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Preventative measures to keep 08 STi pistons healthy?

5K views 25 replies 14 participants last post by  caseyc  
#1 ·
With all of the 08 piston failures we've been seeing I can't help but feel a little frustrated with my situation. I'd love to be able to mod and enjoy this car but I feel like I'm walking on eggshells with the motor. I'm at around 4000 miles now, stage 2 and knock on wood, the motor is still healthy.

I'm looking for some feedback on what might be some good ideas to at least help prevent a piston failure in the future. Obviously anything that prevents detonation is a positive.

Anyone have additional ideas and feedback, good or bad on persuing the following..?

-Air/oil separator. Thinking crawford performance or possibly that hard drive looking unit.

-EL headers? Am I correct to believe this would help keep EGT's down? Seeing that many failures occur after hard prolonged driving I'm thinking heat becomes a contributing issue.

-WMI? Not necessarily used to increase timing or to get aggressive, but to cool the combustion, combat heat and raise the effective octane. So in essence used for safety, only tuned to get the AF sorted.

Any other ideas or should I just pool this cash into a fund for a built shortblock? :confused:
 
#3 ·
I agree with that, and honestly I'd rather R&R a healthy shortblock with a raw performance street sb, than repair an injured sb. At least the R&R option would leave me with a healthy motor that I could sell or build up for something fun. I hate waiting around for the failure and having my back up aginst the wall. Last thing I want to do is replace anything under warranty with MORE of the same inferior parts.
 
#4 ·
The air/oil separator is a good idea. If you are running an off the shelf tune, consider a protune but be careful who you bring your car to. Look for happy customers whose cars perform well. Headers will bring your EGT down. How important EGTs are - I don't know.

I don't like meth/water injection. This is a highly debated topic. Look at how your cars fuel system is set up and then look at the meth/water kits on the market. The factory fuel system is superior in terms of reliability and safety. A failsafe will help but IMO there can still be some knock between the time when the meth kit fails and your failsafe kicks in.

Save for your shortblock - I think it is a mistake to start modding one of these cars without a plan for what to do if something breaks.
 
#5 ·
I was really stressing that idea too, but from what i've learned and read through out the threads, it really depends on your tune and how hard you drive. There is always normal wear and tear, but if youre pushing the max limits of your stock motor there's a bigger chance of breaking! To avoid it stay with a stage 1 or just use a safer tune.
 
#6 ·
I'm thinking in the same way even for my 05 Sti.
Lets assume your car is in perfect working order.
What parts can help keep the engine run more reliable?

-A better/larger intercooler (but needs a tune)
-If you stay with a top mount intercooler get the Zerosports intercooler splitter which helps move the air more effectively.
-Heat wrap the Downpipe and other exhaust components.
-High quality oil and fluids.
-Radiator shroud and higher quality radiator caps.
-Of course the Air oil separator.
-I think a quality tune even on a stock 07 & 08
-Monitoring the parameters of the engine with data logging and having it interpreted.

I think the big concern here is keeping the car from having any blow-by or oil running through the intake issues or keeping our crappy ringlands from cracking.
 
#7 ·
I think its all in the tune, too many ringlands have cracked on bone stock cars.

It may be hardware, but I'm leaning towards software as the main problem.

That said:

• Good ProTune
• A/O Separator (not a catch can)
• 1 step colder plugs (this will keep EGT down as well)
• Gauges to monitor whats going on so you know when theres a problem.
• WI is fine if you're tuned for it to be a safeguard, not a power gainer. Basically, you can be tuned for no meth/h2o, the add a meth kit and you'll never knock. If the kit fails, it won't matter because you're already tuned for the engine to run fine without it. That is a costly safeguard though.

If you're really paranoid, get a used shortblock for about a $1,000, get some forged pistons and associated hardware so you're prepared if something goes awry.
 
#8 ·
Its all about detonation prevention. The biggest problem is knocking when you don't expect it. And I firmly believe contributing factors to unexpected det are excess heat (exhaust valves getting "too" hot, carbon buildup retaining heat and causing det), and excess oil in the charge air (poor design by subaru to apease emissions). This is why I'm really looking into getting a meth kit - the combo of cooling the charge and knock resistence is really unparalleled. And, if tuned for safety even a worst-case senario failure wouldn't (shouldn't) hurt anything. That may only be possible with water-only though as you do need to lean it up for meth in the mixture.
 
