biteme
21-10-2008, 22:46
Q. How often should I change my plugs?
A. Copper based (standard) plugs 4-6,000miles
Platinum 25,000 miles
Iridium 30,000miles
Q. How much are they?
A. Copper plugs are ~£2 each
Platinum plugs are ~£6 each (not £14!!)
Iridium ~£8 each
Q. Why are there different heat ranges? Which one should I use?
A. Part of your spark plug’s responsibilities, in addition to firing a spark, is to remove heat from the combustion chamber. This is accomplished by channelling the heat through the insulator material and metal housing. From there, the heat is transferred to the cylinder head where the engine cooling system can go to work. A spark plug’s heat range is its ability to dissipate heat. The colder the plug, the more heat it can channel out of the combustion chamber. In a performance application, colder heat ranges may be necessary to handle the extreme temperatures brought on by higher compression ratios, forced induction, and high RPM’s. While colder plugs may seem to be the way to go, please remember that the spark plug must achieve its self-cleaning temperature where it can burn off fuel and carbon deposits. Otherwise, the plug could foul out where it is prone to misfiring and poor acceleration. A plug that is too hot can overheat, also causing power loss, detonation, pre-ignition, and possible engine damage. A good, general rule of thumb is to start with the factory recommended heat range. For every 75 to 100 hp you add to your engine, you may go to the next colder step.
NGK and Denso use different heat range grading systems they are;
NGK Heat Grade Denso Equivalent
5 16
6 20
7 22
8 24
9 27
10 31
Q. Iridium’s are very expensive, what benefits do they have?
A. Until recently, platinum was considered the best material to use on the top of an electrode because of its durability. However, Iridium is 6 times harder, 8 times stronger, and has a melting point 1200 degrees higher than platinum. Put that into a harsh environment such as an engine piston chamber, and you have a spark plug that can resist wear much better than platinum. Iridium's extreme durability has also allowed NGK and Denso to develop smaller centre electrodes (0.6mm and 0.4mm respectively). This reduction in size, from a standard copper plug's 2mm electrode reduces the voltage requirements to jump the gap and create a spark. Denso and NGK recommend their Iridium’s only be replaced every 30,000miles (in some applications iridium plugs will last 120,000miles BUT NOT A SPORTSCAR!), and this is 5 times the life a copper plug.
Q. Why do you need to GAP a plug?
A. First off, you must not attempt to re-gap an Iridium plug. Trying to do so will damage the plug's electrode.
For copper plugs...too big a gap will create problems on boost, the spark is literally blown out by the air pressure before it has a chance to ignite the mixture, resulting in a misfire. A decent sized gap must always be maintained though as too small a gap will create problems at idle
and reduce the efficiency of the combustion process. Only adjust a gap by 0.1mm at a time and retest...if you go below 0.6mm and still have a miss-fire on boost I would suggest there is another problem not related to the sparkplugs (unless you are not using a plug in the correct heat range).
Q. Which plug is best?
A. An Iridium plain and simple. They are of superior construction, are more durable, spark better. This is according to the Denso and NGK blurb. Scare stories about Iridium’s causing detonation are not accurate. What is correct though is that unlike the copper plugs that melt and stop working, Iridium’s will continue working and detonation will destroy the next weakest point in the chain (pistons etc). However, one note of caution, in the past some people, have found that the ceramic insulator inside the tip of Denso made Iridiums has failed and sent a chunk of debris into the cylinder...and into the turbo causing damage. There have not been many cases and I believe most cases were in highly tuned vehicles but it is worth noting. In my opinion I believe that these failures have been linked to the mapping or tuning of the whole engine. If Denso had made a bad product, a) by now they would have fixed the issue, and b) they wouldn't risk their reputation on it and would stop selling them (Denso are a huge OEM parts manufacturer). I am happy that a properly tuned car running safe AFR's will run Denso or NGK Iridium's for a long time with no dangers. If you are in the process of tuning or are unsure if you are getting det then I recommend you stick with Copper plugs as these are cheaper to replace if you do suffer det and destroy the tips.
Q. HKS, TRD, Blitz, GReddy etc all make plugs too, shouldn't I buy them?
A. No. HKS and TRD are definitely Denso made Iridium’s. I would expect that the GReddy and Blitz one's are too...you are paying for a badge only, there is no difference between an £8 IK24 Denso Iridium and £11 HKS S40i. £3 per plug premium? No thanks!
Q. What about other makes, you've only talked about NGK and Denso?
A. Denso are the OEM supplier to Toyota. They should be in a stock car anyway which is why their range specifically caters for the Toyota. NGK are Japanese too and likewise have tried and tested plugs that are suitable for our use. Other makes such as champion, bosch etc may well produce something suitable...but it won't have been tested as much as the plugs I've recommended here. It's your engine, your choice.
Q. I've heard you can read plugs to see if you're running lean etc?
A. No you can't, not in an unleaded environment anyway. If you read the plugs all you will see is the evidence of it's last few seconds of use before switching off...so idle...which is closed loop and will be a perfect 14.7:1 afr unless your 02 sensor is up the swanny, but if it was the engine would not be smooth, it would be hunting for an idle and you'd know there was something wrong!
