[AlleyCat]

ADC, Nice writeup.
The only thing that gave me a problem in the past is too much dielectric grease on the boot(s). I've backed off to the point that I just skim the inside if the boot with my pinky finger. The Tip Connector doesnt like the grease - though in theory it shouldnt be a problem. I clean the boots inside and out using ethanol mixed with a tiny bit of distilled H2O. Plug boots dont like salt from the road OR from your sweaty palms; it only takes a little to migrate and cause a high misfire count in humid weather. Same goes for the plug socket insulator. It shouldnt transfer dirty grease onto the plug insulator. I usually weAr clean latex gloves to handle the new plugs, then thread the plugs in with a piece of fuel hose then tighten without the plug socket rubber insert. Another biggie - normal folks dont understand high-tension wires and what they like and dont like; but they surely DONT like to be under strain or torsion; so let them droop naturally the way they want to hang and try to keep that orientation when you re-insert the boot. Add these hints to your tune up list and you should have a car that runs BETTER after a tuneup other than worse. BTW, these are some of my SCCA racing secrets for extra HP, so dont tell anybody

 

[AlleyCat]

I remember my first time.. stupid H.. wished this was a V engine! LOL real lyte..

But NOT a twin turbo mitsubishi V6. You couldnt drop a marble under the hood and have it come out on the road or belly pan. Had to remove the intake manifold and FI to change the back bank 3 plugs:icon_eek:Here's a pic of the NA engine which has a little more room:

 

[AlleyCat]

Couple questions:
1) What was Year and Model, Engine of car serviced
2) What plugs came out ( Make and part#)
3) What plugs went back in
4) Did it run any different afterwards with the Autolites, and how close was the autolite insulator length to the NGK/ND - critical for a pent roof 'hemi' head.

thanks Al.

 

[AlleyCat]

The autolite heat range is not directly comparable to the NGK or ND or Champ heat range. Whatever the plug MANUFACTURER says will work in your app is what you should start with. I would NEVER go hotter. On a champ - higher # is hotter on a NGK a lower number is hotter, NGK: 5 is damn hot for low idle misfire counts, 6 is a typ lamda contriol running stoichiometric cruise mixture, and 7 is level 1 perf adds and/or stock turbo boost, and 8+ would be heavy turbo with a lot of power adders. My older '93 1.8L subaru impreza came with #8 heat range champions from the factory - RC8YC4 ( for 1.1mm gap) RC9YC will not work - you dont want the toe of the gap higher than the heel. USA made green print NGK v-power plugs are JUNK BTW. The OEM light blue print (with "s" in the part #) are OK. I typ prefer ND on subarus in a copper plug. Ive had over 5 subarus and worked as a tech for quite a while and a race mechanic/tuner back in the day.

 

[AlleyCat]

Just to report back. The Autolite Plats ($1.99) gave me the best mileage I have had thus far on the car. (32.4 mpg) ......... I intend to pull the plugs at 20K miles just to examine them.

Autolite#..AP3924

Dont pull them! - you absolutely HAVE to use new crush washers on alum head vehicles to replace them - waste of time and $$ if milage and perf is good. The MORE you mess with high voltage systems the bigger chance you'll get a leaky wire or termination. HT Wires dont like to be flexed. GOOD JOB leave it alone till next service interval. Go fishing instead

 

[AlleyCat]

I will have to search for a concrete source to this accusation by the guys at work...but they all say that your car will run like crap and sometimes causes other problems because of unburnt fuel etc.

They DONT know a thing about plugs. Dont listen to them - talk to professional RACE mechanics and professional tuners. All plugs have a different heat rage chart and dont compare to one another - AT ALL. Just as Temperature in Europe ( and CAN) is in Celcius and in the US it is in Fahrenheit. Does 24 degrees sound too cold to wear shorts? Think you better get a jacket ? Think again - thats = 75 degress in the USA. Not directly comparable.

 

[AlleyCat]

Autolite heat range #3 = 6 NGK, and Autolite #4= a 5 in NGK. Colder #'s are good for those who WHOMP on their cars and may have a pinging problem, hotter for best gas milage at light throttle cruise. Or COLD 6 or 7 for teenagers and hot 5 for Grandma.

 

[AlleyCat]

The plug's heatrange is compromise on street "smog motors" to produce lowest misfire counts during hard ignition scenarios. Two are 1) cold start and warmup and 2) Light throttle ccruise at near closed throttle and stoic or lean mixture. The hotter plugs (they "remove; or "sink" less heat from the plug tip to the cyl head water jacket) will have lower misfire counts and bigger flame kernel in these conditions. Next stressful condition is WOT (wide open throttle and full rich mixture (9-1 to 12-1 air/fuel mix). This is the primary determiner of correct heat range when the plug has to remove enough heat from the plug tip so you dont get knocking from unintended ignition in front of the spark event. The way this is checked on "race cars" is the engine is run full throttle around the upper torque peak for a goodly time then the engine is promptly shut down with no fuel or spark. Then the plugs are pulled to look for signs of overheating or fouling (blistering, bluing or carbon, soot) then the heat range is adjusted as required by the read. The only way to adjust on a pass car is change the plugs, and the only direction to go would be 1 heat range COLDER (lets say #6 instead of a 5 on a NGK) because the owner wants stronger full throttle high rpm power. You can also step up to an IR plug - the best thing since sequential fuel injection. They are easy to light and provide low misfire counts and last 100K miles.

 

[AlleyCat]

Just a caution: I would not use Ir unless you have COP. Ir dont fire backwards properly. NA EJ253 have waste spark ignition. Recall how FORD had used special plugs on the GND>Center firing plug. OTOH, TURBO DOHC EJ255 have COP and require Ir to get low misfire counts.

 

[AlleyCat]

Sorry Al, even though I am old as dirt I got carried away with this internet lingo Ir is an iridium finewire center electrode sparkplug. COP is coil-on-plug ignition system. COP have no secondary "spark plug wires". EJ255 is COP, FB is COP, EJ253 SOHC is waste spark. Waste Spark is one coil for 2 plugs. One plug fires "backwards" all the time. Finewire center electrode plugs (Ir) dont fire backwards reliably with a low misfire count. They also have a diagonal spark path which is bigger than the gap when reverse fired. The engine may run OK with Ir on a wastespark if tune, mixture and ignition are perfect, but will misfire when things get marginal. The good/safe operation margin is wider with Standard electrode plugs or something special like the Denso TT pictured below: