Welcome to the North American Subaru Impreza Owners Club Saturday September 20, 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 > 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.
Reply
 
Thread Tools Display Modes
Old 11-18-2001, 09:44 PM   #1
Longshot
Scooby Specialist
 
Member#: 2359
Join Date: Sep 2000
Chapter/Region: NESIC
Vehicle:
2001 Impreza 2.0 WRS

Default For all you disbelievers..

Okay.. I made a trip recently to a dyno day at Adrenalin Motorsport and I have some good results I thought you guys might enjoy!

This is solid evidence that the S/AFC does do something on 2000+ 2.5 Impreza's...

(LONG)



That is the stock (as far as the S/AFC is concerned) run. You'll note I peaked at about 110hp and 120lb-ft of torque. Solid numbers for an untuned 2.5RS with an intake and exhaust.



That's the stock AFR (Air-Fuel ratio) Its stock at about 13-13.5 at 2000-2500 rpms, then it takes a head-first nose dive into rich territory. It actually continues off the scale to about 9.5 @ 6250 RPM.



Okay heres is the run where I leaned the car out by -30 across the board from 3000 - 6500 RPM. You will note the peak torque drops from 120 to 117 and the hp number stays pretty consistent only going down by about 1.5hp..



This is for all you nay-sayers.. here is the AFR graph for the -30 run. You will note at about 3500 RPM the AFC takes over and the car goes nuts.. this proves the AFC does in fact work.



Here is the run after I dropped the settings to -15.. you will note the car gains power and goes up to 115hp and a little over 122lb-ft of torque!



Okay, now we see the AFR, you will note that the car is almost at 14 early on at 3000 RPM it stays that way until the car begins giving the engine more gas at which point it drops down to a nice solid 12.5 AFR. It begins to taper and drop off toward redline.



Okay this is the money maker! This is a comparison between a stock untuned run and a -15 tuned run. You will note there is both a hp and torque gain throughout the entire rev range! Its also much smoother dropoff towards redline.

So what did I learn? Well I learned that between 3000 - 4000 RPM I should lean it out slight less than -15, probably in the -5 to -10 range, this way it won't be spiking to 14 so early on. I also learned that although -15 is seemingly the lucky number of choice for 4500 - 5500 RPM, it needs more at 6000+ I feel anything between -18 to -20 should be good, you could go more, but you don't want -30 trust me.

I also learned that the car is much faster than before, it bogged down on the first run, but after dropping it to -15 it pulled better. I also noticed the car responds faster and pulls all the way to redline, I have numbers to prove it too.

Bottom line, I *HIGHLY* recommend Adrenalin Motorsports.. the staff was incredible, always helpful, always willing to let me look at their VW/Audi projects and they listened to feedback whenever given. They let us use Kris' OBD-II during the runs and they also re-ran the car when numbers seemed odd, like during Pat's runs... It was a great day and I look forward to getting some new noise-makers so I can go back!

Oh, and as always.. YMMV!

Korey
* Registered users of the site do not see these ads.
Longshot is offline   Reply With Quote
Old 11-18-2001, 09:52 PM   #2
tulit
Scooby Specialist
 
Member#: 338
Join Date: Sep 1999
Chapter/Region: E. Canada
Location: Toronto
Vehicle:
09 STi
White

Default

Hi Korey

Nice results.


With regard to the AFC not working. I think everyone agrees that it does infact work. The problem though is, most feel that over time the ECU negates any changes you made on the AFC.

What would be interesting is if you left the AFC the way it was when you left the dyno. Go back a few weeks later (after not touching the AFC AT ALL) and rerun on the dyno. See if the AF ratio chart stays fairly the same, or if it goes back to your original "untuned" AF ratio...


That would tell us for sure whether the AFC works in the long run or not....
tulit is offline   Reply With Quote
Old 11-18-2001, 10:00 PM   #3
Ripper
Scooby Specialist
 
Member#: 7774
Join Date: Jun 2001
Location: Everything is cat rape.
Thumbs up

Well jeez.... can't argue with that evidence. Very well put together Longshot. Time for me to invest I guess. You get a gold star for the day.
Ripper is offline   Reply With Quote
Old 11-18-2001, 10:04 PM   #4
Kevin Thomas
Street Racing Instructor
Moderator
 
Member#: 110
Join Date: Jul 1999
Location: 1997 OBS, 1996 SVX, 1988 RX
Vehicle:
1989 1989 XT6

Default Nice

Longshot,


This is excellent information. Thanks for taking the time out to show us all the results of your testing and tuning. We REALLY need a dyno section ASAP.

