Welcome to the North American Subaru Impreza Owners Club Tuesday October 17, 2017
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Subaru Conversions

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 06-18-2008, 12:34 AM   #1
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default Compression ratio advice for EJ25 shortblock swap, 11.5 or 10.3 or?

I'd like advice. I'm going to perform the ever popular EJ22 to EJ25 shortblock swap. I'm thinking I should go for the 10.3 CR unless a thicker gasket is available. Advice?


I used the specs from http://wac.addr.com/auto/obs/turbo/ejcalcs.html with the calculator http://www.bgsoflex.com/cr.html -
* Cylinder head Volume (CC) = 40.00
* Piston Top Volume (CC) = 14.50
* Cylinder Bore (Inches) = 3.9
* Cylinder Stroke (Inches) = 3.11
* Deck Height (Inches) = 0.000
* Head Gasket Thickness (Inches) = 0.060
# Computed Compression Ratio is 10.2 to 1

If I use the SOHC gasket thickness of 0.023 # Computed Compression Ratio is 11.3 to 1


For fun I entered the stock EJ22 specs -
* Cylinder head Volume (CC) = 40.00
* Piston Top Volume (CC) = 14.50
* Cylinder Bore (Inches) = 3.8
* Cylinder Stroke (Inches) = 2.95
* Deck Height (Inches) = 0.000
* Head Gasket Thickness (Inches) = 0.060
Computation Results:
# Computed Compression Ratio is 9.4 to 1

Background - This is in my beater Legacy. I've driven it like I stole it every day for the last 130k miles. It runs perfectly, good compression, passes smog great but cylinder #3 is consuming oil at the rate of 1qt per 350 miles. I got the EJ25 for free since the spark plug broke and put a few dents in the piston top (easily removed with the dremel).

Thanks for your ideas.
* Registered users of the site do not see these ads.

Last edited by ciper; 06-18-2008 at 11:22 PM.
ciper is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 06-18-2008, 02:19 AM   #2
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

I found a Subaru compression ratio calculator which verifies the above info -
http://www.jonesboy.com/Media/Matts_CR_calc_v1_01.xls

Using it I get 10.33 for DOHC gasket and 11:5 for SOHC gasket
ciper is offline   Reply With Quote
Old 06-18-2008, 07:25 AM   #3
Storm
Scooby Guru
 
Member#: 5218
Join Date: Mar 2001
Chapter/Region: MWSOC
Location: SAUL'S Motorsports
Vehicle:
96L Most Over-
Developed Beater

Default

I guess it depends on what kind of goals you have, gas you have available and are willing to buy.

I'd go for broke and get as much CR as possible......but I'm not a smart guy......

Jay
Storm is offline   Reply With Quote
Old 06-18-2008, 10:59 AM   #4
Jaxx
NASIOC Supporter
 
Member#: 177
Join Date: Aug 1999
Chapter/Region: NWIC
Location: Austin, Texas, USA
Vehicle:
The 93 W/EJ20K
Series 10 FRS

Default

what em are you gonna use ...
you need it to take advantage of the change ...
Jaxx is offline   Reply With Quote
Old 06-18-2008, 01:43 PM   #5
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

The goal is a daily driver that uses 87 octane fuel. The horsepower outcome doesn't matter much to me as long as its equal to or greater than its current amount.

The increase in displacement is still within the injector sizing and learning curve for the stock computer which I was planning to use.
ciper is offline   Reply With Quote
Old 06-18-2008, 04:21 PM   #6
Jaxx
NASIOC Supporter
 
Member#: 177
Join Date: Aug 1999
Chapter/Region: NWIC
Location: Austin, Texas, USA
Vehicle:
The 93 W/EJ20K
Series 10 FRS

Default

hmmm
it will learn in closed loop but not open loop and a 98ecu won't adjust timing like it will need

its not a b16 ... 11.5 is allot for a ej series engine ..
Jaxx is offline   Reply With Quote
Old 06-18-2008, 05:15 PM   #7
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

The ECU is a 91. I agree that 11.5 is way high. I even feel 10.33 is high but I don't have enough experience with NA Subaru tuning.

A well respected VW builder made a suggestion today that may or may not be applicable. If I use one DOHC gasket and one SOHC gasket together I get 9.6:1 compression or three SOHC gaskets to get 10:1 (assuming the resulting thickness is .083 and .069). The stock CR of the 90-96 2.2 is 9.4 where the 97+ 2.2 is 9.7
The SOHC/DOHC combo is only .023 more than the regular gasket so would my manifolds fit properly?

I know the newest design of EJ25D gasket from Subaru is MLS, Do you know if the SOHC gasket is of similar material and could mate properly in this configuration?

