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Old 01-06-2008, 05:19 PM   #1
wage0052
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Default '06 Stage 2 WRX, logged AFR not matching map targets

I installed an LC-1 with XD-16 WB02 gauge a couple weeks ago. The first thing I noticed was that my car was running quite rich under load. The map values were calling for around 11:1 AFR's, and the car was down at around 9:1 at peak torque and 8.5:1 at redline. Idle and cruise AFR's were steady fluctuating right around 14.7:1.

This was somewhat surprising, as the car seemed to run well and did not stutter or hesitate at all. In addition, the car seemed to behave normally in boost, which hit targets, and did not waver at all.

After spending a lot of time checking for boost/exhaust leaks (of which I've found none), and re-calibrating the WB02 sensor (gauge and logs showed the same values after re-calibration), I decided to simply try leaning out the target AFR tables.

After leaning out the high load target AFR tables by around 2 points, the car now hits right around 10.8:1 during peak torque, and 11.3:1 at redline. The map values now call for 12.3 and 13 AFR respectively.

My first instinct would be to chalk this up to some type of leak, but I can't seem to find any other behavior that is out of the norm (boost seems to behave perfectly normal), other then the fact that actual AFR doesn't match the map targets.

Has anyone seen similar behavior? If this may be caused by a leak, where specifically should I be looking? Is my car just a freak?

Relevant information:
06 WRX
TXS Stealthback exhaust
Maddad Whisper axleback
GMBCS

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Old 01-06-2008, 06:34 PM   #2
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It could be caused by a boost leak, but then you would notice either lower boost or really high wgdc to hit target boost.

Sounds like you need to tune the MAF calibration. Where logged AFR is lower than target, you need to lower the MAF calibration. The ecu thinks it's getting more air than it really is.

Try airboy's spreadsheet, it will graph everything and show the AFR error against maf voltage.

Last edited by ExpO; 01-06-2008 at 06:41 PM.
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Old 01-06-2008, 07:20 PM   #3
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Quote:
Originally Posted by ExpO View Post
It could be caused by a boost leak, but then you would notice either lower boost or really high wgdc to hit target boost.

Sounds like you need to tune the MAF calibration. Where logged AFR is lower than target, you need to lower the MAF calibration. The ecu thinks it's getting more air than it really is.

Try airboy's spreadsheet, it will graph everything and show the AFR error against maf voltage.
Hrm, is this something that is normal even with the stock intake? I am running a foam filter (and not the stock paper filter).
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Old 01-06-2008, 09:04 PM   #4
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Quote:
Originally Posted by wage0052 View Post
Hrm, is this something that is normal even with the stock intake? I am running a foam filter (and not the stock paper filter).
The foam filter is oiled, right? The oil will mess up your MAF readings. Clean it with some isopropyl alcohol. The sensing element (wire) is up inside the "tube" and not the little resin bulb next to the tube.

Remember to flash back to the 11AFR map after cleaning the MAF or you may get a nasty surprise.

Do you have the means to collect data logs?

The stock '06WRX intake ran lean on my car.
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Old 01-07-2008, 12:19 AM   #5
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Originally Posted by Airboy View Post
The foam filter is oiled, right? The oil will mess up your MAF readings. Clean it with some isopropyl alcohol. The sensing element (wire) is up inside the "tube" and not the little resin bulb next to the tube.

Remember to flash back to the 11AFR map after cleaning the MAF or you may get a nasty surprise.

Do you have the means to collect data logs?

The stock '06WRX intake ran lean on my car.
Yeah, the foam filter is oiled. I guess I wasn't aware that an oiled filter can skew things that much..

I've got some MAF cleaner that I've been using regularly to keep the MAF clean. I'll toss in the paper filter and clean the MAF and see what happens.

Yeah, the numbers cited previously are from datalogs. Other's that I've talked to have said the same thing, that the '06 runs just a tad leaner then map targets.
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Old 01-08-2008, 03:00 PM   #6
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Well, I cleaned the MAF and tossed on the stock paper filter. No change in logged AFR. The car is still running ~2.0 points richer then the map calls for. Idle and cruise AFR's are still in range.

