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Old 12-25-2012, 03:02 PM   #1
Pickler
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Default lean wtf

car is always ~14.4 during wot unless i go past 4000rpm!? i thought subarus ran rich? only time it goes rich below 4000 is when revving engine in park/neutral. is this normal?
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Old 12-25-2012, 03:37 PM   #2
berylthemessiah
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Thats about right the car will run very close to stoich until you enter Open-Loop Fueling, so you get better gas mileage. My car was almost the same until I decreased my OL/CL Delay. I'm not sure about revving it when in park or neutral.
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Old 12-25-2012, 06:49 PM   #3
Pickler
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wow so i guess this is good news MPG wise and maybe my car is PZEV too? does this explain the lack of power off the line?

Last edited by Pickler; 12-25-2012 at 07:00 PM.
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Old 12-25-2012, 07:01 PM   #4
berylthemessiah
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Subaru are notoriously hard to launch(properly) because of the AWD systems, also having an automatic doesn't help. The OL/CL delay can affect off the line performance(i think), and also cause a "lag" when you step on it trying to pass someone for example. I'm not positive about of the off the line aspect, somebody with a little more knowledge may offer some insight. Also from your first post 14.4 is not lean. For pump gasoline 14.7 AFR is stoich, lean is anything greater than that. Rich is anything lower than 14.7

As another note 2.5i's are not know to be exceptionally speedy cars.
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Old 12-25-2012, 08:09 PM   #5
Pickler
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what i meant is it's lean for wide open throttle not that 14.4 is lean. on other vehicles i own or have owned wideopen throttle means open loop and rich mixture <13:1 depending on RPM. car is fine when its rolling powerwise. but from stops it feels heavy until it picks up speed, it feels as though there is more power in second gear compared to first.
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Old 12-25-2012, 09:19 PM   #6
NH8991
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Quote:
Originally Posted by Pickler View Post
what i meant is it's lean for wide open throttle not that 14.4 is lean. on other vehicles i own or have owned wideopen throttle means open loop and rich mixture <13:1 depending on RPM. car is fine when its rolling powerwise. but from stops it feels heavy until it picks up speed, it feels as though there is more power in second gear compared to first.
FWIW, at WOT mine is around 14.7 +/- until about 3200rpm, then gradually starts getting richer as the revs increase. This is still in closed loop fuelling, it doesn't switch to open loop until much later in the rev range.

And there's definitely more pull initially in 2nd when changing from 1st, I think it's an inherent characteristic of the 4EAT torque converter, it doesn't lock at all in first gear, so it's potentially bleeding power in first.
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Old 12-25-2012, 10:00 PM   #7
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Originally Posted by NH8991 View Post
FWIW, at WOT mine is around 14.7 +/- until about 3200rpm, then gradually starts getting richer as the revs increase. This is still in closed loop fuelling, it doesn't switch to open loop until much later in the rev range.

And there's definitely more pull initially in 2nd when changing from 1st, I think it's an inherent characteristic of the 4EAT torque converter, it doesn't lock at all in first gear, so it's potentially bleeding power in first.
yep sounds like what im experiencing, never seen this before though. i preferred it a bit more rich at 3000rpm, maybe 13.5:1. and it's unaturaly rich uptop, i think i have seen 10.9:1 at 6000rpm.
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Old 12-25-2012, 10:34 PM   #8
RaceFaceXC
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On the 06-08 (probably the later models also) the target AFR in closed loop is about stoich until above 3k rpm and towards 10ish at redline. In my testing, an LC-2 showed my AFR closer to 9.5. CL-OL delay holds the switch until about 3-4k rpm depending on gear on my 5MT.

changing the CL-OL delay to a value near zero and dialing in some AFR's closer to what produces best torque from 2k and up in the OL fuel map will significantly broaden the tq curve. Keeping it from going richer than 12:1 or so at the top end will help it climb through the top 1000 rpm's, too. I've found 12.5:1 to just under 13:1 to produce the best tq depending on rpm.

Changing the target AFR or ant part of the fueling or air metering system Hardware OR tune without a wideband sensor may be risky.
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Old 12-25-2012, 11:00 PM   #9
Pickler
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Originally Posted by RaceFaceXC View Post
On the 06-08 (probably the later models also) the target AFR in closed loop is about stoich until above 3k rpm and towards 10ish at redline. In my testing, an LC-2 showed my AFR closer to 9.5. CL-OL delay holds the switch until about 3-4k rpm depending on gear on my 5MT.

changing the CL-OL delay to a value near zero and dialing in some AFR's closer to what produces best torque from 2k and up in the OL fuel map will significantly broaden the tq curve. Keeping it from going richer than 12:1 or so at the top end will help it climb through the top 1000 rpm's, too. I've found 12.5:1 to just under 13:1 to produce the best tq depending on rpm.

Changing the target AFR or ant part of the fueling or air metering system Hardware OR tune without a wideband sensor may be risky.
those numbers that you find optimal are exactly what i have seen on other NA cars that i own (ie. 3.2TL). i'm not sure why subaru is suffocating the impreza so much up top, with the oversquare engine design i think this engine could have benefited tremendously with 12.7 AFR @5.5k rpm. i am not aware of any tuning utilities for the 09 4eat 2.5i that could fix this.
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