Spark plug theories and discussion cont...

[troybilt]

continuing on from this thread:

Spark plug discussion (http://www.exriders.com/vbb/showthread.php?s=&postid=3936239#post3936239)

So far the consensus is running a cooler plug is the safer bet, to keep operating temps down. Hotter plug prevents fouling and may or may not be recommended use with richer oil mixtures.

Good website that was linked earlier:
"Spark Plug Basics
The primary function of the spark plug is to ignite the air/fuel mixture within the combustion chamber under any operating condition.

Spark plugs must provide a path and a location for electrical energy from the ignition coil to create a spark used to ignite the air-fuel mixture. A sufficient amount of voltage must be supplied by the ignition system to spark across the spark plug gap. This is called “Electrical Performance.”

The spark plug firing end temperature must be kept low enough to prevent pre-ignition, but high enough to prevent fouling. This is called “Thermal Performance”, and is determined by the heat range selected." read the following to learn more...

NGK Technical Documents (http://www.ngksparkplugs.com/tech_support/spark_plugs/index.asp?mode=nml)

[tritty_wall]

My motor came with a B8ES, should I be running a BR8ES or BR9ES? Its a ESR 350PV with race gas. What are different between BR8 and B8? Thanks

[gandgracing]

The "R" stands for resistor. I have always used these kind of plugs.

[atvmxr]

well this is what Derby said in the other thread:
If I was running motorcross which is tight short bursts of acceleration I would run a std or one step hotter on the plug where temps are not as high as running wot for long periods plus the less chance of fouling the plug especially in competition is important.



which I agree with and thus why I started running the hotter plug in 1995 or so.

but I've never heard a motor builder say this. plus I would think with race gas the bike is going to run cooler and you need a hotter plug, not a cooler one to get oil buildup on the plug under control....

[fearlessfred]

simple put,u should run the coldest plug u can that doesnt foul under the conditions that u ride in. if your motor is stock i would not change a thing. if u have mods done to your motor that have increased combustion temps, than a colder plug is in order.u will not know intill u try it. lowering combustion temps ( that are high from mods like raising compression ) by use of a colder plug makes good sence.it will help prevent detonation.everbodys situation us diff. u should recheck jetting when going to a colder plug . most people jet on the fat side to keep there motors alive and i do it also. just because joeblow is running a hot plug does not mean that everone else is in need of one.

[All250R]

In general I try to recommend to not fix things that aren't broken. We love to modify out bikes. It's almost unavoidable. The thing is to try to be disciplined enough to know when you're changing something for a reason you understand and more importantly that you need.

If you don't understand a modification you're making, you may have a positive effect somewhere, but a negative one somewhere else. After a series of these modifications, you may really have a set of things to unwind if you happen to have an issue and you're not sure what the problem is

If you don't need to make a modification, you're potentially wasting your money. If combined with not understanding it, you're potentially wasting your money on something that makes your ride worse. Though it was fun bolting on some spacer plates and a new head, and got you excited for the moment some restraint might make more practical sense.

I agree with fearless in general. If you're not loading the plug up with dinosaur (non-syn) oil, run the cooler plug. Going hotter will likely not give a performance advantage you can feel or possibly even measure. What's worse is if it somehow makes the aluminum hotter, performance may suffer. Again, make the change for a reason you understand and need. I think that's the best rule of thumb in general.

[wilkin250r]

It's important to note, for for those that aren't familiar with heat ranges, that a colder plug only runs colder ITSELF. It pulls heat out of the combustion chamber, but not enough to actually change your engine temps. It's like pulling a teaspoon of water out of a bathtub, you don't significantly change the level of water in the tub.

