long term fuel trims in open loop ???

jays05 · 07-28-2006, 06:33 AM

Over time my WOT AFR's have been getting richer and richer, and a simple ECU reset has always fixed the issue. I was looking into it some more the other night (before doing an ecu reset) and I see that I have some big long term fuel trims when at WOT (up to +12.16). The long term fuel trims take my AFR's from high 11's to low 10's.

How can this happen in open loop? I'm guessing that somewhere near the cl/ol transition my MAF scaling is off, and it's just carrying the fuel trims over from closed loop to open loop? Or am I missing something big here?

My tune looks "happy" otherwise with my long term knock learning maps having small positive values all across the table.

Christian. · 07-30-2006, 08:42 PM

Quote:

Originally Posted by nhluhr

I think it's mostly gonna be due to an incorrectly calibrated MAF.

Agreed, what intake or MAF housing are you running?

Christian.

***JDM-STI*** · 07-31-2006, 02:53 PM

Scott Siegel has been fighting this on my car for about 2 1/2 months now. It is more than intake calibration. We have tried several kinds of different intake set ups and none of them corrected the problem. Seems to mostly occur on mid/late 2005 year models...????
This is a Cobb and Ecutek issue. We have seen cases with both. My car won't go into open loop till 3V at the MAF instead of 2.5V like its supposed to. Not sure what the answer is at this point.

jays05 · 07-31-2006, 05:36 PM

I'm running the perrin bigmaf with the perrin rotated mount intake. My intake calibration seems dead on but I tried adding a couple % on the top end to see if it makes a difference.

I've been wondering if this is another goofy byproduct of my removing the rear o2. I really need to get another bung welded on.

***JDM-STI*** · 07-31-2006, 06:14 PM

Quote:

Originally Posted by jaygoesfast

I'm running the perrin bigmaf with the perrin rotated mount intake. My intake calibration seems dead on but I tried adding a couple % on the top end to see if it makes a difference.

I've been wondering if this is another goofy byproduct of my removing the rear o2. I really need to get another bung welded on.

Nope! I still have my rear O2.
I run the Perrin big MAF and my intake calibrations were dead on as well. Seems to be some type of flash issue.

Merchgod · 07-31-2006, 06:54 PM

It happens because patterns of correction noticed by the ECU in closed loop are migrated to your open loop fueling. That is why a reset fixes it. The ECU assumes that if has to keep adding, say 10% of fuel in closed loop to hit 14.7, that you are probably running leaner in open loop as well and this is added to your open loop fueling.

WolfPlayer · 08-01-2006, 08:34 AM

Quote:

Originally Posted by Merchgod

It happens because patterns of correction noticed by the ECU in closed loop are migrated to your open loop fueling. That is why a reset fixes it. The ECU assumes that if has to keep adding, say 10% of fuel in closed loop to hit 14.7, that you are probably running leaner in open loop as well and this is added to your open loop fueling.

I agree. OEM ECUs are notorious for applying a learned fuel correction in open loop based off of extrapolation. People often think that open loop means no correction. That is just not true. I remember hacking the GM code back in 2000 to remove this 'feature'. Open loop should be open loop for us hotrodders

. However, in no way is that guaranteed with a stock ECU.

Jay, are you still running around without a rear O2 sensor? As we have discussed here, the rear O2 definitely affects AFRs.

t

ZuMBLe · 08-01-2006, 08:50 AM

I thought I was going crazy or my wideband was off! I saw this also. When I first installed my wideband and ST with my protune map I was seeing afrs in the 11s which was good. Then later on it went in to the 10s at WOT and sometimes 9s! I recalibrated my wideband but I also reflashed a basemap then and it brought everything back to the 11s. I have a 05 FXT. Hmmm..

jays05 · 08-01-2006, 03:25 PM

Quote:

Originally Posted by WolfPlayer

Jay, are you still running around without a rear O2 sensor? As we have discussed here, the rear O2 definitely affects AFRs.

t

Yep, I'm still running without the rear o2. I'm pretty sure that's what's killing my gas mileage. I'm going to have the bung welded on at the same time as some other work (ewg dump tube

, tial bov flange, blow thru maf, etc). It'll be a couple more weeks.

