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Old 09-08-2014, 04:46 PM   #1
rabeck27
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Default 2011 STI Compression/Leakdown HELP!

Need some help here guys. I'm planning to buy a 2011 STI with 29K miles that has had a 20G on it for the last ~20k miles with stock internals. Tuned by Wicked Innovations and supposedly "turned down" for reliability. Pushing 365/340 WHP/TQ. I got a compression/leakdown test done at a Subaru dealer.

Compression Leakdown
CYL #1 155 10%
CYL #2 150 7%
CYL #3 155 5%
CYL #4 145 12%

I am concerned about the #4 cylinder. Anyone got an opinion on these numbers?? I just wanted to make sure I'm not getting a car that's gonna have problems anytime soon.
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Old 09-09-2014, 01:36 AM   #2
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I believe the factory service manual says leakdown should be within 7-10%. I would say that there is probably a bit of oil consumption and the stock motor with those power levels is only a matter of time.

In my opinion, unless you get a good deal or have the funds set aside for a new motor then I would stay away.
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Old 09-09-2014, 01:58 AM   #3
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Those numbers are fairly square. I wouldn't be too concerned IF you do, indeed, plan on dropping in forged pistons any way. I've seen stock turbo '11's with more concerning compression/leak down results.
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Old 09-09-2014, 03:11 AM   #4
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I would bet it will crack a ring land on number 4 very soon.
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Old 09-09-2014, 06:51 AM   #5
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#4 cylinder fails more than any other. It's putting up the worst numbers here. Something to think about.
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Old 09-09-2014, 09:45 AM   #6
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Thanks a lot guys. I have done a lot of research on this but everyone seems to have a different opinion. Some people say <10% some say as long as they are within 10% of each other and on and on so I wasn't sure what to believe. Does anyone have a service manual to verify the numbers?


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Old 09-09-2014, 05:46 PM   #7
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Quote:
Originally Posted by TheFugitiveMind View Post
....and the stock motor with those power levels is only a matter of time.

In my opinion, unless you get a good deal or have the funds set aside for a new motor then I would stay away.
All of this. The motor is pushing 50% more power than stock. It will not last long with the stock pistons. Promise.

<10% across cylinders is the norm for comparison purposes.
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Old 09-09-2014, 10:43 PM   #8
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My bet is a new motor by 90,000-100,000 miles with the current mods. If you get it for the right price, put aside the $$ for a rebuild once it goes.

It's almost a guarantee that you will need a shortblock within the useable life of the car...just think about it that way. Even if it lasts for another 60,000 miles, what are you going to do with a car with a blown engine with less than 100,000 miles on it? Take a loss on the sale or rebuild...

Plan for one or the other and make sure that you are comfortable with the purchase price.
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Old 09-10-2014, 01:14 PM   #9
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that much power on stock block with #4 low already ... im betting because I ive blown 2 engines before I go mine right that you will be lucky to make 40,000 at that power level. One bad detonation could do you in.

if you get a good deal take it and do forged drop in pistons and enjoy it, beat it and save for a new block
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Old 09-10-2014, 04:40 PM   #10
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Why don't you call Wicked Innovations to get more details on the tune?

Matt Miner (of WI) is an exceptional tuner and a great guy. I'm sure he could tell you more about the car as he always keeps this kind of info saved.
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Old 09-13-2014, 09:08 AM   #11
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Thanks guys. I did talk to WI and they said it could use a set of forged pistons sometime depending on how I'm driving it and all that. Decided to get the car and I'm planning to do an engine build soon. Thanks again for all the advice.
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Old 09-14-2014, 11:32 PM   #12
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Dude subi valves are weak sealers to begin with. I bet the ring lands are plenty good. Your #'s are ok. Just know if you beat anything too hard for too long destruction will occur. $1900 for a new short block. BAM cruising again no big deal
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Old 11-02-2014, 10:10 AM   #13
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Hi everyone,

Sorry to resurrect this thread but as a noob looking to purchase a 2011 STI Limited Sedan soon, I am planning on having a compression/leak down test performed. The car has low miles, but some typical bolt-ons: turbo-back, AEM intake, cobb AP stage 2.

Could someone please advise on what the GOOD/CORRECT numbers for these tests should be on this car? I haven't been able to find anything that advises what the numbers SHOULD be, just members reporting on what their test results were.

Thanks in advance for your help.
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Old 11-02-2014, 10:51 AM   #14
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Don't ever buy a modded WRX/STI unless you've got lots of expendable income.

