Just to get good info out there for those that are considering inductive ignition.

All the energy dispatch at the spark plug is generated within the windings of whatever coil you are using.

The igniter add nothing. It has to be capable of carrying high electrical loads but nothing that ends up at the plug tip comes from the igniter.

To run two coils from one igniter channel will always overload the internal transistor within the igniter. They run hot even with one which is why often heat sink paste is used to transmit the heat to a larger heat sink.

It's not that simple.

Here is an interesting read:

Ignition Systems - Basics to High Performance

Inductive Discharge vs Capacitive Discharge Ignition (CD)

All of the above descriptions are examples of Inductive Discharge type ignition systems. The first high performance ignition system design was the Capacitive Discharge Ignition which uses high voltage stored in a capacitor to induce the few hundred volt pulse into the secondary instead of generating it in the primary as with an inductive system. In a CD system a high voltage oscillator circuit charges a capacitor. When it is time for a spark, another circuit discharges the capacitor into the coil primary. The voltage produced from the secondary is in the same proportion as with an inductive system. For example if the capacitor is charged to 400 volts, a 100:1 coil will produce 40,000 volts (or there abouts). CD ignitions have certain limitations depending on design. As an example if the oscillator is not powerful enough, the capacitor will not recharge quick enough and the ignition will have an RPM limitation. As you engineer more powerful oscillators, power consumption also increases. As the size of the capacitor is increased, the output of the ignition also increases, however the oscillator must be made more powerful. Certain tradeoffs must be made in design for a particular application.

Compared to inductive systems of the day, CD systems were more powerful since higher primary voltages could be discharged into the coils. One inherent limitation to a CD system is that the spark duration is short due to small capacitors used. As mentioned earlier, spark duration does the actual work burning an air fuel mixture, the voltage is used to initialize current flow across a spark plug gap. Due to the high primary currents of an inductive system, spark duration is naturally longer. Some Manufacturers of CD ignition systems provide multiple sparks to increase overall spark duration. Of course, as mentioned before, capacitors take time to charge up so there are limitations as to what RPM levels a CD system can maintain multiple sparks.

Today with improvements in technology, inductive ignition systems can be made more powerful with special transistors (Mosfets) switching the coil. These devices have higher breakdown/clamping voltages which allow the primary voltage to increase ( 550+ volts) resulting in higher secondary voltages. This coupled with the inherent long duration makes for a powerful ignition which has the capability of also going multi spark. Inductive ignition systems are emerging as the new high power ignition systems.

If anyone is interested, I ran a test using a single MSD analogue CDI driving two coils. I posted the results here on the pelican forum. http://forums.pelicanparts.com/porsche-911-technical-forum/918015-msd-6a-firing-two-coils-simultaneously.html

Surely actual measured data is not we need on this thread. Let's stick with feelings and opinions. It is alarming how much power there is left on table today. I have been developing some components for a 3.6 liter motor that actually look by the math that I can get 488 Hp. I do not want to tell the client the number because I have learned If I miss by 5 hp I was wrong.. So I am calling it 475HP. I try to over deliver and under promise. This is not always my result but I try. My first two lines are humor, I was not being serious. In the development of these motors I have found we have lost some very large gains by missing some non important small stuff. It is said we do not need such gains from where these motors are presently but my question is why not? William Knight

Wow, Great info !! Thanks for posting that.

I’d still like to hear of others experience and recommendation of a superior CDI system.

The power numbers gained would be shocking.. It seems the more current we apply the happier the motor.. MSD's are weak in my opinion but for a $250 box it has proven more powerful in my experience than a stock Bosch. The reason I said use them is I think a New Bosch was like $700 to the best of my memory if even avaliable. Why not go MSD for the price savings, To get to a high level motor everything in it is different and more expensive. That being said I do not want people to think I only sell exotic parts and builds. I more often than not give cost effective and often free solutions. The euro 3.0 CIS motor with my M1 cam and an MSD will make about 240 HP. inexpensive and great results for the money in my opinion. The Muffler I designed to get the best HP and TQ on this forum I do not even sell, I gave the design to everyone. You can purchase the parts from summit for under $250. We do not have to break the bank to have a fun car but I like that we have the option today to have better than vintage RSR race motors at a fraction of what they cost even if there was enough to go around. I have a factory 1993 3.8 RSR motor in my shop and I often look at it and think how far we have come from that. Speaking of advancements, these barrel throttles have consistently shocked me and make me wonder why did we ever stay with butterflies other than cheeper production cost and more probability. I agree before anyone says anything butterflies may work better than slide valve. I hope all of these post from everyone help some people.