Thanks

Last edited by ciper; 06-18-2008 at 11:24 PM.
ciper is offline   Reply With Quote
Old 06-19-2008, 07:29 AM   #8
Storm
Scooby Guru
 
Member#: 5218
Join Date: Mar 2001
Chapter/Region: MWSOC
Location: SAUL'S Motorsports
Vehicle:
96L Most Over-
Developed Beater

Default

Cometic will make you whatever thickness you want. The SOHC gaskets I have taken off were MLS.

Jay Storm
Storm is offline   Reply With Quote
Old 06-19-2008, 04:38 PM   #9
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

I hope custom cometic parts are better priced than custom ARP parts (good stuff but damn they charge alot).

What do you think about stacking multiple MLS gaskets?
ciper is offline   Reply With Quote
Old 06-20-2008, 01:49 AM   #10
ballitch
Scooby Specialist
 
Member#: 74907
Join Date: Nov 2004
Chapter/Region: NWIC
Location: salem, OR
Vehicle:
98 cam'd EJ251
Wrx Tranny,slowr than ish

Default

You shouldn't use multiple hg's. Just use the stock replacement HG's for EJ25's, the dohc gasket is MLS, and you can get them cheap on Ebay.

You might be able to get away with 89 octane if you go 10.3 CR, but you better not try that with the 11.5 CR, as soon as you start pinging, the ecu retards timing, there goes all the power that would have gained from doing this.

I've had the high CR motor in my car for a while, its alot more powerful than the stock ej22 was. You will definately enjoy it. Make sure to get cams, at least, the EJ22 heads run out of steam up top. Not to mention you'll be trying to stuff another 300cc's of displacement through those heads.

But you still havent told us what phase EJ25 this is.

I use this CR calc. alot, along with a couple others to verify accuracy.



~Josh~
ballitch is offline   Reply With Quote
Old 06-20-2008, 02:25 AM   #11
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

Thanks for the help. Does the data I posted originally look accurate? I've learned not to trust specs from the internet...

I didn't think the cams from a SOHC EJ25 fit on the EJ22 SOHC heads,,, or did you mean aftermarket?

Last edited by ciper; 07-05-2008 at 10:16 PM.
ciper is offline   Reply With Quote
Old 06-24-2008, 04:19 PM   #12
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

double

Last edited by ciper; 07-05-2008 at 10:16 PM.
ciper is offline   Reply With Quote
Old 06-25-2008, 07:22 AM   #13
Storm
Scooby Guru
 
Member#: 5218
Join Date: Mar 2001
Chapter/Region: MWSOC
Location: SAUL'S Motorsports
Vehicle:
96L Most Over-
Developed Beater

Default

Yup....very little, if any upcharge for custom thicknesses. They're pretty much made to order anyway. The have various gauge stock to work from, so getting your desired thickness shouldn't be an issue. I don't think I would stack MLS gaskets to achieve a certain thickness. If I had to....I'd only stack center layers, leaving the outer layers where they are supposed to be.
Quote:
Originally Posted by ciper View Post
I hope custom cometic parts are better priced than custom ARP parts (good stuff but damn they charge alot).

What do you think about stacking multiple MLS gaskets?

Jay
Storm is offline   Reply With Quote
Old 06-25-2008, 03:24 PM   #14
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

I want to make damn sure I order the right size. I don't trust the numbers I posted originally. How can I be certain that a .080 gasket is the right thickness for 9.7:1 ratio?

Secondly give me your advice. Is a 9.7:1 ratio good if I plan to use 87 octane gas?

Response from cometic -
We can gladly make the gasket thickness what ever you like as long as it is a possibility for us. However, I cannot confirm nor deny if your calculations are correct or not. When it comes to volumes I can tell you it is never a safe bet to assume anything or trust information you find on the internet. In theory your numbers make sense but like I said I cannot do the math to verify.
Kevyn Kistner
Technical Sales
Cometic Gasket
ciper is offline   Reply With Quote
Old 06-28-2008, 03:51 AM   #15
ballitch
Scooby Specialist
 
Member#: 74907
Join Date: Nov 2004
Chapter/Region: NWIC
Location: salem, OR
Vehicle:
98 cam'd EJ251
Wrx Tranny,slowr than ish

Default

You do mean .80 mm right? Not .080''.....

And 9.7:1 is the stock CR btw...

The only true way to tell if you have a Phase II EJ25, is to split the block and look to see where the thrust bearing is. 1999 was a big gray year for Subaru.


~Josh~
ballitch is offline   Reply With Quote
Old 06-30-2008, 04:51 PM   #16
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

Cometic is unable to give suggestions or advice on thickness so I am relying on the input of the forum. What target CR should I shoot for (I'm still leaning towards 9.7).
Second can you help me to confirm that a .2cm gasket will give me 9.7:1?

Quote:
Originally Posted by ballitch View Post
You do mean .80 mm right? Not .080''.....