Perhaps someone can host a dyno site for all of us to look at and enjoy.

This makes me want to go to the dyno and tune asap. Thanks again. I can look at this all day long.
Kevin Thomas is offline   Reply With Quote
Old 11-18-2001, 10:17 PM   #5
Ripper
Scooby Specialist
 
Member#: 7774
Join Date: Jun 2001
Location: Everything is cat rape.
Default

Ditto to what Kevin said. Wouldn't take long to have dyno proven results for every mod combination possible with all the people here... so long as we can all afford to go to an AWD dyno test.
Ripper is offline   Reply With Quote
Old 11-18-2001, 11:10 PM   #6
WRSport
Scooby Specialist
 
Member#: 2060
Join Date: Aug 2000
Chapter/Region: BAIC
Location: Bay Area
Vehicle:
00 2.5RS Coupe
01 black boxster hardtop

Default

I thought the issue was after time the s-afc became useless because of the MY2000-1 ECU's ability to learn.

But still, nice to see quanitfied results.
WRSport is offline   Reply With Quote
Old 11-18-2001, 11:32 PM   #7
jagcars26
Scooby Specialist
 
Member#: 2394
Join Date: Sep 2000
Chapter/Region: MAIC
Location: Bel Air Md.
Vehicle:
2005 Legacy GT wagon
2009 Forester X

Default

Nice job dude,,but like tulit said, the long term is the crux of an afc on the 2000/2001 models.
One of these days somebodys goin to crack that gd ECU!
Rudy
jagcars26 is offline   Reply With Quote
Old 11-18-2001, 11:34 PM   #8
HndaTch627
Scooby Guru
 
Member#: 6551
Join Date: May 2001
Chapter/Region: MWSOC
Location: Carol Stream, IL
Vehicle:
'01 GC8 Dinged STM
'09 Concours 14 ABS Black

Default

that's a requirement of OBD-II vehicles...they have to be able to "learn" how to run them clean...IIRC the mandatory date was by year 2k....just like year '02 has mandatory PCV flow monitoring and flash rom capability on the ECU's.

Jeremy
HndaTch627 is offline   Reply With Quote
Old 11-19-2001, 12:09 AM   #9
webkris
NASIOC Supporter
 
Member#: 70
Join Date: Jul 1999
Chapter/Region: NESIC
Location: Long Beach, CA
Vehicle:
I sold WRX to buy
Dodge Neon Rally Car

Default

hmm...

Quote:
able to "learn" how to run them clean...
It would make no sense to me if the ECU was tuning "around" the AFC. Once in open loop mode - (The only place where the ECU gets tricked by the AFC...) Korey was running better air/fuel then stock, using less gas then stock. As long as the O2 sensors see that - I don't see why the ECU would tune around it.

Not saying it couldn't happen, but I'm not sure why...

I'm also basing this "assumption" on spark numbers that got from OBD2 while data logging his last run. Notice the ECU provided a great spark advance while under load - increasing to redline. If the car thought "something was up" with the AFC - it may have changed timing. This also makes me question the value of an ITC...

We'll have to wait to get Jim's car on the rollers for confirmation that the ITC is worth it's CE light.
Lots of data - some answers - more questions.

- Kris
Attached Images
File Type: jpg korey_bestrun_spark.jpg (44.4 KB, 1421 views)
webkris is offline   Reply With Quote
Old 11-19-2001, 12:11 AM   #10
Impreza Rider
Scooby Specialist
 
Member#: 756
Join Date: Jan 2000
Chapter/Region: MAIC
Location: Ashburn, Va
Vehicle:
2003 Legacy L wagon
2009 Kawasaki C14

Default

I don't think that the issue was if they did anything, it's when they worked.

On the MY98-99 RS's, they are able to fool the ECU into richening, or leaning out the fuel at any throttle position.