[fearlessfred]

Originally posted by wilkin250r
It's important to note, for for those that aren't familiar with heat ranges, that a colder plug only runs colder ITSELF. It pulls heat out of the combustion chamber, but not enough to actually change your engine temps. It's like pulling a teaspoon of water out of a bathtub, you don't significantly change the level of water in the tub. that is a good point,but if the plug is to hot and preignition ocurrs because of it than engine temps will rise and possible damage, so it still makes good sence to run a colder plug when mods have that raise combustion temps have been done

[wilkin250r]

Originally posted by fearlessfred
that is a good point,but if the plug is to hot and preignition ocurrs because of it than engine temps will rise

Indeed, but preignition in another level. I'm simply pointing this out because I have seen some that believe a colder plug will actually make them run colder.

Another important thing to note, for those new to spark plug heat ranges, is that the wrong heat range can make plug reading for jetting extremely difficult.

Plug reading has a lot to do with heat, if your plug is too hot your going to have a white spark plug regardless of your jetting, because your plug is burning everything off.

[derby]

Originally posted by wilkin250r
It's important to note, for for those that aren't familiar with heat ranges, that a colder plug only runs colder ITSELF. It pulls heat out of the combustion chamber, but not enough to actually change your engine temps. It's like pulling a teaspoon of water out of a bathtub, you don't significantly change the level of water in the tub.

I disagree I have seen measurable temp drops back to back comparing plugs on the same gas, coolent, temp, and day in the dunes.

[fearlessfred]

Originally posted by wilkin250r
Indeed, but preignition in another level. I'm simply pointing this out because I have seen some that believe a colder plug will actually make them run colder.

Another important thing to note, for those new to spark plug heat ranges, is that the wrong heat range can make plug reading for jetting extremely difficult.

Plug reading has a lot to do with heat, if your plug is too hot your going to have a white spark plug regardless of your jetting, because your plug is burning everything off.
i definitly agree with what u say about reading the plug,and that is my very reason for making the suggetion to go to colder plugs when mods that increase combustion temps have been done. i believe with the correct heat range and corrected jetting that u can get the most horse power that is already there.most everyone fattens up the main jet when having pinging and detonation issuses,when the first thing that should be done is to go to a colder plug.

[jcs003]

what are the coorelation to this as it related to the newer more advanced plugs? i.e. iridium, platinum and etc. they claim these plugs are more efficient and will fire more consistently and withstand fouling.

[wilkin250r]

Originally posted by jcs003
what are the coorelation to this as it related to the newer more advanced plugs? i.e. iridium, platinum and etc. they claim these plugs are more efficient and will fire more consistently and withstand fouling.


It has to do with the size of the electrode.

The reason a spark plug fires is because it has such a high electric field around the electrode that it ionizes the air in the gap, and creates a conducting path through the air from the electrode to the ground strap.

A principle of electricity is that electric fields will concentrate around sharp corners and points.

So, the if you can make a spark plug with a thinner electrode, you'll get a better electric field around that electrode. Better field means it will fire easier, with less voltage, or over larger gaps, or just fire better under adverse condition (like fouling).

The problem is, spark plugs wear out. The constant spark will wear down the electrode, and if it's thinner and more pointy, it will wear down signficantly faster.

And THAT is the beauty of those special plugs. Platinum and iridium are extremely hard substances, so you can make a much thinner electrode that won't wear out.

Two problems. These substances are extremely expensive, so the price goes up. And the benefits, while they can be tested and proven, aren't super significant. The theory is solid, but it's not a night and day difference.

[HondaATC500X]

I've always gotten much more consistent tuning and cooler running engines (That allowed me to jet the motor down to a closer tolerance) with colder series plugs vs hotter ones (IE, 9s vs 8s.) I've never ran a 10 before (Because I can't buy them locally), but I know guys that have and they swear it makes all the difference in the world.

[jcs003]

Originally posted by HondaATC500X
I've always gotten much more consistent tuning and cooler running engines (That allowed me to jet the motor down to a closer tolerance) with colder series plugs vs hotter ones (IE, 9s vs 8s.) I've never ran a 10 before (Because I can't buy them locally), but I know guys that have and they swear it makes all the difference in the world.

well this past saturday i put in a br9es ans to my normal br8es and it definitly ran better.

next time out i will try one of the br8eg than a br9eg. with these future conparisions i will then step up to the iridium.