Twin Spark Firing using single CDI Box

[colingreene]

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.

[Rosco_NZ]

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.

[winders]

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.

[Henry Schmidt]

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

[Fred Winterburn]

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

[KNIGHTRACE]

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.

[targa72e]

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

[KNIGHTRACE]

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.

[KNIGHTRACE]

[KNIGHTRACE]

[winders]

Originally Posted by targa72e

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

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!!!

[Mr Beau]

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.

[Henry Schmidt]

Originally Posted by winders

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!!!

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.

[winders]

Originally Posted by Henry Schmidt

Does anyone else find this statement just a touch bizarre?

It's called sarcasm, dude!

Originally Posted by Henry Schmidt

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.

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.

[Henry Schmidt]

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.

[Henry Schmidt]

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.

[winders]

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.

[winders]

Originally Posted by Henry Schmidt

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.

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.

[trond]

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

[KNIGHTRACE]

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