Does a colder plugs help lean AFR at high rpm?
Thread Starter
Joined: Jan 2009
Posts: 1,106
Likes: 85
From: Lebanon
Cls63 & C32
I changed mine from Denso ik20 to one step colder NGK bkr7eix,11
No change in AFR, but i noticed that the car has lost some power or torque at low rpm and more aggressive at high rpm.
Did anyone feel the same thing?
No change in AFR, but i noticed that the car has lost some power or torque at low rpm and more aggressive at high rpm.
Did anyone feel the same thing?
Super Member
Joined: Mar 2007
Posts: 510
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From: dayton ohio hopefully it will be some place warm and sunny when i finish med school
2002 C32 AMG silver & 2003 Lancer Evolution 8 black very moded
Former Vendor of MBWorld
Joined: Jan 2007
Posts: 3,193
Likes: 3
From: Glendale Arizona
C55,SL55,C63
I've added about 190whp over my stock C55. Strangely enough, I've gotten the best performance out of the stock plugs. That kinda goes against the whole colder plug thing.
I seen the best benefits from correctly gapping "pre-gapped" plugs. I couldn't believe how all over the place the gaps were on NGK "pre-gapped" plugs.
I seen the best benefits from correctly gapping "pre-gapped" plugs. I couldn't believe how all over the place the gaps were on NGK "pre-gapped" plugs.
Thread Starter
Joined: Jan 2009
Posts: 1,106
Likes: 85
From: Lebanon
Cls63 & C32
I've added about 190whp over my stock C55. Strangely enough, I've gotten the best performance out of the stock plugs. That kinda goes against the whole colder plug thing.
I seen the best benefits from correctly gapping "pre-gapped" plugs. I couldn't believe how all over the place the gaps were on NGK "pre-gapped" plugs.
I seen the best benefits from correctly gapping "pre-gapped" plugs. I couldn't believe how all over the place the gaps were on NGK "pre-gapped" plugs.
MBWorld Fanatic!
Joined: Sep 2008
Posts: 3,152
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From: murfreesboro,tn
2003 porsche 996 turbo
the secret to plugs is in the indexing. you want the open end of the electrode pointing at the intake valve so the most spark is aimed at the air fuel mixture coming in
mark the plug at the indexing point and install rotating until the mark is pointed at the intake chamber. then tighten to specs
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MBWorld Fanatic!
Joined: Apr 2005
Posts: 3,784
Likes: 84
From: SCV SoCal
2002 CLK430
In answer to the OP's first question, no. A lean condition occurs when the air:fuel ratio has more air than desired. Based on your question, you may not understand what the hot/cold plug thing is all about.
The job of a park plug is to ignite fuel and dissipate heat. Some people are of the mistaken opinion that plugs *cause* heat. They don’t. Plugs cause fuel to ignite. The burning of fuel causes heat. Spark plugs remove heat by transferring the thermal energy from the combustion chamber, to the metal that holds the spark plug in place (the threads in the cylinder head), where it's eventually absorbed into the engine's cooling system.
Spark plugs have heat ranges and they're typically referred to as hot or cold. The heat range is an indication as to how much heat the plug will pass from the combustion chamber, through the plug, and into the head. It has nothing to do with the voltage passed through the plug, or how hot the spark is. Those are two other pieces of misinformation that are frequently spread.
Regardless as to whether a spark plug is considered hot or cold, the ideal temperature for the center electrode of a spark plug is between 930 and 1560 degrees Fahrenheit. Below 930 degrees, combustion residue (that should have been burned away) builds up on the plugs until they misfire. Above 1560 degrees, the electrode can burn away, preignition can occur, and that is frequently followed by a holed piston. Hot plugs are designed to retain more heat at the insulator tip and cold plugs are designed to transmit more heat to the cylinder head, but both are designed to *operate* in that same temperature range.
To fix the lean condition on an otherwise stock car, some of the usual suspects are a bad injector (plugged with filth), a plugged fuel filter (more filth), or a weak fuel pump (which may be due to filth).
You installed the plugs without gaping them. Depending on the plug, they may have been pre-gapped. Look at the box.An incorrectly gapped plug can cause high HC readings, which is not a lean condition. High HC (unburned hydrocarbons) is a rich condition.
Lastly, How do you know you're running lean?
