correct spark resistance

[Steve Best]

it may have just been coincidence that the cdi went it was over 3 years old , but what I said was I switched from a normal b6hs to a ngkr b6hs the r stands for resistor but I wasn't asked what resistance if 3 types exist it could be any . with the r plug fitted my revometer and Speedo worked fine , with the normal plug the readings on both were going nuts . Is it possible the r plug had too high a resistance?

Not likely, but sometimes the center post can come loose becoming a bad connection.
You can test them.
Sparkplugs are generally 0.5k to 4k ohm. Wires should be 1k to 10k ohm if I remember right.
Any more than 10k you likely have a bad connection or component and it will likely be much higher than 10k ohm.

 

[zippinaround]

Not likely, but sometimes the center post can come loose becoming a bad connection.
You can test them.
Sparkplugs are generally 0.5k to 4k ohm. Wires should be 1k to 10k ohm if I remember right.
Any more than 10k you likely have a bad connection or component and it will likely be much higher than 10k ohm.

right then I will finally have to give in and get a multimeter. thanks will report back after I check

 

[butre]

You are very right about gap resistance and Paschen's law, but both apply to an active arc. Before the arc starts and once the spark stops an entirely different set of rules apply.

Please excuse my loose choice of words. Compared to the huge dielectric (insulating) resistance before the spark jumps, the resistance during arc flow is almost nothing.

My whole point is that resistance wires and plugs do not hinder the spark. Before the spark jumps there is no current flow so there is no resistance to (or reduction of) voltage. It is voltage that jumps the gap. The resistance is MUCH less than the Paschen R value for the gap, so it doesn't hinder the current flow during the arc. What the resistance does is dampen out the counter-emf harmonics during the arc and after the spark. In other works it gets rid of the big radio frequency pulse.

I see what's going down, we're talking different points. I'm talking in response to jaguar's post regarding weak spark, explaining that. you're completely right about EMF and how bad that can be. all I meant to do was explain why it's silly to think that a resistor in series with the plug would improve the strength of the spark. my bad for not being clear.

 

[JAM Power]

If you use a spark plug with resistance (such as Iridium plugs) then you need to use a non-resistor spark plug cap. Otherwise the spark current will be reduced for a weak spark. And if you have a non-resistor spark plug and a non-resistor spark plug cap then the excess spark current may burn out your high voltage coil. With small engines every little nit-picking thing is important.

About this, maybe could you explain this phenomenon:

I bought several spark plugs from B6HS, BR6HS, BR6HS-10, B6HS-10, BPR7HS and their similar in 5 (hotter spark number). And at different gaps, it seems non-projected works better at 11mm gap and protected at 8 or 9mm gap (depends on altitude).

Here we can see, in the oscilloscope, the effects of resistance at spark plugs:
http://www.brightsparkmagnetos.com/faqs/FAQs about magnetos generally/Are suppressors and resistor sparking plugs OK to use with magnetos.htm

About resistive spark plugs caps... Well I have a 5K NGK one.

And this is important because this elevates voltage output theorically as long as higher the resistance, higher the voltage. But as we can see in the link above, is the opposite.

Curiously, adding a resistive spark plugs gave me better results and less vibration, and less misfires, that non-resistive spark plugs (Same gap). Because I feel the power output increase at low and high rpms. (Far, far less vibration at 7700RPM than with non-resistive spark plugs).

And there were 5K from the resistor-cap and 5K from the resistive-spark-plugs. Extrange effect from resistance.

(Top speed, remain the same for both type of spark plugs)

Does anybody knows why this happened?

BTW I have a IRIDIUM spark plug with 1 Mega ohm, and the motor runs smoothly with this one, even if it has the same power output as it has a brighter spark (Same as non-resistive spark plugs) is a lot of less vibration than with the ones with regular electrode.

Also, any idea about how why did this happen?

 

[Frankenstein]

About this, maybe could you explain this phenomenon:

I bought several spark plugs from B6HS, BR6HS, BR6HS-10, B6HS-10, BPR7HS and their similar in 5 (hotter spark number). And at different gaps, it seems non protected works better at 11mm gap and protected at 8 or 9mm gap (depends on altitude).

