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Discussion Starter · #1 ·
Hello!
I have an 08 Sti Hatch with about 14k on the latest motor looking for insight into what may be going on with the car. Subaru performance shop did a leak down and compression test and the results, are not that great...

Cylinder 1: 125 PSI - 25%
Cylinder 2: 130 PSI - 55%
Cylinder 3: 135 PSI - 33%
Cylinder 4: 125 PSI - 28%
And it is noted that ALL 4 cylinders SPARKPLUG GAPS WERE blown open .040-.045 (From the tech who looked at it)

They said I would probably need to spend the money to get a new long block at worst. But at the minimum, they would have to pull the engine to see what was going on for sure.

Images are Attached for Cylinder 2 and a video showing the leak-down test.
Video Link: VEED - C7F61BAF-13CC-4D7D-9A71-263509D2DD51.mov

As far as mods here is what we got:

Engine and Transmission:
  • IAG Performance Stage 2 Tuff short block
  • COBB Tuning Accessport V3
  • COBB Tuning flex fuel kit
  • Boost Controlled Performance X500 turbocharger
  • Injector Dynamics ID1000 injectors
  • Aeromotive 340 stealth fuel pump
  • IAG air-oil separator
  • Go Fast Bits TMS Respons hybrid blow-off valve
  • Motive Autowerks EBCS
  • Motive Autowerks composite TGV delete
  • Killer B Motorsport oil pickup and windage tray
Intake and Exhaust:
  • Perrin cold air intake, turbo inlet, and titanium-wrapped equal-length header
  • Invidia wrapped cat-less downpipe
  • PTP turbo blanket
  • MadDad Essentials Street Series cat-back exhaust
  • GrimmSpeed ceramic coated up-pipe
This car was built at a reputable shop in the Midwest, about 5 years ago. No additional modifications powertrain-wise have been done.

As far as how the car feels:

I have had two close friends that know Subarus very well and say everything sounds and feels fine.
As far as knock I get minor Feedback/Fine Knock Learn of about -1.40 sometimes. It is not consistent by any means. I do not have any CEL's on the only one in recent time has been for the ABS wheel sensor. When I have the car in Sport Sharp it opens the boost up to 25 PSI and Sport at 16 PSI. I have not noticed any boost issues regarding the turbo.
I really want to take it upon myself to learn and disassemble anything myself when I get the time to do so. I don't have the time right now and need the car at least running for my short commute to work for the next couple of months (in between jobs). As far as oil consumption goes. I burn maybe a quart at most every 2500-3000 miles after having a few beating sessions. I know I am probably driving a ticking time bomb, but if she goes, she goes. That's the Subaru Tax!


Any help is appreciated thanks in advance!

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few things. 1 - that gfb bov/bpv, yeah, ditch that. those things are complete shit, constantly leak, and break. i had one, lasted like 3 weeks. although i dont think that was the root of the issue.

just a general question, how much power was this setup making? that turbo has a flow rate of about 60lb/min, and your engine is rated at 675bhp, which, pending dyno, comes to about 525whp (assuming a dynojet). granted this can vary with the type of dyno. Just curious if you were very close to this or above it. if you were, that could possibly be the culprit of the issue. if you were not.....could be a BUNCH of other things.

it's hard to say without tearing apart the motor, could just be that you need a refresh with new rings/bearings (although 14k miles is really, really early for needing that). i too, have an iag s2 tuff block, and mine has around 40k ish miles on it. still going strong, although i'd guess you are making a good bit more power than i am.
 

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Discussion Starter · #3 ·
few things. 1 - that gfb bov/bpv, yeah, ditch that. those things are complete shit, constantly leak, and break. i had one, lasted like 3 weeks. although i dont think that was the root of the issue.

just a general question, how much power was this setup making? that turbo has a flow rate of about 60lb/min, and your engine is rated at 675bhp, which, pending dyno, comes to about 525whp (assuming a dynojet). granted this can vary with the type of dyno. Just curious if you were very close to this or above it. if you were, that could possibly be the culprit of the issue. if you were not.....could be a BUNCH of other things.

it's hard to say without tearing apart the motor, could just be that you need a refresh with new rings/bearings (although 14k miles is really, really early for needing that). i too, have an iag s2 tuff block, and mine has around 40k ish miles on it. still going strong, although i'd guess you are making a good bit more power than i am.
Thanks for your response,
This build is making 430 WHP/TQ I was looking to push it up more. But I had not had a compression test done in a while and wanted to make sure everything was good. The leak-down numbers really shocked me. Is there something I should look for in everyday driving that I am not seeing? It does not make sense the results would be this bad when I have been driving it to and from work and elsewhere. And is there a recommendation you have on a BOV? I did not know if it had anything to do with the leak-down test numbers because a lot of smoke was coming out of it. Would it be wise for me to get a test done elsewhere?
 

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That piston to wall gap looks huge (I know the rings are hiding there, but still) ... was that engine blue printed? The compression looks good, but the leakdown doesn't which means you may have head issues (valve) ... but that's on both sides of the engine, that's sketch looking. Does it smoke when starting? Running? Does it eat oil? What motivated you to do the compression/leakdown?
 