With that said, the numbers should be in the 140-150 range typically but those numbers on dependent on equipment, motor temp, etc. The real telling thing is the consistency across the cylinders. That's really the key.
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Old 11-02-2014, 11:18 AM   #15
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MaddMax,

Thanks for the information. Do you feel it's really risky even with just the mods I listed and only 13k miles on the odometer? From what I've read, stock internals/drivetrain should be able to easily handle stage 2 and an intake. I know a used STI is always somewhat of a risk since it was probably driven fairly hard, but I figured the lower the miles the better.

Any other STI-specific tests or checks you would recommend when I check the car out in person?
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Old 11-02-2014, 06:53 PM   #16
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Yeah, it's the stock turbo so that's good. Less chance of killing the engine. Look for leak down and compression numbers similar or better than the ones posted earlier in this thread. Less than 10% leak down #'s and compression above 130 with all numbers close together. The compression numbers will be lower on s cold motor than if it is done while warm/hot.
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Old 11-02-2014, 10:28 PM   #17
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Kevvv, make sure you check for clutch slip, too, or else make sure it's warrantied. I've known too many subaru owners who had to change their clutches by 20k miles to not suggest it. Typically, up to 14% pressure loss in leak down is considered healthy (15%+ enters the danger zone), but with only 13k miles on a street car, it should show little to no loss. I'd even be concerned if it's over 8%. My 2010 has 75k miles (and still on original clutch ), probably 10k of that was track time, and cylinder two had the most loss at 8%. The compression numbers will tell you, though: as long as they're within 7psi of each other, you're good. Just trying to help. Hope all goes well for you!

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Last edited by supersonicsubawoo; 11-03-2014 at 05:49 AM.
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Old 11-03-2014, 10:38 AM   #18
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Quote:
Originally Posted by kevvv View Post
MaddMax,

Thanks for the information. Do you feel it's really risky even with just the mods I listed and only 13k miles on the odometer? From what I've read, stock internals/drivetrain should be able to easily handle stage 2 and an intake. I know a used STI is always somewhat of a risk since it was probably driven fairly hard, but I figured the lower the miles the better.

Any other STI-specific tests or checks you would recommend when I check the car out in person?
Well, a 20G turbo is MUCH larger than stock. It's beyond "Stage 2" by a good margin so the true quality of the tune comes into play quite a bit. A pro tune that's "dialed back for safety" can still be crap at partial throttle.

When done right, a stock STI engine can handle a 20g and lots of driving abuse for over 150k miles - as one of my close friends has had a 20g on his 07 sti since about 80k on the odometer. He monitors his tune everyday and has painstakingly ensured his AFR's remain safe and accurate at all throttle/load/boost ranges throughout the tune.

I have another friend who took his stock STI running the stock turbo for a custom "safer" Stage 2 map to a Cobb Protuner. He tuned the car on a dyno, no road tune, no datalogging thereafter and within 10k miles he had a cracked ringland w/ 60k miles total on the car, 30k on the engine (the previous owner had the entire engine replaced under warranty due to a cam issue).

So I'd say the better the tune the better, miles within a limit mean nothing on a boosted turbo. They can eat themselves almost immediately when setup incorrectly. Oil matters just as much but that's a different topic considering your results.

IMO, be prepared for a shortblock rebuild regardless and if possible, get some datalogs from the car at 30%, 50%, 70% and 100% throttle and share them here.
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Old 11-04-2014, 06:50 PM   #19
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Quote:
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Yeah, it's the stock turbo so that's good. Less chance of killing the engine. Look for leak down and compression numbers similar or better than the ones posted earlier in this thread. Less than 10% leak down #'s and compression above 130 with all numbers close together. The compression numbers will be lower on s cold motor than if it is done while warm/hot.
Thanks for the information. I'll look for a shop in the area to run the tests before I purchase. Do you know how long these tests typically take?

Quote:
Originally Posted by supersonicsubawoo View Post
Kevvv, make sure you check for clutch slip, too, or else make sure it's warrantied. I've known too many subaru owners who had to change their clutches by 20k miles to not suggest it. Typically, up to 14% pressure loss in leak down is considered healthy (15%+ enters the danger zone), but with only 13k miles on a street car, it should show little to no loss. I'd even be concerned if it's over 8%. My 2010 has 75k miles (and still on original clutch ), probably 10k of that was track time, and cylinder two had the most loss at 8%. The compression numbers will tell you, though: as long as they're within 7psi of each other, you're good. Just trying to help. Hope all goes well for you!

