How very true. You see that so often, be it on a motorcycle or car forum.

I am amazed at some of the conclusions arrived at without any measurement, etc.


I remember watching some of those misleading infomercials aimed at those who can't think...I guess I was bored one Sunday morning.

This infomercial was for an oil additive. A dozen "paid" (as usual) participants would gather around this in-line 6 engine that was treated with this additive previously, but now was running without any oil...and not seizing.

Of course there was no load placed on the engine, and to further impress the mindless masses, the valve cover was off and the product's commentator was spraying water onto the head...how nice of him to provide additional cooling.

I run twin plug with one MSD just fine with a turbocharged engine, i know if the ignition fails the engine will be saved if one of the coils fail well thats another story.



http://forums.pelicanparts.com/uploa...1336879989.jpg

coilshttp://forums.pelicanparts.com/uploa...1336880160.jpg

"..just fine..."

Put it on a dyno and test with and without the second MSD and watch your definition of "just fine" change. Cessna T210 engines run "just fine" with one ignition system "off". So does your's, apparently.

So now we're back to the original comment challenged by Loren; "more spark current = more engine power". Logic says one box splits it's current between two coils. Two boxes provide each coil with full current. Full current to each coil = more power. Loren says there is no correlation between coil current and engine power. Go figure...

What about these M&W CDI units ? They have units advertised as optional twin spark capability. Also, units designed for two rotor rotary engines which have two coils and multiple ignition events per "crank" rotation (very large demands on the CDI)



http://www.mwignitions.com/pg_cdi_ignitions.php




..

I do believe i saw tests that there was a little HP loss shown on the Dyno using 1- MSD to fire 2 coils compared to using 2-MSD's.
in my case, since i am not racing and have close to 400 turbocharged horsepower in a 2200 lb 914 the sacrifice of leaving a little horsepower on the table is not significant to me as is the safety of my engine..

JB Racing did dyno runs on a few different NA race engines from 2.0 up. Their results were about 15 hp with two boxes over one; 200 hp vs 215hp. Do you think in your case that you see spark on both plugs consistently? I would have to say definitely yes or the turbo beast would have popped long ago...

Having/causing 2 separate flame fronts advancing simultaneously through the "cloud" of A/F mixture is a much different issue.

For a CDI system the discharge capacitor size ("volume") is the determining factor insofar as spark "current"/POWER is concerned. Basically, the larger the capacitor the longer the spark, once "struck, will be sustained.

For a COP system the energy is stored within the coil internally therefore the greater the inductance (within reason) the longer the spark duration.

One of the major design issues for both is that with higher values the longer is takes to "restore" the charge after the spark. With the old, legacy, coil/distribitor system that was a very real problem near the RPM limit.

Engine damage due to detonation....dieseling.

It strikes me (purely accidental PUN) that if the engine parameters are so "tight" that the lack of a spark at the correct point in time would be detrimental is a non-issue. If the A/F mixture is heated so much by compression that its already right on the verge, edge, of self igniting then it seems to me that all a spark would do in precipitate that event.

Which says to me that the primary method of preventing inadvertent detonation in a high comression high performance engine is to run the mixture overly RICH.

In point of fact that is EXACTLY how the manufacturers of modern day engines that are designed to run on higher octane fuels can run so easily, non-detrimentally, on regular. Fuel with regular and the engine ECU will detect that such is the case and begin slightly enriching the mixture.

I completely disagree with this. The way the system accommodates poor quality fuel, extreme heat, etc. is by sensing knock and pulling timing out. In this era of fuel efficient engines and emissions, adding fuel is not acceptable and not very effective either. The added fuel particles actually RAISE the dynamic compression ratio and can make the problem worse.

It has been proven on many different side plug 2 valve engines (particularly air cooled engines) that adding a second plug on the opposite side greatly increases the ability to support more compression. Firing that second plug with full power is obviously very important if your engine is built to need it.

Someone finally responded with an intelligent answer; thank you.

but the problem is that we don't know at what rpm's a single box is unable to fire that second plug with full power -- the only test I have heard of was on a race motor at nearly max. rpm's (i.e. at the hp peak)

You know that detonation and dieseling are completely different animals, right? Dieseling is annoying, Detonation usually makes your wallet lighten considerably.



I'm still curious for someone who knows more about CDIs than i do to look at M&W's offerings and tell us if they are a solution for 1 CDI with 2 coils.

"but the problem is that we don't know at what rpm's a single box is unable to fire that second plug with full power"

At ANY RPM! The point is that with that setup a marginal spark system results.
It's just not good automotive engineering to design that type of spark system.
Just like it's not good automotive engineering to have a high compression 911
engine with non-retarded ignition timing, i.e. compared to stock, without twin
plugging the engine.

'if they are a solution for 1 CDI with 2 coils."

The PRO-12 has 2 separate outputs, i.e. one for each coil, not like the MSD with just one output.

Im fairly certain he (wwest) makes up all of his posts as he writes them. he hasn't got a clue on real world reality on most issues. Just read some of his AC posts.

Lindy, Can you explain this - it seems to me that as long as one set of Plugs is firing, you are still getting fire in the hole. Why would your engine blow?

This makes sense to me Loren. But then the question is what is the solution?

The Bosch puts out even less power. So for Twin Plug seems the MSd would be better, but both may be inadequate.

If someone where wanting to twin plug, and asked your advice on ignition, what would you advise.

I like the msd products, and I'm not alone :) Will a better ignition make more horsepower? I wouldn't expect any hp increase on a stock engine. On a high compression engine, way improved engine, it might make a difference.
But you really discussion last century technology ;) Next engine will have a map based ignition system.

BTW I had lots of positive comments from racer friends about the Mallory products as well.