The job of a park plug is to ignite fuel and dissipate heat. Some people are of the mistaken opinion that plugs *cause* heat. They don’t. Plugs cause fuel to ignite. The burning of fuel causes heat. Spark plugs remove heat by transferring the thermal energy from the combustion chamber, to the metal that holds the spark plug in place (the threads in the cylinder head), where it's eventually absorbed into the engine's cooling system.
Spark plugs have heat ranges and they're typically referred to as hot or cold. The heat range is an indication as to how much heat the plug will pass from the combustion chamber, through the plug, and into the head. It has nothing to do with the voltage passed through the plug, or how hot the spark is. Those are two other pieces of misinformation that are frequently spread.
Regardless as to whether a spark plug is considered hot or cold, the ideal temperature for the center electrode of a spark plug is between 930 and 1560 degrees Fahrenheit. Below 930 degrees, combustion residue (that should have been burned away) builds up on the plugs until they misfire. Above 1560 degrees, the electrode can burn away, preignition can occur, and that is frequently followed by a holed piston. Hot plugs are designed to retain more heat at the insulator tip and cold plugs are designed to transmit more heat to the cylinder head, but both are designed to *operate* in that same temperature range.
To fix the lean condition on an otherwise stock car, some of the usual suspects are a bad injector (plugged with filth), a plugged fuel filter (more filth), or a weak fuel pump (which may be due to filth).
You installed the plugs without gaping them. Depending on the plug, they may have been pre-gapped. Look at the box.An incorrectly gapped plug can cause high HC readings, which is not a lean condition. High HC (unburned hydrocarbons) is a rich condition.
Lastly, How do you know you're running lean?
Last edited by MarcusF; Dec 28, 2009 at 02:57 PM.
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Former Vendor of MBWorld
Joined: Jan 2007
Posts: 3,193
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From: Glendale Arizona
C55,SL55,C63
at wide open throttle You should see a AFR of very high 12's (minimum lean) to anything above,... say 12.8 would be considered lean. If you're just putting around town your AFR would be high, but thats normal. Due tot he engine not being under any real load.
Check your fuel trims too, Long term and short term. Long term will give you a better understanding of whats going on fuel wise with your car. For example: If the Long term trims say +8 on both banks (1 and 2) that means the ECU is adding 8% fuel. This is due to the car thinking its to lean or lean a bit. It also works the opposite way. if its way -11% on the LT trims, that means the ECU is pulling 11% fuel out of the car.
To get a CEL for "Bank 1 lean or Bank 2 lean.. Or even both at the same time. I think the Fuel trims would have to jump up to 20% or so to throw a CEL.
Now the "Sort term Fuel Trims will tell you what your car is doing at the moment. Sometime a bit hard to read ans they can fluctuate up and down a bit when you add and release the throttle.
Generally speaking a dead nuts tune should read 0% long term at idle. Thats if the car has no problems. Also Mercedes OEM stock tune is far from dead nuts. In most cases its kinda rich. At least to rich for my taste.
As for gapping. Just a standard gap tool works. IIRC, the gap on my C55 should be 45?? 44??? I was seeing gaps no where close to what OEM called for. So much for pre-gapped plugs.
Check your fuel trims too, Long term and short term. Long term will give you a better understanding of whats going on fuel wise with your car. For example: If the Long term trims say +8 on both banks (1 and 2) that means the ECU is adding 8% fuel. This is due to the car thinking its to lean or lean a bit. It also works the opposite way. if its way -11% on the LT trims, that means the ECU is pulling 11% fuel out of the car.
To get a CEL for "Bank 1 lean or Bank 2 lean.. Or even both at the same time. I think the Fuel trims would have to jump up to 20% or so to throw a CEL.
Now the "Sort term Fuel Trims will tell you what your car is doing at the moment. Sometime a bit hard to read ans they can fluctuate up and down a bit when you add and release the throttle.
Generally speaking a dead nuts tune should read 0% long term at idle. Thats if the car has no problems. Also Mercedes OEM stock tune is far from dead nuts. In most cases its kinda rich. At least to rich for my taste.
As for gapping. Just a standard gap tool works. IIRC, the gap on my C55 should be 45?? 44??? I was seeing gaps no where close to what OEM called for. So much for pre-gapped plugs.
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Joined: Dec 2007
Posts: 5,034
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From: Corona, CA
03 g35 coupe...........02 c32 Sold
In answer to the OP's first question, no. A lean condition occurs when the air:fuel ratio has more air than desired. Based on your question, you may not understand what the hot/cold plug thing is all about.
