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Old 07-18-2008, 06:46 PM   #1
scoobydave
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Member#: 90483
Join Date: Jul 2005
Location: Encino Man
Vehicle:
06 450 whp sti
UGM

Default just found out that i have a cracked piston

i have an 06 sti with a few mods (gt 30r etc.)
it does about 450 whp
stock internals (suck)

and i just found out that my #2 piston is cracked and the car also eats about a quart of oil a week (daily driver) im trying to find out what are my options besides getting a new short block.

thanks for all the help.
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Old 07-18-2008, 07:19 PM   #2
JackHammer
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I want 2 be like
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how many miles?

what needs to happen is the heads have to come off, pistons come out and the cylinders inspected and measured. If ok, buy some CP/JE pistons and have the cylinder's honed.

Install new rings and put it back together.

However, I would strongly suggest splitting the block apart and inspecting the bearings........especially if the block has any mileage.

How long has the 30r been on it? You have detonated so either you got a bad tank of gas, and/or your timing needs to be lowered another degree or so.
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Old 07-18-2008, 07:24 PM   #3
MartinSTi05
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I will buy your damaged block, to help subsidize your new one, lol.
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Old 07-18-2008, 07:27 PM   #4
scoobydave
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the car has 30,000 miles the upgrde was done at about 4,000 miles

and from what i understand that the upgrade has nothing to do with that the shop where everything been done at reasures me that they have stock cars cracking pistons.

so im lost for words (do the subie stock engine suck that much?)
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Old 07-18-2008, 07:28 PM   #5
scoobydave
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Quote:
Originally Posted by MartinSTi05 View Post
I will buy your damaged block, to help subsidize your new one, lol.
oh yeah how much?
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Old 07-18-2008, 07:32 PM   #6
JackHammer
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that's cause the stock cars are detonating!

do you realize what you're asking? you got 26k out of the STOCK engine that was designed for 300hp.........and you're running it over 500hp.

If I were you, i'd quit bitching and count my blessings.
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Old 07-19-2008, 09:12 AM   #7
JMK508
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Its like a STI.....
but it doesn't break

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^^^^^^^ exactly........anything over 400whp for a DD you are playing with fire. To get that many miles out of your stock block is pretty good.
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Old 07-19-2008, 10:56 AM   #8
azrakain
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Quote:
Originally Posted by scoobydave View Post
stock cars cracking pistons.
The picture below is from my stage2 STi. It's an unfortunate thing, but crap happens.

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Old 07-19-2008, 11:50 AM   #9
LiquidForce
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517whp/516wtq (Stage pi)

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I had that happen to me and I needed to fix it on the cheap. I did all the work myself so I saved on labor. Took 6 hours from start to finish and I was back on the road.

I bought 4 new pistons for 50 shipped
Rings 130 had to buy a complete set
1 head gasket 32
2 cam seals 12

I sold the extra pistons and rings and got all my money back. Ended up costing 0.
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Old 07-19-2008, 12:28 PM   #10
flycaster
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Quote:
Originally Posted by LiquidForce View Post
...I bought 4 new pistons for 50 shipped...
Did ya miss a "0" there, amigo?
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Old 07-19-2008, 12:59 PM   #11
flstffxe
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^^I would guess take offs from some ones new Sti short block that got a set of drop in pistons.
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Old 07-19-2008, 12:59 PM   #12
blue05
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Quote:
Originally Posted by flycaster View Post
Did ya miss a "0" there, amigo?
Probably not if he bought stock pistons. Dang, I wouldn't even charge someone for my stockers.
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Old 07-19-2008, 02:46 PM   #13
LiquidForce
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Quote:
Originally Posted by flycaster View Post
Did ya miss a "0" there, amigo?
Nope. they were indeed takeoffs out of new blocks from one of our more prominent engine builders.
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Old 07-19-2008, 05:18 PM   #14
Turbo_Mike
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Quote:
Originally Posted by azrakain View Post
The picture below is from my stage2 STi. It's an unfortunate thing, but crap happens.

either you had a bad injector, or Helen Keller tuned your car... thats not just the old ring land crack that we're talking about, thats seriuos bad uncontrolled detonation...
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Old 07-20-2008, 05:55 AM   #15
azrakain
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Quote:
Originally Posted by Turbo_Mike View Post
either you had a bad injector, or Helen Keller tuned your car... thats not just the old ring land crack that we're talking about, thats seriuos bad uncontrolled detonation...
The car had an OTS Cobb map. It was dyno'd and everything looked fine. AFR right at 12:1 and it made 284awhp 300ft/lbs.

When I pulled the plugs the side electrode had made contact with the center electrode. What is odd is that upon inspection of the piston through the spark plug tube, the top of the piston looked fine. We had no clue what hit the plug, or if something did, as there was not obvious contact marks anywhere. I put new plugs in the car, cleared the codes/reset ECU and started it up. It ran smooth and the codes didn't reappear. I drove the car for about two miles and upon pulling into my neighborhood I gave it a rev and all hell (and the top of the piston) broke loose. We heard metal pass through the exhaust which is strange as the turbo is in perfect shape.

Oh well.
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Old 07-20-2008, 05:59 AM   #16
azrakain
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PSM

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I guess I'll post the other pictures so people can see what we saw:





Original plug from MISFIRE code. I wish I had a picture of the top of this side electrode. There is no obvious marks from any contact.


Second plug from cylinder#4 that was eaten alive. Obvious how this got to this condition.


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Old 07-20-2008, 06:01 AM   #17
azrakain
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And Dave, sorry for jumping in on your thread. I didn't mean for it to turn into a discussion about MY motor.
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Old 07-21-2008, 10:54 AM   #18
Element Tuning
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Quote:
Originally Posted by scoobydave View Post
the car has 30,000 miles the upgrde was done at about 4,000 miles

and from what i understand that the upgrade has nothing to do with that the shop where everything been done at reasures me that they have stock cars cracking pistons.

so im lost for words (do the subie stock engine suck that much?)
The stock STi engine is in no way bullet proof but they don't suck. We've run an entire season road racing at 500 whp using a stock STi engine without any failure. Really what it boils down to is that you had some detonation and it cracked the piston. There really is no other mysterious cause. With the stock pistons and 400 whp it really doesn't take much to crack it. Backing down on the tuning is usually what prevents this as you'll have more room in the tune to account for changes in gas, temperature, overheating, slight over boosting etc.

If we were to build you a motor for instance and you left your tune as is then it would likely suffer the same fate but just a long slow death. The piston might not fail but it would pound your bearings pretty good. A built engine is going to take some pretty severe detonation before it self destructs but it can fail just the same.

Welcome to the "I broke my stock piston club"

Thanks,
Phil
www.elementtuning.com
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