WERK-I

m42racer,
Driving a coil to full saturation is a waste of time. Coils reach over 90% of their capacity within 70% of the saturation curve time line. Striving full that additional 10% is a waste of time/efficiency.
This debate of spark energy vs. duration will go on forever, but I'll take a crank sensor ignition system over a distributor of any type.
Software may or may not use all the trigger signals from the crank sensor, but that is due to the design of the system to improve the granularity of the sample data to improve accuracy. The hardware may use multipliers or dividers to achieve the desired results.

Dave
'85 Factory Slantnose 930

m42racer

"Driving a coil to full saturation is a waste of time"

Are you kidding?

Please explain that theory. I'm very interested in hearing your reasons.

Explain how a Coil that needs 6.5 msecs of dwell verses a Coil that only needs 3.0msecs of dwell. If you used the same Ignition system to drive the Coil that needs only 3.0msecs and changed to the Coil that needs 6.5msecs, do really expect the same spark energy and the same amount of engine performance?

"but I'll take a crank sensor ignition system over a distributor of any type."

Regardless of how good or bad it is?

This seems to be a classic case of the "don't confuse me with the facts, my minds made up" syndrome.

WERK-I

Read the email I posted.
If it takes 6.5 mSec to full saturation, you can reach to over 90% of full saturation in 4.6mSec. I'm not talking about comparing coils. I'm talking about wasting nearly 2 mSec to get less than a 10% return. Study hysteresis curves and you'll know what I mean.

"This seems to be a classic case of the "don't confuse me with the facts, my minds made up" syndrome."

....funny I was thinking the same thing when I read your posts.

m42racer

"....funny I was thinking the same thing when I read your posts."

You may consider anything you wish. I'm trying to understand your point of view here, and if you will not share your point, how can I ever understand it.

Your opinion is not one accepted by experts in this field, but you are entitled to have it.

To take your point, if you had 6 coils and each coil had 10% of its ability not used, that would account for 60% of coil energy not used. Thats wasting time? Maybe I'm not following your point.

"Study hysteresis curves and you'll know what I mean."

I have been shown the scope traces of undercharged Coils and Coils fully charged. Is this what you mean? When I was shown and taken to school over this subject, "Hysteresis curves" were not shown. Did I miss something?

Why would you have a Coil with a certain amount of windings in it and not use all of them. The energy supplied in an Inductive system is all about the Coil.

"I'm talking about wasting nearly 2 mSec to get less than a 10% return."

Where is the waste of time happen? If the dwell time happens before the firing event, where exactly are we wasting time? If I understand where you may be coming from, this speaks to exactly what has been stated before. At high RPM. the time between events gets so short that the coils never reach full charge, especially coils that require longer dwell times. For example the electromotive ones. This is why CDI is better in these sorts of applications. The voltages used here are stepped up to greater values and the time to charge is way less and the capacitor becomes a function of energy, not the Coil.

WERK-I

"You may consider anything you wish. I'm trying to understand your point of view here, and if you will not share your point, how can I ever understand it."

I'm not going to waste time educating you in EMF,hysteresis, properties of ferro-magnetic materials and dialectrics to name a few. You obviously have been shown curves on an ocilloscope by some "expert in the field" and you bought into it without looking behind the curtains.

"Your opinion is not one accepted by experts in this field, but you are entitled to have it."

Huh? This debate has been going on for the last couple of years by research engineers in both camps. I have no idea where you come up such statements...did you do a Harris Poll on the subject?
The whole argument on ignition systems is this; which is better ultra high energy-short duration spark versus high energy-long duration spark. You were shown something I'm sure that goes along the lines of something like this;"look how weak that voltage is on Brand-X and now look at the voltage on my Super Atomic CDI system. Which one DO YOU want?"


"To take your point, if you had 6 coils and each coil had 10% of its ability not used, that would account for 60% of coil energy not used. Thats wasting time? Maybe I'm not following your point."

This clearly illustrates your lack of knowledge and understanding on the subject. The 10% (more like 7%) value I gave you has nothing to do with whether you have 6 coils, 10 coils or a kazillion coils. I was referring to properties of all inductors/transformers, even the transformer driving that CDI system of yours.

"I have been shown the scope traces of undercharged Coils and Coils fully charged. Is this what you mean? When I was shown and taken to school over this subject, "Hysteresis curves" were not shown. Did I miss something?"

You were shown something that only proves the sellers point of view. You can not really see hysteresis, only its effects. It's something like magnetic inertia.

"Why would you have a Coil with a certain amount of windings in it and not use all of them. The energy supplied in an Inductive system is all about the Coil."

The windings are always utilized. The maximum output voltage on the secondary is in direct proportion to the ratio of secondary/primary windings * the input voltage.