I agree, William , and thanks for the humor.

Again I find myself sitting in an airport departure gate waiting for my flight to Florida. About the only time I have to read and post now.

As I have said before, not everyone wants to agree with my posts. That’s ok. If we all agreed it would be a boring world.

I have been using ignition on high performance engine since I started in the 70’s. Ignition is so important and one of my main focus in any engine building.

Like most parts supplied to the aftermarket you have to do your own testing and evaluations. There is way too much hype put out about “how good our stuff is”. Back to back testing should be done or inquire with those that have.

Ignition is a simple mathematic equation. There is one for calculating CDI and one for Inductive. You cannot change the results unless you fudge the input numbers.

For these older Porsche 2V engines with large chambers you need lots of temperature in the chamber. Proper understanding of what actually creates this temperature is important.

In a CDI system the coil acts as a transformer only. The energy is created and stored in the CDI unit. In an Inductive system the coil generates the energy. This is a simplistic explanation but as it works.

There are many COP on the market but none can created the energy a good CDI can. An Igniter is just a simple switch. A little more, but for most it’s just a switch.

If anyone is selling igniters that do more, I would be wary of the hype.

G Gt or those that may be looking for another CDI option, we have been selling one so or over 20+ years with zero failures. You can contact through our PD website.

Like I said before, not everyone wants to agree and there is always someone who will disagree. That’s ok. I base my opinions on what we have tested and proved.

Here’s a simple test anyone can do to prove my opinion. Try starting you engine with fouled plugs with an inductive system. Just make sure you have a spare battery. Now do it with a CDI. It’s the energy released that makes the difference.

William, how are you keeping the rotor in a stock Bosch distributor alive using the MSD CD ? Our experience with the multi spark feature in the MSD, you end up melting the resister in the rotor.
The engineers at MSD offer a solution but I'd like to hear what you did/do.

Great question, I have had that problem before, The problem was actually in the star wheel alignment. Sometimes on rebuilt distributers or ones like I made using the magnetic internals into a 964 distributer the magnetic poles are slightly out of phase or alignment. The thing to look for on a burned up rotor like described is if it is burning up the trailing edge or leading edge but most likely the trailing edge. What happens if the magnetic poles are not aligned correctly is it delivers the energy to a small portion of the rotor and with the greatly reduced surface area over the required and applied energy it will burn them up prematurely. The home made twin plug distributer was made by myself. But I usually can get am minimum of 25,000 miles on an MSD unit with Bosch cap and rotor. On race motors usually can get 100 hours no problem. One other thing with MSD and kind of misleading advertisement is the multiple spark discharge. It is only multiple spark for the first 2000 rpm or so.. I call it more of a sales pitch.

Interesting but how do you explain rotor resister burn out in a stock distributor with proper alignment? Even points distributors experience the resistor burn-out.

I typically do not use rotors with a resister in them therefore I may not have an answer for that. I think the primary purpose of that is reducing radio interference. I also do not use the rotors that act like a rev limiter. I am not worried about how clear my radio reception is in my car. I do use the rotor with a rev limiter in it on E stock race cars as it is required.

I appreciate that answer but in the 35+ years I've been working on Porsches, I have never seen a quality non-resister Bosch style rotor for 911s.
We remove the resister replace with a brass rod and refill the groove with a non-metallic epoxy.
I have seen some pretty cheap/low quality rotors from after market sources but even they are getting harder to find.
Speaking of radio static (I assume you mean RF interference). I have another question about the MSD units you use. They recommend resister wire. All early air-cooled 911s came with solid core wire with resister ends. What do you use and why does MSD require resister core wire? Can you use solid core despite their recommendation?

You really do need to catch up on current state of the art in inductive ignition systems. It's not 1999 any more.....

To all those that are interested in learning I hope some here continue to share their knowledge and experience. I will regardless of cheap shots.

My time on this subject is done, but anyone interested in more, are welcome to email me and I will be happy to give help.

Condensing noise like that is what makes you sound ridiculous.

Let me guess....you're going to claim it was just a joke.....my response is simple ...yes you are.

