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Old 07-09-2019, 10:19 AM   #2
NASIOC Supporter
Member#: 132
Join Date: Jul 1999
Chapter/Region: Tri-State
Location: PA
2006 GT Ltd 5spd sdn
'15 WRX 6spd CWP, '02 WRX


If reliability is a concern, first look at things that can screw up your engine before you add ANY more power.

Fuel injectors. If they are original, have them cleaned and tested professionally and re-install with new seals/grommets. If you plan on replacing them for larger, brand new ones are preferred but if not, again, have them cleaned and tested.

Fuel pump: Replace it. The 255 Walbro plug and play works fine, is a good price, and is a direct drop in. Make sure it is a genuine Walbro though and not a copy. Personally, if you don't mind wiring, the Supra TT(Denso) is probably the better option in terms of reliability, simply because OEM parts are made to be quiet and last 100,000 miles, but you'll have to wire it in yourself.

Sensors: First, genuine oem Subaru parts from a Subaru dealer. I know some buy "Denso" parts from AutoZone or the like, but I avoid that.

MAF sensor. Replace it. The ECU relies far too much on what the MAF sensor is telling it for there to be any question of it's reliability. Old MAFs can cause all sorts of issues that are hard to track down. Replace it.

Temp sensor. Cheap and easy to replace. As they get old, they get a tarnish on them that can have the sensor read inaccurately.

Front 02 sensor. Again, like the MAF, old, original ones can start causing annoying issues that will have you running around in circles to try and fix.

Knock sensor. Original ones don't necessarily "go bad" but corrosion that forms underneath them can hamper it's ability to listen for knock. Replace it and install the new one in proper orientation.

Boost Control Solenoid. They don't often go bad but do control your boost and will get dirty over time. A new one is never a bad idea, and they work perfectly fine in terms of performance.

Coil packs. They do tend to go bad with age. Replace all four with oem coil packs.

Spark plugs. Stock ngks gapped at .028 work fine.

Oil pump. I replaced mine when I did the timing belt. I know it is said they never go bad and whatever, but for the cost and the old one was already removed and the function it performs, I don't know why more guys don't replace them. Use the stock pump. Bigger is NOT better

Oil pick up. Yes, there are instances when the factory pick-up has cracked. But, in the grand scheme of things, the percentage of Subarus with cracked pick ups vs ones that are perfectly fine is virtually non-existent, especially on an ej205. BUT! I did not want to "win the lottery" and have one of mine crack so both of my ej cars have KillerB pick-ups.

Oil and filter. Don't get caught up in what kind of oil to use. Make sure it is always topped off and change it often, especially if you take short trips(like less than 15 minutes). I prefer 5w40 but 5w50 is quite common for WRXs in Japan. I do use the JDM black Subaru oem filters, the blue Subaru filters are fine as well, as are many aftermarket ones.

Oil temp. Never drive the car hard until the oil is up to temp, which takes much longer than the coolant. Oil temp and PSI gauges are very good to have.

Also, don't redline the car all the time. At this point, anything above 6000rpm is likely doing nothing but making noise anyway.

Oil leaks. Fix them. Valve cover gaskets, oil pump, front main, rear main, oil cooler(if your JDM motor has one), power steering lines, are all common culprits.

Equal length header. This is one area where I stray from OEM. The idea of an ELH is to get the exhaust pulses out of the heads, through the manifold, and to the turbo as quickly and efficiently as possible is a sound one. While this does aid in turbo spool, it is also said to get the ultra hot exhaust gas out of the heads far better, possibly aiding in less chance for detonation. I do love the factory reliability of cast iron and all the heat shielding, but the design of an ELH is legit. FWIW, Subaru of Japan has been using factory ELHs since 2003 or around there on their cars that use twin scroll turbos, and switched to an ELH on their WRC car in 1997, so they thought it was a good idea as well. the factory jdm ELH will not work on your car unless you get a custom up pipe done or you use the twin scroll turbo the elh was intended for.