The job of a park plug is to ignite fuel and dissipate heat. Some people are of the mistaken opinion that plugs *cause* heat. They don’t. Plugs cause fuel to ignite. The burning of fuel causes heat. Spark plugs remove heat by transferring the thermal energy from the combustion chamber, to the metal that holds the spark plug in place (the threads in the cylinder head), where it's eventually absorbed into the engine's cooling system.
Spark plugs have heat ranges and they're typically referred to as hot or cold. The heat range is an indication as to how much heat the plug will pass from the combustion chamber, through the plug, and into the head. It has nothing to do with the voltage passed through the plug, or how hot the spark is. Those are two other pieces of misinformation that are frequently spread.
Regardless as to whether a spark plug is considered hot or cold, the ideal temperature for the center electrode of a spark plug is between 930 and 1560 degrees Fahrenheit. Below 930 degrees, combustion residue (that should have been burned away) builds up on the plugs until they misfire. Above 1560 degrees, the electrode can burn away, preignition can occur, and that is frequently followed by a holed piston. Hot plugs are designed to retain more heat at the insulator tip and cold plugs are designed to transmit more heat to the cylinder head, but both are designed to *operate* in that same temperature range.
To fix the lean condition on an otherwise stock car, some of the usual suspects are a bad injector (plugged with filth), a plugged fuel filter (more filth), or a weak fuel pump (which may be due to filth).
You installed the plugs without gaping them. Depending on the plug, they may have been pre-gapped. Look at the box.An incorrectly gapped plug can cause high HC readings, which is not a lean condition. High HC (unburned hydrocarbons) is a rich condition.
Lastly, How do you know you're running lean?
The job of a park plug is to ignite fuel and dissipate heat. Some people are of the mistaken opinion that plugs *cause* heat. They don’t. Plugs cause fuel to ignite. The burning of fuel causes heat. Spark plugs remove heat by transferring the thermal energy from the combustion chamber, to the metal that holds the spark plug in place (the threads in the cylinder head), where it's eventually absorbed into the engine's cooling system.
Spark plugs have heat ranges and they're typically referred to as hot or cold. The heat range is an indication as to how much heat the plug will pass from the combustion chamber, through the plug, and into the head. It has nothing to do with the voltage passed through the plug, or how hot the spark is. Those are two other pieces of misinformation that are frequently spread.
Regardless as to whether a spark plug is considered hot or cold, the ideal temperature for the center electrode of a spark plug is between 930 and 1560 degrees Fahrenheit. Below 930 degrees, combustion residue (that should have been burned away) builds up on the plugs until they misfire. Above 1560 degrees, the electrode can burn away, preignition can occur, and that is frequently followed by a holed piston. Hot plugs are designed to retain more heat at the insulator tip and cold plugs are designed to transmit more heat to the cylinder head, but both are designed to *operate* in that same temperature range.
To fix the lean condition on an otherwise stock car, some of the usual suspects are a bad injector (plugged with filth), a plugged fuel filter (more filth), or a weak fuel pump (which may be due to filth).
You installed the plugs without gaping them. Depending on the plug, they may have been pre-gapped. Look at the box.An incorrectly gapped plug can cause high HC readings, which is not a lean condition. High HC (unburned hydrocarbons) is a rich condition.
Lastly, How do you know you're running lean?
Super Member
Joined: Jul 2006
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From: FT POLK LOUISIANA
1992 Toyota Corolla, 1994 Chevy C1500, 2002 C32, 2012 Prius, 2013 Toyota Sienna
Installed the 185mm pulley, got my Jerry tune back. What should I gap my NGK IX BKR7EIX-11's to? .035? Recommendations appreciated........
Super Member
Joined: Jul 2006
Posts: 691
Likes: 0
From: FT POLK LOUISIANA
1992 Toyota Corolla, 1994 Chevy C1500, 2002 C32, 2012 Prius, 2013 Toyota Sienna
Installed the 185mm pulley, got my Jerry tune back. What should I gap my NGK IX BKR7EIX-11's to? .035? Recommendations appreciated........
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Joined: Jul 2006
Posts: 3,365
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From: Orange County, CA
GMC - Miata - Trek - P-Car
Given your I85mm pulley, to reduce amperage requirements and help eliminate the chance of spark ‘blowout’ during extended WOT Autobahn operation,
I’d suggest no more than .9mm/.035” as a reasonable compromise upon initial installation.