Today as in past years many innovations from race cars spill over into the street world.
This thread has been nothing short of a "DISASTER" in my opinion. I think the questions in the beginning of the thread have been answered. Fred Winterburn gave some good data from his research if anyone still needs help. We need to be careful not to get too technical to the point we do not help the people looking for help. We should help and support each other on these public forums, at least the good guys in my opinion.
My only GOAL was try and help the community.
About Henry at Supertech I have know Henry for close to 30 years.. Henry and myself do not agree on everything but I know Henry is one of the honest resources in the community. We should support the honest people in this trade as there are not that many from what I can tell. When It comes to Niel Harvey I personally do not know him so I can not say but I hope he is a good guy also. I believe it was not my best moment and I was not proud of what I posted, It will not happen again. Thanks, William Knight

So, after all that, who is packing the biggest spark ...?

Sorry, couldn’t resist.

Certainly not a single MSD 6AL controlling 2 coils........

Glenfield well placed need a little humor on a Friday

Scott just seems like one of those people who feels like if they yell the loudest they deserve to be heard.
He himself said that he just asked William lots of questions so I really don't get why he is still in here being a child.
This whole thread really made me regret reading it.

Twin Spark Firing using single CDI Box
 

I’m starting to regret asking the question.

People say some Porsche people take can sometimes themselves too seriously and not be open to other thoughts or ideas. And some of us are earlier on the journey than others, but we need to understand why.

Remain passionate people, just don’t let your version of your truth blur your vision. We’re all shooting for the same team.

Thanks all for your time, insights and contributions. Let’s call this a wrap.

Hey, it is a great question.

All I have been saying is that using a single MSD 6AL ignition with two coils works but is not really ideal. It is best to use two MSD 6AL ignitions for twin plug setups unless you have a compelling reason to not do so (finances, space, rules, etc.).

Fred Winterburn's data pretty much backs up that position. You get lower voltages from the coils and about 1/3 the spark duration. You can get that to work but it kind of defeats the purpose of going twin plug in the first place.

So go with a single MSD 6AL if you want. I never said you had to do anything. I just wanted you to be aware that you certainly are leaving something on the table with that solution.

Well, here we are. Many people on this thread wondering what happened.

I will take some responsibility for it's direction but not it's conclusion and trying to restrict or control the direction seems to me to border on disingenuous.
I've been posting on this forum for almost 20 years and in that time have ruffled a plethora of feathers. I gave up on the cool guy, popularity contest in junior high.
It may be that I see these threads differently than most.
I don't see them as a classroom, a lecture or debate. I see them as a conversation with friends. Sometimes even among friends, emotions get high.
What you get from me is unfiltered honesty, some times bluster but I will never swallow an insulted (no matter how veiled or clever) without responding, just like we were sitting at the bar, having a beer.
It's my style, love it or not, I'm not likely to change.
Cheers

Neil wrote this(in green font) and he's partly right. No fault of his for not being totally right as I do not think even the automotive companies or any of the existing CDI manufacturers know the real reason why CDI is superior at firing fouled spark plugs. They keep touting that it is a fast voltage rise time, when in fact it is something else entirely.

"Here’s a simple test anyone can do to prove my opinion. Try starting you engine with fouled plugs with an inductive system. Just make sure you have a spare battery. Now do it with a CDI. It’s the energy released that makes the difference."

It's not actually more energy, and its not exactly more power either, but that is closer to the truth. The real reason is CDI provides a leading power factor. Inductive systems have a lagging power factor so the voltage rises long before the current catches up. This naturally lowers the power because current and voltage are not in phase, actually nowhere close to being in phase. CDI on the other hand is closer to being in phase which ups the power, but more importantly, the current leads the voltage. While this may seem impossible, it is a fact and a feature well known in power distribution systems. Capacitive loads prefer a leading power factor and appear as very low impedance while inductive loads appear as high impedance to a leading power factor. However, the spark plug gap prior to spark breakdown appears as a leaky capacitor so it is essentially a capacitive load. A shunt resistance is just that, a resistive shunt in parallel with the spark gap. This shunt resistance could be wet ignition wires or otherwise conductive HT insulation or could be carbon fouling of the spark plug. When faced with a resistive load at the same time as a capacitive load, the capacitive load takes the current first providing current leads voltage. This causes the spark to breakdown before an appreciable amount of energy can leak across the shunt resistance. It is somewhat more complicated than this, but that is the gist of it. With an inductive system, the voltage rises first with current coming later and the angle of separation is much wider than it is with CDI. This means that it takes a whopping huge coil driven with lots of current to get anywhere near the power of a low energy CDI. And #2, it means the voltage has to rise quite high before there is sufficient current at the spark gap to fully ionize it for breakdown. In the meantime, faced with a shunt resistance, that resistance will be the preferred current path for the lagging power factor provided by the inductive coil. An inductive system can never be made to overcome fouling as well as a CDI, nor can an inductive system provide the same power output for the same power input. Energy is a different matter as most inductive systems actually deliver more energy to the gap but not with the same shock and awe of a CDI. BTW, peaking capacitors actually make it more difficult to overcome fouling because that capacitance competes with the spark gap (which is capacitive prior to spark breakdown) Peaking capacitors are a bad idea. Fred

