Since 95% of my driving is 2000-2500 rpm 35mpg driving I am not sure heat range 9 is the best choice for my situation. My engine will see full throttle maybe 6 times a day and only for a few seconds at a time.Heat range 9, .028 gap, 0.6mm electrode. These are the plugs most will be running now vs the HKS M45xl plugs. I'll be running these on my next set with lowering the gap as well.
NGK 97312 ILKR9Q7G Laser Iridium Spark Plug
NGK 97312 ILKR9Q7G Iridium Spark Plug - Same Day Shipping. Free Returns. PayPal Accepted. Secure Online Ordering. Est. 1969.www.ngk.com
Plugs for GT
Here is some info I learned this morning. Believe it or not I did not have to go to Facebook to find it either. 
So the stock plugs on the Forte GT are 18849-08080 (NGK 97080 - SILZKR8E8G) heat range 8
NGK.com: SILZKR8E8G NGK 97080 Iridium Spark Plug - Best Car Spark Plug Replacement
The suggested replacement is NGK 1422 - 1LKR8E6 (heat range 8)
NGK.com: ILKR8E6 NGK 1422 Iridium Spark Plug - Best Car Spark Plug Replacement
Heat range 9 suggestion is NGK 97312 - 1LKR9Q7G (heat range 9)
NGK.com: ILKR9Q7G NGK 97312 Iridium Spark Plug - Best Car Spark Plug Replacement
Several people here are using the stock plugs stock gap (.031) with a Racechip with no issues on 87, 91 and 93 fuel
Several people are also using the heat range 9 and also have no issues.
Several people are using stock plugs or upgraded plugs with a closed up gap (.025-.028) and again no issues
I personally feel for under 250 hp the heat range 8 stock or NGK 1422 will do
If getting a more serious tune 250+ hp go with the NGK 97312 heat range 9
One person mentioned getting slight detonation with stock plugs and gap which might be remedied with a tighter gap.
Steve g - I keep my GTS on 7 always with stock plugs and premium fuel (California’s idea of premium) If it’s over 100 degrees outside I can get slight detonation under a really heavy load. Not worth re-gapping plugs over it.
Here is what I found interesting. The difference between the stock plug and the NGK 1422. The stock NGK plug uses a 1mm Iridium center electrode diameter and the NGK 1422 uses a .6mm Iridium center electrode diameter. The reason is that a smaller center electrode diameter requires less voltage to get a strong spark which also means you should not need to reduce gap compared to the stock plug. So the NGK 1422 should have a stronger spark than stock based on this theory. The second change is the stock NKG plug has an extended projection center electrode which puts the spark closer to center of combustion chamber. The NGK 1422 has a standard projection center electrode which pulls the spark slightly closer to the edge of combustion chamber. You can read all day about this projection stuff. One interesting thing is that less projection slightly retards timing and also works better if the combustion chamber temps are high. There are several other things as well but that was interesting.
NGK.com: NGK Center Electrode Designs
I decided to order a set of the NGK 1422 to try for the fun of it. I will let you know in a couple weeks if I notice any differences. Like I said right now I have no issues with my stock plugs and stock gap but maybe these NGK 1422 will make it feel even better. Worth a shot for $50. I have not decided on gap yet but might try them at the stock .031 since the larger gap tends to provide better fuel economy assuming the gap is not too big for the spark under full throttle loads with increased boost.
So the stock plugs on the Forte GT are 18849-08080 (NGK 97080 - SILZKR8E8G) heat range 8
NGK.com: SILZKR8E8G NGK 97080 Iridium Spark Plug - Best Car Spark Plug Replacement
The suggested replacement is NGK 1422 - 1LKR8E6 (heat range 8)
NGK.com: ILKR8E6 NGK 1422 Iridium Spark Plug - Best Car Spark Plug Replacement
Heat range 9 suggestion is NGK 97312 - 1LKR9Q7G (heat range 9)
NGK.com: ILKR9Q7G NGK 97312 Iridium Spark Plug - Best Car Spark Plug Replacement
Several people here are using the stock plugs stock gap (.031) with a Racechip with no issues on 87, 91 and 93 fuel
Several people are also using the heat range 9 and also have no issues.
