Welcome to the North American Subaru Impreza Owners Club Thursday April 17, 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 02-15-2012, 07:23 PM   #1
WrXtaCy2003
Scooby Specialist
 
Member#: 85036
Join Date: Apr 2005
Chapter/Region: MWSOC
Vehicle:
2013 PBP sti ltd
05 LGT 35r 30psi..busted

Default Tuning SD With ATR

So I tuned speed density on my aem for three years. There was two "fuel maps", a boost-fuel curve, and the "actual" fuel map. So, what I would do first is set the boost-fuel curve to a value to get damn near close to the AFR I wanted at that boost pressure. Then I would use the fuel map, which is MRP on the y-axis and RPM on the x-axis, to adjust the afr based on how it changed with rpm. The timing map also references MRP on y-axis vs rpm on x-axis. So if I wanted to be tuning 20psi, I would simply go to the 20psi y-axis on the timing or fuel map and adjust accordingly.

I'm a bit confused as to how you go about tuning SD with ATR. I read the COBB SD tuning guide last night. So Let me start with an example. My car right now is tuned perfectly everywhere up to 20psi on a big maf. Meaning my load axis, timing table, and fuel table is perfect the way it is. If I wanted to start tuning SD, I would first use the SD VE Estimated (MAF) monitor to get an idea of my VE table, covering as much of the table as possible. After I get repeatable results, and make the corresponding changes to my VE table, I would then switch to full SD, and see how my fueling is looking at idle, cruise, etc, correcting as I go, until I start getting into boost areas. So my question begins here.... When you change the VE table, it ALSO changes the corresponding load value. So say my fueling was only off 1AFR from where I wanted to be, so then I begin to change my VE to get my AFR back into check, but then my load values have changed, so now what if my fuel map is requiring a different AFR at this new load value? It is essentially now combating (or maybe helping) get my AFR where I wanted to be by originally changing the VE table. So essentially my question becomes, when do you stop tuning the VE table, and start tuning the fuel map and timing maps (these have to be last, because if your tuning the VE table, then your load values, say for 15psi of boost will constantly be changing, which is not good when trying to tune the timing or fuel tables)?

I feel like what I would do is set the entire boosted portions of the fuel map to some arbitrary value, say 12 afr, then change VE to get very close to the fueling you want at each boost level, then change the fuel map as required to have a nice steady AFR across the whole rpm range (or have it taper, or whatever you want it to do) using the fuel map.

^^^this is essentially what's called hybrid boost-fuel tuning in the AEM world. The boosted portions of the fuel map are all the same value, then you go to the boost-fuel curve, which allows you to increase/decrease the amount of fuel injected as a percentage per psi of boost. Then when your damn near where you want your afr to be at that boost level, you then perfect it throughout the rpm range using the fuel map.

The difference between the AEM and ATR in terms of SD is the AEM always referenced MRP on the y-axis for both fuel and timing. So this value never changed, unless you changed your boost level. But with the ATR, when you tune the VE map, it changes the corresponding load value for the same exact boost pressure, up until you decide to stop tuning the VE table for that boost pressure.

If I had to go about it, this is what I would do. It makes sense to me, and I'm experienced in it.

Cobb please let me know if this would work, my logic says that it would.

Thanks.

DK
* Registered users of the site do not see these ads.
WrXtaCy2003 is offline   Reply With Quote
Old 02-15-2012, 07:24 PM   #2
WrXtaCy2003
Scooby Specialist
 
Member#: 85036
Join Date: Apr 2005
Chapter/Region: MWSOC
Vehicle:
2013 PBP sti ltd
05 LGT 35r 30psi..busted

Default

ppphheeewww.....lol

Last edited by WrXtaCy2003; 02-15-2012 at 07:30 PM.
WrXtaCy2003 is offline   Reply With Quote
Old 02-15-2012, 07:32 PM   #3
WrXtaCy2003
Scooby Specialist
 
Member#: 85036
Join Date: Apr 2005
Chapter/Region: MWSOC
Vehicle:
2013 PBP sti ltd
05 LGT 35r 30psi..busted

Default

and I guess option #2 would be to leave my fuel map the way it is now, and tune my VE table to get my desired AFR's everywhere, then start tuning the timing, now that my load values would be consistent for a desired boost level.


