Dpr9z?s

[REDRIDDER]

Any of you gouys running one? and if so for what reason.I know the difference between the 8 and 9 but was just curious whos running them and the the reason you are.

[NacsMXer]

I run the 9z in mine. Just because its a colder heat range and i'm running 12.5:1 compression.....less of a chance for detonation. I know there's not a huge difference between the 8 and the 9 but it helps me sleep better at night :D

[REDRIDDER]

i was just curious cause i bought two of them just to try out.do you foul your plug any or have any difficulties with staring in cold weather or anything like that?

[drew416ex]

I ran it when i had a 416 with 12.5:1 and now with my 440 stroker with no problems. It gets in the 30's sometimes in winter and it busts right off every time. As long as your jetting is right you wont ever have a problem.

[TRXRacer1]

Originally posted by REDRIDDER
i was just curious cause i bought two of them just to try out.do you foul your plug any or have any difficulties with staring in cold weather or anything like that? It's the same spark so starting will be the same. The only difference is how the tip of the plug is insulated from the head in turn changing combustion temps.

[AutoRoc]

I run them. My Honda manual actually says to run it on a stock engine if you're running it at high speeds for long intervals.

Additional compression+ Hard riding and I'd reccomend it every time along with a slight increase in octance. The hotter the engine, the more likely it will be to ping/detonate.

[F-16Guy]

There was quite a bit of discussion on this subject a while back, and apparently the heat range of the plug has more to do with how hot the plug stays as opposed to changing the temperature of the combustion chamber. A hotter plug will retain more heat in the plug itself, and a colder plug will retain less heat. There is an optimum temperature range in which a plug should operate in order to stay free of deposits and work properly. A hotter plug will retain more heat from the combustion process, but if the heat range is too high, the plug could potentially overheat and fail. Likewise, a plug that doesn't get hot enough could allow deposits to form and carbon foul. A colder plug may slightly affect combustion chamber temperatures, but not nearly as much as proper jetting.

[Wheelie]

I run the 9z in my stroker.

I've read that several engine builders recommend running a cooler plug in a high compression EX.

[GPracer2500]

Originally posted by F-16Guy
There was quite a bit of discussion on this subject a while back, and apparently the heat range of the plug has more to do with how hot the plug stays as opposed to changing the temperature of the combustion chamber. A hotter plug will retain more heat in the plug itself, and a colder plug will retain less heat. There is an optimum temperature range in which a plug should operate in order to stay free of deposits and work properly. A hotter plug will retain more heat from the combustion process, but if the heat range is too high, the plug could potentially overheat and fail. Likewise, a plug that doesn't get hot enough could allow deposits to form and carbon foul. A colder plug may slightly affect combustion chamber temperatures, but not nearly as much as proper jetting.

F-16Guy nailed it.

The reason we have different heat range plugs is to control the temperature of the plug itself. Too cold and it's more likely to foul. Too hot and the plug can overheat. Unless an incorrect heat range plug is creating an abnormal combustion phenomenon (namely pre-ignition caused by an overheated plug), any effect differing heat ranges have on any temperature other than temperature of the plug itself is tiny, difficult to measure, and inconsequential.

Colder than stock plugs are recommended for applications where the engine builds more heat than "normal". This could be from extended, continuous operation at wide open throttle (as mentioned in most manuals), higher than stock compression, advanced ignition timing, or any situation that allows an engine to continuously operate at temperatures above "normal" for that engine.

When in doubt about whether the stock plug or a colder plug is needed for any given application, used plugs can be examined to determine if they are operating at the correct temperature.

Here's an old but good article written by Gorden Jennings (a long time moto-journalist and engine performance author). Some of it is dated (it was written 30 years ago) but the basic concepts outlined are all still valid. Spark plugs and many of the issues surrounding them have remained fundamentally the same for perhaps the last 100 years.

http://www.strappe.com/plugs.html

[TRXRacer1]

Tip temp and combustion temps kind of go hand in hand........ ;)

[GPracer2500]

Originally posted by TRXRacer1
Tip temp and combustion temps kind of go hand in hand........ ;)

How do you figure?

[fastredrider44]

I always ran an 8z in mine. 426 11:5 comp. I never did any extended high speed runs other than the occasional fire road or long field. I'm not sure if one could tell the difference anyway.

