Welcome to the North American Subaru Impreza Owners Club Friday November 24, 2017
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
Go Back   NASIOC > NASIOC Technical > Normally Aspirated 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. 
Thread Tools Display Modes
Old 07-01-2001, 07:23 PM   #1
Scooby Specialist
Member#: 6964
Join Date: May 2001
Location: levittown ny us
2001 impreza
pearl ridge blue

Default piston

i am planning to intall piston heads, valves, valves springs
camshalfs in my01
i want to go n/a then turbo
i want to prepare my engine for what the turbo is going to do to my engine
i going to put a nos kit in too
so what i am get to is that , if i develop such a hig compression ratio , i can 't go turbo, right?
anyone with advice or suggestions
* Registered users of the site do not see these ads.
takumi is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 07-01-2001, 10:11 PM   #2
Subie Blues
Scooby Newbie
Member#: 6438
Join Date: May 2001
Location: Lakewood, Oh USA
01 RS


That's right,, big compression a no-no with forced induction. On production cars adding turbos/SC, the limit is about 8-10psi safely with lots of control on ignition. Forced induction effectively raises the compression ratio. The big drag motors run 30-40 psi with CR's of 6 or 7. Since you are going into the motor, lower the CR to about 7 or 8 and you should get plenty of room for about 20 psi. Look for a knowledgeable shop to do the work and they will keep it straight. If on your own then find a book or two to calculate the effective ratio. Wish I had the money to go at it right now.
Subie Blues is offline   Reply With Quote
Old 07-01-2001, 10:30 PM   #3
Worst Mod Ever
Member#: 369
Join Date: Oct 1999
Chapter/Region: SWIC
Location: Phoenix, AZ
12 Vagon


I wouldn't go as low as 7:1 on compression ratio if the car is street driven. It would be very slow when not in boost. I am switching to 8.5:1 which should allow for pretty high boost pressures street driven on pump gas. I would guess a well managed 12-15psi wouldn't be impossible on pump gas with an 8.5:1 compression ratio.

When I finally get my internals and the car running again I can let you know how much off boost response is lowered by switching from 10:1 to 8.5:1


AaronB is offline   Reply With Quote
Old 07-01-2001, 11:14 PM   #4
Scooby Specialist
Member#: 6935
Join Date: May 2001
1999 Impreza 2.5RS
Rally Blue


8.5 or 8.6 to one is supposed to be the ideal compression ratio for a supergharged or turboed motor.
imprezadan is offline   Reply With Quote
Old 07-02-2001, 10:38 AM   #5
Dirty Underwear Gang

An 8.5:1 compression ratio running 15psi on a 2.5L engine would get you somewhere close to 300hp & a broken tranny... Be careful.
  Reply With Quote

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
FS VA: **NEW**2010 STi OEM pistons, rings, pins, and clips**$120 Shipped** moorebl Engine/Power/Exhaust 17 07-01-2010 10:01 AM
Ej251 Longblock, many many parts. EJ22t, Wiseco Pistons, STI Coils hustleshark206 NWIC Private Classifieds 7 06-14-2010 05:55 PM
STI 4 piston, Perrin 4 piston, or Wilwood 4 piston nos Brakes, Steering & Suspension 18 12-15-2004 11:45 AM
Piston slap after I changed pistons to Arias forged pistons tomoking Service & Maintenance 9 11-06-2003 09:48 AM
6 piston caliper has less clamping force then 4 piston ones on WRX - any truth? HM3SC Brakes, Steering & Suspension 12 06-27-2001 06:54 PM

All times are GMT -4. The time now is 02:33 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.