Spark plug cap resister source?

[CaptonZap]

Has anyone found a source for the little resister in the spark plug cap?
One place wanted $29 for one cap, so buying a cap for the resister is not gonna fly.
Thanks, CZ

[BA80]

http://www.motorcycle-superstore.com...T.ac=SLIsearch

[natemoen]

long cap, XB05F

http://www.amazon.com/gp/product/B00...A2ZHLU57RWEDX2

Short cap, LB05F

http://www.amazon.com/gp/product/B00...A2F5NN4BGKFD8K

[TopCatGr58]

This brings up a chance for a discussion regarding the plug caps.

Do you use resistor plugs? IF so, then why worry about resistor caps?

Our TCI's are not subject to problems from RFI emitted by the plugs, and the resistor's purpose was to cut down RFI....or at least that's what I've read. I could care less about whether a car stopped next to me gets radio static.

I'll be happy to be corrected if there is another purpose for the cap resistor. I vaguely remember reading about having some resistance in the spark plug line to help increase the plug spark by requiring more energy before it can jump the gap, but I'm no electronics guru, so I don't know if this is true or just myth?

Zap, I've heard about folks putting a compression spring inside the cap to bypass the resistor and still be able to use the cap??j

As has been posted, lots of places to get replacements much cheaper than $29.00 ! MikesXS.net sells simple 90 degree units for $5.00 each, with or without resistor.

T.C.

[BA80]

Here's a little something I came up with in a short search TC........

http://www.ultralightnews.ca/articles/resistorcapsandplugs.htm

[TopCatGr58]

Hey Greg,

Thanks, that helps confirm my thoughts. With OEM coils, they are producing barely 15KV, add 5kv resistor and plug resistor and it seems like you're dropping the voltage very close to the 7kv minimal voltage necessary to generate a spark!

But now, let's play devil's advocate! The combustion process inside the engine is or can be rather complicated. Too low octane, and multiple flame fronts can be generated(Pre-ignition/knock), too high octane and the fuel burns too slowly and possibly incomplete. The purpose of the spark plug is to initiate the burn, flame front, but once started it should continue through to completion. So...a short "STRONG" spark burst should be sufficient, so I don't think having a longer spark duration would necessarily be wanted or needed. I know about the MSD(Multi-Spark Discharge) type systems, but I think they are for special very hi compression race engines and such.

So....I vote for a strong quick spark...one of the reasons I put on the DynaTek hi output coils, and don't use resistor caps or plugs.

[crazy steve]

As with just about anything on an internal combustion engine, there's always compromises involved....

Spark duration is important, as explained here: http://www.msdignition.com/page.aspx...erms=Why%20MSD
.... so adding a resistor inline with the plug isn't neccesarily a bad thing when it increases spark duration. But as the link Greg posted shows, some care must be used in deciding how much resistance. The main thing to remember is while voltage is important in getting the spark started, once it is it's the current that does the 'work' of igniting the mixture. Adding a resistor in series has no effect on current.

The RFI issue used to be a bit of a big deal (I know of at least one guy who got ticketed 'back in the day' by a LEO for 'interfering with a police radio') and I believe you can still make a complaint to the FCC against a RFI source. Whether or not they still do anything about it or if most modern electronics are affected as much by this, I can't say...

[MPittma100]

Spark Plug Caps

RFI is the only duty of the resisitor. Using resistor plugs requires no resistor in the spark plug cap/wire.

Summit Racing has these at a good price. http://www.summitracing.com. See part numbers: NGK-8070 and NGK-8031.

MP

[MPittma100]

Spark Plug Caps

If you want a non-resistor NGK cap, the NGK part number is LZFH. Dennis Kirk sells them for $1.50. The resistor caps can be had in 1K or 5K ohm resistance.

MP

[natemoen]

If you want a non-resistor NGK cap, the NGK part number is LZFH. Dennis Kirk sells them for $1.50. The resistor caps can be had in 1K or 5K ohm resistance.

MP

You need 2 different part numbers though.

[MPittma100]

Spark Plug Caps

You need 2 different part numbers though.

Nathan, I have seen the use of a combination of short and long on some engines. I have also used 4 90 degree as well with no problem.



MP

[PapaBear1950]

So what would happen with resistor caps and non resistor plugs?

[natemoen]

So what would happen with resistor caps and non resistor plugs?

Nothing. It is usually one or the other has the resistor. Doesn't matter which. Could do both, but that is just redundant.

As to using all 4 short 90 degree plug caps, yeah it works fine, just makes it more difficult to reach the center plugs. Just like you can use all long 120 degree plug caps but then you are more likely to break off a plug accidentally. Just cause something works doesn't mean it Is the best option (nor the worst). Just saying, the long 120's make it easier to not burn yourself pulling a hot plug.

[MPittma100]

Another Option

I have seen on the forum where some have opted for the rubber spark plug caps such as the ones used on cars and trucks. Just have to get the right size (7MM) for the plug wire. MSD, ACCEL, are two of the performance brands. Summit Racing or Jeg's carry these brands for a decent price. There are many others. NAPA has them in their brand (Echlin). All of these mentioned come in straight or 90 and are non-resistor.

MP

[TopCatGr58]

Originally Posted by PapaBear1950
So what would happen with resistor caps and non resistor plugs?

Nothing. It is usually one or the other has the resistor. Doesn't matter which. Could do both, but that is just redundant.

Hey PapaBear,

It could possibly be worse than just redundant.

Did you see and read the page from the first link? Using info from that site I mentioned about the possible problem with OEM coils of 15KV output, then using 5K caps and also resistor plugs of ~5k, and that produces 10k ohms, which would drop the coil output to about 5 KV, which would be below the 7kv minimum voltage needed to have the spark jump the gap! With a newer hi output 35+KV coil, then using both resistor plugs and caps would be okay, but with OEM coils, you are running the risk of greatly reducing the actual POWER/energy of the spark.

T.C.