This discussion has turned into something a little more helpful that the train wreck I felt it was. I will chose my position on the single box vs two. Neither is right or wrong that depends on your application. I have to agree with Winders and not because he is my client. I feel what he posted pretty much matches what Fred has posted and I agree with that. I have little to no experience using one MSD on two coils and others have done it with some success. I do agree 100% with Winders it is better to have two.. I feel Winders was 100% trying to help someone get the better outcome and he was not treated as well as I would like to have seen. I was not proud of my post either and I changed it. What Fred just posted is very informative but maybe over the head of a lot of the people trying to understand this. There are people reading this that are really intelligent but not in Electrical.
I am going to try and give a simpler understanding and I am not contradicting what Fred stated.
When we speak of fire power and energy, it is not that simple. I am over simplifying below for the help of understanding.
Voltage like 20,000 vs 50,000 is not actually an indicator of power, current is not determined by voltage but it is a factor. Current is in simple terms Amperage. Amperage is like Torque in a motor, Voltage is like Horse Power. Here is an easy to understand: Picture a 60 watt incandescent light bulb in your house look at it. Now go turn your bright lights on in your car and look into it. It is also 60 watts most likely. The reason it is so bright is because it is 10 times the amperage.
60 watts/ 120 volts = .5 Amp's. (home) 60 watts/12 volts = 5 amp's (car) so while their both the same wattage one has 10 times the current. The reason the car bulb is so much brighter is the energy is 10 times as much.
The reason most of the cars on the road are COP is because the energy is higher to reduce hydrocarbons for emissions.
Also as you raise the voltage you reduce amperage. Some of these new COP systems can give an amperage that is staggering high.

One more OVER simplified analogy:

A CDI ignition and coil work more like a flash on a camera and a COP works more like the glow of an arc welder.

I think we are past someone telling me the COP is not a welder and the CDI box is not a camera. God I hope.

Good explanation fred.
The lightbulb analogy is wrong as it relates to energy. Both bulbs use the same energy. Electrical energy is defined as:
Energy= Watt over time (E=Pt). Since both bulbs are the same watt they use the same amount of energy. The current is higher because the voltage is lower, energy is the same. The 120V 60W bulb puts out less light (lumens) because it is made cheaply and much of the energy is wasted as heat. The car bulb is brighter because it is more efficient and gives off more lumens. This is accomplished by making the bulb more efficient with exotic gasses (halogen) and a filament design that gives off more light than heat.
Back to fighting about who and what ignition is best.

If you really want to dig into why there is not one good answer of what ignition is best (depends on goals) there are many technical papers (SAE etc) that discuss the difficulty of igniting and when to ignite mixtures in modern engines.

"The reason most of the cars on the road are COP is because the energy is higher to reduce hydrocarbons for emissions."
It is debatable that stock street car COP all offer higher energy than other options. COP or individual coils with short leads are used in most new cars for a variety of reasons . One being as computing power has increased strategies for engine control have changed. Many modern ECU's employ a strategies where each cylinder is run as a independent engine. This allows individual fuel and ignition trim per cylinder for best performance. Inductive COP also offers a long spark duration so there is a better chance of ignition and burning all the fuel in the cylinder for better emissions

For what it is worth modern FI engines generally use some type of stored energy spark initiation system with coil on plug systems. The rules from a few years ago limited to ignition to 5 firings per cylinder per ignition event.

Maybe Winders could experiment with a COP CDI system like the units from M&W and let us know if it made more or less HP compared to his inductive COP system. They have a unit made to work with Motec

M&W Ignitions

john

I am almost in shock. I tried to keep it simple so that people could understand energy. I will be professional rather than loosing it.. "Question John" and
I copy what you posted above word for word.

"Many modern ECU's employ a strategies where each cylinder is run as a independent engine. This allows individual fuel and ignition trim per cylinder for best performance. COP also offers a long spark duration so there is a better chance of ignition and burning all the fuel in the cylinder for better emissions"


MIGHT ? one conclude since I am burning more fuel in the combustion chamber and the spark on the plug is much longer I might increase the volumetric efficiency of the engine resulting in more power per liter ? Or would I be better to change to a system that burns less fuel in the combustion chamber and sends unburned fuel out the exhaust rather than converting it to energy.