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Thanks for your response,
This build is making 430 WHP/TQ I was looking to push it up more. But I had not had a compression test done in a while and wanted to make sure everything was good. The leak-down numbers really shocked me. Is there something I should look for in everyday driving that I am not seeing? It does not make sense the results would be this bad when I have been driving it to and from work and elsewhere. And is there a recommendation you have on a BOV? I did not know if it had anything to do with the leak-down test numbers because a lot of smoke was coming out of it. Would it be wise for me to get a test done elsewhere?
430 on what type of dyno? because that seems LOW for a 60lb/min turbo at 25psi on e85. heck my 20g on pump gas puts out 377, and it's a 47lb/min turbo, on e85 at 24psi it will make 410....so 430 seems pretty darn low for that setup. granted even on a mustang dyno, still seems like that would be under the worry number.

question, did you do anything to the heads? or are they oem. I ask because when i got my motor, IAG suggested we not go over 24psi, because the valves/springs would be the weak point and could possibly fail after 24psi, they did say if yo uupgraded valves/springs you'd be fine pushing a bit further. so maybe that had something to do with it, it's definitely a possibility. and if so, might just need a rebuild of the heads adding in upgraded valves/springs/etc. which is not all that expensive.

the questions praha asked above are also good. i can answer that yes the short block is blue printed, as i have the same engine from iag.
 

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Bad tune could have burned out the rings which causes lower than expected horsepower, or you have lower than expected horsepower due to bad rings or head issues ...just a guess. What is in the 4th picture up? Valve seat or? Oily or carbon buildup? Those marks on the cross hatch look kinda like detonation, but not really (usually it's "whiter"). What is the AFR at idle? Is it steady?
 

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Discussion Starter · #8 ·
That piston to wall gap looks huge (I know the rings are hiding there, but still) ... was that engine blue printed? The compression looks good, but the leakdown doesn't which means you may have head issues (valve) ... but that's on both sides of the engine, that's sketch looking. Does it smoke when starting? Running? Does it eat oil? What motivated you to do the compression/leakdown?
It was blue printed, the heads were machined onto the shortblock, it uses the OEM heads and valves. I wanted to do a leak down test because I noticed some amount of an oil consumption. Between a half quart and quart every 2500-3000 miles. Is there any other values besides knock I should be checking on the access port for anything that could be wrong? Otherwise as far as smoke goes. There was a very minor amount of white smoke last week that came out of the hood scoop after I parked. I was not able to replicate it. Otherwise I get some exhaust smoke (very minor) under WOT full boost. Otherwise on startup, there is always some condensation, but no blue smoke or white smoke beyond that.
 

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Discussion Starter · #9 ·
430 on what type of dyno? because that seems LOW for a 60lb/min turbo at 25psi on e85. heck my 20g on pump gas puts out 377, and it's a 47lb/min turbo, on e85 at 24psi it will make 410....so 430 seems pretty darn low for that setup. granted even on a mustang dyno, still seems like that would be under the worry number.

question, did you do anything to the heads? or are they oem. I ask because when i got my motor, IAG suggested we not go over 24psi, because the valves/springs would be the weak point and could possibly fail after 24psi, they did say if yo uupgraded valves/springs you'd be fine pushing a bit further. so maybe that had something to do with it, it's definitely a possibility. and if so, might just need a rebuild of the heads adding in upgraded valves/springs/etc. which is not all that expensive.

the questions praha asked above are also good. i can answer that yes the short block is blue printed, as i have the same engine from iag.
Dynojet..
OEM heads and values, this tune was made so it was more consistently drivable. And with keeping in mind the heads are OEM, so that is why. If I have to rebuild heads. Should I do the IAG kit? Or buy OEM heads and build them?
 

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Discussion Starter · #10 ·
Was the test done hot or cold? There can be a huge variation in results cold vs hot.

Generally (very generally) compression results show condition of ring seal, leak-down shows how well the valves are sealing.
They did the compression test after doing an inspection on the car to make sure everything else was good. And then the Leak Test after that. I would guess the car was probably sitting for a half hour before the compression test, and maybe an hour at most before the leak test. I am not 100% certain, they did not give me all the details. I was more concerned that they were saying I should not even drive the car home, even though I have been driving it for a while.
 

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Discussion Starter · #11 ·
I should also note, as far as the last time it was on the dyno was 5 years ago. Since then adding the 14k miles onto the newest block. I was looking with this shop of what they could do power wise, and that was another reason I wanted to get this test done. For the sake of engine health. I know there should be more headroom in what I can get done with it. But it seems that since I still got the stock heads, it is probably the thing that is limiting me the most.
 

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Discussion Starter · #12 ·
Bad tune could have burned out the rings which causes lower than expected horsepower, or you have lower than expected horsepower due to bad rings or head issues ...just a guess. What is in the 4th picture up? Valve seat or? Oily or carbon buildup? Those marks on the cross hatch look kinda like detonation, but not really (usually it's "whiter"). What is the AFR at idle? Is it steady?
I am not entirely sure about the photos. But as far as AFR on idle, after a cold start it will bounce between 14.6-14.1 and then after a min, when it settles it will stay at 14.1.
 

