External coils, ignition control, spark results

[OROutdoors]

I am considering an improvement to the current ignition in my SOHC B6, though I am intending on swapping a DOHC BP this summer (I will be getting the BP this saturday). I was figuring on just adding a better external coil, cooler plugs and 8 mm wires. So I did a search and found some posts, but not exactly what I need...

This one, from March of last year, was good. PATDIESEL said:

...First the stock ignition is weak for the motor and for a high performance motor at that. Of course this is inherent in any distributor set-up, especially with an internal coil. So a good external coil will definately help in the top end when the stock internal starts to run out of power.
Indexing and opening the gap is a good idea and will also benefit from the external coil. ... I'd also suggest some 8.5mm Magnacore wires to go along with the upgrade.
As for the Mega Squirt being needed you know that there are plenty of other systems that will controll the spark if that is your aim. I'm currently working on the wiring for a MSD multi-coil set-up myself, but really won't have the parts to acutally assymble and try it out till later this year.
...

I'm familiar with cylindrical 2-post coils, but the small E-coil that is in my 93 mx-3 RS is new to me. It seems the coil has a 4 wire connection, not just 2 posts. Is there an external coil that is in the 30k to 40k range that can be added without adding a suplpemental ignition control (such as the MSD 6AL)? Are there mods to allow for the use of the 2-post coils?

Why not ignition control? Well, ignition control seems to still rely on the ECU for timing (as far as I know), the distributor for distribution, and the coil for increasing voltage. As far as I can tell, ignition control mainly extends the duration of the spark, that is the amount of time it takes for the electrical field to collapse -- almost as if the voltage to the coil is turned off slowly, instead of instantaneously.

I should think that with a sufficiently strong spark, that the duration of the spark is of negligible difference. Of course there are other benefits from ignition control, such as rev limiting and rev-holding for fast starts. Maybe I am wrong... Your input is greatly apprecaited -- no need to flame me if you are a strong believer in supplemental ignition control.

[Steeb]

ignition timing control does not control the duration of the spark. fuel control controls the duration of the injector.

ignition timing control is for controlling when during the compression/combustion cycle the spark plug fires. this dictates how much torque is applied to the piston down the rod to rotate the crank. this is why changing timing makes a difference in power out put.

example 1:
fire the spark plug at -90 degrees btdc and the crank will want to go backwards

example 2:
fire spark plug at tdc and the rod wants to go thru the crank and cause u to spin a bearing, blow a piston, break a rod etc.

example 3:
fire spark plug at 90 atdc and the rod will rotate the correct way

different ignition changes when combustion begins and in turn dictates how much torque is actually applied to moving the crank. too much timing and u will go boom. discretion should be used at the hands of a properly trained tuner.

ignition systems like msd are used in situations where a stronger spark may be needed. situations where high compression ratios and/or f/i is blowing out the actual spark from occuring. as discussed in the other forum with the "aftermarket spark plugs" with larger diamater wires or lower resistance, these modifications will not gain you any power.

[OROutdoors]

ignition timing control does not control the duration of the spark.

Spark duration is one of the keys to high performance ignition.

ignition timing control is for controlling when during the compression/combustion cycle the spark plug fires. this dictates how much torque is applied to the piston down the rod to rotate the crank. this is why changing timing makes a difference in power out put.

Well, yes, but that is easily accomplished with the current distributor and ECU. The ignition control modules that you can buy, such as the MSD 6a, still rely on the ECU for timing -- unless the module is actually a replacement ECU. Further, they still rely on the distributor pointing to the right plug wire electrode, and they still rely on an external coil to create the high voltage.

example 2:
fire spark plug at tdc and the rod wants to go thru the crank and cause u to spin a bearing, blow a piston, break a rod etc.