On the MY00+ the SAFC only works at WOT, when the ECU is going off an internal map. At all other times, the ECU is relying on data from all the emission sensors and what not. Since dyno runs are done at WOT, of course you're going to see a difference with the numbers. I bet if you installed an AFC, and allowed the ECU to learn for a couple of weeks, did a dyno run at 50% throttle, and then took it off, let it learn for a couple more weeks, then did another dyno run, you wouldn't see a difference in the numbers

Still, kudos to you for going out and having this done.
Impreza Rider is offline   Reply With Quote
Old 11-19-2001, 12:20 AM   #11
Eric SS
Sooby Guru
 
Member#: 1914
Join Date: Jul 2000
Chapter/Region: SWIC
Location: 2013 335i, 2011 G37 coupe
Vehicle:
2000 2.5RS w/ EJ22T
swap and N20. gone. : (

Default

Like everyone said, the issue is not that the S-AFC doesn;t work on MY00+ cars. It's the fact that over time, the computer remaps the discrepency between what the sensors tell it and what it does, therefor negating the S-AFC after a while.

I would suggest doing a dyno run with no S-AFC, then setting the S-AFC.

Then. come back in a couple weeks and run it again with the same settings and then putting the S-AFC to 0 again and see what you get.

Eric
Eric SS is offline   Reply With Quote
Old 11-19-2001, 12:38 AM   #12
Kevin Thomas
Street Racing Instructor
Moderator
 
Member#: 110
Join Date: Jul 1999
Location: 1997 OBS, 1996 SVX, 1988 RX
Vehicle:
1989 1989 XT6

Default Longshot or anyone

Excuse me Longshot,

I'm not trying to jump on your thread but do you or anyone else know of a dyno shop in the Delaware Valley that has the O2 sensor tuning capabilities and graphing like the place you got yours done? I'm really impressed with this type of dyno tuning. It seems really helpful. Thanks!

BTW: I was thinking about your shop but I believe they are in Tennessee.
http://tomllong.tripod.com/adrenalinemotorsports.html
Kevin Thomas is offline   Reply With Quote
Old 11-19-2001, 07:52 AM   #13
wac
Scooby Specialist
 
Member#: 689
Join Date: Dec 1999
Chapter/Region: NESIC
Location: Lebanon, NH, USA
Vehicle:
2005 Outback 2.5 XT
Champagne Gold Opal

Default

In light of everyone's arguments above, I hope someone can help me out here... (long)

1. MAF-based cars run in closed loop* relying primarily on the O2 sensor. The ECU will "learn" over any sensor corrections.
2. MAF-based cars run in open loop* relying almost exclusively on the MAF sensor. AFAIK, the ECU will not "re-learn" sensor corrections.
3. MAP-based cars run in closed loop* relying primarily on the O2 sensor. The ECU will "learn" over any sensor corrections.
4. MAP-based cars run in open loop* relying almost exclusively on the MAP sensor. I have not seen evidence that the ECU "re-learns" sensor corrections. Where's the proof? (Besides getting Longshot to spend more of his own money to provide the proof for you.)

*Closed loop is defined as low-load conditions, and is generally seen when the throttle is less than 20%. Open loop is defined as high-load conditions, and is generally seen when the throttle is greater than 20%. This is what I've seen on both MAF-based and MAP-based cars.

I'm wondering why a number of people think that the MAP car would run such a differently program compared to a MAF car. Many people have complained that fuel corrections on a MAP-based car is lost over time due to the ECU re-learning over sensor corrections. But you must consider that MAP-based tuning is usually performed by people reading rear O2 sensor voltages, while MAF-based tuning is always performed by people reading front O2 sensor voltages. Not exactly apples-to-apples comparisons, are they?

I've tried to do MAF-based tuning using the rear O2 sensor, and I've encountered the same results as those with MAP cars. The catalytic converter adds as much as 2-3 seconds of delay to AFR reading at the rear sensor, and it also creates a large discrepancy between the front and rear O2 sensor readings. S-AFC corrections of less than 20% appear to have little effect on the rear sensor, while the front O2 sensor will noticeably react to 3-5% changes.

For now, webkris and Longshot have done plenty of independent experiments for me to believe their theory that the ECU does not learn over MAP corrections in open-loop mode. They've datalogged with an OBD-II scanner, while most people have only tuned with rear O2 sensor readings. My infrequent experiences with MAP-based cars seems to support their theory as well.

