Spark Plug Gurus..... Hutto's room mate Matt and others. need your opinion.
05-28-2007, 09:31 PM
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Spark Plug Gurus..... Hutto's room mate Matt and others. need your opinion. I was having KR issues with my GTP.... i had a set of old autolite 605 copper core plugs with between .080 and .085 gap each, thanks to nice wear on em!
I have put a low lift VS Cam, ported manifolds, 3.2 pulley, and full 3 inch exhaust with downpipe....... the car was having serious KR issues.... I thought it was everything from the darn exhaust pipe rubbing on the rack and pinion hydrolic line.... to tuning issues. It was so bad the car got drug by 6 car lengths by a mostly stock neon ????. Well..... after going to autozone to pick up some new plugs, i just figured they needed to be replaced... i did a bit of research, it seems that I had a plug that was way to hot for the mods.
I have a tuner... but no laptop to check the tune out.
I wanted someone elses opinion on the subject as well as why or why not run a autolite copper core plug on my new 408 / 250 nitrous shot setup?? vs NGK's?
************************************************** **************
Which Spark Plugs Should I Run?
Give me a spark plug 101
A spark plug has two main tasks: to ignite the air/fuel mixture properly, and to remove heat from the combustion chamber to maintain an optimal temperature.
Platinum, some hear that word and think BAM these are premium plugs. What makes platinum different? Well the answer is in the design of a platinum plug. So lets start there.
A spark plug's firing task is to transfer electrical current or "spark" between a power and a ground electrode to ignite the air and fuel mixture. We want this spark to be powerful, to promote a nice clean burn of the mixture, as this will promote the best efficiency and therefore the most power. Now imagine two spheres electrically charged, hold them closely together and you'll see spark jump across it. Now try and separate them and you'll see the spark disappear. NOW try this with two sharp pointed electrical rods and you'll see you can hold them further apart and the spark will still jump between them. What does this mean? Sharp points will transfer the spark the most effectively. Ever notice the tip of the spark plug and how most platinum plugs are sharp tipped center electrodes?
Sharp tips are all well and fine, but thats a hot environment down there. Infact the biggest problem is withstanding the heat. A sharp center electrode will get very hot, this promotes easy ignition (less charge to spark the plug) and a clean running plug free of deposits, but try this with a standard copper plug and it'll melt! Platinum has a much higher melting point than copper which is used on the classic style spark plug, thus the tip can be sharpened like it is. Iridium is the new guy on the block; same thing, it has an even higher melting point, thus the tip can be sharp. Now a copper plug needs to have a wide body to disperse the heat over a larger area so its tip can run cooler. Now did that set off any light bulb on where that would be beneficial? If you said forced induction or nitrous applications, pat on the back! In applications where you want to minimize existing heat in the combustion chamber, platinum may not be a good thing.
Here is another stick in the spokes of the platinum bandwagon wheel: Platinum does not conduct electricity very well. Platinum was chosen due to its resistance to heat and erosion, however it conducts electricity about a third as well as copper. The new iridiums are an attempt to find a metal with similar heat and erosion resistance as platinum but better conductivity of electricity; however, iridium is still only about half as good a conductor as copper, iridium plugs are one of the best marketing tools for spark plugs today and nothing more in the authors opinion. Now this disadvantage of platinum is offset to an extent by the ease of firing that platinum plug design offers, with its sharp pointed tip. Whether a copper plug can produce as much spark energy with a smaller gap however, than a platinum counterpart with a wider gap, is a good point of debate. The author’s viewpoint is yes.
Before I read further, what plug do you recommend for my application?
My recommendation for GTPs is to use a copper Autolite plug whenever possible. Copper runs cool, will perform better than exotic metals in my experience, should last its user about 2 years, and best of all are inexpensive.
For a stock pullied car, if you are unmodified and looking for a maintenance recommendation for plugs rather than a performance one, look for Autolite platinums which are part number coded AP for platinum and APP for double platinum at the very beginning of the part number.
