I know that in NGK higher the number colder the plug
but they have so many different code/numbers
14mm 5/8 hex 3/4" reach , resistor or non resistor is the category

I like to try different heat ranges but:
Bkr7 is colder than bkr6 is colder than bkr5 ...

FR5 is colder than di FR4 ...

R5672A-9/7405is colder than R5672A-8/7173

How (for example ) are related FR4 to bkr6?
OR
R5672A-9 to Bkr7 ?

I mean...when I ended to try the FR's ones ... Where I have to start with a BKR's?

OR
when I tested the BKR's.. Where I have to start with R5672A's?
Thanks

 

I would think the same heat range applies. A 5 is a 5 regardless of whether or not it's a resistor type? That's just my guess. Why are you trialing so many plugs?

 

So do you think that (regardless of the resistor) the order should be:
from hotter to colder
FR4
FR5
BKR5E
BKR6E
BKR7E
R5672A-8
R5672A-9

?

Im asking because I'm also using these kind of plugs on my dual plugged Harley too that it's prone to detonation and I'm searching the coldest plug (without fouling )

 

Is Your Harley fuel injected or carbureted? The reason I ask is that if you are having detonation issues with an air cooled engine like that you might try the old fashioned way of de-carbonizing your engine. I have heard of people doing the same trick to water cooled engines as well. When Air cooled VW's start detonating it was usually because of carbon in the head but frequently on the top (crown) of the piston. It is a fairly common problem on certain engines like the flat four VW with it's low compression ratio or just plain old bad gasoline or low quality gasoline could cause it. People used to put the cheapest gas they could find in their air cooled VW's and I de-carbonized many of them afterwards.

The solution was simple, we would add small amounts of room temperature water down the intake. This would make the car run rough and cough so you give it a bit more throttle and keep on adding the water. Do not use more than a few tablespoons unless you have to. The water would go down into the cylinder where it would break up the carbon and out the exhaust would come all kinds of nasty stuff. It always amazed me how much hard stuff came out of the exhaust when we did this. Afterwards the engine would run much cooler and not have any issues. BTW a professional mechanic taught me this trick, it is not some old wives tale.

Best regards!

 

Thanks, It's a carbed High compression Sportster.
I made this process just 2 weeks ago. Not impressed by the "hard stuff came out" because nothing came out. Pistons and cylinder are new and I was expecting to see some decarbonization of the combustion chambers. I usually spray some nebulized water just on the throat of the Mikuni carb. I think I can achieve some clean combustion chambers only with a Water injection kit , so I can inject water/alchool in a continuative manner. (but this in unfeasable on my bike)
But the problem with my bike is the Fuel. I need 100 octane fuel and it doesn't detonate. STOP. I'm trying to lower a bit the temp on heads. Lowering the oil temp doesn't helps so much.

 

-9 NGK plugs are very cold, usually used for boosted applications.

 

I have a 1968 C3 with 12.25-1 compression ratio and it wants the "old 106 Octane" fuel of the late sixties. I have experimented and am now doing final installation of a methanol/water injection system from a company called Snow Performance. The system they sell is a nice compact unit (unfortunately, too big for a bike) that sends pressurized methanol/water into the two little jets mounted in my intake manifold. The water/methanol combo gives my car the equivalent of 115 octane fuel and a bunch of extra horsepower all while cooling down my combustion process. I have a vacuum controlled device that activates the pump when the engine is under load, it works very nicely and cools the engine down a bit. Call Snow performance and tell them you want a "compact version" of the injection system

I don't think that you will stop detonation by changing your spark plugs. One mistake you do not want to make is trying aircraft fuels. I am a private pilot so I used to mosey over to the airport and fill my Corvette up with 100 Octane low lead which was less than a dollar more per gallon than regular was. I learned that aircraft rated fuels have 8 times as much lead as automobile gas did even in the 1960's. I was dealing with lead deposits everywhere, I ended up taking the heads off and doing them over to get rid of the excess lead fouling.

At one point I was sold some Tetra-ethyl lead in liquid form that would change your gas into leaded gas but bumped the octane up enough for my motor. Bad stuff, gets through your skin and all kinds of warnings about that stuff. If worse comes to worse loose some of the compression in your Harley or retard the ignition when she detonates. I heard that the newer cars can hear a single knock and retard the ignition of a single cylinder without affecting the others, it then returns the timing and if it knocks again then it holds it back longer. It might be something that might show up on bikes in the near future.

Are you absolutely sure that your engine is getting enough gasoline? Have you checked it with a AFR meter or gauge? My Corvette acts really funky when it is too lean, that can aggravate the knocking or detonating. I heard that the later Harleys are running really close to the point of too lean to improve their emissions.

Again I wish you the very best in finding a solution that works for you and makes your engine happy while cruising around!

P.S. Spraying an very fine mist of water onto each of your heads would help remove the heat, used this on high HP air cooled VW's. It would not be hard to build a system to do this!