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what does open loop and close loop due and mean?

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Old Apr 23, 2010, 04:48 PM   #1
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what does open loop and close loop due and mean?

question is in title

and also when you u ever need to change in EcuFlash the loop throttle or loop load?
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Old Apr 23, 2010, 05:08 PM   #2
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Old Apr 23, 2010, 05:20 PM   #3
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if i understand correctly. open loop is used during WOT and maybe warmup (not sure on warmup). the ecu will target whatever values are in the fuel map. during closed loop, the ecu will target a stoich afr or 14.7

someone else can go into details
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Old Apr 23, 2010, 05:29 PM   #4
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Quote:
Originally Posted by McLaren F1 2003 View Post
if i understand correctly. open loop is used during WOT and maybe warmup (not sure on warmup). the ecu will target whatever values are in the fuel map. during closed loop, the ecu will target a stoich afr or 14.7

someone else can go into details
so if i understand correctly, under WOT ur in open loop on the A/F Table..

closed loop is driving normal NOT WOT

when you u ever need to change in EcuFlash the loop throttle or loop load?
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Old Apr 23, 2010, 10:13 PM   #5
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Quote:
Originally Posted by 5LEEPERISAH23I View Post
so if i understand correctly, under WOT ur in open loop on the A/F Table..

closed loop is driving normal NOT WOT

when you u ever need to change in EcuFlash the loop throttle or loop load?

Can you rephrase the question? Also you've created a bunch of new threads all with one question. Can you just use one thread to ask all the questions you want to ask? Its clear you want a basic understanding of how tuning/logging works but you also should try searching around for open loop in this forum since its defined a couple times in different threads.
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Old Apr 23, 2010, 10:17 PM   #6
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Open loop means your ECU calculates the fuel to inject and looks at the fuel map and it just puts in whatever amount of fuel it thinks is correct. In closed loop it uses the o2 sensor to target the stoichiometric (14.7:1 AFR on gas) mixture, ignoring the fuel map but correcting the mixture based on feedback from the o2 sensor.

Last edited by jrohner; Apr 23, 2010 at 10:21 PM.
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Old Apr 24, 2010, 12:58 AM   #7
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Open loop means your ECU calculates the fuel to inject and looks at the fuel map and it just puts in whatever amount of fuel it thinks is correct. In closed loop it uses the o2 sensor to target the stoichiometric (14.7:1 AFR on gas) mixture, ignoring the fuel map but correcting the mixture based on feedback from the o2 sensor.
so when would u every go into the open loop table on Ecu Flash? could u give me an example
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Old Apr 24, 2010, 06:38 AM   #8
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Just if you wanted to change when the car goes into open loop; most people would leave it alone.

If you cruise fast enough on the interstate to get out of closed loop, you could raise the throttle and/or load tables so you stay in closed loop instead to try for a gain in fuel mileage. If you have really big cams, you could change it so it idles in open loop so you can make the idle better by richening it up.

I prefer to just totally disable closed loop so I can run whatever AFR's I want at any time (going by my fuel table).
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Old Apr 24, 2010, 09:41 AM   #9
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just to clarify , when in open loop the ecu does not think, it uses your inputs from the fuel map.
when in closed loop the ecu does "think".

you might want to use the open loop if, you want to lean cruise a bit for better fuel mileage at the cost of some extra nox. 2, you need to control idle afr better than you are able to in closed loop, (maybe because of large cams or some mitigating problem, injectors etc.), 3, ?
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Old Apr 24, 2010, 11:50 PM   #10
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Quote:
Originally Posted by codgi View Post
Can you rephrase the question? Also you've created a bunch of new threads all with one question. Can you just use one thread to ask all the questions you want to ask? Its clear you want a basic understanding of how tuning/logging works but you also should try searching around for open loop in this forum since its defined a couple times in different threads.
thank you.
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Old Apr 25, 2010, 10:13 PM   #11
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Yes, in closed loop feedback, the ECU poles the primary o2s and uses a set of fuel trims to keep AFR steady at stoichiometric (14.7:1).

In open loop, the ECU ignores primary o2s and relies on fuel tables to manipulate fueling.

There are many reason why a tuner would not allow the ECU to go into Closed Loop Feedback. Here are only a few:

1. Better idle stability; Depending on cams being used and other factors, it is advantageous to lean or richen idle AFRs. Some people prefer to richen AFR at idle, as this helps with idle stability on large cams. Some tuners will actually lean AFR at idle, along with tweaking ignition advance to stabilize idle. This is the method i prefer to use, as fuel economy can be further increased without any costs to performance. Since the engine is basically "free spinning" at idle and has no real load, AFRs upwards of 17-18:1 can be used safely, with the correct ignition timing. It's also very important to properly tune idle - part throttle transitions using this method. I tune for 16.5-17:1 @ idle w/AC off. Don't try this unless you know what you're doing.

2. Part throttle/cruise; a AFR of 14.7:1 is actually not the most efficient AFR. A AFR of about 15.2-15.7:1 is best economy AFR. Forcing open loop at part throttle/cruise allows the tuner to lean AFR out in these areas, for best economy. 14.7:1 is for best emissions(nOx). I tune light part throttle(low load) and cruise for about 15.2-15.5:1.

3. Closed loop feedback - open loop transition; It's much easier to control AFR at spool up, if the ECU stays out of closed loop feedback and stays out of the way. You can tune the spool up transition areas to perfection with relative ease.

I run forced open loop, with the exception of part throttle cruise over 4,000 rpm and less than 110 load. Tuning for forced open loop means you have to tune all areas of the maps you intend to run open loop. This can be a time consuming task, but much worth the time if you know what you're doing and do it correctly.
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Last edited by iTune; Apr 25, 2010 at 10:20 PM.
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Old Apr 25, 2010, 10:13 PM
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