Spark Plug Change - How To?
Checking to make sure I was not caught on any wires, I heated them with a heat gun, pulled and tugged on them until they came loose.
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Joined: Jun 2015
Posts: 132
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From: FL
#1. I want to get this Champion or Denso Iridium plug one heat range colder than these. How do I find that plug? What is the stock heat range? What are the part numbers?
Last edited by Sterling Smith; Aug 15, 2018 at 11:40 AM.
Joined: Oct 2007
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From: PHX some of the time
Why do you think you need to change the spec?
Champion:Champion indicates the heat range in the middle of the plug number. For example, RV15YC6 has a heat range of 15. (The 6 at the end of this part indicates the Gap setting.) Champion plugs are hotter the higher the number, colder the lower the number. Starting with part # RCJ7Y (Heat Range 7), a colder plug would be # RCJ6Y (heat range 6), a hotter plug would be # RCJ8Y (Heat Range 8).
Denso:Denso indicates the heat range in the middle of the plug number. For example, SK20PR-A11 has a heat range of 20. The number at the end of the part indicates the Gap. Denso Iridium Power plugs feature the Heat Range at the end of the part number. For example, IK20 has a Heat Range of 20. Denso plugs get colder the higher the number, hotter the lower the number. Starting with part # IK20 (Heat Range 20), a colder plug would be # IK22, a hotter plug would be # IK16.
Champion:Champion indicates the heat range in the middle of the plug number. For example, RV15YC6 has a heat range of 15. (The 6 at the end of this part indicates the Gap setting.) Champion plugs are hotter the higher the number, colder the lower the number. Starting with part # RCJ7Y (Heat Range 7), a colder plug would be # RCJ6Y (heat range 6), a hotter plug would be # RCJ8Y (Heat Range 8).
Denso:Denso indicates the heat range in the middle of the plug number. For example, SK20PR-A11 has a heat range of 20. The number at the end of the part indicates the Gap. Denso Iridium Power plugs feature the Heat Range at the end of the part number. For example, IK20 has a Heat Range of 20. Denso plugs get colder the higher the number, hotter the lower the number. Starting with part # IK20 (Heat Range 20), a colder plug would be # IK22, a hotter plug would be # IK16.
Senior Member
Joined: Aug 2016
Posts: 198
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From: Kaunas
I have changed sparkplugs on my xf 4.2SC to Bosh double platinium after car clocked 160 000miles. Bosh double patinmium was good up to 3km, then I give car WOT and recticeted performance and misfires. took them out, 3 of them were dead. changed them to NKG LPG Laserline, 10000 miles no problems. I would avoid Bosh in that car
Senior Member
Joined: Jun 2015
Posts: 132
Likes: 64
From: FL
Why do you think you need to change the spec? I plan on getting tuned with the Arden Headers with a full header x-pipe exhaust setup with pulleys. I also plan on tracking the car at Daytona and Sebring late this year and next year. I have done some research and read articles that Jaguar engineers puts the hottest plugs they can get away with for emissions reasons from the factory. So that being said, A plug that is too hot for the power you are making will set off pre-ignition in the cylinder. If I am going to go from 440whp to ~560whp, that should be plenty enough heat to make the factory plugs cause pre-ignition, especially on a big power track like Daytona or Sebring. So to be safe I want to get one or two ranges higher heat handling plugs if that makes sense to have insurance I wont cause pre-ignition on a 20 min session on a big power track.
I was looking at the Denso Iridium Twin Tip plugs, https://www.ebay.com/itm/Set-of-8-Spark-Plugs-Iridium-TT-Long-Life-DENSO-Twin-Tip-4711-Made-in-USA-V8/332462017392 but I don't see any of those heat range numbers in there. Ideally I would like a .040 gap with a one or two range colder plug.
Champion:Champion indicates the heat range in the middle of the plug number. For example, RV15YC6 has a heat range of 15. (The 6 at the end of this part indicates the Gap setting.) Champion plugs are hotter the higher the number, colder the lower the number. Starting with part # RCJ7Y (Heat Range 7), a colder plug would be # RCJ6Y (heat range 6), a hotter plug would be # RCJ8Y (Heat Range 8).
Denso:Denso indicates the heat range in the middle of the plug number. For example, SK20PR-A11 has a heat range of 20. The number at the end of the part indicates the Gap. Denso Iridium Power plugs feature the Heat Range at the end of the part number. For example, IK20 has a Heat Range of 20. Denso plugs get colder the higher the number, hotter the lower the number. Starting with part # IK20 (Heat Range 20), a colder plug would be # IK22, a hotter plug would be # IK16.
I was looking at the Denso Iridium Twin Tip plugs, https://www.ebay.com/itm/Set-of-8-Spark-Plugs-Iridium-TT-Long-Life-DENSO-Twin-Tip-4711-Made-in-USA-V8/332462017392 but I don't see any of those heat range numbers in there. Ideally I would like a .040 gap with a one or two range colder plug.
Champion:Champion indicates the heat range in the middle of the plug number. For example, RV15YC6 has a heat range of 15. (The 6 at the end of this part indicates the Gap setting.) Champion plugs are hotter the higher the number, colder the lower the number. Starting with part # RCJ7Y (Heat Range 7), a colder plug would be # RCJ6Y (heat range 6), a hotter plug would be # RCJ8Y (Heat Range 8).
Denso:Denso indicates the heat range in the middle of the plug number. For example, SK20PR-A11 has a heat range of 20. The number at the end of the part indicates the Gap. Denso Iridium Power plugs feature the Heat Range at the end of the part number. For example, IK20 has a Heat Range of 20. Denso plugs get colder the higher the number, hotter the lower the number. Starting with part # IK20 (Heat Range 20), a colder plug would be # IK22, a hotter plug would be # IK16.
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