It seems like I can rule out a boost leak (as boost seems to behave normally), where else (would have to be post-MAF) should I be checking for a leak, and what would be the best way to check?

One additional thing of note: I get the impression that WOT/high load AFR seems to be bouncing around more then normal. This would be in indication of a leak, correct? I'll grab some logs to toss 'em up tonight.
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Old 01-08-2008, 03:13 PM   #7
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I have never seen a DBW Subaru match real world AFR with the fuel map targets from the factory. So no, your car is not a freak.
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Old 01-08-2008, 03:29 PM   #8
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Originally Posted by Master2192 View Post
I have never seen a DBW Subaru match real world AFR with the fuel map targets from the factory. So no, your car is not a freak.
Ok, fair enough. But is a 1.5-2 point difference common?
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Old 01-08-2008, 10:20 PM   #9
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where did you tap the sensor to?
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Old 01-08-2008, 10:40 PM   #10
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The sensor is in the downpipe, around 15" from the turbo.
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Old 01-09-2008, 09:14 AM   #11
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Just a thought, but check in LM Programmer for the WBO2 that you have the correct fuel specified. The AFR is merely a representation of the ratio based on the fuel that you have selected. The WBO2 actually measures lambda.
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Old 01-09-2008, 01:27 PM   #12
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Yeah, the LC-1 has the 14.7:1 (Gasoline) fuel type selected. Many of the guys local to me seem to be convinced the cause is simply a the car running off from the fuel mapping. It's been suggested that raise the injector scalar to bring the open loop map and logged AFR values closer. I may try playing with that this weekend.
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Old 01-09-2008, 01:40 PM   #13
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Quote:
Originally Posted by wage0052
Ok, fair enough. But is a 1.5-2 point difference common?
Yup, in my experience anyhow. On a 05 STI I had to take the fuel map out to the 13s to get the AFR to 12.5 (101 octane tune), while on a 07 STI the fuel map says low 10s to get the AFR into the mid to high 11s. I just tune for real world AFR and don't worry about the differential unless I am running out of resolution. It takes a long long time to manually smooth the MAF table to get the AFRs to match and even at that if you change the targets in the fuel map later it won't equal the same 1:1 change in real world.
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Old 01-09-2008, 04:21 PM   #14
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where can i get a copy of airboys spreadsheet for the maf
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Old 01-09-2008, 05:40 PM   #15
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Quote:
Originally Posted by Master2192 View Post
Yup, in my experience anyhow. On a 05 STI I had to take the fuel map out to the 13s to get the AFR to 12.5 (101 octane tune), while on a 07 STI the fuel map says low 10s to get the AFR into the mid to high 11s. I just tune for real world AFR and don't worry about the differential unless I am running out of resolution. It takes a long long time to manually smooth the MAF table to get the AFRs to match and even at that if you change the targets in the fuel map later it won't equal the same 1:1 change in real world.
OK, good to know. For the reasons you stated, I am hesitant to re-scale the MAF, as in this case, it would most likely be more of a headache then worthwhile.

The current resolution is adequate, but I was simply concerned, as a 2 point differential seemed like a high tolerance for a car with the stock airsystem.

Thanks much for the info!
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Old 01-13-2008, 04:17 PM   #16
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Quote:
Originally Posted by wage0052 View Post
Ok, fair enough. But is a 1.5-2 point difference common?
Mine is 1.1 different from whats in the map. i.e. when Im targeting 12.1 during boost onset, Im actually getting 11.0.

I think 06rexwagon had the same thing if I remember correctly. Ive seen two other 06's where the fuel maps didnt match the actual AFR's as well.
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Old 01-13-2008, 05:08 PM   #17
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Originally Posted by cucamelsmd15 View Post
Mine is 1.1 different from whats in the map. i.e. when Im targeting 12.1 during boost onset, Im actually getting 11.0.

I think 06rexwagon had the same thing if I remember correctly. Ive seen two other 06's where the fuel maps didnt match the actual AFR's as well.
Yeah, after talking to a number of '06 WRX owners/tuners, it appears like there is a fairly large tolerance around the stock fuel table, and what I'm seeing is fairly normal.

