Let's Talk Spark Plugs!!

[dlaing]

I am sure TLM is correct that it will work, but I'll bet the output per plug has got to drop, not 50%, but significantly.

Nope. Dwell time is more than adequate for the coil to saturate the core. The two sides of the coil aren't separate either, they're bifilar wound. They're going to act identical and any difference between the two plugs off of one dual-plug coil will be solely the result of the wires, plugs (gap) and the mixture resistance in the combustion chamber at that specific plug when it fires.

So if twice the energy is being used by a dual plug coil, than does that put the ECU at greater risk for failure?

[callison]

So if twice the energy is being used by a dual plug coil, than does that put the ECU at greater risk for failure?

 

No. The energy that produces the spark from the secondary winding(s) of a coil is stored as magnetic flux in the iron core. It takes several tens of milliseconds for the 12 volts passing through the primary of the coil to acheive magnetic saturation of the core and charge the magnetic field to it's highest density. So, as soon as 12 volts starts passing through the primary, it is charging, but as the charge time is long (in electronics anyway), the current draw is limited. This is dwell time, the time the points are closed or the ECU is in conduction. When it's time to fire the plug, the points open, or the ECU stops conducting and the current return path for the primary is broken. There is no current flow to maintain the magnetic filed induced on the core, so the magnetic field collapses releasing all of the energy stored as magnetic field. The magnetic field, which took so long to build up, collapses in a couple of microseconds, which is orders of magnitude quicker than the time it took to build it. The rapid collapseof the magnetic field induces a voltage on the secondary windings. Those windings have a very high ratio to the primary. Because the secondary windings have such a high ratio, they generate a very large voltage that causes the spark plug to arc over. Since the points/ECU are NOT conducting during the discharge time, they see no current flow (well, some, but it's inductive kickback). During the charge cycle, the primary sees very little of the secondary winding resistance because the secondaries are "open" , there is no load - the plug is not firing. Additional secondary windings add very little to the charge current on the primary so the ECU effectively does not see a change of charge current for one or more seconary windings (there is some, but it's relatively little).

 

What it works out to is energy storage. You take a hundred 1 gallon buckets of water up the stairs, dump 'em into a 100 gallon container at the head of the stairs and when it gets full, you dump the whole thing all at once down the stairs. Ond hundred small trips makes for one big splash. Same thing with the coil, you spend a long time building the magnetic field and then you dump it all at once.

 

This is a messy explanation, the next time I run across my old automotive electroncs books in the garage (probably never as I never clean the place up), I'll try to find a more succinct explanation.

[al_roethlisberger]

...I think that was an excellent explanation, and I'm glad to hear yet another opinion that the ECU should be just as safe with the dual-plug outfit as the OEM single

 

Now, as soon as I get that special turned 10mm socket from Mike Rich(on it's way) and can take some time away from painting the closets and kids' room.... I can hook all this up, including my new PCIIIusb

 

I'll update the voluminous "dual plug" thread with news of success or failure once I have a chance to report.

 

al

[Guest mnsmax]

I'd try it if the distance from the electrode to the piston at TDC was significantly greater than the plug gap.

The plug gap looks like about 3 or 4 times the stock gap, so you better get good wires to go with it.

I like the concept, but their are a lot of ifs and buts to be concerned about.

I agree with Dave.

Manufacturer of Brisk spark plugs doesn't play with 'length' of plugs for fun.

You can burn a hole in your piston by overheat in case if your piston is too close, but not by spark.

 

Design of Brisk spark plugs opening more surface area where sparks can hit electrode, and no ground electrode to slow down fuel mixture expansion, which makes it more efficient, which gives better idle, gas mileage and etc.

 

About a heat

Every bike has a personality and may run better with different plugs and heat ranges.

Heat range is important and critical in high performance engines, as is tip design. This design allow plug tip to be further into cylinder for better mixture ignition, as well as 360 deg. radius firing.

[jrt]

 

No. The energy that produces the spark from the secondary winding(s) of a coil is stored as magnetic flux in the iron core. It takes several tens of milliseconds for the 12 volts passing through the primary of the coil to acheive magnetic saturation of the core and charge the magnetic field to it's highest density.

