Top 50 Subaru WRX/STI FAQs

This is as many of the most commonly asked questions regarding Subaru WRX, STI, Impreza etc that I have seen and been asked. For the most part I already have detailed videos diving into almost all of these topics so this is more of a rapid-fire Q&A. Hopefully this will save you from having to post in some of the FB groups or digging through some forums for a quick answer.

[TeamCupNoodles-nnog]

My guy got so tire of sanding he decided to take a break to make a FAQ video

[adambarnard]

You want racecar stuff, you're going to have racecar problems. Truer words haven't been spoken

[Haven]

That EJ20X/Y bit is gonna hurt alot of 4th gen legacy guys😂😂 love it!

[is_blue_subaru]

You almost made me mad about your 04 sti comment until you reasoned it, which is completely valid haha

[boosTiMon]

Web info “There is a significantly high number of piston ringland failures on the later model Subaru WRX and WRX STI. The goal of this article is to help you avoid becoming one of them. Some of these may seem like common sense to most, but for many younger or first time turbo car owners it may be new.
What is a Piston Ringland?
The ringlands are the areas of the piston adjacent to the rings and ring grooves. All of the turbo 2.5L (EJ25) and 2.0L (EJ20 / FA20) pistons feature three ringlands which accomodate the two compression rings and one oil control ring.

The first ringland (aka top land) is located between the top of the piston (known as a crown or deck) and the primary compression ring. This ring seals out the majority of the heat and combustion gases from the crankcase.
The second ringland bridges the primary and secondary compression ring. The secondary ring seals out any gasses that get past the primary ring. Its unique shape also scrapes any oil that has gotten past the third ring (aka the oil control ring) off the cylinder walls.
The third ringland bridges the secondary and third ring, the oil control ring. The oil control ring is shaped completely different from the two compression rings. The ring's design scrapes oil from the cylinder walls and forces it into oiling holes and onward to the wrist pins.
What is Ringland Failure?
Ringland failure is when excessive heat and pressure cause the ringland to fracture. The fractured ringland no longer supports the ring properly which allows combustion gasses to blow down into the sump, often pressurizing it. This in turn causes excessive oil burn-off from a combination of blowing it through the PCV system, burning it off the cylinder wall(s), and flashing off oil in the crankcase / sump.

Why Do Subaru Ringlands Fail?
Detonation is the mechanism that physically damages the pistons. Anything that promotes detonation such as low octane fuel, lack of proper tuning, and prolonged hard driving can potentially cause piston ringland failure.

Detonation is when the mixture auto-ignites and forms an additional flame front in the combustion chamber. This spontaneous ignition causes the flame fronts to slam into each other and produce a pressure spike well in excess of typical combustion. This pressure wave will continue to bounce off of the cylinder walls producing a strong cyclical load.

This "jackhammering" effect either shatters the ringland immediately, or contributes to a future failure from fatigue and/or overstress. This is due to the material's inability to absorb energy through deformation or flexure (ductile behaviors), in conjunction with the rapid onset of stress due to detonation.
Piston ring gap is also a growing concern with the more recent motors. The gap is tight from the factory which makes the primary compression ring prone to binding. Binding occurs when the ring heats up and runs out of expansion room. The ring then flexs and puts a point load on the piston ringlands. Given enough stress, this can crack the ringland outright, or contribute to its failure.
Are the Pistons Just Weak?
Weak? ... No
Brittle? ... Absolutely
While detonation is what damages the pistons, it's important to know that the EJ20 (EJ207 / EJ205), EJ25 (EJ255 / EJ257), and FA20 all have brittle pistons due to Subaru's material and design choices. The pistons are cast hypereutectic aluminum-silicon (Al-Si) alloy; a very common material choice for modern engines. Well proven engines like the 2JZGTE, 4G63, SR20DET, RB26DETT, LSX, K-Series, and others all use Al-Si alloys.
However, Al-Si alloys can vary depending on the percentage of silicon in the material. Subaru has opted for a "hypereutectic" alloy which is a high-silicon (12+%) mix. This makes the piston have extremely low thermal expansion, and allows Subaru to run an extremely tight piston-to-bore clearance. The high-silicon content also makes the piston considerably stronger than aluminum itself. For example, a 9% silicon (by wt.) alloy has a 14% higher yield strength than a 7% silicon alloy. This strength comes at a cost: fracturing.
When you take a sledgehammer and hit a steel hood, the steel simply deforms under the pressure of the hammer strike, leaving a dent. When you take the same sledgehammer and hit a window, the block shatters the window. That is because the window material reacts to the strike by fracturing rather than deforming. When you add silicon to aluminum it acts more and more like the window glass.
Detonation energy ironically enough, acts like the hammer”