There's lots of good info in this thread. I'll datalog in a couple days to see what's happening with my long term fuel trims, and if my last change made a difference.

crystal_Imprezav · 08-02-2006, 05:59 AM

BTW don't use a mechanical fix on your rear o2 either. I got a new bung welded for my wideband but it still stays at 13.9 during closed loop but for a much shorter time than when the o2 sensor was just ziptied. It seems like something that was changed in Cobbs firmware when they upgraded since I have read that others didn't see an issue with it until it was upgraded. I think maybe we all need some fresh maps from Cobb like Jorge stated with the problems he has been having with 05's. I know I am going to be reading my ROM tomorrow when my Tactrix cable arrives

and say hello to protuner features.

WolfPlayer · 08-02-2006, 07:33 AM

Quote:

Originally Posted by crystal_Imprezav

I know I am going to be reading my ROM tomorrow when my Tactrix cable arrives

and say hello to protuner features.

Affirmative. Been there, done that

It's a great solution. Also, the tactrix + ECUFlash is SOOOOOOOOOO much quicker than flashing with the AccessPORT.

t

crystal_Imprezav · 08-02-2006, 08:10 AM

Oh really, thats a VERY good thing to know since I had no idea what to expect. I got a couple of questions though, I have noticed when I rescale a table in Enginuity and then open it in ecuEdit, it has completely changed. I actually thing I prefer ecuEdit b/c it has access to more tables the enginuity only has in debug mode meaning it is untested. Also did you unmarry your AP/ST before you flashed? I don't want to comprimise losing the license of the AP by trying to change one parameter like IAT timing retard.

R4ND0M_AX3 · 08-02-2006, 11:43 AM

Quote:

Originally Posted by WolfPlayer

I agree. OEM ECUs are notorious for applying a learned fuel correction in open loop based off of extrapolation. People often think that open loop means no correction. That is just not true. I remember hacking the GM code back in 2000 to remove this 'feature'. Open loop should be open loop for us hotrodders

. However, in no way is that guaranteed with a stock ECU.

Jay, are you still running around without a rear O2 sensor? As we have discussed here, the rear O2 definitely affects AFRs.

t

I know my old civic applied long term correction to the open loop stuff. But I thought the STi didn't do this and the WRX did.

Am I wrong?

***JDM-STI*** · 08-02-2006, 03:51 PM

Jaygoesfast and Nhluhr, at what MAF voltage are your cars going from closed to open loop. Mine has a bad negative fuel trim correction in closed loop and once it learns this correction it won't go into open loop until 3 volts instead of the desired 2.5 volts. We have been fighting this for a while with out any solution so far. So I want to compare mod set ups to mine and whatever other info you guys have to offer.

jays05 · 08-02-2006, 04:16 PM

Stupid question, but how can I tell when the car switches from closed loop to open loop ? I always assumed that high rpm @ wot was open loop, but never knew how to determine which mode it was in.

07-28-2006, 06:33 AM	#1
jays05 Spec C Club Car: Blue 05 STI Fav Mod: Synapse FMIC Location: Upstate NY Posts: 1,714 Join Date: Nov 2004 Trader Rating: (0)	long term fuel trims in open loop ??? Over time my WOT AFR's have been getting richer and richer, and a simple ECU reset has always fixed the issue. I was looking into it some more the other night (before doing an ecu reset) and I see that I have some big long term fuel trims when at WOT (up to +12.16). The long term fuel trims take my AFR's from high 11's to low 10's. How can this happen in open loop? I'm guessing that somewhere near the cl/ol transition my MAF scaling is off, and it's just carrying the fuel trims over from closed loop to open loop? Or am I missing something big here? My tune looks "happy" otherwise with my long term knock learning maps having small positive values all across the table. This ad is not endorsed by this member. Please register or login to hide this ad.

08-02-2006, 04:16 PM	#15
jays05 Spec C Club Car: Blue 05 STI Fav Mod: Synapse FMIC Location: Upstate NY Posts: 1,714 Join Date: Nov 2004 Trader Rating: (0)	Stupid question, but how can I tell when the car switches from closed loop to open loop ? I always assumed that high rpm @ wot was open loop, but never knew how to determine which mode it was in. This ad is not endorsed by this member. Please register or login to hide this ad.

