I never criticised MSD, just stated a common misconception about the brand name.

Personally, if I was buying what is heavily promoted as a multi spark system and it couldn't do the one thing it's name implies, I'd be pretty miffed.

This will be news to a lot of people which is what forums are all about, no?

Heavily promoted? No, not really.

It's right in the documentation so anyone that has read the documentation should know this. You should only be miffed if you don't do any research and then you should be miffed at yourself.

Again, it's clear you wanted to jump in an plug your product even though you had nothing of value to add to the conversation about using a single MSD or dual MSD setup when running twin plug.

This is a commercial website, it's very purpose being to sell products. That includes MSD products and Classic Retrofit products.

if you review the original post, Chris wanted to run a single box and get the benefit of multiple sparks. The general concencus was that he will need two ignition boxes.

What if his desire for a single igntion box solution outweighed that of twin plugging the engine and he still wanted to benefit from two sparks?

So Chris actually has two options to benefit from an additional spark:

1) Get the second spark at all RPM by fitting another box and twin plug the engine.
2) Get the second spark at all RPM from a true multispark ignition system.

Yes, I wanted to 'jump in' to say that another option now exists that previously didn't. Shame the water was so cold. :rolleyes:

That's not quite how it works. We don't want to see ads in every thread. In other words, every thread that mentions ignition systems does not need to have you advertising your product.

Chris did not ask about multiple sparks. He asked how to wire two coils to a single MSD 6425 unit. Others mentioned that you wanted to use two MSD units for two coils, which is quite true. Yes, someone did mention the multi-spare aspect of the MSD units, but it wasn't Chris.

Finally, a true multi-spark single plug setup does not do the same thing as a twin plug single spark setup. You need to get that straight right now.

^ I posted a dyno plot, hardly an advertisement.

Anyone care to post up a plot from a normal 2.0 vs a twin plugged 2.0?

Again, this is a thread about using one or two MSD units in a twin plug twin coil setup. It's not about the stock CDI or your CDI in a single plug setup. Yet, here you are promoting your CDI in a single plug setup....

Something has being overlooked here.

In a CDI system, the coil acts as a transformer not as a "normal" coil. All of the ignition energy that is used in the combustion process is generated within the CDI circuitry and stored in the capacitor.

So when you use 1 CDI for twin plug applications, (12 plugs) you are 1/2'ing the energy released.

Also, multi spark is a function that has no real benefit if the CDI used has any power.

In a distributor setup, multi spark has limitations. As the RPM's increase, the angular distance between the poles in the cap will limit the multi spark condition. You can fire the spark plug as many times as you can, it will make no difference if there is no energy present. It takes heat to start the combustion process and the level of temperature in the combustion process is a factor of the energy released by the Ignition system.

This statement is only partly true. It depends on the spark interval.

For example, the spark interval in an MSD unit is 1ms. This means, as you say, that the benefit of the multispark is lost in the higher rev range which probably explains why MSD units revert to single spark beyond 3400 RPM.

Our CDI+ unit has a tuneable spark interval and when used in conjunction with an original Bosch coil can fire sparks down to 200us intervals (5 times faster than MSD). The Bosch coil can recharge much faster than the 'Blaster' coil. The effect of this is that benefits are seen up to 7000 RPM and beyond as the second spark is still well before TDC. Our 2.0 race car test bed runs a standard distributor with points and revs to 8500 RPM.

We are only ignition manufacturer who has designed a system like this and we have dyno, road and race car data to back it up. The system has been developed and tested in collaboration with BS Motorsport and Historika, both leading 911 names in the UK.

Your point is well taken. However, multiple sparks will not increase the combustion rate (flame speed), cylinder temperature and cylinder pressure which in turn makes for more performance if the electrical energy released is low.

If cylinder pressure can be created in less crankshaft rotation, the more power is transferred to the crankshaft verses Cam shaft opening and closing events. Both when the spark is initiated and when the flame travel reaches the end gas verse degrees of rotation after TDC. The larger the chamber volume the more advance needs to be added along with more time to reach the end gas (ATDC) hopefully without any detonation. I can see that a second spark could help in some instances, but if the gas kernal around the plug has already being used, the end gas would be the the part that the second spark would ignite. But if the second spark has the same energy level or slightly less, I cannot see how it will help. I guess I don't understand how the second spark increases the cylinder temperature?

I can understand if the first energy released is very high, giving the highest electrical energy, which will turn the chemical energy of the fuel type used into highest mechanical energy.

If multi spark doesn't lower the performance any, why not. Ignition is the most important part of the whole process and the last process to take place before the combustion event.

The physics/chemistry is complex and I would not profess to know the details.

What we do know is that both a combustion analyser and AFR gauges both confirm that more fuel is being burnt.

Generally speaking, if an engine is running the correct mixture on a Bosch CDI and then CDI+ is installed (using the exact same timing), an exhaust mounted AFR gauge reads leaner. 'Correcting' the mixture back then produces more power.

The results are more pronounced on the early 2.0 engines which could have something to do with the domed piston design.

Well done.