Several people are using stock plugs or upgraded plugs with a closed up gap (.025-.028) and again no issues
I personally feel for under 250 hp the heat range 8 stock or NGK 1422 will do
If getting a more serious tune 250+ hp go with the NGK 97312 heat range 9
One person mentioned getting slight detonation with stock plugs and gap which might be remedied with a tighter gap.
Steve g - I keep my GTS on 7 always with stock plugs and premium fuel (California’s idea of premium) If it’s over 100 degrees outside I can get slight detonation under a really heavy load. Not worth re-gapping plugs over it.
Here is what I found interesting. The difference between the stock plug and the NGK 1422. The stock NGK plug uses a 1mm Iridium center electrode diameter and the NGK 1422 uses a .6mm Iridium center electrode diameter. The reason is that a smaller center electrode diameter requires less voltage to get a strong spark which also means you should not need to reduce gap compared to the stock plug. So the NGK 1422 should have a stronger spark than stock based on this theory. The second change is the stock NKG plug has an extended projection center electrode which puts the spark closer to center of combustion chamber. The NGK 1422 has a standard projection center electrode which pulls the spark slightly closer to the edge of combustion chamber. You can read all day about this projection stuff. One interesting thing is that less projection slightly retards timing and also works better if the combustion chamber temps are high. There are several other things as well but that was interesting.
NGK.com: NGK Center Electrode Designs
I decided to order a set of the NGK 1422 to try for the fun of it. I will let you know in a couple weeks if I notice any differences. Like I said right now I have no issues with my stock plugs and stock gap but maybe these NGK 1422 will make it feel even better. Worth a shot for $50. I have not decided on gap yet but might try them at the stock .031 since the larger gap tends to provide better fuel economy assuming the gap is not too big for the spark under full throttle loads with increased boost.
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Swapped the plugs today. I installed the NGK 1402 NGK.com: SILKR8A-S NGK 1402 Iridium Spark Plug - Best Car Spark Plug Replacement
The "special gasket" on the NGK 1402 was thinner than the other replacement plugs but did not seem to make any difference installing them.
I have zero issues with the stock plugs but like to experiment to see if there might be something better. I want the largest gap I can without having any negative effects with the added boost from the Racechip. I set the gap at .032 which should give the best fuel economy and burn efficiency assuming the spark is strong enough under full boost. Since the stock plug has a 1mm iridium center electrode using .6mm should make a stronger spark since it requires less energy, This is the theory anyway. I took it for decent ride and really noticed nothing different. Idle might be slightly smoother and power feels identical, this was on 87 octane. Full throttle with Racechip on level 5 had no problems. I will fill up with 93 octane and see how these feel for the next couple weeks.
The thing that surprised me the most is how much longer the stock plugs are from all the plugs that are supposed to be the same length. All of the NGK replacement plugs change the spark location a pretty large amount. These NGK replacements all move the spark closer to the edge of the combustion chamber. Not sure what affects that has to combustion.
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The "special gasket" on the NGK 1402 was thinner than the other replacement plugs but did not seem to make any difference installing them.
I have zero issues with the stock plugs but like to experiment to see if there might be something better. I want the largest gap I can without having any negative effects with the added boost from the Racechip. I set the gap at .032 which should give the best fuel economy and burn efficiency assuming the spark is strong enough under full boost. Since the stock plug has a 1mm iridium center electrode using .6mm should make a stronger spark since it requires less energy, This is the theory anyway. I took it for decent ride and really noticed nothing different. Idle might be slightly smoother and power feels identical, this was on 87 octane. Full throttle with Racechip on level 5 had no problems. I will fill up with 93 octane and see how these feel for the next couple weeks.
The thing that surprised me the most is how much longer the stock plugs are from all the plugs that are supposed to be the same length. All of the NGK replacement plugs change the spark location a pretty large amount. These NGK replacements all move the spark closer to the edge of the combustion chamber. Not sure what affects that has to combustion.
Any spark plug experts have feedback on my stock plugs after 8000 miles. From what I can find on the internet they seem perfect.
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