Welcome to the North American Subaru Impreza Owners Club Monday July 24, 2017
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
Go Back   NASIOC > NASIOC Technical > Built Motor Discussion

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 03-11-2006, 01:51 PM   #1
Scooby Specialist
Member#: 94494
Join Date: Aug 2005
Chapter/Region: NWIC
Location: Seattle
2005 Element 92x

Default forced induction is forced induction?

I know this article is from a honda site, but it's actually a pretty reputable site for serious Honda builders. Came across this article, and I was actually surprised to what I read. I assumed NOS would be more dangerous than turbo boost, but according to this, it's not. I'm posting in this forum instead of the 2.0 or 2.5l forums because the explanation references compression ratios, which is usually discussed here.

* Registered users of the site do not see these ads.
keaniegenie is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 03-11-2006, 01:57 PM   #2
Scooby Specialist
Member#: 5810
Join Date: Apr 2001
Chapter/Region: Tri-State
Location: Easton PA
2001 S366 2.5RS


nitrous doesnt raise compression any measurable amount .. it raises cylinder temps. It doesnt "force" air into the motor, just increases the oxygen content.
Nitrous isnt any safer than turbo/supercharging. Its actually a very unpredictable way to add power.

Last edited by sidewayz; 03-11-2006 at 02:12 PM.
sidewayz is offline   Reply With Quote
Old 03-12-2006, 12:50 PM   #3
Scooby Guru
Member#: 18446
Join Date: May 2002
Chapter/Region: MAIC
Location: Stratford, CT
2002 WRX wagon


I am no guru and have no personal experience with n2o, but when I thought about it, effective is interchangeable with dynamic. Meaning, the static cr on an engine is just that...when the engine is static, these factors go into an equation and produce what the static cr would be. Using only one factor, forced induction, increasing the load (an increased percentage of oxygen per original volume based on engine speed, which is what forced induction is) you increase effective or dynamic compresson ratio. The main difference is that n2o provides a cooling effect, while turbos and superchargers charge air are heated (hence the need for intercoolers and aftercoolers.)

http://forums.nasioc.com/forums/showthread.php?t=400503 (see John Banks comment)

Originally Posted by unabomber
The other issue, often missed in the 'street tuner market', is the concept of Dynamic Compression Ratio. This is your “real” Compression Ratio where you take things like camshaft profile, bore and stroke, rod lengths/ratios, altitude, inlet boost pressures, and exhaust gas backpressures into consideration. The Static Compression Ratio that works on your buddy's EVO motor, or even someone's EJ20 is all but meaningless unless your entire SYSTEM is the same.
gpatmac is offline   Reply With Quote
Old 03-12-2006, 02:50 PM   #4
Scooby Specialist
Member#: 49087
Join Date: Nov 2003
Chapter/Region: RMIC
Location: Inside your carnot cycle
1998 RST V8 STi swap
'05 R6 '95 BMW V8 hotness


Nitrous causes much more fatigue on internal components than FI. Your peak cylinder pressures during combustion aren't much higher. All the power comes from an increase in duration of your peak pressure. The metals need time to rebound to their original form between firing cycles and they don't have as much time to do this with N20. This can cause certain parts to still be stressed by the time the next firing cycle comes around.

This is why very stiff (not necessarily strong) components are needed moreso than in FI setups. The OEM EJ257 stuff is very strong mechanically, but not very stiff. If you stripped off the turbo and tried to run 400whp all nitrous on a stock STi block you wouldn't come anywhere close to that. However with a turbo this is a very do-able figure.
no-coast-punk is offline   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
Zerosports exhaust manifold, ARC Induction box, HKS induction kit Syms-STI Engine/Power/Exhaust 2 08-06-2008 03:06 AM
Forced Performance is looking for representation on NASIOC Nick Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 33 03-29-2006 10:22 AM
Anyone know how thin brake pads have to be before dealer is forced to change... thsiao Service & Maintenance 20 12-11-2005 01:55 PM

All times are GMT -4. The time now is 06:08 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.