For anyone else researching this issue: In open loop, my car is right at 1.5 points richer then target.
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Old 01-15-2008, 08:54 PM   #18
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If you have the stock MAF housing you can update your MAF scaling pretty quickly to adjust your AFR to match targets. Probably take about 3-5 WOT runs and a few flashes.

Easiest way to do it is log RPM, MRP, MAF v, EL, and WBo2. I generally log MRP to show changes in onset fueling which is tough to dial in. But once that is stable you can modify the voltages on the MAF table to fall in line. Add voltage to lean it out, subtract to richen.

I would recommend setting your Target fuel to 11:1 from 2800-redline during this time to keep the maf tuning easy, then adjust your fuel curve after the MAF is dialed.
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Old 01-16-2008, 12:14 AM   #19
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Quote:
Originally Posted by Master2192 View Post
It takes a long long time to manually smooth the MAF table to get the AFRs to match and even at that if you change the targets in the fuel map later it won't equal the same 1:1 change in real world.
I disagree. For open loop, it takes 2-3 pulls if you have an idea of the compensation required for a given % error. In my experience, it allows for damn near a 1:1 change in real world.

Last time I did my afr's I ran a 10.5-10 map, scaled the maf, then bumped it to 11.5-11 with no issues.

Doing it this way also eliminates the possibility of a rich/lean run if your load/rpm cell goes into a part of the fueling table in which you haven't logged the afr error.

Anyone know for sure if there are any other compensations that apply or use either table?

Last edited by ExpO; 01-16-2008 at 12:20 AM.
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Old 01-16-2008, 02:19 PM   #20
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Quote:
Originally Posted by turboge View Post
If you have the stock MAF housing you can update your MAF scaling pretty quickly to adjust your AFR to match targets. Probably take about 3-5 WOT runs and a few flashes.

Easiest way to do it is log RPM, MRP, MAF v, EL, and WBo2. I generally log MRP to show changes in onset fueling which is tough to dial in. But once that is stable you can modify the voltages on the MAF table to fall in line. Add voltage to lean it out, subtract to richen.

I would recommend setting your Target fuel to 11:1 from 2800-redline during this time to keep the maf tuning easy, then adjust your fuel curve after the MAF is dialed.
Yup, I plan to give the MAF scaling tool integrated with Enginuity beta 785 a shot when I get a chance, and playing with OL by hand.

Last edited by wage0052; 01-16-2008 at 06:02 PM. Reason: clarity.
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Old 01-16-2008, 03:01 PM   #21
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Quote:
Originally Posted by Master2192 View Post
I have never seen a DBW Subaru match real world AFR with the fuel map targets from the factory. So no, your car is not a freak.
+1.....& yes a 1.5-2 point AFR difference is normal for DBW subaru's.

I use an unorthodox way of correcting this that most don't do BUT I've used it on just about every car I've tuned & its worked flawlessly. I see jacking w/ the MAF table as a last resort.

Instead of jacking w/ the MAF table, raise the injector scalar. My reasoning, if you jack w/ the MAF tables you'll end jacking with more tables, most of them that include the Load reference values.

By raising the injector scalar you are linearly raising the fuel table. I'd start by dropping the AFR back down to a ~11.0:1(assuming you are on 93octane) at peak load, then raising the scalar 20-30cc/min since your tailpipe is ~2 points off of matching the AFR table. This is generally the first thing I do when tuning a car.
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Old 01-16-2008, 03:24 PM   #22
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testes,

does this apply to DBC or only DBW cars? Interesting approach.
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Old 01-16-2008, 03:28 PM   #23
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testes,

does this apply to DBC or only DBW cars? Interesting approach.
I do this as well on non-stock injector DBC cars. Typically stock injector DBC cars are within 1.# AFR.
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Old 01-16-2008, 04:09 PM   #24
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Testes, if the injector scaling is the actual problem, then fixing it rather than MAF scaling is the correct thing to do.

However, if the AFR targets weren't being met because the MAF scaling was off, then in stock form you're getting bad load data anyway. Fixing the MAF scaling would fix both the AFR targets AND give you correct load data.

The real question is what's wrong in the stock tune.
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Old 01-16-2008, 04:24 PM   #25
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The real question is what's wrong in the stock tune.
We can all agree that the stock tunes are a joke.....especially the newer cars.
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