Kevin: it's www.adrenalinmotorsport.com There's also a new 4WD dyno at Curry's Auto Service in VA. www.currysauto.com

-WaC
Wayne
(Stoking the fire once again)
wac is offline   Reply With Quote
Old 11-19-2001, 08:51 AM   #14
subarumantoo
Scooby Specialist
 
Member#: 3257
Join Date: Dec 2000
Location: Houston, TX
Vehicle:
2000 ImprezaRS
Blue Ridge Pearl

Default My two cents

Open loop: The engine is running without looking at the O2 sensor. This is usually because the sensor is not warmed up enough to make voltage. The engine operates on fixed values until the sensor is hot enough to make voltage. (The reason it makes voltage is because there is a difference in the amount of oxygen on the outside of the sensor as compared to the exhaust side of the sensor.)
Using the rear sensor: Please understand that the rear sensor cannot really give you any indication of the air/fuel ratio coming out of the engine because the catalytic convertor removes a significant portion of the unused oxygen in the exhaust stream. The reason the have a rear sensor is to determine how well the catalytic convertor is cleaning the exhaust. They may actually "tune" the air/fuel ratio just to increase the efficiency of the catalytic convertor. In order to do that, they must have some feedback as to how well the convertor is working...
subarumantoo is offline   Reply With Quote
Old 11-19-2001, 10:48 AM   #15
Longshot
Scooby Specialist
 
Member#: 2359
Join Date: Sep 2000
Chapter/Region: NESIC
Vehicle:
2001 Impreza 2.0 WRS

Default

Okay.. first of all I was not posting this for the ECU override myth, I was posting it for the ppl that say the AFC does nothing.

You guys need to understand once a myth starts it only gets worse.. I had someone tell me for 15 minutes at the dyno that the AFC does nothing on his 2000 RS... and I just proved it does in fact do something, its like the telephone game.. you start out by telling someone something doesn't work at certain points and twenty people later they say it doesn't work at all... simple as that.

I am pretty sure the AFC does not work in low throttle (closed loop) mode, but since I am not concerned about my idle AFR I will continue to tune the AFC as such.

Also, as Wayne pointed out it works above 20% throttle, and 20% throttle happens when you accelerate on an on-ramp or go to pass someone, I noticed this morning under my normal to work cruise that the AFC was correcting exactly when it should be.. like when I get on the highway.

Korey
Longshot is offline   Reply With Quote
Old 11-19-2001, 01:52 PM   #16
inpreza kid
Scooby Specialist
 
Member#: 3334
Join Date: Dec 2000
Location: Calgary, Alberta, Canada
Default

i think the ecu relearning the settings is just a myth that someone started on i-club. i do firmly believe that a afc does work and hold its settings.
inpreza kid is offline   Reply With Quote
Old 11-19-2001, 02:15 PM   #17
10th Warrior
Scooby Specialist
 
Member#: 2230
Join Date: Aug 2000
Chapter/Region: MWSOC
Location: Toronto these days
Vehicle:
2000 2.5RS
Silverthorn, PGT #671

Default

all cars when started are in open loop. all this means is that the ECU is ignoring the O2S and delivering fuel/timing off of preset tables stored in memory. btw, this is usually a rich a/f to warm the engine quicker. once the engine is warm, as determined by the thermostate opening usually AND after a preset amount of time has passed (this can be over a minute or more in some cars, on the ej25 cars at least, it seems to be negligible and temp is the determining factor) the ECU enters closed loop. this means that the ECU now uses the 02S to adjust the a/f. however, under high load, open throttle conditions, the ECU will say damn the O2S and create a rich, power producing mixture, as shown in the graphs above. anyway, i hope this clears up any issues on open/closed loop operation.

longshot-thanks for posting this info. its really nice to see hard data for a change.
10th Warrior is offline   Reply With Quote
Old 11-19-2001, 08:47 PM   #18
munkis
Scooby Guru
 
Member#: 1847
Join Date: Jul 2000
Chapter/Region: Tri-State
Location: brokenmotorsports.com
Vehicle:
Team Broken: V6 GF
rallyarmor.com

Default

subarumantoo and 10th warrior get an A+ on their "closed loop and what is it" descrptions.

Longshot, great job documenting all of this, you da man! hehe, *checks wallet for money for safc*

Jay McDade
Auto Tech--Lincoln/Mercury/Jaguar
www.hometown.aol.com/impreza25rs2000
munkis is offline   Reply With Quote
Old 11-20-2001, 09:42 AM   #19
EJ25
Scooby Newbie
 
Member#: 10768
Join Date: Oct 2001
Location: Canada... bent and broken 2000RS Rally
Default Thanks Longshot

Thanks man,

I have a 2000 RS and tuned my S-AFC to what you said. It got rid of a hesitation in the car and it also pulls slightly harder to red-line. My sube is setup for performance rallying, I'll be testing it this weekend at the Tall Pines.