Below is a very simple table so anyone can use.http://forums.pelicanparts.com/uploa...1612048865.png

This is how simple it is
 

I did all my research BEFORE I decided what ignition system to use on my race engine.

But, you know what? I screwed up as my engine just doesn't work right. You should never use an inductive ignition system. You will not make any power and your engine just won't run properly. Please, anyone that is building an engine for PCA GT3, use a CDI ignition system!! Thank you!!!

If you have 'enough' ignition energy, adding more won't change horsepower.

If plugs are fouled, the 'quality' of this energy can matter (i.e. CDI).

Non-resistive plugs and wires won't add any horsepower. And are prone to causing issues with other electrical systems.

Does anyone else find this statement just a touch bizarre?

Back in the early 90s while competing at Riverside in my first automobile race, I drove a 2.0 914-6. During practice, I was able to perform with relative competence given the nature of all the givens.
Low funded car, very little tarmac experience (even though I had a 12 year pro motorcycle career) under-powered and no tire budget.
While standing on the grid for the Sunday mornings race, I was talking to the driver of the poll sitting car, an Alan Johnson GTU 914-6. In my exuberance I uttered the words “If I only had a little more power and better tires, I’d be right up there with you guys”…..He smiled and with a non-judgmental tone he said the words that powered my racing endeavors from that day forward. “Maybe a little more seat time”.
Racing is about race-craft. It’s not about more power or better tires. You win by making your last lap better than first. The satisfaction that, as a driver, you seem to be figuring it out.

There is no magic ignition that will make that happen.

It's called sarcasm, dude!

Riverside Raceway closed on July 2nd, 1989 and the last event, a club event, was held on July 1st, 1989.

Racing, at the club level, is different things to different people. Some just like to participate and don't care where they finish. Some just want to be competitive while others want to win.

If you want to win in a competitive class, you need more than just "seat time". You need to have some talent. You need "race craft". But you also need a competitive car. That means you need enough power and enough tires and enough handling. So, to win, you may very well need more power and better tires. The ignition system is just part of the engine equation.

You win by finishing ahead of your opponents. You don't win "by making your last lap better than first". It doesn't matter how slow or fast the laps are as long as you cross the finish line before anyone else. Lap times are irrelevant. Lap times only matter in qualifying. Lap times change based on traffic, track conditions, fuel loads, the condition of your tires, and how hard you are racing someone else. Gaps matter. Especially in multi-class racing. My crew chief (my wife) is on the radio during the race telling me what is goin on. She never tells me what my lap times are. She tells me what my competition is doing relative to me. What is the gap? Is the gap shrinking or growing? The only time I look at lap times is after the race to see what I was doing relative to my competition.

There were a host of club events after the "official" closing of Riverside raceway.
I think they started calling them, The annual "last race at Riverside". It was a while ago but I think I remember the 3rd annual "Last Race at Riverside".
Actually, three events after the story I related in the earlier post, I lost two cars that day. My customer was a trail-breaking fiend who over revved an RSR going into 6 and missed a gear in turn 9 to park the second car, a 914-6 just a few hours later.

Just so we're clear, DUDE.
Your arrogance is mesmerizing.....like a train wreck, hard to look away.
Now you're dismissing the efforts of all the "club" racers who compete in time trails.
Most of them will never have an "FTD" but see themselves as winners because they managed to hustle their modest little racer just a little faster this time out.

According to the records I can find, the last professional race at Riverside was in 1988. The last club race was held on July 1st, 1989 and the track closed on July 2nd, 1989. The Moreno Valley Mall opened in 1992 so construction had to start no later than 1990.

I can't find any record of any kind of race at Riverside after July 1st, 1989. I remember the track closing then because a bunch of my POC friends were not happy about it.

Arrogance? Dismissing efforts? What are you talking about? You are ranting like a mad man.

Time trials is not "Club Racing". It is "Time trials". In time trials, lap times are all that matter because there is no wheel to wheel component. There is no race craft.

As I said about club racing, time trials are different things to different people. Some just like to participate and don't care where they finish. Some just want to be competitive while others want to win.

I encourage everyone to take a deep breath and calm down. Don't scare all of us newbies away..

Trong, I am sorry the thread got so carried away. Please accept my apology. I value and appreciate people who add helpful information to the community from this country as well as other countries. I have made great connections and friendships through this forum. I am thankful for the forum and the contributions made by many. This with absolute certainty will be my LAST post on this thread. William Knight