Non-intercooled:
3.8” factory: Autolite 605 @ .055-.057” gap (or AP605/APP605 platinums @.060”)
3.4-3.25” pulley: Autolite 104 @ .052-.054” gap
3.1-3.0” pulley: Autolite 103 @ .047-.050” gap
2.9-2.7” pulley: Autolite AR94 (4 range colder race plug) @ .044-.046”
Intercooled
3.25-3.0” pulley: Autolite 104 @ .050-.052”
2.9-2.7” pulley: Autolite 103 @ .046-.048”
2.6-smaller: Autolite AR94 @ .044-.046”
Why does the author not recommend platinums in a GTP, aren’t they better?
Better? No, not in my book. And there is a good reason I recommend not using platinums in a supercharged application, and that’s because they run HOT. The small platinum tipped plugs are designed to run very hot to promote easy firing for mileage and emissions at idle and low vehicle speeds, along with erosion resistance so the owner of the car can neglect its maintenance for 100,000miles (yes, neglect is IMHO the appropriate word here!). These reasons are why they are considered better, but now that you know the whys, you know enough to make a judgement call for your own application.
Why do we step down heat ranges?
With a supercharged motor, the process of adding boost also adds heat to the incoming air. This is a normal byproduct of compressing the air. By running 10psi of boost from an M90 on a 3800, with pulley sizes anywhere from 3.8” to 2.7”, we are also adding 170-320F temperatures to the inlet air.
One of the spark plug’s functions is to remove heat from the combustion chamber, contrary to whatever you may have heard about spark plugs adding heat. We can use this function to remove or counter balance the heat which we are adding to the combustion chamber from the supercharger. By fine tuning the heat range of the spark plug we use, we can ensure an optimal temperature in the cylinders for proper combustion without pre-igniting the mixture from excessive heat.
How many heat ranges should I step down with my L67/L32 supercharged motor?
This will vary greatly on what pulley size you run. By going smaller and smaller to keep boost levels up, we are adding more and more heat by spinning the supercharger faster, even though we’re running the same amount of boost. As such, pulley size is a good basis for choosing a spark plug.
Stock pullied cars may find it beneficial to step down up to 1 heat range in plug, even without any mods. But many can also stick with stock heat range, since we assume if you’re running such a large pulley still that you are not entirely interested in any additional horsepower
3.4-3.25 pulleyed cars should step down 1-2 heat ranges, 3.1-3.0 2-3 heat ranges, and any 2.x” pulley sizes should really be running a race-engine-bread 4 range colder plug as offered by NGK and Autolite.
If you have an intercooler, you should step down one heat range less than normal. So if you were running a 3.0 before the intercooler on a 3 range colder plug, step up to a 2 after the IC. If you were running a 2 range colder plug on a 3.25 before and are moving to a 3.0 after the IC, you should be able to run the same plug. Reason being is that the intercooler drops the inlet air temperatures, thus less is needed to be removed from the combustion chamber with your plug selection.
Why does the gap decrease as the plug heat range goes down, whats the link there?
The reason for the decrease in plug gap is in relation to the pulley size being run, not necessarily the plug itself.
First off, I think its unwise to run a copper plug at anything over .055” without a very powerful aftermarket ignition control box, so all copper plugs I recommend that gap as a maximum.
As you step down in pulley sizes, more air is being moved into the cylinders as more power is being made. This results in an increase in pressure in the cylinders on the compression stroke. It’s the author’s belief that more power is lost from incomplete combustion from a wider gapped plug than most realize. Due to the rise in pressure, it makes sense to decrease the plug gap slightly to correspond, to ensure good combustion for more power, and even less knock retard in some instances in my experience. Wider is not always better.