Since the fuel/air mixture does not burn instantaneously, igniting at TDC would not build too much pressure that it would cause havoc... as the mixture burns, the crank shaft continues to turn, and the piston moves away from the head. As the piston moves away from the head, pressure is reduced; by the time mixture is burned, the piston could have moved a relatively far distance away from the flame front. At low RPM this is not of too much cause of concern. At higher revs, the speed of the piston is of major concern and hence timing is advanced to give the fuel/air mixture enough time to burn before the piston moves away.

situations where high compression ratios and/or f/i is blowing out the actual spark from occuring. as discussed in the other forum with the "aftermarket spark plugs" with larger diamater wires or lower resistance, these modifications will not gain you any power.

Hunh? Blowing out the spark? You can blow out a candle or match by blowing hard enough that the ignitable gasses become too dilute to burn and the heat is remove from the gass source (the wood or wax). This is unlikely to occur in an engine -- the heat has no where to go, and what would be "blowing" on the spark would be combustibly mixture. If a properly set fuel/air mixture fails to ignite even with a good spark, it could be because the post on the spark plug could be sheilding the gap from the fresh mixture, and hence still retain some exhaust from the previous cycle (which wouldn't ignite).

At high compression and high fuel/air mixture ratios, the mixture has a higher resistance to electrical conductance and hence the spark has a more difficult time bridging the gap of the spark plug. High voltage permits a stronger spark which burns hotter, and longer, yeilding a greater chance of igniting the mixture, or ingiting the mixture more thoroughly.

[Steeb]

Spark duration is one of the keys to high performance ignition.

I should think that with a sufficiently strong spark, that the duration of the spark is of negligible difference

this would be more of a cdi vs inductive ignition topic as many tests have shown that there is minimal difference in power output for a initial stronger spark vs a longer duration spark. it is true, a sufficiently strong spark, will have a negligble difference from a longer duration spark considering the strength of both are sufficient to ignite an a/f mixture. a stronger spark will be less likely to get "blown out"

Well, yes, but that is easily accomplished with the current distributor and ECU. The ignition control modules that you can buy, such as the MSD 6a, still rely on the ECU for timing -- unless the module is actually a replacement ECU. Further, they still rely on the distributor pointing to the right plug wire electrode, and they still rely on an external coil to create the high voltage.

products like the 6a do not give you control of the ignition timing if you are using the ecu to control it, however if it is hooked up to an ems that is controlling ignition timing it is a different story. what you have done is make the spark stronger. msd has products that can modify ignition timing as well as increase the voltage but the 6a only increases voltage

Since the fuel/air mixture does not burn instantaneously, igniting at TDC would not build too much pressure that it would cause havoc... as the mixture burns, the crank shaft continues to turn, and the piston moves away from the head. As the piston moves away from the head, pressure is reduced; by the time mixture is burned, the piston could have moved a relatively far distance away from the flame front. At low RPM this is not of too much cause of concern. At higher revs, the speed of the piston is of major concern and hence timing is advanced to give the fuel/air mixture enough time to burn before the piston moves away.

yes, you are correct, the examples are to give general ideas of how timing changes effect the rotation of the crank and where the cylinder pressure goes. i like to keep some explainations very simple in case there is someone that does not have as much knowledge or understanding of an efi system. obviously you have more understanding of an efi system which is definately good +1 to u for that

Hunh? Blowing out the spark? You can blow out a candle or match by blowing hard enough that the ignitable gasses become too dilute to burn and the heat is remove from the gass source (the wood or wax). This is unlikely to occur in an engine -- the heat has no where to go, and what would be "blowing" on the spark would be combustibly mixture. If a properly set fuel/air mixture fails to ignite even with a good spark, it could be because the post on the spark plug could be sheilding the gap from the fresh mixture, and hence still retain some exhaust from the previous cycle (which wouldn't ignite).

actually you can and your explanation is along the right lines

At high compression and high fuel/air mixture ratios, the mixture has a higher resistance to electrical conductance and hence the spark has a more difficult time bridging the gap of the spark plug.

and this is what people call "blowing out the spark plugs" this is where an msd 6a or any type of ignition amplifier would come in handy.

High voltage permits a stronger spark which burns hotter, and longer, yeilding a greater chance of igniting the mixture, or ingiting the mixture more thoroughly.

again, cdi vs inductive ignition. depending on what kind of ignition system you use will decide the characteristics of the actual spark.

