Welcome to the North American Subaru Impreza Owners Club Friday July 11, 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

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 06-01-2004, 07:50 AM   #1
Hitokiri
Scooby Specialist
 
Member#: 2604
Join Date: Oct 2000
Chapter/Region: NESIC
Location: CA
Vehicle:
1999 2.5RSt
RBP

Default Airflow modification Vs. IDC modification

I was wondering if anyone has any experience with modifying the IDC's rather than the airflow as a method of tuning. My greddy emanage has the ability to change airflow via 16x16 RPM vs. Throttle, and IDC by 16x16 Airflow (MAF) vs. RPM.

I was wondering this because of the report of people having there AFC's canceled out by the ecu tuning around their changes. On my RS (soon to be RSt) I wonder if it would work better to give a general scaling of the Airflow in the airflow map. Maybe just a simple -30% or -40% accross the board or something (I have WRX inj 420cc = ~50% larger than stock) and then added fuel in after the ECU to the IDC via my other map.

It seems to me that this would be a nice way to keep fueling more consistent as the ECU would not be seeing a radically changed MAF voltage operation from stock, and therefore would try to tune around my corrections less assuming it saw resonable o2 readings from the exhaust.

My question to the gurus is: How specifically does the RS ecu (or subaru ecu's in general) retune? Are there maps of short / long term fuel trim that it modifies? I know the WRX ecu uses some pretty complicated timing adjustment, but how is fuel trim modified? Is it mostly o2 / AF based?

I have seen some pretty interesting things happen messing with the car NA with the emanage so far. Messing with the IDC makes a larger impact than the Airflow adjustment which makes sense I suppose because there is more going into IDC than simply airflow. The other thing I have noticed is that if I reset the ECU, it starts pig rich above .91 narowband, which is about the top of narrowband's resolution. If I quickly attempt to tune it down into the .8-.84 range (14 ish), I can get it to run pretty well and stay in those o2 values with a few spikes. But If I reset the ECU and leave it alone completely with zero correction, drive hard on it for a few nights, and then take data from the ECU (OBD2 scantool). I get NEAR PERFECT .84 o2 readings extremely consistantly at WOT in almost every gear!!!

I was pretty surprised. So I guess my question is.... when my turbo goes in, would to be better to change the IDC after the ECU rather than the airflow (except for simple scaling) in order to give the ECU a nice airflow curve to do its handywork on? And clean up after with IDC modification???

thanks everyone,

Todd
* Registered users of the site do not see these ads.
Hitokiri is offline   Reply With Quote
Old 06-01-2004, 03:28 PM   #2
Hitokiri
Scooby Specialist
 
Member#: 2604
Join Date: Oct 2000
Chapter/Region: NESIC
Location: CA
Vehicle:
1999 2.5RSt
RBP

Default

no comments??
Hitokiri is offline   Reply With Quote
Old 06-02-2004, 09:43 AM   #3
john banks
Scooby Specialist
 
Member#: 11669
Join Date: Oct 2001
Location: UK
Vehicle:
Evo IX 345 WHP

Default

Thought the e-manage only allowed you to extend injector pulses?
john banks is offline   Reply With Quote
Old 06-02-2004, 11:06 AM   #4
Hitokiri
Scooby Specialist
 
Member#: 2604
Join Date: Oct 2000
Chapter/Region: NESIC
Location: CA
Vehicle:
1999 2.5RSt
RBP

Default

thats correct. It does only allow you to extend injector pulses

But if I take out more airflow to beginwith- and increase IDC up to where I need to be via inceased IDCs, I would then be able to remove pulsewidth by decresing that additional injection I built in.

This might get way to confusing though if I don't understand what the ECU is doing in the backround.

Todd
Hitokiri is offline   Reply With Quote
Old 06-02-2004, 12:07 PM   #5
john banks
Scooby Specialist
 
Member#: 11669
Join Date: Oct 2001
Location: UK
Vehicle:
Evo IX 345 WHP

Default

The ECU will retard the ignition if you increase the airflow signal. You will also be more likely to saturate the airflow limits in the ECU and hit the ends of the maps.

I think that there is an ignition control facility available on the e-manage though?

For these sorts of reasons I prefer reflashing or stand alone ECUs.
john banks is offline   Reply With Quote
Old 06-02-2004, 04:39 PM   #6
lotusTT
Scooby Specialist
 
Member#: 23359
Join Date: Aug 2002
Chapter/Region: NESIC
Location: San Francisco
Vehicle:
2002 BMW M Coupe
Steel Gray

Default

I'm not really sure, which method is better in terms of the ECU learning around the adjustments, although I've been using the air flow map exclusively for about 6 months now and it seems to be working well.

The reason I went with the airflow map was to try and get the most accurate timing values. The more you reduce the airflow map, the more the ECU will advance your timing. So if you take fuel out with the airflow map then add it back with the additional injection map, you're gonna have to mess with the timing a lot.

One other consideration, I've been thinking of making a new map that uses only the injector scalling function and the additional injection map. This would let you run one map, regardless of your current boost level. If you tune with just the airflow map, you'll need to switch maps if you switch to a different boost level.
lotusTT is offline   Reply With Quote
Old 06-04-2004, 09:51 AM   #7
SlideWRX
Scooby Specialist
 
Member#: 3803
Join Date: Jan 2001
Chapter/Region: MWSOC
Location: South Carolina
Vehicle:
07 Mustang GT
285 is a wide tire!

Default

Quote:
Originally posted by Hitokiri
My question to the gurus is: How specifically does the RS ecu (or subaru ecu's in general) retune? Are there maps of short / long term fuel trim that it modifies? I know the WRX ecu uses some pretty complicated timing adjustment, but how is fuel trim modified? Is it mostly o2 / AF based?
below ~60% throttle the WRX ecu uses the O2 sensor to adjust to ~14.7 A/F. It will always try to hit that mark, even when adjustments are put into the MAF.

Above 60%, it ignores the O2 sensor. That's why my UTEC comes in at 60%, because fuel tuning below that can get cancelled out.

I've adjusted my fuel at 750 rpm a bit, because the ECU base map was a bit off - it would pull fuel at idle but add it else where. This was to keep the adjustments the ECU did to a minimum, to keep the fuel trims more consistent.

Tom
SlideWRX is offline   Reply With Quote
Old 06-07-2004, 03:48 PM   #8
Hitokiri
Scooby Specialist
 
Member#: 2604
Join Date: Oct 2000
Chapter/Region: NESIC
Location: CA
Vehicle:
1999 2.5RSt
RBP

Default

bump for more thought on this
Hitokiri 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
Co-axial vs Components metoo Car Audio, Video & Security 2 06-02-2010 09:15 PM
TEC-II, IDC and lots of boost thoughts kastle Normally Aspirated with bolt-on Forced Induction Powertrain 21 08-18-2002 03:24 AM
Boost vs Airflow and engine life tthew002 Factory 2.0L Turbo Powertrain 1 07-07-2002 01:39 PM
IDC on Stock Injectors with upgraded pump & regulator (VF-30?) mynew02 Factory 2.0L Turbo Powertrain 1 03-21-2002 01:47 PM
Warranty vs. Modification wrx55 Vancouver Impreza Club Forum -- VIC 6 03-03-2001 12:57 AM


All times are GMT -4. The time now is 06:14 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.