[Crewchief]

They fit in great. Car runs great, even though I really dont see any difference. Well I didnt have any instructions, I've just done some reading and asked a few questions from some of the mechanics at the local subaru dealership. It took me about an hour, but it was my first time doing it. If I were to do it again then it would probably only take me 30 minutes or so. It's very easy. As long as you know what a spark plug looks like and know how to turn a bolt you can do this. Anyways, I havent read anywere on here on DIY's and I know alot of people ask how this is done so I figure I'd draft one up for those interested. I tried to break this down so even the most unskilled mechanics could do this. The pictures are labeled with the step number there refering too. Here it is.....

Step 1: Removing the battery and windshield washer fluid resevoir. This is simple, its just four bolts holding the battery and two bolts (<< seen in step one), a hose and a clip (<< seen in step 1.1) holding the washer resevoir in.

Step 2: Removing intake and assembly. Now this I will have a hard time breaking down, because I dont have my stock intake. I have the K&N typhoon, and if you also have this then you obviosly know how to remove it. The stock intake is very easy just a couple of bolts, clamps etc. Seriously, VERY EASY to remove. Though I still included instructions. (<< steps 2 and 2.1)


Continued on next post.........

[Crewchief]

Steps 3, 3.1, and 3.2: Removing the spark plug coils. One gold colored bolt on each of the coils (they look like little grey boxes). There is one coil for each cylinder (total of 4, two on each side). Remove the four bolts and coils. See Steps 3, 3.1.

Once the coils have been removed this is what it should look like (see step 3.2 pic).

Step 4: Removing the old spark plugs. You'll need a spark plug socket, with a small extension. Get the socket seated on the spark plug and remove them. It took quite some torque to get them out. I damn near had to use a breaker bar, lol. Get all four of them out.

Steps 5: Installing the new spark plugs. To install the new ones just put the spark plug onto the sparkplug socket (which is connected to the small extension.) Once you get a hold on the spark plug which is in the coils whole, tighten it. It should be very easy to tighten at first (85% of the tightening was done by hand.) If its hard to tighten at first, then your crossthreading, back it out and try again. Do this to all 4 spark plugs and make sure there tight.

Continued on next post.......

[Crewchief]

Step 6: Installing the coils. This is just like steps 3. Line the coil back over the spark plug and re-install the bolt. Remember on the left rear side (facing car) there is the bracket that needs to connect with the coils bolt. Each coil must connect to its spark plug. The coils with the shorter wires go to the spark plugs closer to the firewall. Even though when removing these, it felt like they had a clip holding them in, THEY DO NOT CLIP BACK IN, they just seat there and you tighten them down

Step 7: Re-install battery, washer resevoir, and intake. If you forgot how to do this look at the pics in steps 1 and 2 again.

Your done! Start the car up and go for a ride.

Additional Info:

Spark Plugs Used: Denso Ultra-Fine 0.4mm Iridium Spark Plugs, part# IKH22.
These are one step colder over the stock spark plugs
Price: Around $50 bucks
Gapping: These spark plugs DO NOT need to be gapped at all. They come pre-gapped for the STI. Just put them in and tighten them down.


Torque Specs:

Tightening torque (spark plug):
21 N·m (2.1 kgf-m, 15.2 ft-lb)

Tightening torque (coil):
16 N·m (1.6 kgf-m, 11.7 ft-lb)


NOTE:
• Be sure to place the gasket between the cylinder
head and spark plug.
• If a torque wrench is not available, tighten the
spark plug until gasket contacts cylinder head: then
tighten further 1/4 to 1/2 turns.
• Anti-seize can be used to prevent the sparkplug from seizing to the aluminum. Though I didnt use anit-seize when doing this, it wouldnt be a bad idea to of done so.



Why colder spark plugs can be better......

Colder spark plugs help prevent knock when running higher boost levels. They also help run lower EGT's. Running to cold could cause pre-ignition. One step colder is recomended once about 75 hp over stock.