"Where is the waste of time happen? If the dwell time happens before the firing event, where exactly are we wasting time? If I understand where you may be coming from, this speaks to exactly what has been stated before. At high RPM. the time between events gets so short that the coils never reach full charge, especially coils that require longer dwell times. For example the electromotive ones. This is why CDI is better in these sorts of applications. The voltages used here are stepped up to greater values and the time to charge is way less and the capacitor becomes a function of energy, not the Coil."

There are so many things one can do with software(firmware). I will save the dissertation of how to overcome your "dwell" restrictions to the designers. The Electromotive coils has sufficient time to reach saturation. Do I need something that will provide sufficient firing capacity at 12,000RPM? Of course not! My turbo engine will rarely see over 6,000 RPM....I'm more concerned about an ACCURATE and COMPLETE burn and NO Pre-ignition. That's why I twin-plugged my engine and chose a (DIS) high energy long duration spark.

m42racer

"I'm not going to waste time educating you in EMF,hysteresis, properties of ferro-magnetic materials and dialectrics to name a few. You obviously have been shown curves on an ocilloscope by some "expert in the field" and you bought into it without looking behind the curtains"

Please do!! The person who designs and manufactures the Ignition systems, (CDI and Inductive) used by Motec, Link, Autronic I think, and many others is all ears!!

"The whole argument on ignition systems is this; which is better ultra high energy-short duration spark versus high energy-long duration spark."

How can you have high energy spark if you don't fully charge the Coils?

"You were shown something I'm sure that goes along the lines of something like this;"look how weak that voltage is on Brand-X and now look at the voltage on my Super Atomic CDI system. Which one DO YOU want?"

Not at all. The person who schooled me designes and manufactures both CDI and Inductive. He showed me the formula's and the lab tests to prove them. Both tests were done with his coils.

"This clearly illustrates your lack of knowledge and understanding on the subject. The 10% (more like 7%) value I gave you has nothing to do with whether you have 6 coils, 10 coils or a kazillion coils. I was referring to properties of all inductors/transformers, even the transformer driving that CDI system of yours."

You are correct about that. I have asked the EXPERT for his opinion on this to make sure I have not mis spoken. I look forward to hearing what he has to say about yours.

"You were shown something that only proves the sellers point of view. You can not really see hysteresis, only its effects. It's something like magnetic inertia."

Again, not at all. See above for same answer.

"The windings are always utilized. The maximum output voltage on the secondary is in direct proportion to the ratio of secondary/primary windings * the input voltage."

And time, correct?

"There are so many things one can do with software(firmware). I will save the dissertation of how to overcome your "dwell" restrictions to the designers. The Electromotive coils has sufficient time to reach saturation. Do I need something that will provide sufficient firing capacity at 12,000RPM? Of course not! My turbo engine will rarely see over 6,000 RPM....I'm more concerned about an ACCURATE and COMPLETE burn and NO Pre-ignition. That's why I twin-plugged my engine and chose a (DIS) high energy long duration spark."

Glad you are satisfied. I tried it your way and found the other to be better.

WERK-I

You've lost any creditability you had. I suppose this was the "same" expert who stated distributor driven CDI systems are superior to DIS systems.
I feel sorry for you. I have read some of your posts on other threads. You seem to be a bitter person. I'm sorry I have taken such a negative posture on this subject.....you bring out the worst in people. This is a community of well wishers. They are people of generousity and you go around touting how things should be done your way, because you have been shown the light. Then you get in some sort of pissing contest if someone disagrees with you.
I'm leaving this "debate"....I leave it to the people of Cosworth, Ilmore, Porsche, GM, Ford, Daimler, BMW and many others to research and debate. They have far more talent and resources.

You have proven nothing, sir.

m42racer

I have not tried to "get into anything" with anyone.

I have stated facts here, or opinion. I am interested in yours. Just maybe, I have it wrong and you are correct. Then I and others can learn something. If you get your shorts all twisted because I question your opinion, then I'm sorry.

There is formula's to calculate the energy available with either Inductive or CDI Ignition. I was shown these, shown how they can be used and shown the differnce between the results in lab tests. I have also felt the difference in my own cars thro the "butt Dyno"

I have not trashed Electromotive or any other system. I have just stated that the Coils and Ingniter control could be better and if they were, the system would be even better than it is. That goes for any Inductive system. I was shown if the AMP rating of their system was increased, as with others, the coil energy would be greater. The issue I have with Electromotive is not with the product, but the sales line they take. Attend the Trade shows and listen to it.

Your comment about the Ignition Distributor and the person who suggested it, if directed towards Geoffery, is out of line. He adds to debates here. Yes, often I do not agree with him, and with others, but to imply what you appear to have, is not fair to him. I hope I am worng here.

Please continue here with me. We all can learn something. Its out of debate that we learn, and often from different opinions.

