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SRT-4 NGK Spark plug info

hey guys,

Due to a lot of questions about cooler heat ranges on SRT-4 plugs I though I would post up some numbers to help you guys out

factory heat range
LZTR5AIX-13 (.052" gap)

one heat range colder
LZTR6AIX-13 (.052" gap) one range cooler version of stock range plug
LTR6IX-11 (.044" gap) and less projection-good for higher boost and or nitrous

two heat ranges colder
LTR7IX-11 (.044" gap) and less projection

The 7 heat range is the coldest plug we currently offer with the CORRECT 25mm thread reach.

You do NOT want to use a TR5 TR6 TR7IX or TR8IX series plug as these have a shorter 19mm thread reach and can severely hurt your engine as well as cause very poor performance.
Platinum is still not recommended for nitrous applications although it is fine for boosted applications

Iridium works extremely well for nitrous applications due to its high melting and oxidation points

If you ever have any questions or need a recommendation feel free to call me at my desk at 248 926 6315 or call 877 473 6767 option 2

Brandon Peeler (AKA saturnterminator)
Technical Support Representative
Aftermarket division
NGK Spark Plugs USA
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