Spark Plug
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Joined: Aug 2011
Posts: 43,971
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Here's the NGKs side by side.
For the later models like 93 and up, is the plug on the left, a 7252.
For Renix and 91 to 92 HOs is the 7373 on the right.
I'm gonna try the projected tip 7252s in my 90 MJ.
For the later models like 93 and up, is the plug on the left, a 7252.
For Renix and 91 to 92 HOs is the 7373 on the right.
I'm gonna try the projected tip 7252s in my 90 MJ.
CF Veteran
Joined: Aug 2010
Posts: 8,357
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From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
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Year: 2015, 2012
Model: Grand Cherokee (WK2)
Engine: 3.6L
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
Me thinks the heat range switch (Champion) from RC9YC to RC12LYC (92/93) may have been the phase out of leaded gasoline.
In 1973 the EPA mandated production of unleaded gasoline to protect catalytic converters. In 1976 phase out of leaded gasoline began. In 1985/86, further reduction took place. An amendment to the Clean Air Act of 1990 required complete elimination of Lead from gasoline by 1996.
It could be the heat range change was to accommodate burning of unleaded gasoline in the 4.0 (and other Chrysler engines).
In 1973 the EPA mandated production of unleaded gasoline to protect catalytic converters. In 1976 phase out of leaded gasoline began. In 1985/86, further reduction took place. An amendment to the Clean Air Act of 1990 required complete elimination of Lead from gasoline by 1996.
It could be the heat range change was to accommodate burning of unleaded gasoline in the 4.0 (and other Chrysler engines).
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Me thinks the heat range switch (Champion) from RC9YC to RC12LYC (92/93) may have been the phase out of leaded gasoline.
In 1973 the EPA mandated production of unleaded gasoline to protect catalytic converters. In 1976 phase out of leaded gasoline began. In 1985/86, further reduction took place. An amendment to the Clean Air Act of 1990 required complete elimination of Lead from gasoline by 1996.
It could be the heat range change was to accommodate burning of unleaded gasoline in the 4.0 (and other Chrysler engines).
In 1973 the EPA mandated production of unleaded gasoline to protect catalytic converters. In 1976 phase out of leaded gasoline began. In 1985/86, further reduction took place. An amendment to the Clean Air Act of 1990 required complete elimination of Lead from gasoline by 1996.
It could be the heat range change was to accommodate burning of unleaded gasoline in the 4.0 (and other Chrysler engines).
And NGK went extended tip instead? I'm trying a set of -1s in my Renix.
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
I emailed NGK tech about the purpose that extended shell some time back (year +).
I'll look around for their reply and if I find it I will post it.. They basically said it was a Chrysler requirement. You can't tell me Chrysler wasn't in bed with NGK/NTK.
There was a thread going on the FR5-1 on another forum around the same time I emailed NGK tech. As I recall the OP of the thread was convinced the FR5-1 plugs were as good as sliced bread. But after awhile he came back and said they didn't work good. Can't recall all of the conversation.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
I emailed NGK tech about the purpose that extended shell some time back (year +).
I'll look around for their reply and if I find it I will post it.. They basically said it was a Chrysler requirement. You can't tell me Chrysler wasn't in bed with NGK/NTK.
There was a thread going on the FR5-1 on another forum around the same time I emailed NGK tech. As I recall the OP of the thread was convinced the FR5-1 plugs were as good as sliced bread. But after awhile he came back and said they didn't work good. Can't recall all of the conversation.
I'll look around for their reply and if I find it I will post it.. They basically said it was a Chrysler requirement. You can't tell me Chrysler wasn't in bed with NGK/NTK.
There was a thread going on the FR5-1 on another forum around the same time I emailed NGK tech. As I recall the OP of the thread was convinced the FR5-1 plugs were as good as sliced bread. But after awhile he came back and said they didn't work good. Can't recall all of the conversation.
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
Couldn't find that email from NGK.
But did run across this text from the NGK catalog (I think).
Spark plugs do not produce heat in the combustion chamber. One of the functions of the spark plug is to dissipate some of the heat produced during combustion. This is mostly transferred into the cylinder head. The 'Heat Range' indicates the measure of the spark plug's ability to do this. A 'hot' spark plug is designed to maintain a sufficiently high temperature at the insulator nose to burn off carbon and oil deposits. A 'cold' spark plug is designed to allow a faster transfer of heat to the cylinder head thus preventing overheating and premature failure.
Copper wire used in place of the iron core in conventional plugs is the secret of NGK's Wide Heat Range. Copper's superior heat conductivity dissipates heat quicker. It cools the electrode tip and insulator tip which prevents hot spots that could cause pre-ignition. Increased heat resistance does not affect fouling resistance, which is primarily determined by the insulator nose length. The longer the nose, the more susceptible it is to heat and the more free from fouling. By raising the pre-ignition rating with the high conduction copper and leaving the insulator nose long, NGK produces the Wide Range Plug. One that meets the broad thermal requirements of engines under high and low RPM conditions. All the spark plugs in the Automotive Catalogue have a copper core.
