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Is closed loop necessary for a street car?

 
Old Aug 30, 2011, 10:43 AM
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Is closed loop necessary for a street car?

I would like some opinions on eliminating the front O2 sensor. Basically I would set the ecu to run in open loop only (I would still tune the car with my wideband).

What are some cons to this. I know the O2 sensor/ closed loop helps with emissions. Other drivability advantages? I couldnít find any discussion in old threads for thsi topic.

Also the easiest way to do disable this? Maybe the open loop versus load/ or throttle table? And eliminate the check engine light?
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Old Aug 30, 2011, 10:48 AM
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Uh helps with gas mileage a lot. That is unless you are on e85 because 14.7 is kinda rich for e85.

You will notice a difference in AFR when running open loop from night and day (temp difference), differences in humidity, seasonal temps, etc. So you will be changing your fuel map a lot...

If anything, you should try to use a wideband to simulate your front o2(as long as its far upstream enough).
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Old Aug 30, 2011, 11:03 AM
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Originally Posted by SyZyGy1394 View Post
Uh helps with gas mileage a lot. That is unless you are on e85 because 14.7 is kinda rich for e85.

You will notice a difference in AFR when running open loop from night and day (temp difference), differences in humidity, seasonal temps, etc. So you will be changing your fuel map a lot...

If anything, you should try to use a wideband to simulate your front o2(as long as its far upstream enough).

How exactly does it help with gas mileage? I was going to use speed density, so I would think temperature is accounted for in calculating load.
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Old Aug 30, 2011, 11:09 AM
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Originally Posted by benderrodriguez View Post
How exactly does it help with gas mileage? I was going to use speed density, so I would think temperature is accounted for in calculating load.
Because I was messing with mine by running open loop for a highway trip and had it running at ~16 AFR a few months ago. Accidentally flashed that rom back on my car and my cruise was pretty rich as well as my light accel.(which is odd because I'd expect it to go leaner because the air is cooler) Heck our cars have temperature compensation, but its not perfect.
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Old Aug 30, 2011, 11:23 AM
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You can disable all O2 feedback through the periphery bits in FAA. I think there are 3 of them related to O2 feedback, can't recall which ones they are though.

I was running open loop in this manner and while my mpg was perfectly fine (possibly even better) it did give some odd drivability issues. Not really troublesome issues, just annoying.
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Old Aug 30, 2011, 11:26 AM
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Originally Posted by 03whitegsr View Post
You can disable all O2 feedback through the periphery bits in FAA. I think there are 3 of them related to O2 feedback, can't recall which ones they are though.

I was running open loop in this manner and while my mpg was perfectly fine (possibly even better) it did give some odd drivability issues. Not really troublesome issues, just annoying.
What kind of driveability issues did you have?
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Old Aug 30, 2011, 11:27 AM
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Originally Posted by 03whitegsr View Post
You can disable all O2 feedback through the periphery bits in FAA. I think there are 3 of them related to O2 feedback, can't recall which ones they are though.

I was running open loop in this manner and while my mpg was perfectly fine (possibly even better) it did give some odd drivability issues. Not really troublesome issues, just annoying.

Did you use the open loop tables at all, or just the periphery bits?

Also does anyone know or have a recommendation for which bits?

Last edited by benderrodriguez; Aug 30, 2011 at 12:13 PM.
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Old Aug 30, 2011, 02:49 PM
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You'll have to use the periphery bits to disable the DTC. I ran mine for a few months with no front 02 feedback on SD and set a buddy up with SD and no front 02 sensor and his seems to be doing well.

There will be some rich/lean conditions where the ECU would normally correct for you. But its nothing you cant learn to live with.

If you're going the original 2d SD route, I had the best luck with mostly using the Maf Comp table with some changes to the RPM VE table to dial it all in. If your using 3D SD (2.0), just use the 3D RPM VE map.
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Old Aug 31, 2011, 12:11 PM
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Drivability issue was primarily just off idle the car would want to go very lean. Happened under about 2000 RPM. The car would either run rich at idle and be decent off idle, or be lean off idle and idle well. I never could get it to do both well on the 2D SD patch.

I don't think it was due to using open loop directly, but closed loop would help "cover up" the issues normally.

Only used the periphery bits to kill it.
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Old Aug 31, 2011, 12:31 PM
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I've been running my car at about 15.2:1 for a long time (not stock ecu) and there are no drivability issues. If you go too lean, the car will jolt and hesitate, and will not be smooth. I've heard of evo guys running up to 15.7:1 on pump gas, i'm going to try about 16:1 (1.09 Lambda) on my next tune
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