So some of the very high revving sportbikes must be getting close to the dwell time. If it takes 10 ms to saturate the core, then that translates to an ability to spark at or below 12K rpm- 24K really, since it's a four stroke.

 

Nice explanation Carl.

 

J

[dlaing]

Nice explanation Carl.

Ditto!

Thanks Carl, I've read stuff like that before and been confused. Since you answered the description of what is happening as it relates to real world current issues, it makes alot more sense.

 

Dave Gross, from what mnsmax said, go one step cooler to start, but have them send you two heat ranges, especially if they are giving you a good price!

I am not sure how you read the color on those plugs, but you will probably get a good idea.

 

The Brisk plug should cope very well with the cross flow of fuel mixture and obviously require no indexing. The most likely problem is that the piston will be exposed to the flame front too soon, because it is not blocked by the ground electrode like on the stock bike. So, the piston may get too hot. A good test may be to shine a flashlight into the sparkplug hole and take a look at the condition of your piston before and after trying the Brisk plug. Signs of arcing will be very obvious to an aluminum piston. Signs of heat damage will take longer to show, but should also be apparent after a fast half hour ride. Any increased pinging, pull the plugs immediately.You may be able to use indexing washers to back the plug away from the piston.

Let us know how they work!

[Guest dkgross]

I'm not COMPLETELY sure I'm going to be brave enough to try this..But, I'll probably pick up the plugs and take them to Moto I and get their opinions as well.

 

I just thought one of you more knowledgeable folks would like to try them

 

Sure is fun reading all this stuff. You guys know WAY too much.

 

[gthyni]

So some of the very high revving sportbikes must be getting close to the dwell time. If it takes 10 ms to saturate the core, then that translates to an ability to spark at or below 12K rpm- 24K really, since it's a four stroke.

Make that 6k sparks/minute for 12k RPM

since is it a 4-stroke and each cylinder has

it's own coil.

[Cliff]

It may take 10ms to saturate but you don't need to saturate to get a spark.

I use 2.5 - 3ms of on time with My16M. The weber was around that also.

[al_roethlisberger]

Well, I'll be interested to hear how these Brisk plugs work out. I actually had never heard of them before this thread....

 

al

[callison]

Guys, I grabbed at the 10ms time simply because I don't know what it is in reality, but I wanted to show that the difference in time required to build and collapse the magnetic field is different on the order of magnitudes. Cliff is much closer to actual times, he has a scope and I don't/

[Guest dkgross]

I had Max from BRISK read this thread. Here's what he emailed me (his English is a little rough...)

--------------------------------------------------------------------------

 

Dave,

 

I found very interesting chart on www.v11emans.com , but really I don't know

what to tell a folks.

 

Kind funny response from someone who worries too much about pistons hit by

sparks. Actually, most of new ignition systems, like you know, use advanced

ignition, which will fire fuel before spark will reach flywheel dead point.

In this case sparks will never hit the piston.

 

Anyway, would you be interested to get set to try somewhere?

 

Best regards,

 

Max

-----------------------------------------------------------------

 

 

So, I'll probably have him send one of each pair, and try to cooler ones first.

 

fwiw..MANY MANY folks on the BMWRT.COM website love these things...

 

 

dave

[dlaing]

Kind funny response from someone who worries too much about pistons hit by

sparks. Actually, most of new ignition systems, like you know, use advanced

ignition, which will fire fuel before spark will reach flywheel dead point.

In this case sparks will never hit the piston.

 

I am always hearing claims about spark duration, so I assumed that the spark is still active at TDC.

How long does a spark last?

I got an answer from this website,

but they are talking a condensor and point system:

" The effect of this is to generate an output pulse, and hence a spark, of about 10 thousand volts that lasts for about 2 thousandths of a second (i.e. 2 milli-seconds, or 2mS). Not very long, you might think, but at 3600 rpm any one cylinder is firing 30 times a second i.e. every 33mS, so at that speed the spark lasts for 22 distributor degrees, which is 44 crankshaft degrees!"

 

Is the distance from plug to piston greater on a BMW?

[Guest dkgross]

Is the distance from plug to piston greater on a BMW?

 

I have no idea...

[al_roethlisberger]

So whatever happened with the experiment with the Brisk plugs?

 

al