DK
WrXtaCy2003 is offline   Reply With Quote
Old 02-15-2012, 09:55 PM   #4
Cobb Tuning
NASIOC Vendor
 
Member#: 4803
Join Date: Mar 2001
Location: Austin, DFW, Portland, SOCAL
Default

Quote:
Originally Posted by WrXtaCy2003 View Post
I feel like what I would do is set the entire boosted portions of the fuel map to some arbitrary value, say 12 afr, then change VE to get very close to the fueling you want at each boost level, then change the fuel map as required to have a nice steady AFR across the whole rpm range (or have it taper, or whatever you want it to do) using the fuel map.
You could do that, but a more direct approach would be to simply log "Commanded Fuel Final", which is the "targeted" open loop fueling value after all compensations, and reference that against your measured tailpipe AFR, then adjust VE to correct the discrepancy.

Quote:
Originally Posted by WrXtaCy2003 View Post
The difference between the AEM and ATR in terms of SD is the AEM always referenced MRP on the y-axis for both fuel and timing.
AEM's system is not a true "speed density" implementation what-so-ever. It's a very simple injector on-time table -- at Y RPM and X MAP, open injector for Z amount of time. We are doing a true Volumetric Efficiency calculation to determine the mass of air entering the engine. We're calculating MAF using all required variables instead of measuring it

This is one of the reasons there is no need for the background Boost Comp table that exists in AEM. AEM is completely blind to the actual fueling change necessary with boost changes (from say 12psiG to 24psiG). It relies entirely on either a Boost Comp table or primary fuel table that is setup as such. A true SD/VE calc, however, simply "knows" that airflow is 2x when boost is 2x because pressure is an inherent part of the calculation (PV=nRT !).

Quote:
Originally Posted by WrXtaCy2003 View Post
So this value never changed, unless you changed your boost level. But with the ATR, when you tune the VE map, it changes the corresponding load value for the same exact boost pressure, up until you decide to stop tuning the VE table for that boost pressure.
Yes, load will change with VE table changes. The VE table is really one of the "first" items to address on the tune. Once the VE table is appropriately setup for the car, tuning is narrowed to adjusting the actual fuel and timing tables to make the changes as desired. By and large you will likely find that the VE table is relatively unchanged between "low" and "high" boost -- the last SD custom tune I did used essentially identical VE values between 26psiA and 40psiA.


Long story short - think of the VE table as the MAF curve as their end function for your purposes is identical. Anytime MAF is changed, be it through a VE/SD calc'd version or a good-ole MAF curve, load changes. If you would normally change the MAF curve to fix X/Y/Z tuning problem, you now would change the VE table instead to impact the same result (change in MAF g/s and thus load).

Hope this helps. Lemme know if I can be of assistance in any other way!

Cheers

Lance
Cobb Tuning is offline   Reply With Quote
Old 02-15-2012, 10:43 PM   #5
WrXtaCy2003
Scooby Specialist
 
Member#: 85036
Join Date: Apr 2005
Chapter/Region: MWSOC
Vehicle:
2013 PBP sti ltd
05 LGT 35r 30psi..busted

Default

Quote:
You could do that, but a more direct approach would be to simply log "Commanded Fuel Final", which is the "targeted" open loop fueling value after all compensations, and reference that against your measured tailpipe AFR, then adjust VE to correct the discrepancy.
What I think your saying here is that I should set my fuel map up to the desired AFR that I would like to see on my wideband, then adjust my VE map to attain this value? Correct? (this may sound goofy because you might be thinking, well that's what you should have been doing when tuning by MAF anyways, But i'm THAT guy who doesn't car if his Wideband AFR is 3pts off from his fuel map, lol. I've yet to have issues doing it this way, so I got stuck in my habits)

Quote:
AEM's system is not a true "speed density" implementation what-so-ever. It's a very simple injector on-time table -- at Y RPM and X MAP, open injector for Z amount of time. We are doing a true Volumetric Efficiency calculation to determine the mass of air entering the engine. We're calculating MAF using all required variables instead of measuring it

This is one of the reasons there is no need for the background Boost Comp table that exists in AEM. AEM is completely blind to the actual fueling change necessary with boost changes (from say 12psiG to 24psiG). It relies entirely on either a Boost Comp table or primary fuel table that is setup as such. A true SD/VE calc, however, simply "knows" that airflow is 2x when boost is 2x because pressure is an inherent part of the calculation (PV=nRT !).
I completely understand. And being a physicist by trade I like your implementation better!

