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Old 01-02-2015, 11:34 PM   #1
slatere17
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Default High AFR

Installed a wideband a few weeks ago and have had some time to take a couple decent logs. Car is stock w/ stock map, but I've observed some high AFR through the mid engine range when it should be dropping. In general, things look alright but I'm curious about the AFR readings. I've also noticed slight hesitations around 3500 rpm, near a rise in the AFR. I know there are quite a few that attribute driveability issues to the stock tune but I don't know how bad it is.

Any thoughts on what's going on with the AFR?

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Old 01-03-2015, 08:15 AM   #2
quazimoto
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Where is the wideband sensor installed? The general issue is the OL/CL fueling delays. I would look into getting a "Stage 1" tune regardless.
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Old 01-03-2015, 11:20 AM   #3
slatere17
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Between the turbo and the first cat. I'm surprised to not see knocking issues with that high an AFR into the higher engine loads. Perhaps timing is playing a role there. Obviously there is some room for improvement.

A stage 1 tune and hopefully more is definitely on the table and probably not too far off. At this point I'm just working on understanding how the ecu functions with limited free time.
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Old 01-04-2015, 09:08 PM   #4
slatere17
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Default CL-OL delay impact on AFR

For those interested in the CL-OL delay impact on AFR during a pull, I flashed a map with the delay reduced to 200 from a default of 750. I left it at 200 as opposed to 0 to see if the delay was still noticeable while driving but it was very faint. High AFR's are still carrying into the high load region (~2.0 g/rev) but they richen up earlier than before as shown in this plot.

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Old 01-19-2015, 08:27 PM   #5
feelingsupersonic
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Do you have any fuel pressure data? I just finished dealing with an issue where I was way too rich under 2500 rpm, turned out to be a faulty FPR (non-Subaru car).
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Old 01-22-2015, 09:13 PM   #6
mr.nicknasty8
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That's still a little too lean. You would want to be right around 11.1-11.3 AFR right before peak boost
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Old 01-23-2015, 06:54 PM   #7
slatere17
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No, I haven't had any inclination to log fuel pressure. This car is still on a stock tune with exception of the CL/OL delay so I doubt there is anything going on there.

I never realized how lean it was running thru most of the power curve until I got the wideband installed. There was never any knock and IAM has always been pinned at 1 prior to the new map. Maybe the stock O2 could have caught this because it wasn't richening up, not sure whether it's the boost pressure or the rich limit of the sensor that renders it useless under boost.

I would bet that once I drop the delay to 0, the AFR will look close to what it should be. It will be rich (~10.3) but I haven't got around to tweaking that. This was mostly just an effort to establish how big of an impact the delay has on the AFR. I am sure anybody who does any tuning knows how important it is to eliminate that delay.
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Old 01-25-2015, 11:45 AM   #8
mr.nicknasty8
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That's why they crack ringlands. Just because it's not knocking, doesn't mean it's not doing damage

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Old 01-25-2015, 12:02 PM   #9
slatere17
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Good point
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Old 02-24-2015, 06:46 PM   #10
slatere17
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To come full circle, the car did not like the 200 delay as much. IAM was pegged at .9375 after a week of intermittent driving. Eliminated the delay and that problem was gone. Boost target is 14.2 with the most recent map, the stock map was pulling a little bit of boost for intake temp and atm. pressure compensations.

I'm aware of other methods to eliminate the effects of the delay, but this was more just a demonstration of the effects of the delay.

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Old 02-24-2015, 07:42 PM   #11
ride5000
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just take the delay out. there's no reason to keep it in. you can tune the ecu to keep you in closed loop for cruising (ie, up to wastegate boost) to preserve fuel economy.
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