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Good information. Thank you. Is a slipping STI clutch best tested by going open throttle and making sure the engine doesn't rev out faster than the speed increases? I've experienced a case like this but never had to purposely test a clutch for slipping before. Based on what you said I'll definitely be alarmed if the leakdown numbers aren't very low. Do brand new engines have 0%, or is there always at least a little loss even when brand new?

Quote:
Originally Posted by BrandonDrums View Post
Well, a 20G turbo is MUCH larger than stock. It's beyond "Stage 2" by a good margin so the true quality of the tune comes into play quite a bit. A pro tune that's "dialed back for safety" can still be crap at partial throttle.

When done right, a stock STI engine can handle a 20g and lots of driving abuse for over 150k miles - as one of my close friends has had a 20g on his 07 sti since about 80k on the odometer. He monitors his tune everyday and has painstakingly ensured his AFR's remain safe and accurate at all throttle/load/boost ranges throughout the tune.

I have another friend who took his stock STI running the stock turbo for a custom "safer" Stage 2 map to a Cobb Protuner. He tuned the car on a dyno, no road tune, no datalogging thereafter and within 10k miles he had a cracked ringland w/ 60k miles total on the car, 30k on the engine (the previous owner had the entire engine replaced under warranty due to a cam issue).

So I'd say the better the tune the better, miles within a limit mean nothing on a boosted turbo. They can eat themselves almost immediately when setup incorrectly. Oil matters just as much but that's a different topic considering your results.

IMO, be prepared for a shortblock rebuild regardless and if possible, get some datalogs from the car at 30%, 50%, 70% and 100% throttle and share them here.
Sorry for the confusion here but I am not the original poster looking at a car ith a 20G. I just noticed this thread very similar to what I was about to post about and continued the discussion. The car I am looking at is just stage 2 - turboback, AEM intake, and AP. Stock turbo and internals.
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Old 11-04-2014, 07:42 PM   #20
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0-4% warm cylinder leakdown test is where it's at considering it's low mileage. I've only tested a handful of cars with 0% leakage across the board even at 140k+ miles and those cars tend to be factory freaks on the get go and respond to simple mods very well.
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Old 11-04-2014, 08:13 PM   #21
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Quote:
Originally Posted by BURNING4ORCE View Post
0-4% warm cylinder leakdown test is where it's at considering it's low mileage. I've only tested a handful of cars with 0% leakage across the board even at 140k+ miles and those cars tend to be factory freaks on the get go and respond to simple mods very well.
This. And, yes, wot in 2nd or 3rd should have steady rpm. You could also put the car in 2nd or 3rd gear and release the clutch at a stop. It should stall almost instantly, say, roughly within 2 inches of pedal lift. If the RPMs shoot up without any forward movement before stalling, clutch is most likely wearing.

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Old 11-05-2014, 07:30 PM   #22
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Quote:
Originally Posted by BURNING4ORCE View Post
0-4% warm cylinder leakdown test is where it's at considering it's low mileage. I've only tested a handful of cars with 0% leakage across the board even at 140k+ miles and those cars tend to be factory freaks on the get go and respond to simple mods very well.
Quote:
Originally Posted by supersonicsubawoo View Post
This. And, yes, wot in 2nd or 3rd should have steady rpm. You could also put the car in 2nd or 3rd gear and release the clutch at a stop. It should stall almost instantly, say, roughly within 2 inches of pedal lift. If the RPMs shoot up without any forward movement before stalling, clutch is most likely wearing.

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Thanks for the info guys. Much appreciated. Anything else major I should try to test or look for when I see/drive the car?
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Old 03-17-2015, 11:19 PM   #23
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Guys, I wanted to update everyone on my situation here. I just dropped off my engine at IAG yesterday and they called me today saying I have two cracked pistons (can't remember which ones they said). The engine was still running strong when I pulled it out to take it to IAG so luckily I didn't have a catastrophic failure. I have put 3,000 miles on it since I got the compression/leakdown test done about 6 months ago and they haven't been hard miles either. Who knows how long the ring lands were cracked. So long story short, there is good reason to be worried if you're looking at a modded WRX or STI especially if it has a bigger turbo. This corroborates what most people said in this post obviously. I just wanted to share a real story and not some "I heard this happened to my buddy's girlfriend's sister's uncle". If you find one with compression/leakdown similar to mine, I would negotiate on purchase price like I did :-)
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Old 03-20-2015, 08:09 AM   #24
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Thanks for the update. To clarify, does it have cracked Pistons or cracked ring lands?
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