[TRXRacer1]

Originally posted by GPracer2500
How do you figure? A hotter tip will result in hotter combustion temperatures and vise versa, they're both playing in the same field. I tend to over simplify at times so I pasted in the following article from NGK:

The term spark plug heat range refers to the speed with which the plug can transfer heat from the combustion chamber to the engine head. Whether the plug is to be installed in a boat, lawnmower or racecar, it has been found the optimum combustion chamber temperature for gasoline engines is between 500°C–850°C. When it is within that range it is cool enough to avoid pre-ignition and plug tip overheating (which can cause engine damage), while still hot enough to burn off combustion deposits which cause fouling.

The spark plug can help maintain the optimum combustion chamber temperature. The primary method used to do this is by altering the internal length of the core nose, in addition, the alloy compositions in the electrodes can be changed. This means you may not be able to visually tell a difference between heat ranges. When a spark plug is referred to as a “cold plug”, it is one that transfers heat rapidly from the firing tip into the engine head, which keeps the firing tip cooler. A “hot plug” has a much slower rate of heat transfer, which keeps the firing tip hotter.

[GPracer2500]

Originally posted by TRXRacer1
A hotter tip will result in hotter combustion temperatures and vise versa, they're both playing in the same field. I tend to over simplify at times so I pasted in the following article from NGK:

The term spark plug heat range refers to the speed with which the plug can transfer heat from the combustion chamber to the engine head. Whether the plug is to be installed in a boat, lawnmower or racecar, it has been found the optimum combustion chamber temperature for gasoline engines is between 500°C–850°C. When it is within that range it is cool enough to avoid pre-ignition and plug tip overheating (which can cause engine damage), while still hot enough to burn off combustion deposits which cause fouling.

The spark plug can help maintain the optimum combustion chamber temperature. The primary method used to do this is by altering the internal length of the core nose, in addition, the alloy compositions in the electrodes can be changed. This means you may not be able to visually tell a difference between heat ranges. When a spark plug is referred to as a “cold plug”, it is one that transfers heat rapidly from the firing tip into the engine head, which keeps the firing tip cooler. A “hot plug” has a much slower rate of heat transfer, which keeps the firing tip hotter.

It's all about the temperature of the spark plug itself. When NGK says, "...help maintain the optimum combustion chamber temperature..." they are talking about the temp of the plug--NOT the temperature of the actual combustion. The heat produced by burning fuel will not change because of the heat range of the plug. The temperature of the plug tip itself will change with differing heat ranges. Only in that way does plug selection change combustion chamber temperature (since the plug is part of the combustion chamber).

If you can show me evidence supporting the notion that changing the heat range of the plug will change combustion temperatures, I'm all ears. I've looked in the past and have not found anything I can hang my hat on. To the contrary, the evidence I've found shows spark plug heat ranges are about one thing: the temp of the plug. Any side-effect plug temp has on other temperatures inside the engine too small to matter (barring abnormal combustion).

[AutoRoc]

All I know is if it gets too hot in a max effort tune, you will get in trouble. Luckily we don't stress these engines that hard.

You guys can split hairs!:):eek2:

[TRXRacer1]

Originally posted by GPracer2500
If you can show me evidence supporting the notion that changing the heat range of the plug will change combustion temperatures, I'm all ears. LOL, I already did so I think we need to agree to disagree on this one.

[Wheelie]

High performance cars running boost utilize cooler spark plugs. Why? To help prevent detonation and to keep combustion chamber temps down.

[GPracer2500]

Originally posted by TRXRacer1
LOL, I already did so I think we need to agree to disagree on this one.

No worries. I think we're just looking at it differently. :)

[NacsMXer]

Originally posted by Wheelie
High performance cars running boost utilize cooler spark plugs. Why? To help prevent detonation and to keep combustion chamber temps down.

True, same reason I run colder Motorcraft plugs with a smaller gap in my F-150 running 12 psi of boost.

[F-16Guy]

It's kind of a "chicken or the egg" argument. I think a plug that physically gets too hot can possibly be a source of ignition for preignition (kind of like a glow plug), but if you have the correct fuel mixture and octane rating, the intake charge shouldn't be that close to igniting that a hot spark plug sets it off. If you're running a boosted or high compression engine, it's potential energy is greater, therefore the combustion process is stronger and should create more heat. The extra heat may cause failure of a plug that can't dissipate it fast enough. It's basically the same concept as the engine's cooling system. If you double the engine's HP, there's a good chance that the existing cooling system may not be able to keep up, and you get an overheated engine. Keep pushing it and eventually you get failure. Think of switching to a colder plug as "upgrading the plug's cooling system". It's primarily for the plug's benefit so that it stays at the correct temperature, but may also have side effects such as lowering the combustion chamber temps a few degrees. If you're running on the razor's edge, that few degrees may be what you need, but I don't feel comfortable pushing it that far.