Here we can see, in the oscilloscope, the effects of resistance at spark plugs:
http://www.brightsparkmagnetos.com/faqs/FAQs about magnetos generally/Are suppressors and resistor sparking plugs OK to use with magnetos.htm

About resistive spark plugs caps... Well I have a 5K NGK one.

And this is important because this elevates voltage output theorically as long as higher the resistance, higher the voltage. But as we can see in the link above, is the opposite.

Curiously, adding a resistive spark plugs gave me better results and less vibration, and less misfires, that non-resistive spark plugs (Same gap). Because I feel the power output increase at low and high rpms. (Far, far less vibration at 7700RPM than with non-resistive spark plugs).

And there were 5K from the resistor-cap and 5K from the resistive-spark-plugs. Extrange effect from resistance.

(Top speed, remain the same for both type of spark plugs)

Does anybody knows why this happened?

BTW I have a IRIDIUM spark plug with 1 Mega ohm, and the motor runs smoothly who's this one, even if not the same power output (Same as non-resistive spark plugs) is a lot of less vibration than with the ones with regular electrode.

Also, any idea about how why this happened?

Well if you want to be completely equal you need the gap the be the same between plugs and the gap itself should face the exhaust every time you bed the plug. Slight differences in manufacturing will face that gap in different directions which does have an effect on how well the engine burns and cycles.

Iridium plugs seem to clean up how these fire but haven't seen it make less power, you may just be running a cooler plug that just won't burn as hot, gap shouldn't be touched on the iridium plug, if you bump up to a better cdi you'll see the most you can get from electrical improvements. Everything else is basically mechanical (like the direction of a gap for example, or the compression ratio, all physical changes that change how fuel is delivered.)

 

[gary55]

I think your backwards on your gap direction. Should face intake, but probably doesn't matter much in center plug heads with squish bands.

 

[Deleted member 12676]

If you are using a standard CDI then the timing is too advanced and a weaker spark will produce a slower flame front which equals the effect of retarding the ignition which is needed with a stock CDI.

 

[gary55]

I Think I see what your getting at. If the ground was facing the intake rather than the gap it would shield the kernel, and retard the timing.

 

[Street Ryderz]

Indexing the plug helps for finely tuned engines looking to shave fractions of seconds while racing other than that the average user will never see the difference.timming retard from resistance would be a small fraction of a second and again not noticeable by the average user other than if it was to rich,The bigger problem is that the resistive plug and boot deliver less spark strength and then only supports a leaner burn cleanly witch means less power overall now due to lack of cylinder fill.The stock cdi can support upto 11,000 rpm with the right air fuel ratio and the cylinder fill maximized,with the stock head and modded stock muffler I have a couple engines with a thousand plus miles and two seasons on them allready this will be there third untouched since mounted that will turn this rpm and cruise at 30 all day.These engines can take alot for the price and crappy quality,and they can easily far exceed the manufactured intent and everyone will get different results due to their ability.

 

[JAM Power]

I think your backwards on your gap direction. Should face intake, but probably doesn't matter much in center plug heads with squish bands.

Due to your post I tested several spark plugs, with different gaps and resistance, and I always buy a couple or more of the same sonI have a control spark and some others modified of the same "code number".

They usually are 1/8-1/4 turn more or less from the control, I test all of them before modifications (in order to check carburation).

In off-set cilinder heads I always try to have the spark plug's ground electrode facing upwards +-1/8 turn, no more.

Some gaps are pointing left, other right ,other exhaust, other intake, and some in between, and yes, my tops are all having a squish band, so I found, in these cases, where the go.is pointing seems not to be that important.

However I never tried them without a squish band.

Does somebody have tested spark plug's gap orientation? Or know if there is a thread about it?

BTW I re-checked a Bosch iridium spark plug that works the best among all the diferent tested spark plugs, an I have tested (even) with a gap of 3.6 mm gap and it has 1 Mega-ohm, and it gave me a nice response.

I tried a resistive spark plugs (5Kohm) with a max of 2.9mm (35.3mph/56.8kph some sputtering in mid range RPMs) , however, it seems the best power (accord to having a timing retarding due gap increasing) is about 2.5-2.6mm gap (top speed 33.3mph/53.6kph great continuous aceleration, no-sputtering).

However 1Kohm resistive Bosch iridium performances with a better aceleration and never misfired, even on cold conditions.