Compression test results - who's right? - Subaru Impreza WRX STI Forums:
STI Forum
Start New Thread Create Account Advertise FAQ Members List Contact
Compression test results - who's right?
Compression test results - who's right?
Go Back   STI Forums > > > Compression test results - who's right?
Thread Tools
Old 05-02-19, 06:38 PM   #1
Becoming A Contributor
Feedback Score: 0 reviews
Car: White STI '06 auto-x
Fav Mod: Coming Soon
My Threads
Posts: 17
My Subaru Parts for sale

Join Date: Jul 2012
Pault1 is an unknown quantity at this point
Default Compression test results - who's right?

Just want to get people's experience on this. Here's my situation:
'06 STI, was supposedly given an ECUTek tune with Perrin CAI and a de-catted downpipe back in 2007. But when I bought it and moved it to Cali, had to replace 100% of OEM hardware to get it smogged. I never changed the supposed tune. FWIW no dealer or smog tester has ever mentioned finding a tune....

It's at ~105K miles, and is used as a daily driver with multiple autocrosses / year. So brief hard use for 1 minute at a time, maybe 120 runs/year, generally NOT beat on at any other times.

At around 90-95K started having issues (coolant level changes) finally diagnosed as head gaskets. At that time, heads done, valves done, new OEM turbo due to a visible crack.

Last few months, it has seemed to be down on power, has a tip-in hesitation, and occasional blue smoke on start-up. I asked three different garages to diagnose; one was clueless as to cause; two have done compression tests.
First one:
- Cylinder 1: 140 psi
- Cylinder 2: 105 psi
- Cylinder 3: 140 psi
- Cylinder 4: 80 psi
- Cylinder 1: 5%
- Cylinder 2: 40%, intake and exhaust valves leaking
- Cylinder 3: 5%
- Cylinder 4: 60%, intake valves leaking
Diagnosis of valves leaking was determined by the sound. Valve clearances not checked at that time. AVCS confirmed operating normally. Garage is a Subie specialist and tuner.

Second one, I don't have the results in a file yet, but basically 2 and 4 found to have low cold compression, consistent with first one's test. But valves checked and only #4 exhaust valve was found to be very slightly tight (0.7 instead of 0.8, I think I heard) and on leak-down both 2 and 4 were blowing by. They stated that when pressurized, air could be heard coming out of the oil filler. Stated diagnosis is probable cracked ring(s). Recommended new short block. Garage owned by a friend but the mechanics are not specifically Subie specialists.

Now, I could be paranoid, but second garage is who was responsible for the head gaskets and valves last year. They are OK with standing behind any problem that their subbed out head and valve machining resulted in but don't think that it is the valves.

So comment away. Please try to give meaningful comparison to the way a leak down test may be interpreted. And would start-up blue smoke be more likely to be a cracked ring or some problem with guides/seals? Thanks.
Pault1 is offline  
Likes 0 Dislikes 0
Reply With Quote

Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Compression test results Dahozy 2.5 Liter/Litre Factory Motor 3 04-22-11 12:22 PM
Compression test results. #'s too low? STdIe 2.5 Liter/Litre Factory Motor 48 08-15-10 12:38 PM
Oh boy...My compression test numbers, not looking good. 2gnt2wrx 2.5 Liter/Litre Factory Motor 16 08-12-09 02:58 PM
compression test results? psusti12 2.5 Liter/Litre Factory Motor 5 08-06-09 06:35 PM
Compression Test Results Normal???? sowopsti 2.5 Liter/Litre Factory Motor 41 05-30-09 06:17 AM

New To Site? Need Help? More

All times are GMT -8. The time now is 03:42 AM.

Powered by vBulletin
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Designed & Powered by Domain Architect
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.