Welcome to the North American Subaru Impreza Owners Club Saturday July 12, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Factory 2.5L Turbo Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 01-14-2013, 02:17 PM   #1
magman007
Scooby Newbie
 
Member#: 224012
Join Date: Sep 2009
Default Compression Test Results?

Hi guys, I'm getting ready to buy an 06 sti and had the owner take the car in for a ppi, compression and leak down test. The dealer was unable to do the leak down due to not having a proper tool? But my real question is with the results.

Cyl 1 was 115 and 2-4 were all 110. I understand that "spec" is between 140 and 170. I have spoken to a tech independent from the situation and they say its not the number but the consistency between the cylinders that matters. The car has 45 k miles on it, was stage 2 AP then pro tuned for the last 2 years and has been returned to stock. The tech that performed the test says he has seen plenty of "healthy" STIs in the 115 120 range.

Now I'm not the smartest or most mechanically inclined but I do understand that compression has a direct correlation to power generation if the compression was 30psi less than spec wouldn't the car be down on power? Am I buying myself a rebuild shortly down the road or should I feel confident in buying an otherwise clean car?

The engine was not "Cold" it still had some heat in it, but was definitely not at operating temp. I have yet to speak to the tech (calling tomorrow) The owner has been nothing short of awesome and great to work with, and I have tickets to go get the car next Saturday. So Nasioc I need to make a decision and i need some assistance.
* Registered users of the site do not see these ads.
magman007 is offline   Reply With Quote
Old 01-16-2013, 12:25 AM   #2
BrendanTheGreat408
Scooby Specialist
 
Member#: 271207
Join Date: Jan 2011
Chapter/Region: BAIC
Location: Morgan Hill, CA
Vehicle:
2011 WRX
SWP

Default

First off i am not a subie expert by any means, from my knowledge 110 doesn't sound too healthy. Down on compression can and probably will mean down on power as well and possibly a weak engine. Here are the results from my compression test, the engine is "very healthy"

http://farm9.staticflickr.com/8343/8...fb5a1ebd_b.jpg
BrendanTheGreat408 is offline   Reply With Quote
Old 01-16-2013, 01:10 AM   #3
mod maniac
NASIOC Supporter
 
Member#: 300551
Join Date: Nov 2011
Chapter/Region: SCIC
Location: mariposa ca.
Vehicle:
2&4 fxt & fxt sti
Fullers Garage

Default

I don't know if my snap-on gauge reads low but i usually see around 120 on most of the wrx's I test. I would say the numbers look close there probably isn't a problem. There gauge probably just reads low like mine.
mod maniac is offline   Reply With Quote
Old 01-16-2013, 03:59 AM   #4
esteve
Scooby Specialist
 
Member#: 28716
Join Date: Nov 2002
Chapter/Region: SCIC
Location: Los Angeles
Vehicle:
2006 STI

Default

I wouldn't buy a used turbo Subaru, especially one that's been modded, without a leakdown test too. Compression tests don't always tell the whole story so try to have the owner take it to a shop that can do a leakdown test.
esteve is offline   Reply With Quote
Old 01-16-2013, 10:45 AM   #5
myblusti
Scooby Newbie
 
Member#: 337871
Join Date: Nov 2012
Chapter/Region: South East
Location: beaufort
Vehicle:
2010 5-door STI
blue/gold

Default

it depends on how he performed the test and the tester on the readings. to get the best results you want to get the car to op temp then remove all plugs and the fuel pump fuse then perform the test at wot for about 5 revolutions. if it isnt done at wide open throttle on a warm engine the results will vary, but you do want a consistant number across all cylinders.
myblusti is offline   Reply With Quote
Old 01-16-2013, 01:28 PM   #6
aboothman
Scooby Specialist
 
Member#: 127745
Join Date: Oct 2006
Chapter/Region: NWIC
Location: Humboldt County
Vehicle:
06 WRX 30r 6 speed
99L EJ255 6 Speed

Default

Quote:
Originally Posted by myblusti View Post
it depends on how he performed the test and the tester on the readings. to get the best results you want to get the car to op temp then remove all plugs and the fuel pump fuse then perform the test at wot for about 5 revolutions. if it isnt done at wide open throttle on a warm engine the results will vary, but you do want a consistant number across all cylinders.
agreed
aboothman is offline   Reply With Quote
Old 01-16-2013, 03:14 PM   #7
danger1138
Scooby Specialist
 
Member#: 279525
Join Date: Apr 2011
Location: QUEENS NY
Vehicle:
04 rex luger!

Default

Quote:
Originally Posted by myblusti View Post
it depends on how he performed the test and the tester on the readings. to get the best results you want to get the car to op temp then remove all plugs and the fuel pump fuse then perform the test at wot for about 5 revolutions. if it isnt done at wide open throttle on a warm engine the results will vary, but you do want a consistant number across all cylinders.
Thats that little 15amp fuse behind the change bin?
danger1138 is offline   Reply With Quote
Old 01-17-2013, 08:18 AM   #8
myblusti
Scooby Newbie
 
Member#: 337871
Join Date: Nov 2012
Chapter/Region: South East
Location: beaufort
Vehicle:
2010 5-door STI
blue/gold

Default

lol. it should say fuel pump. im not sure in your car. in my 240 it is a 15amp. but my sti is at the shop so i cant check. but it should be labeled. you could also probably just unplug the injectors but thats kind of a pita on subaru's.
myblusti is offline   Reply With Quote
Old 01-17-2013, 09:45 AM   #9
AkumaMotorsports
Former Vendor
 
Member#: 214570
Join Date: Jun 2009
Chapter/Region: Tri-State
Location: NJ/SLC
Vehicle:
2008

Default

I would definitely recommend bringing the car to a place that can do a proper leak down test. The results of this would help you get a better understanding if that reading is accurate and if so why it is down on compression.

By doing the leak down test it will give you more specific reason as to why there is low compression. It will indicate things such as blown head gasket, bad intake or exhaust valves, worn out or damaged piston rings from over heating, constant abuse etc..

Right now there is not enough information to see whats going on.
AkumaMotorsports is offline   Reply With Quote
Old 01-20-2013, 10:35 PM   #10
jaboyd
Scooby Newbie
 
Member#: 247304
Join Date: May 2010
Chapter/Region: South East
Location: Knoxville, TN
Vehicle:
2011 STI
WR Blue

Default cyl pressure

STIs should be around 140 psi (cold reading) and ideally with no more than a 10-15 psi spread across all cylinders. Mine read 135 on 2 cyls and 140 on 2 cyls avg 137.5.
jaboyd is offline   Reply With Quote
Old 01-21-2013, 02:14 PM   #11
revD
Scooby Newbie
 
Member#: 270705
Join Date: Jan 2011
Default

Mine read ~125 cold cranking when I was investigating some things on my last motor. Ran great at the time, but this is also cold.
revD is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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


All times are GMT -4. The time now is 06:31 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.