And 9.7:1 is the stock CR btw...
I mean .080 inch because the stock "thick" gasket from Subaru is .060 inch.
In metric thats .152cm for the thick gasket, 0.058 for the thin one and about .2cm to get 9.7:1 if my calculations are correct.

9.7:1 is only stock for the 97 and later ej22 with single port exhaust and solid rockers. Mine is a phase 1 with dual port exhaust, hydraulic lash adjustment and a 9.4:1 ratio.

The 90-94 EJ22 was 130hp @ 5.2k and 144tq @ 4k
The 97-98 was 137 @ 5.4k and 145 at 4.4k
The 99+ got 142hp at 5.6k and 149tq at 3.6k
ciper is offline   Reply With Quote
Old 07-01-2008, 06:14 PM   #17
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

Alright I plan to try for 9.7:1 ratio using a .215cm gasket unless anyone says otherwise.

Is an increase .152cm to .215cm going to cause an issue? Perhaps too much change in timing since the heads are father apart or maybe exhaust/intake manifold fitment.

Now my question is - should I get a 9.96 bore gasket that has coolant and oil passages like the EJ22 or a 9.96 bore gasket with coolant and oil passages like the EJ25

Last edited by ciper; 07-02-2008 at 04:16 PM.
ciper is offline   Reply With Quote
Old 07-01-2008, 07:57 PM   #18
Storm
Scooby Guru
 
Member#: 5218
Join Date: Mar 2001
Chapter/Region: MWSOC
Location: SAUL'S Motorsports
Vehicle:
96L Most Over-
Developed Beater

Default

Timing change will be unnoticable. Get the gaskets with a bore that matches the block.

Jay
Storm is offline   Reply With Quote
Old 07-02-2008, 04:15 PM   #19
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

Storm: My question wasn't worded very well. I was trying to ask if I should get a 9.96 bore gasket that has coolant and oil passages like the EJ22 or a 9.96 bore gasket with coolant and oil passages like the EJ25?
ciper is offline   Reply With Quote
Old 07-02-2008, 10:24 PM   #20
Storm
Scooby Guru
 
Member#: 5218
Join Date: Mar 2001
Chapter/Region: MWSOC
Location: SAUL'S Motorsports
Vehicle:
96L Most Over-
Developed Beater

Default

Ahh.....Kevyn recently developed a hybrid headgasket just for this type of buildup. I had the PN in an email from him, posted it here somewhere and deleted it from my boxes. It's got the EJ25 bore and EJ22 coolant passages, just like you want....if I'm reading this correctly.

Jay
Storm is offline   Reply With Quote
Old 07-03-2008, 02:01 AM   #21
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

Storm : Yes I think you are right -
Quote:
.215cm should equate to 2.15mm or after converting will be about .085” of an inch. This seems like a pretty thick gasket for what you are trying to do but if this is what your math shows then the numbers don’t lie. I can make you a gasket at .086” compressed and I have already setup a gasket in our system that is for your EJ22/25 setup. Because of the thickness being so much greater than stock you will be looking at $107.88 per gasket plus shipping. Let me know if you would like to get these on order.
I'm seriously bummed. I did not expect to pay 230$ for headgaskets! I especially didn't expect such a price since I just payed 40$ for a pair of Subaru OEM MLS gaskets!

Any advice on a less expensive alternative to get my EJ25 shortblock working with my original intake manifold? I also have a complete phase one DOHC EJ25 with a spun bearing if any of its parts can help. (still runs decently too)
ciper is offline   Reply With Quote
Old 07-05-2008, 10:22 PM   #22
ciper
Scooby Guru
 
Member#: 15543
Join Date: Feb 2002
Location: san francisco, ca
Vehicle:
90BJ Legacy LS ABS
AWD 946 Rio Red Jpn built

Default

I don't know how I missed this before but the Phase 2 EJ25 has significantly less piston volume than the phase 1. I picked the bock up and verified that it is in fact a phase 2 which means all of my above calculations are invalid.

I don't think I can increase the volume enough just using the gasket thickness to get a low CR with the stock heads. I may have to sell this shortblock and find another route.

Are there any other heads (with increased capacity) work with the first generation EJ22 SOHC intake and ecu?
ciper 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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Compression ratio matrix for EJ-series engines Marnix Built Motor Discussion 26 10-11-2016 05:21 PM
ej20 to usdm ej25 shortblock swap, need some help! xxxjuhstenxxx Subaru Conversions 1 01-21-2008 10:15 PM
Engine swap advice for an '05 saabaru 2.5? MrSaabaru Normally Aspirated with bolt-on Forced Induction Powertrain 13 05-30-2005 03:05 AM
EJ25 Shortblock swap RyansJDMgc8 Subaru Conversions 13 09-16-2004 06:30 PM

All times are GMT -4. The time now is 04:27 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2017 Axivo Inc.
Copyright ©1999 - 2017, North American Subaru Impreza Owners Club, Inc.