More in depth:

A spark plug's heat range has no relationship to the actual voltage transferred though the spark plug. Rather, the heat range is a measure of the spark plug's ability to remove heat from the combustion chamber. The heat range measurement is determined by several factors; the length of the ceramic center insulator nose and its' ability to absorb and transfer combustion heat, the material composition of the insulator and center electrode material.
The insulator nose length is the distance from the firing tip of the insulator to the point where insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling. Whether the spark plugs are fitted in a lawnmower, boat, or a race car, the spark plug tip temperature must remain between 500C-850°C. If the tip temperature is lower than 500°C, the insulator area surrounding the center electrode will not be hot enough to burn off carbon and combustion chamber deposits. These accumulated deposits can result in spark plug fouling leading to misfire. If the tip temperature is higher than 850°C the spark plug will overheat which may cause the ceramic around the center electrode to blister and the electrodes to melt. This may lead to pre-ignition/detonation and expensive engine damage. In identical spark plug types, the difference from one heat range to the next is the ability to remove approximately 70°C to 100°C from the combustion chamber. A projected style spark plug firing tip temperature is increased by 10°C to 20°C.

Worth a sticky?

[Sti-lysh]

What does the one step colder plug do? sorry if its a dumb question

[Crewchief]

No questions is dumb, thats why I said "If you got a questions, post up"

Originally Posted by Sti-lysh

What does the one step colder plug do? sorry if its a dumb question

Well colder spark plugs help prevent knock when running higher boost levels. They also help run lower EGT's. Running to cold could cause pre-ignition. One step colder is recomended once about 75 hp over stock.

More in depth:

A spark plug's heat range has no relationship to the actual voltage transferred though the spark plug. Rather, the heat range is a measure of the spark plug's ability to remove heat from the combustion chamber. The heat range measurement is determined by several factors; the length of the ceramic center insulator nose and its' ability to absorb and transfer combustion heat, the material composition of the insulator and center electrode material.
The insulator nose length is the distance from the firing tip of the insulator to the point where insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling. Whether the spark plugs are fitted in a lawnmower, boat, or a race car, the spark plug tip temperature must remain between 500C-850°C. If the tip temperature is lower than 500°C, the insulator area surrounding the center electrode will not be hot enough to burn off carbon and combustion chamber deposits. These accumulated deposits can result in spark plug fouling leading to misfire. If the tip temperature is higher than 850°C the spark plug will overheat which may cause the ceramic around the center electrode to blister and the electrodes to melt. This may lead to pre-ignition/detonation and expensive engine damage. In identical spark plug types, the difference from one heat range to the next is the ability to remove approximately 70°C to 100°C from the combustion chamber. A projected style spark plug firing tip temperature is increased by 10°C to 20°C.

[Sti-lysh]

So if im Cobb Stg 2 93 would this be necessary or prob. not?

-Leo

[Crewchief]

Well I have the cobb stage 2 and the k&n typhoon. havent see any problems with the plugs yet. I would say you should be just fine.

[Sti-lysh]

the theory makes sense, plus we have been having 90 + degree days so it might not hurt to play it safe.

[NCWSTi]

damn nice write up

love the pics with tabbed instructions
thanks for sharin and DIYen for us

[gixxer6]

very nice write up, i defenetely think it's worth being a sticky

[Justin B]

Ahh, that's where the spark plugs are

Good write up Crewchief, I vote sticky

[Barista]

It should be worth mentioning that you should use anti-seize compound on the new plug threads.

Having had experience with NOT doing this with aluminum heads, I can tell you your next change could get very, VERY ugly. Without anti-seize the plugs will seize to the aluminum, and you're next change could be replacing a stripped head.

Also, I think it would be a good idea to torque the plugs to the factory spec. Ft-Lb. Too little or too much is not usually a good long term result.

Good write up!! I always wondered how the heck you replaced the plugs on these engines. Neat!

[Boxer]

Nice post, thanks, I'll have to agree with Barista on the factory torque specs. (anyone know offhand what they are for plugs?). There's a reason the stockers were in there tight.

[WolfPlayer]

Two huge thumbs up for giving to the community.

[STLSTI]

Crewchief, Thanks for a really nice write up any change of posting the part # for the plugs and what gap are you using.