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The NGK copper is a standard OEM replacement and good for 45,000 miles in the stock engine.
If you are not getting that kind of mileage out of them, then there is some issue with the setup or tuning.
The NGK plugs we pulled from 1992-2002 sr20det engines with 88,000km to 144,000km , they all used these plugs for 10 to 20 years with great success before coming to America.
I have also used NGK copper plugs for tuning a hundred sr20 engines and have no issues for 10~ years.
The correct gasoline a/f ratio to use which will preserve these plugs is:
Idle: 14.7 to 15.2
cruise: 14.8 to 15.5
part throttle -2psi of boost: 13.3 to 13.5:1
0psi of boost threshold: 13.0 to 12.8:1
0 to 7psi of boost: 12.4 to 12.7:1
7 to 15psi of boost: 11.8 to 12.2:1
15 to 22psi of boost: 11.5 to 11.8:1
22+ psi of boost: not recommended for 93 octane gasoline unless you are a professional tuner
The engine needs a fully intact OEM pcv system. The crankcase pressure should be monitored at least initially to verify the pcv is working.
The engine needs a high quality paper air filter, similar to OEM style paper.
If the engine has a MAF it needs a recirculated bypass. This is the number one offender of spark plugs and cylinder walls, people not using a recirculated bypass for their blow-off valve causes gasoline to wash down the cylinder walls and fouls plugs ruining their life span and the engine's life span.
If you lack these tuning a/f ratios or crankcase PCV system, or a sufficient air filter, or recirculated bypass, the plugs will seem to not last very long.
Recap:
-tuning: poor tuning fouls the plugs. If plugs are fouled once they should be replaced.
-After engine tuning, replace the plugs.
-lack of recirculated bypass from blow-off ruins plugs and cylinder walls.
-lack of high quality air filtration ruins plugs and trashes the engine (internally it will erode, degrade, and oil passages will clog and the enngine block will become unsalvagable and unreusable)
-lack of pcv system causes myriad issues related to oil quality and oil aspiration, hydrocarbon-oil contamination, which leads to plug fouling
*The most important thing for any piston-engine is cleanliness. These features and goals are all aimed towards cleanliness. If the air is not clean, the oil will not be clean. If the oil is not clean, the engine will quickly become ruined, trash. Air filters, pcv, proper tuning, all help keep the engine clean internally which will maximize service life and intervals.
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