07-31-2006, 02:53 PM	#3
*JDM-STI* Platinum Member Car: 2005 & 2008 STI Fav Mod: UR 35R and Hydra tune by Scott Siegel :) Location: Columbus, GA Posts: 1,908 Join Date: Mar 2005 Trader Rating: (11)	Scott Siegel has been fighting this on my car for about 2 1/2 months now. It is more than intake calibration. We have tried several kinds of different intake set ups and none of them corrected the problem. Seems to mostly occur on mid/late 2005 year models...???? This is a Cobb and Ecutek issue. We have seen cases with both. My car won't go into open loop till 3V at the MAF instead of 2.5V like its supposed to. Not sure what the answer is at this point.

07-31-2006, 05:36 PM	#4
jays05 Spec C Club Car: Blue 05 STI Fav Mod: Synapse FMIC Location: Upstate NY Posts: 1,714 Join Date: Nov 2004 Trader Rating: (0)	I'm running the perrin bigmaf with the perrin rotated mount intake. My intake calibration seems dead on but I tried adding a couple % on the top end to see if it makes a difference. I've been wondering if this is another goofy byproduct of my removing the rear o2. I really need to get another bung welded on.

07-31-2006, 06:54 PM	#6
Merchgod Junior STI Driver Posts: 105 Join Date: Apr 2006 Trader Rating: (0)	It happens because patterns of correction noticed by the ECU in closed loop are migrated to your open loop fueling. That is why a reset fixes it. The ECU assumes that if has to keep adding, say 10% of fuel in closed loop to hit 14.7, that you are probably running leaner in open loop as well and this is added to your open loop fueling.

08-01-2006, 08:50 AM	#8
ZuMBLe Senior STI Driver Car: 05 CGM FXT Location: NY Posts: 323 Join Date: Feb 2006 Trader Rating: (2)	I thought I was going crazy or my wideband was off! I saw this also. When I first installed my wideband and ST with my protune map I was seeing afrs in the 11s which was good. Then later on it went in to the 10s at WOT and sometimes 9s! I recalibrated my wideband but I also reflashed a basemap then and it brought everything back to the 11s. I have a 05 FXT. Hmmm..

08-02-2006, 05:59 AM	#10
crystal_Imprezav Spec C Club Car: Slow 05 STi Fav Mod: Loping Idle Location: Chewy's Garage Posts: 1,880 Join Date: Mar 2005 Trader Rating: (12)	BTW don't use a mechanical fix on your rear o2 either. I got a new bung welded for my wideband but it still stays at 13.9 during closed loop but for a much shorter time than when the o2 sensor was just ziptied. It seems like something that was changed in Cobbs firmware when they upgraded since I have read that others didn't see an issue with it until it was upgraded. I think maybe we all need some fresh maps from Cobb like Jorge stated with the problems he has been having with 05's. I know I am going to be reading my ROM tomorrow when my Tactrix cable arrives and say hello to protuner features.

08-02-2006, 08:10 AM	#12
crystal_Imprezav Spec C Club Car: Slow 05 STi Fav Mod: Loping Idle Location: Chewy's Garage Posts: 1,880 Join Date: Mar 2005 Trader Rating: (12)	Oh really, thats a VERY good thing to know since I had no idea what to expect. I got a couple of questions though, I have noticed when I rescale a table in Enginuity and then open it in ecuEdit, it has completely changed. I actually thing I prefer ecuEdit b/c it has access to more tables the enginuity only has in debug mode meaning it is untested. Also did you unmarry your AP/ST before you flashed? I don't want to comprimise losing the license of the AP by trying to change one parameter like IAT timing retard.

08-02-2006, 03:51 PM	#14
*JDM-STI* Platinum Member Car: 2005 & 2008 STI Fav Mod: UR 35R and Hydra tune by Scott Siegel :) Location: Columbus, GA Posts: 1,908 Join Date: Mar 2005 Trader Rating: (11)	Jaygoesfast and Nhluhr, at what MAF voltage are your cars going from closed to open loop. Mine has a bad negative fuel trim correction in closed loop and once it learns this correction it won't go into open loop until 3 volts instead of the desired 2.5 volts. We have been fighting this for a while with out any solution so far. So I want to compare mod set ups to mine and whatever other info you guys have to offer.