Thanks for the info.
EJ25 is offline   Reply With Quote
Old 11-20-2001, 09:50 AM   #20
JGard
pooptastic
 
Member#: 1904
Join Date: Jul 2000
Chapter/Region: TXIC
Location: Austin, TX
Vehicle:
2014 Lexus IS 350
01 Miata red

Default

wow...all of this makes me really wish that my AFC wasn't stolen...

...now I have to decide if one is theoretically worth $600 or so... ugh...
JGard is offline   Reply With Quote
Old 11-20-2001, 12:16 PM   #21
skeptik
Scooby Newbie
 
Member#: 3055
Join Date: Nov 2000
Location: San Diego, CA
Vehicle:
my04 sti
blue and gold

Default Split Second Programmable Map

jgard and others -

you may want to check this thread for a more reliable and cheaper alternative. don't need to be boosted to take advantage of it.

mark
skeptik is offline   Reply With Quote
Old 11-20-2001, 01:02 PM   #22
Pinochle
Scooby Guru
 
Member#: 638
Join Date: Dec 1999
Chapter/Region: Tri-State
Location: http://www.djforums.com
Vehicle:
93 L, 00 RS, 04 TS
pat + nat

Default

Anyone get a visit from the evil li'l CEL guy. I did last night.

P.
Pinochle is offline   Reply With Quote
Old 11-20-2001, 01:50 PM   #23
inpreza kid
Scooby Specialist
 
Member#: 3334
Join Date: Dec 2000
Location: Calgary, Alberta, Canada
Default

i've never had any problems with CE lights with the afc. the itc on the other hand................
inpreza kid is offline   Reply With Quote
Old 11-20-2001, 03:01 PM   #24
Jewbaru
Scooby Specialist
 
Member#: 1994
Join Date: Jul 2000
Location: "Teh Hebro Town"
Vehicle:
2013 Impreza WRX
WRB

Default Yea, I'm turbo, but I have my questions...

This intrests me considering I'm going to working with fuel tuning soon... not with the S-AFC tho.

My question, when EXACTLY does the ECU enter open loop aside from warm-up?

I say this because I have an aftermarket O2 sensor welded into the stock header (just ahead of my up-pipe) with an A/F guage hooked up to it. The ECU can handle 3psi(4.8v) before it throws a hissy fit and causes all kinds of problems, so my car is clamped at around 4.7v with a zener diode. Well, when I'm driving in say 4th gear, and I give it a good jab, the A/F still reads like the ECU is correcting based off of the O2 sensor untill over 3psi.

Under normal cruise it jumps around so quickly it looks like as many as 4 leds are lit at one time (Autometer). When I hit it(maybe 35% throttle), and it starts building boost, it still reads the same, only it jumps a little rich (because the RRFPR kicks in). The ECU still fights the RRFPR and the lights still jump around. BUT, as soon as it hit's 3psi, or if I'm at WOT, the guage reads a solid rich, 2 leds lit, and not even fluxuating(sp?).

So, what is a high load condition for the engine? Is there a chance that on the 2000+s high load is a little later than it would be on a 98/99 considering the incredibly complex front O2 sensor?
Jewbaru is offline   Reply With Quote
Old 11-20-2001, 03:26 PM   #25
HndaTch627
Scooby Guru
 
Member#: 6551
Join Date: May 2001
Chapter/Region: MWSOC
Location: Carol Stream, IL
Vehicle:
'01 GC8 Dinged STM
'09 Concours 14 ABS Black

Default

Joel...only 2 other times....WOT and limp home mode...otherwise it will be under closed loop operation.

Jeremy
HndaTch627 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
For all you disbelievers out there - RE SOHC engine swap! 2.5GT Normally Aspirated Powertrain 5 12-10-2001 11:03 AM
('93-'01) For all you WRX owners, how tall are you??... WhatRULookinAt Impreza Forum 22 10-24-2001 10:41 PM
A custom license plate for all you new WRX owners, get it while you can. Andrew Bay Area Impreza Club Forum -- BAIC 2 03-08-2001 09:06 AM
Turbo Setup Idea For all you Turbo designers!!!! Everyone tell me what you think Turk General Forum Archive 14 07-18-2000 08:39 AM
Turbo Setup Idea For all you Turbo designers!!!! Everyone tell me what you think Turk Technical Forum Archive 3 07-17-2000 09:24 AM


All times are GMT -4. The time now is 09:36 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.