Quote:
Yes, load will change with VE table changes. The VE table is really one of the "first" items to address on the tune. Once the VE table is appropriately setup for the car, tuning is narrowed to adjusting the actual fuel and timing tables to make the changes as desired. By and large you will likely find that the VE table is relatively unchanged between "low" and "high" boost -- the last SD custom tune I did used essentially identical VE values between 26psiA and 40psiA.
Referencing the bolded part ^^^... this is my confusion exactly. What are you classifying as appropriate? Let's say I set my fuel map up by making all the values in the fuel table the EXACT value I want to read out my wideband. Then I start tuning my VE table. Let's say i'm targetting 15psi of boost. So I do a pull, find out I have perfect VE fueling at peak boost/torque but as I climb in rpm, at the same boost level, it gets richer (i.e. my fuel map was targeting 12.0 afr but i'm getting 11.0 AFR out my wideband) should I change my VE table to bring my AFR's back to 12.0?

I may have figured it out on my own so stay with me here...

This is what the SD tuning guide says "You may be tempted to simply manipulate the VE table to hit the fueling target you desire for a given MAP/RPM area regardless of the commanded fuel final (and the primary open loop fueling table). While this is certainly possible, it does have a few downsides. First, tuning this way would result in VE values that are not representative of actual. That is, you could not easily compare them to other tunes. It can be quite useful to compare VE tables across tunes as it gives you an idea of VE changes with different mods (and cam timing)."

I think I figured out your logic of the above bolded sentence, which I didn't so much understand before, but correct me if i'm wrong, here it goes...

So what you guys are saying in the guide is that I should target my wideband to read the commanded fuel final by adjusting the VE table. This way I am ACCURATELY representing the VE of the motor, therefore if changes in say AVCS tuning make my car leaner, I have thus increased the VE of the motor, since I know I had previously ACCURATELY calibrated my VE table, by matching my wideband to the commanded fuel final (which may be different from the primary fuel maps afr)?

***as a side not, at WOT I'm assuming the primary fuel map afr vs commanded fuel final values are identical, assuming no long term fuel trims are being added in this range? (sorry I've never actually logged commanded fuel final, which I will be doing from now on)

^^^^Did I figure it out?

BIG THANKS again!

Dustin

P.S. Thanks for your response to my PM! I really appreciated it! I love the idea of adjusting the throttle tables to target, say only 45% TPS, at 100% accelerator angle. I think this way, I can accurately use some road dyno software to target the 0-15psi range of my timing maps. Even though PTB pressure doesn't seem to stay the same across an rpm range even if the throttle opening angle is constant, I think as long as I can floor it, get a consistent say 50% throttle opening angle, which than say producing 1psi at peak but maybe creeps to 3psi at redline...As long as it's consistent, I can actually tune the timing tables using road dyno software. So, I'll first do 3 back to back runs (using the previous mentioned method) and see if the road dyno software gives me consistent readings. If it does, I'll start tuning away. Thanks again, that was a brilliant idea!
WrXtaCy2003 is offline   Reply With Quote
Old 02-16-2012, 12:12 AM   #6
Cobb Tuning
NASIOC Vendor
 
Member#: 4803
Join Date: Mar 2001
Location: Austin, DFW, Portland, SOCAL
Default

Quote:
Originally Posted by WrXtaCy2003 View Post
What I think your saying here is that I should set my fuel map up to the desired AFR that I would like to see on my wideband, then adjust my VE map to attain this value? Correct? (this may sound goofy because you might be thinking, well that's what you should have been doing when tuning by MAF anyways, But i'm THAT guy who doesn't car if his Wideband AFR is 3pts off from his fuel map, lol. I've yet to have issues doing it this way, so I got stuck in my habits)
I don't stress it all of the time in MAF mode, either But technically yes, you should be able to get them to line up reasonably well, or at least follow some kind of consistent trend. So in that regards, VE is the same principle -- if you're only worried about what's coming out of the tailpipe in OL, get a decent VE table setup and do your dirty work in the primary fuel table. Or, be anal and get the VE table "right" through iterative tweaks so that the fuel table becomes a close representation of the tailpipe. It's a totally pick-your-poison situation