A. Copper based (standard) plugs 4-6,000miles
Platinum 25,000 miles
Iridium 30,000miles
Q. How much are they?
A. Copper plugs are ~£2 each
Platinum plugs are ~£6 each (not £14!!)
Iridium ~£8 each
Q. Why are there different heat ranges? Which one should I use?
A. Part of your spark plug’s responsibilities, in addition to firing a spark, is to remove heat from the combustion chamber. This is accomplished by channelling the heat through the insulator material and metal housing. From there, the heat is transferred to the cylinder head where the engine cooling system can go to work. A spark plug’s heat range is its ability to dissipate heat. The colder the plug, the more heat it can channel out of the combustion chamber. In a performance application, colder heat ranges may be necessary to handle the extreme temperatures brought on by higher compression ratios, forced induction, and high RPM’s. While colder plugs may seem to be the way to go, please remember that the spark plug must achieve its self-cleaning temperature where it can burn off fuel and carbon deposits. Otherwise, the plug could foul out where it is prone to misfiring and poor acceleration. A plug that is too hot can overheat, also causing power loss, detonation, pre-ignition, and possible engine damage. A good, general rule of thumb is to start with the factory recommended heat range. For every 75 to 100 hp you add to your engine, you may go to the next colder step.
NGK and Denso use different heat range grading systems they are;
NGK Heat Grade Denso Equivalent
5 16
6 20
7 22
8 24
9 27
10 31
Q. Iridium’s are very expensive, what benefits do they have?
A. Until recently, platinum was considered the best material to use on the top of an electrode because of its durability. However, Iridium is 6 times harder, 8 times stronger, and has a melting point 1200 degrees higher than platinum. Put that into a harsh environment such as an engine piston chamber, and you have a spark plug that can resist wear much better than platinum. Iridium's extreme durability has also allowed NGK and Denso to develop smaller centre electrodes (0.6mm and 0.4mm respectively). This reduction in size, from a standard copper plug's 2mm electrode reduces the voltage requirements to jump the gap and create a spark. Denso and NGK recommend their Iridium’s only be replaced every 30,000miles (in some applications iridium plugs will last 120,000miles BUT NOT A SPORTSCAR!), and this is 5 times the life a copper plug.
Q. Why do you need to GAP a plug?
A. First off, you must not attempt to re-gap an Iridium plug. Trying to do so will damage the plug's electrode.
For copper plugs...too big a gap will create problems on boost, the spark is literally blown out by the air pressure before it has a chance to ignite the mixture, resulting in a misfire. A decent sized gap must always be maintained though as too small a gap will create problems at idle
and reduce the efficiency of the combustion process. Only adjust a gap by 0.1mm at a time and retest...if you go below 0.6mm and still have a miss-fire on boost I would suggest there is another problem not related to the sparkplugs (unless you are not using a plug in the correct heat range).
Q. Which plug is best?
A. An Iridium plain and simple. They are of superior construction, are more durable, spark better. This is according to the Denso and NGK blurb. Scare stories about Iridium’s causing detonation are not accurate. What is correct though is that unlike the copper plugs that melt and stop working, Iridium’s will continue working and detonation will destroy the next weakest point in the chain (pistons etc). However, one note of caution, in the past some people, have found that the ceramic insulator inside the tip of Denso made Iridiums has failed and sent a chunk of debris into the cylinder...and into the turbo causing damage. There have not been many cases and I believe most cases were in highly tuned vehicles but it is worth noting. In my opinion I believe that these failures have been linked to the mapping or tuning of the whole engine. If Denso had made a bad product, a) by now they would have fixed the issue, and b) they wouldn't risk their reputation on it and would stop selling them (Denso are a huge OEM parts manufacturer). I am happy that a properly tuned car running safe AFR's will run Denso or NGK Iridium's for a long time with no dangers. If you are in the process of tuning or are unsure if you are getting det then I recommend you stick with Copper plugs as these are cheaper to replace if you do suffer det and destroy the tips.
Q. HKS, TRD, Blitz, GReddy etc all make plugs too, shouldn't I buy them?
A. No. HKS and TRD are definitely Denso made Iridium’s. I would expect that the GReddy and Blitz one's are too...you are paying for a badge only, there is no difference between an £8 IK24 Denso Iridium and £11 HKS S40i. £3 per plug premium? No thanks!
Q. What about other makes, you've only talked about NGK and Denso?
A. Denso are the OEM supplier to Toyota. They should be in a stock car anyway which is why their range specifically caters for the Toyota. NGK are Japanese too and likewise have tried and tested plugs that are suitable for our use. Other makes such as champion, bosch etc may well produce something suitable...but it won't have been tested as much as the plugs I've recommended here. It's your engine, your choice.
Q. I've heard you can read plugs to see if you're running lean etc?
A. No you can't, not in an unleaded environment anyway. If you read the plugs all you will see is the evidence of it's last few seconds of use before switching off...so idle...which is closed loop and will be a perfect 14.7:1 afr unless your 02 sensor is up the swanny, but if it was the engine would not be smooth, it would be hunting for an idle and you'd know there was something wrong!