[Real Lyte]

Dubaya, keep in mind many ppl at parts stores don't know this but...when it comes up in the computer as saying it "fits", this purely means it will fit but not necessarily be the right heat range. I was looking through the plugs recommended for my foz autozone, the NGK coopers were the only correct heat range out a list of maybe 15 plugs it says will fit.

 

[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.

 

[Real Lyte]

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.

Lol. I like how this thread has evolved, good info though. IMHO, I'm sticking with the manufacturer recommended NGK heat range 6 copper plugs. It isn't that bad doing them every 12k (maybe an hour's work).

 

[dubaya1]

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.

So why does a colder plug give you more get up and go and a hotter plug is more suitable for light throttle and cruising?
And what does a ping sound like, because I def have other than engine noises coming from my car. Something like the noise you make to get a horse to start walking. *nk nk*, giddy up!

 

[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.

 

[dubaya1]

:biggrin: :huh: :icon_frown: :icon_mad: uke: :icon_idea: I think I got it.


Thats what I get for asking. Thank you.:icon_biggrin:
I needed new plugs anyways.:icon_cool:

 

[adc]

OK..another update.:crazy: :

Did my daughter's 08 'X' yesterday. 44K miles on the clock. Plugs condition: "Excellent" The stock plugs probably could go 100K although I wouldn't do it for lots of reasons. But if you don't get to it by 30K, 40K, or 50K miles..don't feel guilty.

I have the Subaru bucks so I got the Plats (In the subaru packaged container) for 15 bucks each. :banana: . Job went like clockwork. I really do suggest that you have a socket that really holds onto the plug tight as you are gonna have one that just won't come out of the hole. Also tape the socket onto the extension.

As mentioned..the plugs on the passenger side can be torqued after you remove the airbox and use a 10" extension. I torqued them to13 ft. lbs using a very, very slight amount of antisieze on the threads. I found that the plug rotated just about 3/4 of a turn after contact between the plug and block. So on the driver's side I used contact + 3/4 turn in lieu of torquing. Again as mentioned use a very short handle socket wrench for the driver's side.

Oh..one other thing. Resistances were from 8 K Ohms to 16K ohms depending on the length of the wire. The 16 K Ohm was about 3K ohms higher than the other of about the same length. I probably should have replaced.

 

[exume]

These instructions are for SOHC only. The DOHC with the coil over plug are a totally different story, you can give it a go but in the past i have dropped the sub frame and lowered the engine. BIG JOB!

 

[British-G]

On my 98 L EJ25 I can get at the plugs from underneath. Only have to take the skid plate off.

 

[shaggenstein]

two quick questions. I have a 98, and have been getting a blinking CEL, and it's been running rough. Pulled the numbers and it says cylinder 3 is misfiring. Swapped out wires already, but that didn't fix it, so now going to try to change the plugs, which I have never done before. So how do I know which one is the third cylinder? And also, if I am using just a regular old socket wrench, how do I know how much torque I've put on the plug?

 

[2.5x_sleeper]

two quick questions. I have a 98, and have been getting a blinking CEL, and it's been running rough. Pulled the numbers and it says cylinder 3 is misfiring. Swapped out wires already, but that didn't fix it, so now going to try to change the plugs, which I have never done before. So how do I know which one is the third cylinder? And also, if I am using just a regular old socket wrench, how do I know how much torque I've put on the plug?

I see this is your first post, so welcome to the forum! :biggrin:

If not the sparkplug, it may be the coil pack. As to your question on where cylinder #3 is. Take a look here. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

 

[shaggenstein]

I see this is your first post, so welcome to the forum! :biggrin:

If not the sparkplug, it may be the coil pack. As to your question on where cylinder #3 is. Take a look here. :wink:

Bobby...

Yah joined a little while ago when I got my used Subaru, been diggin around for info here and there up till now. The coil pack is where I'm going to go next if this plug swap doesn't solve the problem. Thanks for the diagram. Just want to know so when I pull them out I take an extra careful look at the plug from cylinder 3.

 

[2.5x_sleeper]

The coil pack is where I'm going to go next if this plug swap doesn't solve the problem. Thanks for the diagram. Just want to know so when I pull them out I take an extra careful look at the plug from cylinder 3.

I've read that you can check the coil pack by misting it when it's dark. If you see arching (sparks), it's bad. :wink:

As to tightening the spark plugs, it's best to use a torque wrench & anti-seize compound to prevent the steel sparkplugs from seizing to the aluminum heads. :smile:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

 

[adc]

And also, if I am using just a regular old socket wrench, how do I know how much torque I've put on the plug?

I have found that its hand contact plus 3/4 Turn.

Disclaimer:

Don't go anymore than 3/4 turn.....and this is the value that I use. Do at your own risk. And make sure there is a NEW gasket on the plug.

Using anti-sieze on the plug should reduce the torque from around 15 ft. lbs. to about 11 ft lbs. But it should not affect the 3/4 turn after contact.

 

[shaggenstein]

thanks for all the great info, guess I should go out and by some anti seize before I try this

 

[2.5x_sleeper]

thanks for all the great info, guess I should go out and by some anti seize before I try this

I get the little squeeze pouch that they sell at the auto parts counter. Keep in mind, a small amount is all you need... a very small amount. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

 

[natenut]

I just changed the plugs in my 07 XT. There were around 50k miles on them and i noticed a tremendous difference in high torque scenarios such as letting out the clutch at low rpm. Before the plug swap there was some shuddering and afterward much smoother power delivery though the low rpm range.

I went with the factory NGK plugs from my dealer. The ones i took out looked fine (brown/tan) but the gap had eroded about .5mm larger. Is it this gap change that effects the performance? Does it modify the timings enough for the power issues i mentioned?