To add to my opinion, I was shown where a certain Inductive system used the Mitsubishi Coils. These Coils require over 6Msecs to fully charge. The ignition system would only allow for 3.5Msecs. Customers could never achieve the same amount of power as the stock system produced, until the dwell function was corrected. I have seen this with Electromotive, and others as well. Its common with most Inductive systems, as dwell only applys to this type of Ignition. The correct matching of Coil type and dwell is so important. At least with end results.

If it comes across that it should be done my way, then I need to change the way I write my posts.

This debate is not about one type over another. It was from my point of veiw, how important it is in aftermarket systems to fully control the Coils used. OEMS typically do this as they design the system from scratch. Aftermarket systems often fall short here. Your position is that it is not that important to fully charge them. Here is the topic.

Please continue with me here, so we can all learn.

Geoffrey

I'd also like to reiterate that for a CIS fueled 930, the XDI igntion sytem is far better than stock, and a good choice considering the lack of anything else out there.

My comments about distributors were specific to EFI controlled igntion systems, not distributor triggered systems. With aftermarket engine management systems you generally have the ability to control the dwell of an inductive ignition, and I check each one with a current probe to ensure the dwell is set properly so the coil is fully charged. It happens that I just tuned a car that has the Mitsubishi coils Simon speaks of and they required 5.2ms of dwell to become fully saturated. I wish I had saved the scope trace to post here.

I also think that for the most part the comparisons made between inductive and CDI are not totally fair in that most inductive ignition systems available are primarily production based where CDIs are very high quality racing systems. As a point of reference, the F1 cars are split about evenly between those that use CDI and those that use Inductive, so obviously there are merits to both.

Miles965uk

Just want to say even tho you guys are at each others throats its been very very informative and ive just learnt a hell of lot about ignition. thanks. More passionate debates should happen

m42racer

Geoffrey,

You have added some good points.

I was shown where often the Igniters in OEM systems are current limited to 7.5A. If this number was increased, the Inductive system would have far greater energy, upwards of some CDI units and at less the cost.

I'm not against Inductive nor pro CDI. I used to think CDI was better, but recently have found out reasons why so many Inductive system fall short. Yes, certain applications suit a particular Ignition better than the other. But if Inductive was made as a racing system, or high performance, instead of copying the OEM spec's it would be a great system for the money. The cost od multi channel Inductive is far less than CDI. That was my point with the Coil charging.

Geoffrey

Yes, and I remember not so long ago "discussing" CDI vs Inductive igntions here with you.

On your point of inductive ignition energy, if you raise the current, then you'll also raise the coil charge time or dwell required. In multi channel inductive ignitions this isn't going to be an issue at the RPM ranges we are working with, but try that with a distributor and that will be an issue. In fact, this is one of the major issues with the stock 993tt ignition system where the coil requires about 3.2ms of time for dwell, so after about 6000rpm, the ignition system is not being fully charged. As these guys raise the boost pressure and install larger turbos, they are finding that they need to reduce the spark plug gap to keep the engine from misfiring. A swap to a CDI unit, even somthing like a Crane HI-6 makes a big difference.

I chose a high quality digital CDI box for my RSR rather than a multi channel inductive unit mainly due to packaging and convience. However, I also know that the CDI with a .060-.080 plug gap, will outperform the inductive units available in a similar cost structure. I also didn't want to run a wasted spark environment. I could have chosen to run 12 coil on plug Bosch units from their motorsport catalog, however, they are based on street parts when I checked.

JoeMag

From a power to the plug and spark duration, is the electromotive crank fire better than an MSD 6al? ...6AL multiple sparks below 3.5k rpm or something, but I don't run that lower rpm

m42racer

Miles,

There is so much to Ignition that most take for granted.

Joe, this is the old debate again. The problem here as I see it, its still Inductive verses CDI, but in your comparision, it is also about how you drive the MSD verses the Electromotive. If you drove the MSD with a really good Distributor and good gear, I would go that route. If you drove the MSD with an Ignition unit triggered from the Crank, hands down I would still go the MSD route. No dwell control required. Choose a CDI type Coil and you would have the better Ignition. Now if you were to choose a higher end CDI( cost no object) now you would have the best.

Now if Electromotive or any other Inductive Ignition system similar had better dwell control and you could match the Coil to the dwell, and be sure to fully charge the Coils, then the Inductive system would be a really good choice, if the RPM's are under a certain number or it was run as wasted spark.

Miles965uk

Guys - could anyone comment on this coil pack.... apparently its a bosch one but I dont know the model or what it comes off or how good it is. This guy from TurboKraft is running it on his Motec twin turbo 650HP conversion- so im asumming it cant be bad! Any comments will be helpfull for me as im going to doing this myself.