____________________________
http://www.cardomain.com/ride/2249111/1
11.80 @ 116.10 MPH 1.75 60'
"WHEN THIS BABY HITS 88MPH,YOUR GONNA SEE SOME SERIOUS SH*T"
I have put a low lift VS Cam, ported manifolds, 3.2 pulley, and full 3 inch exhaust with downpipe....... the car was having serious KR issues.... I thought it was everything from the darn exhaust pipe rubbing on the rack and pinion hydrolic line.... to tuning issues. It was so bad the car got drug by 6 car lengths by a mostly stock neon ????. Well..... after going to autozone to pick up some new plugs, i just figured they needed to be replaced... i did a bit of research, it seems that I had a plug that was way to hot for the mods.
I have a tuner... but no laptop to check the tune out.
I wanted someone elses opinion on the subject as well as why or why not run a autolite copper core plug on my new 408 / 250 nitrous shot setup?? vs NGK's?
************************************************** **************
Which Spark Plugs Should I Run?
Give me a spark plug 101
A spark plug has two main tasks: to ignite the air/fuel mixture properly, and to remove heat from the combustion chamber to maintain an optimal temperature.
Platinum, some hear that word and think BAM these are premium plugs. What makes platinum different? Well the answer is in the design of a platinum plug. So lets start there.
A spark plug's firing task is to transfer electrical current or "spark" between a power and a ground electrode to ignite the air and fuel mixture. We want this spark to be powerful, to promote a nice clean burn of the mixture, as this will promote the best efficiency and therefore the most power. Now imagine two spheres electrically charged, hold them closely together and you'll see spark jump across it. Now try and separate them and you'll see the spark disappear. NOW try this with two sharp pointed electrical rods and you'll see you can hold them further apart and the spark will still jump between them. What does this mean? Sharp points will transfer the spark the most effectively. Ever notice the tip of the spark plug and how most platinum plugs are sharp tipped center electrodes?
Sharp tips are all well and fine, but thats a hot environment down there. Infact the biggest problem is withstanding the heat. A sharp center electrode will get very hot, this promotes easy ignition (less charge to spark the plug) and a clean running plug free of deposits, but try this with a standard copper plug and it'll melt! Platinum has a much higher melting point than copper which is used on the classic style spark plug, thus the tip can be sharpened like it is. Iridium is the new guy on the block; same thing, it has an even higher melting point, thus the tip can be sharp. Now a copper plug needs to have a wide body to disperse the heat over a larger area so its tip can run cooler. Now did that set off any light bulb on where that would be beneficial? If you said forced induction or nitrous applications, pat on the back! In applications where you want to minimize existing heat in the combustion chamber, platinum may not be a good thing.
Here is another stick in the spokes of the platinum bandwagon wheel: Platinum does not conduct electricity very well. Platinum was chosen due to its resistance to heat and erosion, however it conducts electricity about a third as well as copper. The new iridiums are an attempt to find a metal with similar heat and erosion resistance as platinum but better conductivity of electricity; however, iridium is still only about half as good a conductor as copper, iridium plugs are one of the best marketing tools for spark plugs today and nothing more in the authors opinion. Now this disadvantage of platinum is offset to an extent by the ease of firing that platinum plug design offers, with its sharp pointed tip. Whether a copper plug can produce as much spark energy with a smaller gap however, than a platinum counterpart with a wider gap, is a good point of debate. The author’s viewpoint is yes.
Before I read further, what plug do you recommend for my application?
My recommendation for GTPs is to use a copper Autolite plug whenever possible. Copper runs cool, will perform better than exotic metals in my experience, should last its user about 2 years, and best of all are inexpensive.
For a stock pullied car, if you are unmodified and looking for a maintenance recommendation for plugs rather than a performance one, look for Autolite platinums which are part number coded AP for platinum and APP for double platinum at the very beginning of the part number.