[PATDIESEL]

You question is one of dabate and not answers IMO. Also, I don' think that anyone on here really has the knowledge to debate it propery.
However, spark duration does positivly effect the power. The longer the spark the better the burn of the gas and thus more power. This is of course only to a point. Higher grade gasoline acutally is less combustable and burns more slowly. The slower burn is more effective at creating power. (funny huh, but true.) The hotter the spark, same as above, better burn, more power etc. etc.. Stock ignitions have less coil capacity wether it be individual coils, external or internal coils. Ususally starting with individual being the best of the stock and working downhill to the right of the list above. Thus a aftermarket spark controller and subsiquent upgrade of coils, wires and plugs will create a significant amount more power. Why, b/c the aftermarket controller will hold the spark longer than a traditional disty cap (where it only sparks for the tiny split second that the rotor passes over the tit in the cap), it will bea hotter spark b/c the aftermarket set-up will have a much higher capacity coil to sustain a large amount of voltage for the extended spark time. It can controll timing more minutely than the stock set-up and thus you get more "real" controll over the timing of the spark. The better wires will chanel the voltage to the plug with less loss of voltage, see above about benefits of more voltage. Lastly a better plug will conduct the voltage more efficiently.
In the end what you are asking if for very specific knowledge and tests done on aftermarket vs. stock set-ups. What is obvious is that the spark set-up on our cars is old and outdated. It could definately use a make-over and greatly benefit from it. Both gas milage and power will benenfit, but the acutal gains on a stock motor have not been specifically tested since most upgrade the spark system when they do major upgrades and know that it will be Needed.

[OROutdoors]

Okay, so I did some more research on the 6 series of Capacitance Discharge ignition systems. Here's some info, as I understand it, though I may be wrong, feel free to correct me.

Some things are as I had suspected, some are different. Yes, the 6 series ignitions are passive in that they don't include a microprocessor, don't do their own timing, and still rely on the distributor, points or magnetic pickup, external coil and ECU. But, they do: condition the electricity going to the coil by transforming it to a higher voltage, choking it and temporarily storing it in a capacitor; reduce the amount of voltage necessary to transfer through points -- greatly extending the life of the points if used; and can limit revs in either one or two steps.

Since the output voltage of the CD is higher, going to the coil, the output of the coil should be higher too. Also, since the voltage is being transformed and store is a capacitor, there should be less of a voltage fade at high RPM. This should be noticably beneficial to high RPM power. I can see where CD would be good. It does seem that a new (stronger) coil, wires and plugs would be all the help that many people need -- especially if on a tight budget. I wonder if there is a coil which would normally be used as part of a CD system, which could also be used natively. This could allow a person to do a small step up, and then add the CD later.

For that matter, I wonder how hard it would be to build your own CD system.

[OROutdoors]

UPDATE: I recently went to Nology's site and checked out their stuff. They are definately in the no-MSD camp. And they make a persuasive arguement about duration of spark at high RMP equals wasted energy since the crank shaft is moving so fast. Wasted energy means for the same strength of spark, you would need more elecrticity for the longer spark, which would mean bigger draw on the alternator, which in turn reduces wheel HP. Or, for the same power draw, the spark over a shorter period would mean a hotter spark.

Their main objective is a short-lived but massively powerful spark. That also seems to make sense to me.

Anyway, one question I posed at the beginning of the thread was if there is an external coil that can work with an otherwise stock mx-3 ingition. The answer is yes, Nology makes one called ProFire. I also saw that they make an item called PowerCore, which is suppised to make your normal coil charge faster and put out a higher voltage. I'm pretty sure it is a capacitor itself, which uses it's capacitance to assist the coil, without it actually being a CD system. Anyway I decided to order both from Summit Racing. I plan to test them out individually and together. I'll let you know what I find out.

[jr4wdtrbo]

Get a cam angle sensor and run a distributorles ignition with a miata coil.