Changes in fuelling systems and the fuel itself have meant some special features being adopted at the ‘firing end’ of the spark plug. Extra projected types (FR5-1) push the spark position into the heart of the combustion chamber to promote better combustion of the fuel/air mixture, which is weaker than ever in an effort to improve economy. Modern engine manufacturers often require increased spark gaps to allow a longer spark duration, which again aids more efficient combustion.
But did run across this text from the NGK catalog (I think).
Spark plugs do not produce heat in the combustion chamber. One of the functions of the spark plug is to dissipate some of the heat produced during combustion. This is mostly transferred into the cylinder head. The 'Heat Range' indicates the measure of the spark plug's ability to do this. A 'hot' spark plug is designed to maintain a sufficiently high temperature at the insulator nose to burn off carbon and oil deposits. A 'cold' spark plug is designed to allow a faster transfer of heat to the cylinder head thus preventing overheating and premature failure.
Copper wire used in place of the iron core in conventional plugs is the secret of NGK's Wide Heat Range. Copper's superior heat conductivity dissipates heat quicker. It cools the electrode tip and insulator tip which prevents hot spots that could cause pre-ignition. Increased heat resistance does not affect fouling resistance, which is primarily determined by the insulator nose length. The longer the nose, the more susceptible it is to heat and the more free from fouling. By raising the pre-ignition rating with the high conduction copper and leaving the insulator nose long, NGK produces the Wide Range Plug. One that meets the broad thermal requirements of engines under high and low RPM conditions. All the spark plugs in the Automotive Catalogue have a copper core.
Changes in fuelling systems and the fuel itself have meant some special features being adopted at the ‘firing end’ of the spark plug. Extra projected types (FR5-1) push the spark position into the heart of the combustion chamber to promote better combustion of the fuel/air mixture, which is weaker than ever in an effort to improve economy. Modern engine manufacturers often require increased spark gaps to allow a longer spark duration, which again aids more efficient combustion.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Couldn't find that email from NGK.
But did run across this text from the NGK catalog (I think).
Spark plugs do not produce heat in the combustion chamber. One of the functions of the spark plug is to dissipate some of the heat produced during combustion. This is mostly transferred into the cylinder head. The 'Heat Range' indicates the measure of the spark plug's ability to do this. A 'hot' spark plug is designed to maintain a sufficiently high temperature at the insulator nose to burn off carbon and oil deposits. A 'cold' spark plug is designed to allow a faster transfer of heat to the cylinder head thus preventing overheating and premature failure.
Copper wire used in place of the iron core in conventional plugs is the secret of NGK's Wide Heat Range. Copper's superior heat conductivity dissipates heat quicker. It cools the electrode tip and insulator tip which prevents hot spots that could cause pre-ignition. Increased heat resistance does not affect fouling resistance, which is primarily determined by the insulator nose length. The longer the nose, the more susceptible it is to heat and the more free from fouling. By raising the pre-ignition rating with the high conduction copper and leaving the insulator nose long, NGK produces the Wide Range Plug. One that meets the broad thermal requirements of engines under high and low RPM conditions. All the spark plugs in the Automotive Catalogue have a copper core.
Changes in fuelling systems and the fuel itself have meant some special features being adopted at the ‘firing end’ of the spark plug. Extra projected types (FR5-1) push the spark position into the heart of the combustion chamber to promote better combustion of the fuel/air mixture, which is weaker than ever in an effort to improve economy. Modern engine manufacturers often require increased spark gaps to allow a longer spark duration, which again aids more efficient combustion.
But did run across this text from the NGK catalog (I think).
Spark plugs do not produce heat in the combustion chamber. One of the functions of the spark plug is to dissipate some of the heat produced during combustion. This is mostly transferred into the cylinder head. The 'Heat Range' indicates the measure of the spark plug's ability to do this. A 'hot' spark plug is designed to maintain a sufficiently high temperature at the insulator nose to burn off carbon and oil deposits. A 'cold' spark plug is designed to allow a faster transfer of heat to the cylinder head thus preventing overheating and premature failure.
Copper wire used in place of the iron core in conventional plugs is the secret of NGK's Wide Heat Range. Copper's superior heat conductivity dissipates heat quicker. It cools the electrode tip and insulator tip which prevents hot spots that could cause pre-ignition. Increased heat resistance does not affect fouling resistance, which is primarily determined by the insulator nose length. The longer the nose, the more susceptible it is to heat and the more free from fouling. By raising the pre-ignition rating with the high conduction copper and leaving the insulator nose long, NGK produces the Wide Range Plug. One that meets the broad thermal requirements of engines under high and low RPM conditions. All the spark plugs in the Automotive Catalogue have a copper core.
Changes in fuelling systems and the fuel itself have meant some special features being adopted at the ‘firing end’ of the spark plug. Extra projected types (FR5-1) push the spark position into the heart of the combustion chamber to promote better combustion of the fuel/air mixture, which is weaker than ever in an effort to improve economy. Modern engine manufacturers often require increased spark gaps to allow a longer spark duration, which again aids more efficient combustion.
Last night I pulled the FR5s out of my 90 MJ.
They all looked perfect according to a spark plug chart after 36,000 miles.
Gap was .042 across the board. Center electrodes were barely rounded off and the tips looked real good.
I regapped them to .035 and called it a night. I'll probably drive it today.
The FR5-1s are getting more and more interesting to me.