Non-intercooled:
3.8” factory: Autolite 605 @ .055-.057” gap (or AP605/APP605 platinums @.060”)
3.4-3.25” pulley: Autolite 104 @ .052-.054” gap
3.1-3.0” pulley: Autolite 103 @ .047-.050” gap
2.9-2.7” pulley: Autolite AR94 (4 range colder race plug) @ .044-.046”
Intercooled
3.25-3.0” pulley: Autolite 104 @ .050-.052”
2.9-2.7” pulley: Autolite 103 @ .046-.048”
2.6-smaller: Autolite AR94 @ .044-.046”
Why does the author not recommend platinums in a GTP, aren’t they better?
Better? No, not in my book. And there is a good reason I recommend not using platinums in a supercharged application, and that’s because they run HOT. The small platinum tipped plugs are designed to run very hot to promote easy firing for mileage and emissions at idle and low vehicle speeds, along with erosion resistance so the owner of the car can neglect its maintenance for 100,000miles (yes, neglect is IMHO the appropriate word here!). These reasons are why they are considered better, but now that you know the whys, you know enough to make a judgement call for your own application.
Why do we step down heat ranges?
With a supercharged motor, the process of adding boost also adds heat to the incoming air. This is a normal byproduct of compressing the air. By running 10psi of boost from an M90 on a 3800, with pulley sizes anywhere from 3.8” to 2.7”, we are also adding 170-320F temperatures to the inlet air.
One of the spark plug’s functions is to remove heat from the combustion chamber, contrary to whatever you may have heard about spark plugs adding heat. We can use this function to remove or counter balance the heat which we are adding to the combustion chamber from the supercharger. By fine tuning the heat range of the spark plug we use, we can ensure an optimal temperature in the cylinders for proper combustion without pre-igniting the mixture from excessive heat.
How many heat ranges should I step down with my L67/L32 supercharged motor?
This will vary greatly on what pulley size you run. By going smaller and smaller to keep boost levels up, we are adding more and more heat by spinning the supercharger faster, even though we’re running the same amount of boost. As such, pulley size is a good basis for choosing a spark plug.
Stock pullied cars may find it beneficial to step down up to 1 heat range in plug, even without any mods. But many can also stick with stock heat range, since we assume if you’re running such a large pulley still that you are not entirely interested in any additional horsepower
3.4-3.25 pulleyed cars should step down 1-2 heat ranges, 3.1-3.0 2-3 heat ranges, and any 2.x” pulley sizes should really be running a race-engine-bread 4 range colder plug as offered by NGK and Autolite.
If you have an intercooler, you should step down one heat range less than normal. So if you were running a 3.0 before the intercooler on a 3 range colder plug, step up to a 2 after the IC. If you were running a 2 range colder plug on a 3.25 before and are moving to a 3.0 after the IC, you should be able to run the same plug. Reason being is that the intercooler drops the inlet air temperatures, thus less is needed to be removed from the combustion chamber with your plug selection.
Why does the gap decrease as the plug heat range goes down, whats the link there?
The reason for the decrease in plug gap is in relation to the pulley size being run, not necessarily the plug itself.
First off, I think its unwise to run a copper plug at anything over .055” without a very powerful aftermarket ignition control box, so all copper plugs I recommend that gap as a maximum.
As you step down in pulley sizes, more air is being moved into the cylinders as more power is being made. This results in an increase in pressure in the cylinders on the compression stroke. It’s the author’s belief that more power is lost from incomplete combustion from a wider gapped plug than most realize. Due to the rise in pressure, it makes sense to decrease the plug gap slightly to correspond, to ensure good combustion for more power, and even less knock retard in some instances in my experience. Wider is not always better.
____________________________
http://www.cardomain.com/ride/2249111/1
11.80 @ 116.10 MPH 1.75 60'
"WHEN THIS BABY HITS 88MPH,YOUR GONNA SEE SOME SERIOUS SH*T"
05-28-2007, 11:19 PM
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I just put in some Autolite 103's gapped @ .039 for this NA cam only car Mike is putting together. He's asleep now but im sure you have his number or his email. If not PM me and ill swing it your way so you can tickle his brain tomorrow at work. Its not like he works hard at his day job..LOL