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430 on what type of dyno? because that seems LOW for a 60lb/min turbo at 25psi on e85. heck my 20g on pump gas puts out 377, and it's a 47lb/min turbo, on e85 at 24psi it will make 410....so 430 seems pretty darn low for that setup. granted even on a mustang dyno, still seems like that would be under the worry number.

question, did you do anything to the heads? or are they oem. I ask because when i got my motor, IAG suggested we not go over 24psi, because the valves/springs would be the weak point and could possibly fail after 24psi, they did say if yo uupgraded valves/springs you'd be fine pushing a bit further. so maybe that had something to do with it, it's definitely a possibility. and if so, might just need a rebuild of the heads adding in upgraded valves/springs/etc. which is not all that expensive.

the questions praha asked above are also good. i can answer that yes the short block is blue printed, as i have the same engine from iag.
AFAIK, IAG is a reputable builder and doesn't build junk ... where they the tuner as well?
 

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I am not entirely sure about the photos. But as far as AFR on idle, after a cold start it will bounce between 14.6-14.1 and then after a min, when it settles it will stay at 14.1.
At idle, even my ID2000s hit 14.7 ... I don't think 14.1 is super bad, but I'm sure at some point it was tuned to be 14.7 and has dropped? Or did your tuner tune it that way? That may be a clue ...
 

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I should also note, as far as the last time it was on the dyno was 5 years ago. Since then adding the 14k miles onto the newest block. I was looking with this shop of what they could do power wise, and that was another reason I wanted to get this test done. For the sake of engine health. I know there should be more headroom in what I can get done with it. But it seems that since I still got the stock heads, it is probably the thing that is limiting me the most.
When you say stock heads, you mean stock cams, springs, valves? If yes, that 25psi is pushing them and they're probably fatigued a bit and causing the leak. Just a guess. If you have stock heads (ie... non-ported), but after market springs and valves, you'd be ok. I have ran 650/700 HP with E85 on my stock heads (not ported) with BC280 cams, BC valves and BC springs/retainers without issue.
 

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Discussion Starter · #16 ·
AFAIK, IAG is a reputable builder and doesn't build junk ... where they the tuner as well?
Tuner is Boost Controlled Performance in Michigan. As far as the AFR goes, since I have had it has been 14.1 I am not the person who had the car built. I did call them up this morning and explained what was going on, they were leaning towards ring land failure. And a possible issue in the crank case. I would also note that the people who did the actual tests yesterday notated crank case leaks on all 4 cylinders and on 2 and 3 intake/exhaust leaks.
 

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Discussion Starter · #17 ·
When you say stock heads, you mean stock cams, springs, valves? If yes, that 25psi is pushing them and they're probably fatigued a bit and causing the leak. Just a guess. If you have stock heads (ie... non-ported), but after market springs and valves, you'd be ok. I have ran 650/700 HP with E85 on my stock heads (not ported) with BC280 cams, BC valves and BC springs/retainers without issue.
Stocks heads, with stock cams, springs and valves.
 

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Dynojet..
OEM heads and values, this tune was made so it was more consistently drivable. And with keeping in mind the heads are OEM, so that is why. If I have to rebuild heads. Should I do the IAG kit? Or buy OEM heads and build them?
still seems like a low power number. granted i dont know the whole car, but with a turbo that size, on e85, i'd have guess an additional 30-40whp at that boost level. mine is also stock heads. and a much smaller turbo, and doesnt make that much less than yours. so that's the suprise.

you can honestly just rebuild your current heads, i'd suggest at a minimum valves/springs as that's the weak point in the heads. so far as if you should build them, that will come down to your goals and your budget. it's really not all that necessary unless you are going for major power. a pocket port would be nice, but again, not necessary.

based on the info above, my first guess would be that the heads are fatigued, but without a tear down to really see everything that is going on internally, it's speculation.
 

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I don't know what 'crankcase leaks on all 4 cylinders' would mean. I've never heard that before. Likely not related, but idle on any modern ECU car should be 14.7. You may have a vacuum leak or sensor issue.

I would still recommend a hot leak-down.

At those miles and boost level, even with all stock components, I doubt the valves are going to be shot... unless the heads were rebuilt poorly.
 

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I don't know what 'crankcase leaks on all 4 cylinders' would mean. I've never heard that before. Likely not related, but idle on any modern ECU car should be 14.7. You may have a vacuum leak or sensor issue.

I would still recommend a hot leak-down.

At those miles and boost level, even with all stock components, I doubt the valves are going to be shot... unless the heads were rebuilt poorly.
Good compression numbers but with such leak-down numbers ... in all 4 cylinders, strange indeed! Did they do the leak-downs with the piston TDC? If one cylinder was off, it would be easier, but with all going crazy,, but the car still running -- it has to be valve train related. Sounds fun! :)
 
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