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Implement Alley Discussion Forum

hot or cold spark plugs

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Frank in Sask

10-22-2006 21:19:31




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You here of a hot or cold plug for different situations for engines. What is there in the make up of the plug that makes it hotter or colder besides the number on the plug? Frank




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Glen in TX

10-23-2006 22:37:51




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 Re: hot or cold spark plugs in reply to Frank in Sask, 10-22-2006 21:19:31  
Here is a link I like that shows it a bit better than the one Bob posted. When you look down in a plug and it's shallow it will run colder than one that looks deeper. Simple enough? For gasoline engines you will run a lot hotter plug than for LPG and natural gas engines which run a colder plug because the fuel is already vaporized. You'll also close down the plug gap by about half because it won't take as much fire to ignite the vaporized natural gas or LPG fuel either compared to gasoline mixture.

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buickanddeere

10-23-2006 06:02:23




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 Re: hot or cold spark plugs in reply to Frank in Sask, 10-22-2006 21:19:31  
Most lawn mowers, small farm equipment and small engines will use an Autolite 216 non resisitor plug. Otherwise a non resisitor Autolite 3116. As long as you are not using a AM Ham radio on the machine. Or operating next to an airport. Chuck the reisitor core wires and install solid core wires.



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Allan In NE

10-23-2006 03:16:58




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 Re: hot or cold spark plugs in reply to Frank in Sask, 10-22-2006 21:19:31  
Hi Frank,

It is a lot simpler than it sounds.

It has to do with the center electrode and how far it is recessed into, or how far it extends out of the plug itself.

If you look at a cold plug, it will have a short stubby electrode and the hot plug will have a long center electrode extending more out into the combustion area.

General rule of thumb is to use a cold plug in long, continuous, steady engine operation and the hot plug would be used for short duration, stop and go type work to combat the effects of fouling and deposits.

The plug itself is not changing the heat of anything nor does it throw a different �temperature� spark than its counterpart. It is just a question of what area of the combustion fire the plug actually operates in.

Allan

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Bob

10-23-2006 08:23:46




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 Re: hot or cold spark plugs in reply to Allan In NE, 10-23-2006 03:16:58  
Allan,

You're running "heat range" and "reach" together!

"Reach" is how far the electrodes extend into the combustion chamber, "heat range" is how well the spark plug tip sheds heat to the surrounding metal, due to the design of the insulator.

Just because the "reach" of the plug is longer, it is NOT NECESSARILY a "hotter" plug.

Whip out your AC or Champion spark plug manual, and you can confirm this, or look at the illustration showing the different insulator designs relating to heat range in the DENSO link I previously provided.

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Allan In NE

10-23-2006 11:55:04




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 Re: hot or cold spark plugs in reply to Bob, 10-23-2006 08:23:46  
Who wrote that bunch of Internet crap?

Been turnin' wrenches for almost 60 years and I damn well sure know the difference between a hot and cold plug.

It hasn't got a thing to do with how much thread is on the body either.

Good Grief!

Allan



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Bob

10-23-2006 18:38:31




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 Re: hot or cold spark plugs in reply to Allan In NE, 10-23-2006 11:55:04  
The way I was always taught about spark plug heat ranges matches the information on the DENSO site, and also information in the AC and Champion master catalogs.

You're saying the information on the DENSO Corporate site is a bunch of internet CRAP?????

I think you need to take a break from wrench'in BROKEN RED tractors, or punch'in cows for a little while, and UNWIND!



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Allan In NE

10-24-2006 03:21:47




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 Re: hot or cold spark plugs in reply to Bob, 10-23-2006 18:38:31  
Dunno,

Maybe with the advent of the aluminum heads and their widespread use, the standards have totally changed to take into consideration the "heat dissipation" factor of a spark plug.

Perhaps this is what they are teaching nowadays. Could be.

Allan



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CENTAUR

10-22-2006 22:44:42




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 Re: hot or cold spark plugs in reply to Frank in Sask, 10-22-2006 21:19:31  
I will give you a simple ans. to your question.GM has used AC sparkplugs for years.They have #44-#45-&46.The #45 is for a regular sedan.If the same engine is used in a one ton truck it would come with #44. the 45 runs hotter then a #44 and will run better since it runs hotter if the engine tends to oil foul the plugs as it gets worn.In this example the#46 would be the hotter running.How ever if you go too hot the hot plug will pre-ignite the fuel before it should be ignited in relationship to the piston position.CENTAUR

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Bob

10-22-2006 22:41:54




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 Re: hot or cold spark plugs in reply to Frank in Sask, 10-22-2006 21:19:31  
The internal design is such that the center electode of a HOT plug sheds heat to the metal shell, and then to the engine head or, in some cases, the block, to a lesser degree than a COOLER plug. Therefore, in a given engine, the center electrode/insulator of a HOT plug will heat up quicker and run hotter than a cooler plug, making it more resistant to carbon deposits and fouling.

However, if the plug is TOO HOT for a given application, the mixture charge being compressed by the upward-moving piston will be "pre-ignited" by the HOT sparkplug, causing severe knock soon leading to engine damage.

There's good information on the Denso site, showing how differences in insulator contruction affect the plug's "Heat Range".

Go to the link below, and scroll down to "Low heat range and high heat range".

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