green and blue is our CDI+ on standard dizzy.
Red and purple are CDI+ on standard dizzy with an 'overlay' map.

http://www.classicretrofit.com/media...s_combined.jpg

We think this is the sort of gain approaching twin plug and are dyno testing at the end of the month to make the comparison.

Jonny,

I see nothing here that shows your product to be superior to an MSD setup, much less a dual MSD setup in a twin plug application. Since this is a thread about using one or two MSD units in a dual setup, don't you think that would be useful information?

Or are you just doing more advertising for your product even though there is no direct application?

Really? As stated, our product is multi spark right through the rev range. MSD can't do multi spark above 3400 rpm. Also, at 1ms spark intervals it is my belief that MSD subsequent sparks are too late to be of benefit at higher revs.

Also as stated, we are about to embark on dyno testing to compare the results of running our true adjustabke dual spark (with adjustable intervals down to 200us) against a proper twin plug setup.

if the test shows comparable results, isn't being able to get twin spark type performance from a single box that looks and fits like a stock unit of huge benefit to the Porsche community?

I'm sorry if you see this as pure advertising. I wish we had the marketing budget of MSD and sold thousands of units per year!

Our product has been created from pure passion for the flat six, not to mention in conjunction with probably the #1 engine builder in the UK. As we have actually taken the time and effort to do these dyno tests, I thought folks might like to see them?

Beliefs, wishes, and passion are not hard cold facts. If you are not going to do a direct comparison against the two possible MSD setups, why post in the thread about MSD setups?

We are back at advertising again.....

Dyno plot is pretty factual isn't it?

I don't see a dyno chart with MSD units involved.

Hold off criticism of the twin plug MSD setup and stop pushing your setup over it UNTIL you have data showing you have something better.

Also, twin plug is about more than just power.