NGK spark plug numbers

[naughtyG]

Re: May have found a cheap coil/wire replacement option

I'm not quite sure I fully understand the hotter/cooler spark plug theory thingy. Could anyone explain this properly?

Also, how do you find out which is the appropriate cooler or hotter plug for any given motorcycle? Can you tell by the plug's name/numbering system?

Finally, what's the difference between a resistor or non-resistor type plug, how are they identified, and will they make a difference to the coils' secondary circuit load?

 

[maleko89]

Re: May have found a cheap coil/wire replacement option

The hotter the plug the farther up the plug the heat goes before going to cylinder head to cool. Cooler plugs have less distance to travel to dissapate the heat.

Here's a picture to help with NGK's numbering system. You can tell the heat range and whether it's a resistor plug by looking at the numbering.

Plugs with a long insulator nose, which leads heat high into the plug body before it turns back toward the cooler cylinder head, are "hot." Short-nosed plugs, with a shorter heat path, are "cold." The Vmax plug is DPR8EA-9. The 'R' tells us it's a resistor plug. You can also get DP8EA-9's for the Vmax which is what I run. The resistor help against RFI interfence.

 

[rollin thunder]

So whats the best plug for the max?.

 

[AMechEng]

If you have the correct air fuel mixture I would think the stock plug would be good. If your bike is run rich, you can run a hotter plug. If its running lean, a colder plug. I think this is how it works.

 

[one2dmax]

Stock plug works well for 95% of most situations.

 

[rollin thunder]

Thanks ! Are there any aftermarket plugs that give a more powerfull spark?.

 

[MaxMidnight]

Depends what you mean by 'a more powerful spark'.

A plug can only use what is generated by the coil - there is no miracle plug that can increase this.
In fact it is the opposite - all they will do is reduce the spark over the course of their service life due to an incorrect gap or fouling.

There are plugs that claim to give a better spark (e.g. Iridium) but any benefit (IMHO) is because new plugs have been fitted rather that the type.
I wonder if anyone has done ab back-to-back dyno test with standard and (say) an Iridium plug?
My money is that you won't notice one iota of difference.

The other point to consider is if an allegedly 'better' spark will allow the fuel to burn quicker. Again I have my doubts.

If you want to throw some extra money at the HT system use it to make sure the leads and plug caps are in good fettle rather than on expensive plugs.

 

[wildweasel_pt]

Agree with him ^. I had Iridium on my bike that i inadvertently flooded when rebuilding the bike and i needed to make it run so i got a set of standard stock ones and i noticed no difference whatsoever. May make a difference on high performance bikes not on a vmax.

 

[dillrepair]

someone did back to back dynos with the iridiums and stock (both were new sets of plugs) on the xs650 forums somewhere (my other bike) and got a couple extra horsepower out of it which is why i use them on my 650 bobber, and just bought a set for my newly acquired vmax. I never noticed that much of a difference but i do think they probably help it run a little more consistent. the set i bought is dpr8eix-9 which should fit.

 

[RaWarrior]

The idea with iridiums is the spark is concentrated to a very fine and extremely durable electrode. They're more resistant to fouling/misfires, and in most cases last the life of the engine.

In a good running engine, there really isn't any seat of pants difference other than your wallet is considerably lighter since they cost 4-5x as much than a regular. But if you want to "set and forget" your plugs go for it.

 

[Suave Cowboy]

I guess I'll get the iridiums! I've always wondered about this, glad to finally have it put to rest. Reading random threads on here is so helpful! I could chill on here all day :surf:

 

[davesax36]

Proper gap makes a bigger difference than electrode material.

Sent from my Galaxy Nexus using Tapatalk 4 Beta