[Bryan-kwod]

i love you smeedia, i’m building my new engine in my parking lot bc of you bc im a broke college student

[CoreyWilliams-eghn]

1:50 tanner you should mention about being forged, always go for thicker oil when forged I personally run 10w-60 Fuchs titan racing oil but and 10w from 10w-40 will be just fine

[charlesdylancobb]

17:00 finally someone said it, been NA/T on my 97 legacy for over 6 years and it really woke it up. Now it's on a DIY standalone (speedyefi) with 05 sTI yellow side feeds, using the same unopened 244k ej22e longblock the cars had it's entire life, and it's been great.

[churchsparkchaser]

I'm picking away on an EJ253 N/A build, (I know, slow life, but it ain't gotta be fast to be fun) so I'm a bit sad that you won't be building one. That said, I genuinely love your content, and appreciate the care and dedication you have in what you do. Thank you, Smeedia, for making your content, it is beyond helpful in so many ways.

[GargantuanMetal]

I really feel like the timing chain is a HUGE win for VA and VB wrx's. Most wrx owners just want a fun daily, maybe bolt ons, it seems nice to have the timing chain more than likely last the life of the engine, for a daily. I may just feel this way because I've had to do the timing belt on my same wrx 3 times, and since I'm nice to the car, my motor lasts, yet I've pulled it 5 times now. 3 timing/valve jobs, and 2 clutches.

[patrikkrywult]

Hi. great video as usual... what's your oil recommendation for higher mileage engines? 5w40 or 10w60? Our EJ255 with 310k kilometers, already takes a lot of oil. About 1 liter per 1000-1500 kilometers. And what is your opinion on forged components? Yes or no? For our weekend car, so it's mainly for the joy of the ride. No long drives. Just to clarify, we have a 2010 LGT with an automatic transmission.

[Telesko]

I got an RA block to replace my blown up 257 and the secondary air pump stuff didn't fit. I deleted it but that's not an option for some people.
We need a Matt appearance again, he was such a nice young man.

[TimberWulfIsHere]

I'd argue that the hawkeyes are the best non sti wrxs. Why? Because they share some parts from stis in previous models or just have improved parts overall. For example, you have the same fuel injectors as the sti, so all you need to do is a fuel pump and intercooler upgrade, as well as a larger downpipe, and you can go faster than the sti of the same year, with the same turbo (assuming you swapped the same turbo from the sti to the wrx)

[HeidiFegles]

Fact aos is mainly for the broken ringland mask up job. But after all that mess I continue to use it on all my motors after and seams to help for sure but I blow by to atmosphere.

[kheff]

Great video! Overall will have a great viewer count. Great job as always Tanner!

[philberenbeck]

Hey tanner,
Are you able to do a video of the complete detailed intake manifold plumbing system (PCV, AOS, breather/coolant hoses) thanks man love the videos 👌

[Conpaz]

Great!! Set of FAQ'S. Thank you!!!

[HeidiFegles]

You can put any Subaru into any car some need more love than others but it can work. Trust me.

[AudioHead]

Good video bro. Curious why you think the 15-17 sti doesn’t measure up to the 18+? I have a 17 sti. Just hit 23k miles and she’s been great so far.

[russellfoster]

Good video- efficient. Question that maybe you haven't seen too much... Is it better to do all the mods you want to do at once, or a little bit at a time? Or does it even matter? I want to do some moderate mods, turbo, downpipe, fuel rails, injectors, other bolt-ons, but I've been wondering if all that at once is a lot of sudden stress on an ej. 2012 STI hatchback