Downpipe: Any good quality one will do the job and last a while. I prefer bell mouth designs but that is splitting hairs.

Up pipe: Your JDM engine may or may not have a cat in it, but if it does, replace the up pipe with a catless version. I prefer an oem catless up pipe simply because you cannot beat the fitment and longevity. Get as new as possible since the heat shields do tend to come loose.

Intake: Use the factory air box. The power that you give up(if any) is worth it knowing the MAF reading will be 100 percent accurate just as the Subaru engineers intended. It is also a "cold air" intake by design.

Turbo Inlet tube. If your original factory one isn't torn yet by the turbo, it will be. Replace with a new oem factory piece or and aftermarket tube. A new factory one will require you to remove the intake manifold for installation, an aftermarket one will not.

Vacuum lines. Replace all of them. There are some like the boost control return line that routes back to the front of the inlet turbo, that will turn solid and literally snap in half. Old vacuum lines suck to work with and will never seal properly again once removed. Replace them all. Vacuum leaks are trouble makers.

Coolant line. Replace them all. There are a lot of them. The will swell up and begin to not seal in a best case scenario. Worst case is that they just split and fail when you are driving to work.

Water pump. Replace it.

Getadomtune's #4 cylinder coolant mod kit is engineered to get some of the hot coolant out of the head around the number 4 cylinder. This evens out the coolant temps a bit better, which is good. But, Subaru listens to the number 4 cylinder for knock, since that is the hottest, most aggressively tuned cylinder, thus, keeping knock out of that cylinder should definitely keep the others safe as well. But, many feel between the tune and the higher temps, it's too aggressive for the US drivers/fuel/etc. I have it installed on our ej205 as I like the idea of things being a bit more even.

Timing belt, tensioner and running gear. Replace it all if you are not sure when it was done.

Fluids: Make sure to have new fluid in everything. This includes brake/clutch fluid, rear diff/transmission fluid, etc. Use oem Subaru gear oil for the trans/diff.

Replace the alternator. High mileage ones will not give you peace of mind when traveling long distances. A genuine Subaru reman one will work perfectly.

For performance, to get to the level you want(assuming that's brake horsepower and not to the wheels), I would do this:

Find a super low mileage VF48 from a newer STi. They are factory turbo's and as long as they are taken care of properly, will likely last 100,000 miles with no issues. DO NOT get VF turbo such as a 39 that has been "rebuilt". The last time I looked, IHI doesn't offer genuine parts for their turbos so the parts these rebuilders are using are always in question.

Intercooler. No need for a front mount unless you are going to do track days often. An STi intercooler and splitter is by far the best bang for the buck.

Injectors/exhaust-see above.

Tune: Get a tune from an ultra reliable tuner. This can not be stressed enough. Not the popular local guy, the popular nation-wide shop that has tons/years of experience with tuning Subarus. If you don't know anyone in your area, call COBB or someone similar and ask who they would recommend in your area. Do your research!

This will give you a very fun, reliable street car. At this power level, I would be far more worried about the stock 5 speed than the engine. The ej205 is a wonderful motor that can take far more of a beating than "STi-everything" guys give it credit for.

The stock 5 speed will work fine for a daily driver/commuter. However, there is no comparing it to an STi 6 speed. Keep a stock clutch in the 5 speed. If you are making enough power that a new clutch begins to slip badly, it's time for a 6 speed. You will always find a few guys that have been running 350 whp through a stock 5 speed that don't drive like fools that can get them to last, but the odds will not be in your favor.

Not too many people enjoy spending money on all the things that don't result in immediate gratification. And you will spend a lot of money just getting the car back to great mechanical condition. But, this is also why so many guys new to Subarus buy a car that's 15-17 years old, bolt a big turbo and exhaust on, blow something up, then go on facebook and make stupid memes about how Subarus are unreliable.

Best of luck with it. My biggest piece of advice is to search here. There is so much fantastic info on NASIOC from extremely knowledgeable guys, there is very little you will not find here.
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