#9 ·
...That may only be possible with water-only though as you do need to lean it up for meth in the mixture.
You can just leave the tune the way it is and use water injection, but you'll loose power doing that. If safety is the primary concern here, stay away from any injection system that does not have a dead certain fail-safe.

I agree with the other posters here: the best way to prevent engine damage is to use a proper tune, with conservative timing and target boost. As soon as you start upping the power levels (using headers, injection, bigger turbo, whatever), the risk of lower end failure goes up proportionately - it's just the nature of the beast. Last, as for an A/O separator, it's not a bad idea at all, but I seriously doubt it's gonna make or break a piston failure...
 
#10 ·
To the OP, just drive the car and TRY to enjoy it, dont abuse it, I have a 2007 STi and since summer 2007 when all the stories came out, I have been thinking about my engine health. This sucks, oyu cant really enjoy wuth out thinking of the possible smoke out of the exhaust of CEL's.

ALSO............

I don't understand how WAT/METH injection would make the car running safer, IF in most instances the tuner would increase the timing, lean the fuel and maybe raise the boost.

Sounds to me like you are defeating the purpose of the METH by doing the above mentioned. NOW if you just install the METH kit and maitain the other variables where they were, I see a safety margin, otherwise is still walking very close to knock or an engine failure!
 
#12 ·
ALSO............

I don't understand how WAT/METH injection would make the car running safer, IF in most instances the tuner would increase the timing, lean the fuel and maybe raise the boost.

Sounds to me like you are defeating the purpose of the METH by doing the above mentioned. NOW if you just install the METH kit and maitain the other variables where they were, I see a safety margin, otherwise is still walking very close to knock or an engine failure!
I would leave timing and boost levels at thier pre-meth levels and simply sort out the AF. The margin of safety created by using meth goes beyond just the octane boost - the cooler flame front and reduction in carbon buildup lend to significant det prevention (in theory I guess). I'm a huge fan of it myself, but I hadn't considered using it for safety's sake until recently.

True, I do try to enjoy the car for what its worth. But we all pay a nice chunk of change to drive these cars, I want some sense of security against toasting a piston you know? And yea pay to play, been there done that. I melted a piston in my last car, rebuilt the engine from the ground up and stuffed so much cash into that money hole I'm still regretting it. I bought the sti to AVOID this crap!!!
 
#15 ·
My stock 08 with an STU tune lost #4 ring and piston at it's first autocross Sunday. 3400 miles. Dealer is replacing entire engine and turbo under warranty. I'm probably going to drop forged pistons in the new engine. This is insane, my 02 and 05 were bullet proof, each enduring 2 years each of autocross and DE's. THat's why I buy these cars, not to put back and forth to work in. I could do that in a Neon.
 
#16 ·
#17 ·
I truly believe that a good tune will give you the same reliability that the 04-06 STI's enjoyed. Ours has been on a non-stock tune since day one and has over 8500 miles on it without any problems. Zero oil consumption too. ;)
 
owns 2019 Subaru WRX STI Base FP Green Flex Fuel
#20 ·
So you are saying the 04-06 piston design and materials used along with the QC back then is on par with the 08/09 motor? :confused:

If you don't experience any harsh detonation sure, you will have a nice reliable motor. But what about people with SOLID protunes who pop an engine after a few auto-x runs? There are factors coming into play outside of anything a good tune can prevent. Factors that just werent playing a role from 04-06.
 
#18 ·
Mine was tuned by Doug just after break in.
 
#19 ·
Siegel tuned here. ;)
 
owns 2019 Subaru WRX STI Base FP Green Flex Fuel
#21 ·
From what I have been told, the same short blocks are used 04-09 on the STI's. Pistons included. That doesn't mean that there wasn't a bad batch of pistons and or bearings in the 08+ STI's. But I truly don't think that we have a blanket issue. I have no worries on our 08. I'm even planning my 30r upgrade soon. ;)
 
owns 2019 Subaru WRX STI Base FP Green Flex Fuel
#24 ·
I have a coolingmist kit on the way as well, i want to run a moderate tune on it though. I keep hearing guys running like 25-26psi on a stock block. They say it works fine but there is only a matter of time and then something is gonna go wrong, very wrong!!!I dont want to push the threshold of the 20g turbo or engine until i get some new rods and pistons put in it. But im hoping for a safe tune!