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Old 11-19-2020, 12:51 PM   #1
2015STI909
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Default Stock compression EJ257?

Hey all. My STI seems to have lost ALOT of its power over time. Just starting to get in touch with this engine family again. Tendencies you guys know of around 100k? Do they tend to lose compression? Burn oil? Anybody know the stock compression? TIA!
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Old 11-19-2020, 01:01 PM   #2
rtv900
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mine has 118,000 and burns basically no oil and runs the same as new

maybe you are beating on yours too hard?
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Old 11-19-2020, 07:29 PM   #3
truck7575
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Throw some seafoam in the oil for a couple thousand miles and see if that don't help free up some power seafoam is really good at dissolving carbon composites and can help your compression
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Old 11-19-2020, 10:24 PM   #4
AliBenn
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Any OBD2 codes????
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Old 11-19-2020, 10:30 PM   #5
2015STI909
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Thanks for the input. I mean, I don't drive exactly softly; but not abusive, either. No check codes. Used nothing but synthetic always, and stuck to the old-school 3k-ish oil changes. Doesn't seem to be outright consuming oil (blue smoke level consumption), but levels do tend to be noticeablely low at oil change time. I'll look into the seafoam thing. Just feels "old", and I don't really see a reason why...
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Old 11-19-2020, 11:51 PM   #6
AliBenn
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Crap
I forgot to answer your initial Q
On my brand new OE short block was installed
140 140 141 140 compression readings
After 1500miles running break in tune

With 100k miles IMO healthy engine should be 120-130 at bare minimum

Last edited by AliBenn; 11-19-2020 at 11:53 PM. Reason: ***8216;S
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Old 11-20-2020, 03:09 PM   #7
Max Capacity
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At 140,000 miles my ej257 still feels as good as it did when I installed it.

Have you done a boost leak test ? or smoke test?
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Old 11-20-2020, 03:43 PM   #8
Zak6182
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Could it be that you have just got used to it?

When I had a my street bike and didnt ride for a while it felt insanely fast. Then as I drove it more I got used to it and it felt slower. Put it up for a few months and bam..insanely fast again.

Have you done something to compare when it was new, like raced it and noticed a drop in time or something?

Just as a general maintenance thing, if you haven't, you may want to check your plugs, especially if you're burning oil.
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Old 11-20-2020, 04:12 PM   #9
blurred
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Quote:
Originally Posted by 2015STI909 View Post
Hey all. My STI seems to have lost ALOT of its power over time. Just starting to get in touch with this engine family again. Tendencies you guys know of around 100k? Do they tend to lose compression? Burn oil? Anybody know the stock compression? TIA!
Seems?

take it to a dyno and check.
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Old 11-22-2020, 08:50 PM   #10
Jay11STI
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To answer your question i believe the numbers should be 145 or 140psi. Keep in mind the numbers will vary abit based on guage and also elevation. One thing to keep in mind is that they should all be relativly close to each other.

There are many reasons the car could feel like its lost power over time. Since you said you dont have any faults, im guessing you also dont have a check engine light or anything like that. Before doing a compression test, have you done a boost leak test or atleast a smoke test to see if you have any air and or boost leaks?

Its possible you could just be used to the car but if everything comes back good and inconclusive, the peace of mind will be worth it lol.

Also what kind of miles and the mods are on the car? Up to date with maintenance?
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Old 11-30-2020, 12:35 AM   #11
connoredm
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My EJ255 with ~150,000 miles read 140-145 psi across all cylinders. If your compression and leak down test results are all normal I'd say the only other thing you can do to check is run it on a dyno and see if its really down any power
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Old 11-30-2020, 12:42 AM   #12
cdska
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Your gauge can also be inaccurate and the readings can vary greatly on testing conditions. More important that they are within 10% given they are above 100 psi
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Old 11-30-2020, 10:27 AM   #13
BlackFighter
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Quote:
Throw some seafoam in the oil for a couple thousand miles
I would stay way from seafoam for our cars, i have seen and heard some horrible stories with it reacting differently in our engines.
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