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Joined: Jul 2006
Posts: 691
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From: FT POLK LOUISIANA
1992 Toyota Corolla, 1994 Chevy C1500, 2002 C32, 2012 Prius, 2013 Toyota Sienna
Interesting as always....Thanks
Note the “-11” suffix on NGK plugs indicates they’re supplied gapped to ~1.1mm/.043 inch. Our OE NGK IFR6D10s are 1mm/.039” as delivered.
Given your I85mm pulley, to reduce amperage requirements and help eliminate the chance of spark ‘blowout’ during extended WOT Autobahn operation,
I’d suggest no more than .9mm/.035” as a reasonable compromise upon initial installation.
Given your I85mm pulley, to reduce amperage requirements and help eliminate the chance of spark ‘blowout’ during extended WOT Autobahn operation,
I’d suggest no more than .9mm/.035” as a reasonable compromise upon initial installation.
Senior Member
Joined: Mar 2011
Posts: 325
Likes: 2
From: Bella Vista, AR
05 C55 AMG
In answer to the OP's first question, no. A lean condition occurs when the air:fuel ratio has more air than desired. Based on your question, you may not understand what the hot/cold plug thing is all about.
The job of a park plug is to ignite fuel and dissipate heat. Some people are of the mistaken opinion that plugs *cause* heat. They don’t. Plugs cause fuel to ignite. The burning of fuel causes heat. Spark plugs remove heat by transferring the thermal energy from the combustion chamber, to the metal that holds the spark plug in place (the threads in the cylinder head), where it's eventually absorbed into the engine's cooling system.
Spark plugs have heat ranges and they're typically referred to as hot or cold. The heat range is an indication as to how much heat the plug will pass from the combustion chamber, through the plug, and into the head. It has nothing to do with the voltage passed through the plug, or how hot the spark is. Those are two other pieces of misinformation that are frequently spread.
Regardless as to whether a spark plug is considered hot or cold, the ideal temperature for the center electrode of a spark plug is between 930 and 1560 degrees Fahrenheit. Below 930 degrees, combustion residue (that should have been burned away) builds up on the plugs until they misfire. Above 1560 degrees, the electrode can burn away, preignition can occur, and that is frequently followed by a holed piston. Hot plugs are designed to retain more heat at the insulator tip and cold plugs are designed to transmit more heat to the cylinder head, but both are designed to *operate* in that same temperature range.
To fix the lean condition on an otherwise stock car, some of the usual suspects are a bad injector (plugged with filth), a plugged fuel filter (more filth), or a weak fuel pump (which may be due to filth).
You installed the plugs without gaping them. Depending on the plug, they may have been pre-gapped. Look at the box.An incorrectly gapped plug can cause high HC readings, which is not a lean condition. High HC (unburned hydrocarbons) is a rich condition.
Lastly, How do you know you're running lean?
The job of a park plug is to ignite fuel and dissipate heat. Some people are of the mistaken opinion that plugs *cause* heat. They don’t. Plugs cause fuel to ignite. The burning of fuel causes heat. Spark plugs remove heat by transferring the thermal energy from the combustion chamber, to the metal that holds the spark plug in place (the threads in the cylinder head), where it's eventually absorbed into the engine's cooling system.
Spark plugs have heat ranges and they're typically referred to as hot or cold. The heat range is an indication as to how much heat the plug will pass from the combustion chamber, through the plug, and into the head. It has nothing to do with the voltage passed through the plug, or how hot the spark is. Those are two other pieces of misinformation that are frequently spread.
Regardless as to whether a spark plug is considered hot or cold, the ideal temperature for the center electrode of a spark plug is between 930 and 1560 degrees Fahrenheit. Below 930 degrees, combustion residue (that should have been burned away) builds up on the plugs until they misfire. Above 1560 degrees, the electrode can burn away, preignition can occur, and that is frequently followed by a holed piston. Hot plugs are designed to retain more heat at the insulator tip and cold plugs are designed to transmit more heat to the cylinder head, but both are designed to *operate* in that same temperature range.
To fix the lean condition on an otherwise stock car, some of the usual suspects are a bad injector (plugged with filth), a plugged fuel filter (more filth), or a weak fuel pump (which may be due to filth).
You installed the plugs without gaping them. Depending on the plug, they may have been pre-gapped. Look at the box.An incorrectly gapped plug can cause high HC readings, which is not a lean condition. High HC (unburned hydrocarbons) is a rich condition.
Lastly, How do you know you're running lean?
Since the C55 has two spark plugs it doesn't seem like it makes sense for the electrode gap to face eachother, inward. Would it be better to face them the opposite direction?
