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Discussion Starter #1
I own a 2015 Subaru STI. The car was stock when I bought it. These are the first modifications it has seen.

I have been having issues with my DAM dropping below 1. My knock feedback and fine knock learn have also been showing concerning readings (more than -2.8). About once per month I have to reflash my tune because the DAM drops to 0.8xx. It always happens when I am ripping on her. I currently have a Cobb Intake with a Cobb Stage 1+SF 93 Tune. I have a Grimspeed Air/Oil Seperator as well. I need feedback from experienced tuners/Subaru Enthusiast. I have a few data logs attached.

Other than the concerning guage readings, I briefly looked over my datalogs and noticed that peak boost was around 16.8psi when it is normally around 19psi? I have not done a leakdown test in a while. Also, the car seems to stall/hesitate more than it should between shifts. I can over come this by "riding the clutch" more than usual but it makes me nervous because I've driven other STI's like mine and that hesitation is not there. This hesitation was present when the car was also bone stock
 

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I'm a noob and still learning but from what I hear, other than a leak down and compression test you can check boost leak with a smoke test.

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DAM dropping during WOT or hard driving is never good.

Do not reset your ECU when your DAM drops. DAM is designed to protect the engine in case something is wrong. Resetting the ECU is a bandaid, and you need to figure out the original problem.

If this were me, I'd flash the cobb Stage 1 SF+ with 91 map and run 93. it sounds like you are getting knock and the ECU is compensating by pulling timing(as it should).
 

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This is exactly the correct thing to do. :tup:
DAM dropping during WOT or hard driving is never good.

Do not reset your ECU when your DAM drops. DAM is designed to protect the engine in case something is wrong. Resetting the ECU is a bandaid, and you need to figure out the original problem.

If this were me, I'd flash the cobb Stage 1 SF+ with 91 map and run 93. it sounds like you are getting knock and the ECU is compensating by pulling timing(as it should).
 

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Discussion Starter #6
So I took your guys advice and re-tuned the car to Cobb Stage 1+ SF 91 while still running 93 octane. I notice the car has been running better (more smooth) less hesitation between shifts/smoother pulls and boosting. The hesitation between shifts is still there but less intense. I also notice that my Fine Knock Learn and Fine Knock Feedback is back within tolerable levels. However, today on my way home I watched the these value change and hold during WOT on the freeway. This freaked me out so I started logging as soon as I got off and gave her a balls out pull from 3rd to 6th.

I have two data logs attached. One is with 93 tune and the other is with 91 tune. Again, I notice that the boost logged is around high 16lbs when my stock boost guage is reading 2lbs higher? I also noticed after my WOT pull I could smell some oil?! This made me think that maybe i'm getting too much blow by from my Grimspeed AOS and need to upgrade? My turbo is stock and only a stage 1 OTS Cobb Tune so I wasn't that worried about crankcase pressure until now?

Any help is greatly appreciated!
 

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It looks like Cobbs maps run too much timing. but I am not a tuner and know just a bit to make myself dangerous when it comes to STI tuning.
 

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It looks like Cobbs maps run too much timing. but I am not a tuner and know just a bit to make myself dangerous when it comes to STI tuning.
In general the COBB OTS maps are pretty conservative but I agree the 93 oct map has too much timing for his car.

Matt, you might want to try the 91 oct stg1+ high wastegate map to get a little more boost. You should be able to run ~19lbs on 93oct no problem.

Just wanted to verify you have a COBB SF intake on there?
 

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Discussion Starter #10
In general the COBB OTS maps are pretty conservative but I agree the 93 oct map has too much timing for his car.

Matt, you might want to try the 91 oct stg1+ high wastegate map to get a little more boost. You should be able to run ~19lbs on 93oct no problem.

Just wanted to verify you have a COBB SF intake on there?

Yes. I have the Cobb SF Intake on my car. I also have the Grimmspeed AOS as well. I also added a catch can in line with the Grimmspeed AOS. I removed that last night and again I noticed the car running smoother. What do you guys think is causing this?? The Cobb 93 OTS Map was doing great for first 2 months. Why has it changed? I seriously think I'm getting too much blow by from the Grimmspeed. I noticed there was oil residue around it last night when I removed the catch can. I also just changed the oil. I'm using Redline 5w-30.
 

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We use the COBB AOS, I'm not familiar with the Grimmspeeed system but if you are getting oil into the intake it is going to make the engine more knock prone. That could be the entire issue.

Yes. I have the Cobb SF Intake on my car. I also have the Grimmspeed AOS as well. I also added a catch can in line with the Grimmspeed AOS. I removed that last night and again I noticed the car running smoother. What do you guys think is causing this?? The Cobb 93 OTS Map was doing great for first 2 months. Why has it changed? I seriously think I'm getting too much blow by from the Grimmspeed. I noticed there was oil residue around it last night when I removed the catch can. I also just changed the oil. I'm using Redline 5w-30.
 

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We use the COBB AOS, I'm not familiar with the Grimmspeeed system but if you are getting oil into the intake it is going to make the engine more knock prone. That could be the entire issue.
The Grimmspeed one is located on top of the oil filler neck and retains the factory PCV valve. I had one but it wasn't overly effective. They also have an issue with colder climates where they froth up.
 

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I had the same issue with the IAG AOS. I'm fully stock now and my intercooler hose is much cleaner than before.
yeah I've come to the conclusion that they are pretty useless. If OEMs cared so much about blowby, they would have these come stock.

Likely going to take mine off and sell it. Just have to redo my coolant lines.
 
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