Ignition Coil

I am not sure why you think Indi cars are the hardest working engines. They are limited to 10300rpm according to Wiki.

Think of the 1960s Honda motorcycle engines that used to run at 20000rpm, well before CD ignition.

Yes. I had a Honda 125 twin many years ago which ran at up tp 12,000rpm. And Formula 1 cars run at up to about 18,000rpm.

Perhaps the number of cylinders firing per crank revolution might influence something

The limit is not with the firing system, it is the flame front of the fuel in the cylinders.This is determined by the piston stroke.

The flame front of regular pump gasoline is around 5000 feet per second.So, if an engine has a stroke of 3 inches,then every revolution it travels 6 inches, so the theoretical limit would be 10,000 rpm.Remember this is theoretical max rpm.

Shorter stroke engines, like motorcycles, can turn faster.

Indy cars run different fuel to get higher rpm.

The super fuel rail dragster cars are running such rich mixtures, and high compression that if a cylinder fails to ignite, the engine goes into hydraulic lock up and self destructs.(The fuel mixture actually turns into a liquid).

The newest technology will replace spark plugs with lasers for ignition, with multiple focused ignition points.

I recently read up on the laser plugs. I'm not sure when they would be available for the consumer. I know you can get "pulse plugs" now that act like a tiny capacitor to store a much bigger punch.

Thank you guys for your info. Didn't know other engines run faster than Indi cars.

I have a rotary 6 engine on the drawing board. 2 spark plugs and fuel injector 180deg

apart. Estimated RPM 33 to 40 k, meaning 3 sparks / rev for each plug. Now you know

my reason for the question. Is there a system on the market that would fire so many

times per rev.

Interesting project. Sounds like you're going to be writing a lot of code to manage your engine. You'll have to have numerous "anticipation circuits" to account for the high revs. Existing coils will work, your task will be in writing code.

Question, why so high? That brings in so many other problems.

Fredsky you seem to be a smart guy. Don't let me hear from ya "pulse plugs" again.

I'm not smart, I just play a smart guy on TV

you can have one coil per "cylinder" to reduce how hard the coil works. I have had motorcycle engines that turned 16k on one coil. 33k on two should be no problems.

One coil per cylinder has been the way motorcycles have operated for decades. The modern car often has a coil-over-plug arrangement, started by Saab I think, that allows for less losses in the high voltage circuit and they deliver a vicious voltage around 60,000volts, for better ignition.

It is easier to distribute a low voltage (12v) supply than a high voltage one, lower losses, less EMC, less tracking etc etc.

''......It is easier to distribute a low voltage (12v) supply than a high one, lower losses, less EMC, less tracking, etc etc.....''

1. '...less losses...' how do you figure? Higher voltages allow lower current, reducing losses.

2. What is 'EMC'? A tech company of some sort right? Do they have an aversion to low voltage?

Loosen-up. It will take more than grammar corrections to gain the respect that you may or may not deserve on this forum.

Anonymous Poster; '...lighten up....'

Brighten up.

I wasn't correcting grammar, I was commenting on the idea that lower voltage systems allowed for lower losses. I made transpositional error and substituted a word. Actually I dhink either is grammatically correct.

hmmm...an anonymous poster lecturing me on deserving respect... interesting.

I have enough self respect to be not overly concerned with those who cannot see well enough to appropriately value my input.

At any rate I hope anyone reading my comments, or anyone's comments, does so with a critical discriminating eye, evaluating each comment on its own, instead of granting some forgivemess for inaccuracy (or discounting what is valid) based on a general opinion about the agreement or validity of unrelated comments written by the same person... I suppose I should give you credit to that end (allowing me to close on a positive note). As an anonymous poster, you have made sure no one could unfairly assign value to your comment based on previous remarks. Good work. :-)

Fair enough,

I hoped you'd know what I was talking about, but the point of answers to forums is that you should not assume others will know, so explain everything.

A distributor for high voltage ignition usually has a rotating cap and the current has to jump the gap to the electrode that connects via the spark plug lead. As well, high voltage leaks out through the leads. They may be an insulator, but every metre of lead adds to the losses. Try running a lead for 100 metres and see if the spark is still the same. That is not quite fair, because the other loss is capacitance. At high voltage you could expect this to be significant, but I couldn't give you a figure for it.

EMC probably was not the right word, that means electromagnetic compatability and is really relates to electromagnetic noise, hence the use of suppressors on ignition leads either built into the lead itself in the form of resistance or through a separate resistance in the cap, lead or even spark plug. The high voltage leads act like aerials.

Keep smiling :-)

Many new car manufacturers realize that it is easier to control a low voltage than a high voltage, for reasons mentioned elsewhere.In high power transmission lines, yes, it is more efficient for high voltage than low voltage,but since the OP mentioned an engine ignition system,the latter does not apply.When controlling ignition timing via computer, the components required for low voltage switching are much cheaper than for high voltage.In addition, as you mentioned there is less radiated noise from the coil-on plug system, and less places for the high voltage to escape the insulation.

Please guys keep this discussion civil. Some of you have a legitimate question , why the high RPM. No in and out valve action, no connecting rod , no piston that runs up and down and fires every 4 th rev. of the drive shaft. my R6 engine , plug 1 fires every 120 deg. plug 2 fires 60 deg. later and also at 120 deg. I have no formula to figure out the low and high RPM this could run. No need for a turbo charger. Air pressure can be varied form 140 to 150 psi and fuel adjusted accordingly.

Theoretically, if the RPM can be between 30k and 40k , one coil has to discharge 180k to 240k or use 3 coils per plug .The size of this engine would be 1/3 the size of my Ford Ezpl. V6.

Please hold discussion to possible ignitions.

The revs an engine can run to are usually limited to mechanical stresses (includes rotational stresses) and flame speed, but could also include mixture preparation (evaporation and turbulence effects).

If the ignition rate is too high, duplicate your ignition system. Some vehicles found it advantageous to have twin spark plugs per cylinder (Alfa Romeo and Mazda rotary). The latter because of the long combustion chamber (hence a good engine for hydrogen as fuel because of its high flame speed).

At this point twin spark plugs per combustion chamber can't be used. the length of the combustion chamber would be 70 deg. before the rotor reaches the exhaust port.This can't be changed, it's the same for any size of the engine.

As with most things, the devil is in the detail.

I appreciate the explanation. I was only considering i^2r losses. I've got what looks to be some interesting reading ahead.

Truth is not a compromise, it is an opinion.(IMHO)

There are no pistons in a rotary engine just loaded combustion chambers that is the reason for the high RPM. Combustion times radius of rotor = torque , should be 20 to 25 % higher than any piston engine with equal displacement.

I'll go back to your orginal post.

Limitations on ignition coil discharges per second are limited only by the design of the coil's tuned circuit. A "normal" ignition coil is simply a step up transformer and is designed for it's application (I4, V6, V8, etc). The tuned circuit the coil resides in determines its discharge rate. Smaller coils that run at high engine RPMs are possible thanks to individual or shared coil on plug or wasted spark ignitions, respectively. If you were to take "high energy" coils and place them on individual cylinders of a V8 engine, you would reduce the rate at which the coil charged/discharged. This would lower the mechanical requirements placed on the coil and theoretically extend its life. However, the capacitave side of the coil network would need to be redesigned, as discharge rates would decline and increase capacitor charge times.

CD is a completely separate discussion. I tried those capacitor plugs, they didn't do squat and fouled faster than regular plugs in my truck.