1004ron Posted October 26, 2024 Report Share Posted October 26, 2024 Installed the new NGK's this morning. The old plugs looked very good and no change in gap - just thought that there may be benefits with the revised heat range plugs. Looked into the cylinders and they're all pristine, like brand new. 2 Quote Link to comment Share on other sites More sharing options...
boostededge Posted December 30, 2024 Author Report Share Posted December 30, 2024 (edited) Edited because I'm even more confused now. Using the NGK part finder is looks like OEM plugs were heat range 7? and the now NGK recommended plugs are heat range 6 wheras Ford is recommending a hotter plug heat range 8 possibly on SP-578? Going to that hot of a plug doesn't sound good, I can see why people would see less timing and be able to run less boost. @1004ron you originally installed the LTR7BHX which are heat range 7 now your going to a COLDER plug LTR6BHX heat range 6. Ford SP-542 is heat range 7 SP-578 is heat range ?8? Iridium NGK ILTR7N8 is heat range 7 (original OEM equivalent) NGK ILTR6S8 is heat range 6 Ruthenium NGK LTR7BHX is heat range 7 NGK LTR6BHX is heat range 6 Edited December 30, 2024 by boostededge 1 Quote Link to comment Share on other sites More sharing options...
1004ron Posted December 30, 2024 Report Share Posted December 30, 2024 NGK 6 is hotter than NGK 7. NGK.com: Heat Range Conversion Chart Quote Link to comment Share on other sites More sharing options...
boostededge Posted December 30, 2024 Author Report Share Posted December 30, 2024 7 minutes ago, 1004ron said: NGK 6 is hotter than NGK 7. NGK.com: Heat Range Conversion Chart Thanks I had it backwards! Quote Link to comment Share on other sites More sharing options...
Metroplex Posted March 17 Report Share Posted March 17 I contacted NGK about this and they said they worked with Ford in 2019 and found the heat range 6 plugs (hotter) could be used in all Nano engines, and hence the change from SP-542 (ILTR7 NGK Laser Iridum) to SP-578 (and now SP-594) which are NGK heat range 6 plugs. They found the hotter plugs reduced fouling. However, Ford's SP-578/SP-594 are different from NGK's Laser Iridiums in that they use narrow ceramic insulators at the firing side for better cold performance and reduced carbon fouling. So that's why the original SP-542 are exact dead ringers for NGK Laser Iridium ILTR7 while SP-578/SP-594 are slightly different from ILTR6. If you look at NGK's ILTR6 and Ruthenium LTR6BHX, their ceramic insulator tips at the firing side are thiccer than the SP-578/SP-594. Personally from my datalogs and experience, the colder plugs don't really yield much benefit for spark advance under full boost with a tune. Maybe at best 2-3 degrees advance even with E40. The only current/new Fords to use the CYFS-092 (cold heat range, original factory for 2.7) plugs instead of CYFS-12 (hotter/stock heat range for 3.5) are the 2020-2022 GT500 and the Ford GT (SP-583). To buy the Ford GT plugs, the dealer asks for your VIN and mileage for your GT. 1 Quote Link to comment Share on other sites More sharing options...
boostededge Posted Sunday at 09:05 PM Author Report Share Posted Sunday at 09:05 PM On 3/17/2025 at 4:21 PM, Metroplex said: Personally from my datalogs and experience, the colder plugs don't really yield much benefit for spark advance under full boost with a tune. Maybe at best 2-3 degrees advance even with E40. I will take my advance and some more psi as well please 😁 1 Quote Link to comment Share on other sites More sharing options...
boostededge Posted Sunday at 09:06 PM Author Report Share Posted Sunday at 09:06 PM I have a set of SP-542 I found in a box from when I bought the ST in 2019. 6 years later I'm getting around to installing them 😅 1 Quote Link to comment Share on other sites More sharing options...
boostededge Posted Tuesday at 11:18 PM Author Report Share Posted Tuesday at 11:18 PM (edited) Got around to installing the SP-542 (.028 gap). Interesting the OEM plugs on my 2019 that I removed are in fact SP578 CYFS12YPT. They didn't look great at 45K miles. Idles and drives maybe a little smoother. A few notes from the install - As simple as it was a screwdriver popped the plastic clips off Ford's favorite 8mm nut stud. Otherwise they were not fun. Before the intercooler pipe can be moved, the blow off valve/diverter valve dump tube needs to be removed. It's a PITD. I used a spray bottle with some really really hot soapy water and it came off a lot easier. Once you get the intercooler pipe / air cleaner outlet pipe moved left (passenger) of the wiring harness it becomes more easily moveable. Once the pipe is to the left of the wiring harness, it makes sense to secure it with something (zip-tie, wire, tie-down, shoe-lace, or even duct tape like I had within reach). Now there's plenty of clearance for that coil. Was able to fit my CDI (1501MRMH) 1/4 torque wrench on every plug. 133 in-lbs / 15 Nm / 11 ft-lb Edited Wednesday at 04:53 PM by boostededge 1 Quote Link to comment Share on other sites More sharing options...
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