Welcome to the North American Subaru Impreza Owners Club Thursday September 18, 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 > Engine Management & Tuning > AccessPort

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 07-11-2006, 01:05 AM   #1
brokenarrow
Scooby Newbie
 
Member#: 119767
Join Date: Jul 2006
Vehicle:
2006 wrx
silver

Default what is this LEAN talk???

What is this lean talk??

I have read on here ..in a few places that 12.0 IS LEAN???

LOl.....please flame or correct me but Thats RICH right?

14.0 is In the middle and 15 is lean and 12 is where you WANT to be...when your at WOT..and then 14 when you are just putting around....????..

Is this not correct???

thanks ..and i am just wondering this cuz its what i have always thought and tuned for ..
* Registered users of the site do not see these ads.

Last edited by brokenarrow; 07-11-2006 at 01:17 AM.
brokenarrow is offline   Reply With Quote
Old 07-11-2006, 01:09 AM   #2
slidez
Scooby Newbie
 
Member#: 112185
Join Date: Apr 2006
Chapter/Region: SCIC
Location: West Covina, CA
Vehicle:
2005 WRX STi
WRB

Default

Yeah I've also heard that when you tune a motor you want to be as close to 12.0 as possible from a guy that builds motors in England. Im not sure if they take into account the crappy quality of fuel from the USA though. But take it with a grain of salt since I don't know anything about tuning.
slidez is offline   Reply With Quote
Old 07-11-2006, 01:25 AM   #3
hotrod
Scooby Specialist
 
Member#: 14141
Join Date: Jan 2002
Location: 13.239@102.85 @ 5800 ft on 13T
Vehicle:
2002 Impreza WRX
e85forum.net

Default

Quote:
I have read on here ..in a few places that 12.0 IS LEAN???

LOl.....please flame or correct me but Thats RICH right?
Rich of what or with respect to what?


Depends on what engine your talking about, and the context. There is no absolute "correct" fuel air mixture without knowing the application and conditions.
Acceptable mixtures vary depending on the engines compression ratio load, and if it is NA or boosted, and the intent of the tuner. What is a "correct" mixture for emissions is terribly lean for power and detonation protection at high engine load.

Max power on gasoline fuel in an engine that is not working at max potential, occurs between about 12.0 and 13.0 AFRs. Most folks accept that the safe max power mixture for such an engine is about 12.5:1. Now that is based on a NA, water cooled engine that is not knock limited (ie does not have so much compression that it is at risk of detonation) with fuel of proper octane, reasonable intake air temperatures,and sensible ignition advance. When the engine is under moderate load the "correct" or ideal mixture from a power or performance point of view is about 12.5:1.

Most turbocharged engines cannot run under high load at mixtures that lean, and are run much richer than that to prevent detonation and to cool combustion temperatures. For them the "correct" mixture for high power is from about 10.5:1 -to- about 11.5:1. In a specific turbocharged engine 11.5:1 might be too lean to prevent detonation. In another engine 12.2:1 might be possible under the same load and boost conditions.

14.7:1 is a stoichiometric mixture (ie exactly enough fuel as necessary to burn all the available air). This is the "correct" or ideal mixture only in the context of chemistry. At any significant engine load it is very very lean for most engines.

Fuel air mixtures are load and condition dependent you cannot define a mixture as lean or rich without defining the tuners intent or condtions.

Larry

Last edited by hotrod; 07-11-2006 at 01:31 AM.
hotrod is offline   Reply With Quote
Old 07-11-2006, 02:11 AM   #4
brokenarrow
Scooby Newbie
 
Member#: 119767
Join Date: Jul 2006
Vehicle:
2006 wrx
silver

Default

This is very very helpfull.
thanks you very much!

So for are cars ( wrx or sti) we should be running from 11 to 10 ?
i am understanding what you have said about the tuner intent or condtions ... and then also what does Cobb run a stage 3 at on are cars ...??


thanks ALOT again

AND what you have just posted Should be a sticky that is very good info..for some one that might be wondering what to tune his a/f's to.
brokenarrow is offline   Reply With Quote
Old 07-11-2006, 02:28 AM   #5
hotrod
Scooby Specialist
 
Member#: 14141
Join Date: Jan 2002
Location: 13.239@102.85 @ 5800 ft on 13T
Vehicle:
2002 Impreza WRX
e85forum.net

Default

Quote:
So for are cars ( wrx or sti) we should be running from 11 to 10 ?
Not exactly, but those are common ratios folks see on the stock ECU under certain conditions. You don't tune an engine to a single air fuel ratio with EFI, like you did with a carburator. On carburated engines you picked jets that gave a good average mixture for most of the engine rpm range and just lived with what you ended up with at other places in the power band.

On EFI the tuner tunes each specific load cell independently. At a single RPM there might be a dozen different possible fuel air ratios and ignition advance settings depending on boost and engine load for example.

In a "general sense" folks talk of attempting to hit a certain "target" AFR under heavy engine load, but there is no certainty that they will be at that exact AFR under all condtions.

To answer your intended question ---
Yes the stock WRX and STi frequently hits AFR's in the mid 10 - 11:1 AFR range under load. Most performance tuners try to lean the mixture out to get as close as they can to the ideal 12.5:1 for max safe power, but in most cases they can get no closer than 11.5 - 11.8:1 depending on boost, ignition timing and the specific setup on the car.

Also some tuners are more agressive than others and will (if they trust the customer) tune to the ragged bleeding edge for performance while in other cases they will use a more conservative tune to protect the customer.

Larry
hotrod is offline   Reply With Quote
Old 07-12-2006, 12:04 AM   #6
theicewall
Scooby Specialist
 
Member#: 70532
Join Date: Sep 2004
Vehicle:
2004 WRX
WRB

Default

^^yup, that's why a tune needs to be on 3 axes of space. Often RPM vs Load vs A:F and then I guess a 4th axis would be target boost for a given tps at a given load but that needs its own graph.

Last edited by theicewall; 07-12-2006 at 12:09 AM.
theicewall 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
what is this part called? what is it's part number? OUScooby Private 'Wanted' Classifieds 8 04-21-2010 04:08 PM
Whats all this football talk about? tommy2hotty Off-Topic 10 03-01-2006 02:55 PM
What is this girl talking about? automatic1977 Off-Topic 19 11-09-2005 05:26 PM
what the hell is this n00b talking about? Handsdown Off-Topic 26 07-30-2005 11:20 PM
('93-'01) what is this and what does it do? shimstock Impreza Forum 4 04-10-2001 09:53 AM


All times are GMT -4. The time now is 05:59 PM.


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.