Quote:
Originally Posted by WrXtaCy2003 View Post
So what you guys are saying in the guide is that I should target my wideband to read the commanded fuel final by adjusting the VE table. This way I am ACCURATELY representing the VE of the motor, therefore if changes in say AVCS tuning make my car leaner, I have thus increased the VE of the motor, since I know I had previously ACCURATELY calibrated my VE table, by matching my wideband to the commanded fuel final (which may be different from the primary fuel maps afr)?
Yep, this is technically the more accurate way to do it and the one I would encourage, but again, there's more than one way to skin the cat as discussed above

Quote:
Originally Posted by WrXtaCy2003 View Post
***as a side not, at WOT I'm assuming the primary fuel map afr vs commanded fuel final values are identical, assuming no long term fuel trims are being added in this range? (sorry I've never actually logged commanded fuel final, which I will be doing from now on)
Good assumption, reasonably correct. One big discrepancy you will see, especially on a big turbo'd FMIC car in MAF mode, is the spool "rich dip". It's looks like an inherent compensation that you can see happen with a large rich dip in Commanded Fuel Final during that time. And yes, we hope to figure out specifically where that comp is some day, but I have found the issue to at least be greatly reduced in SD mode. Bill and I were able to identify a table (will be defined in a future update) on the 2L ECUs that limits the maximum rich AFR that can be targetted one day when I noticed a large discrepancy in Commanded Fuel Final compared to the map values (which can be logged as well to observe the exact discrepancy at any given time) during a custom tune.

Quote:
Originally Posted by WrXtaCy2003 View Post
^^^^Did I figure it out?

BIG THANKS again!

Dustin

P.S. Thanks for your response to my PM! I really appreciated it! I love the idea of adjusting the throttle tables to target, say only 45% TPS, at 100% accelerator angle. I think this way, I can accurately use some road dyno software to target the 0-15psi range of my timing maps. Even though PTB pressure doesn't seem to stay the same across an rpm range even if the throttle opening angle is constant, I think as long as I can floor it, get a consistent say 50% throttle opening angle, which than say producing 1psi at peak but maybe creeps to 3psi at redline...As long as it's consistent, I can actually tune the timing tables using road dyno software. So, I'll first do 3 back to back runs (using the previous mentioned method) and see if the road dyno software gives me consistent readings. If it does, I'll start tuning away. Thanks again, that was a brilliant idea!
No problemo, best of luck and lemme know how it goes

Cheers

Lance
Cobb Tuning is offline   Reply With Quote
Old 02-16-2012, 12:30 AM   #7
WrXtaCy2003
Scooby Specialist
 
Member#: 85036
Join Date: Apr 2005
Chapter/Region: MWSOC
Vehicle:
2013 PBP sti ltd
05 LGT 35r 30psi..busted

Default

Lance, you're the man!

Thanks for everything!

DK
WrXtaCy2003 is offline   Reply With Quote
Old 03-13-2013, 03:14 PM   #8
wgr73
Scooby Specialist
 
Member#: 232458
Join Date: Dec 2009
Chapter/Region: SWIC
Location: Las Cruces, NM
Vehicle:
2008 STi (OBP)
CAMTuned

Default

Yes, I know I'm over a year late, but....

Sweet thread. Some very good points in here for the SD tuners! Thanks everyone.
wgr73 is offline   Reply With Quote
Old 03-13-2013, 03:20 PM   #9
endrswrd
Scooby Newbie
 
Member#: 323908
Join Date: Jun 2012
Chapter/Region: MWSOC
Location: Dayton Ohio
Vehicle:
2013 BRZ ltd
ISM

Default

SD tuning is awesome because you can blow a boost pipe off and drive home no problems! The only weirdness is location of IAT and people argue about that till the cows come home!

I hope to get into SD tuning some day!
endrswrd 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
Tuning SD on Version11 2008 STI RSMike Open Source Reflashes 3 09-21-2011 12:30 AM
FS : 2002 Honda Ruckus 150cc GY6 swap with ATR kit, mounts , front disc ETC. billy boi Tri-State Area Private Classifieds 18 12-09-2010 07:30 AM
Anyone near SD with a new 5spd? tom@kartboy Legacy Forum 1 08-22-2004 12:03 AM
Anybody working with ATR? Wrecked WRX South East Region Forum 0 09-13-2001 03:54 PM


All times are GMT -4. The time now is 03:08 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.