open loop vs closed loop efi
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open loop vs closed loop efi

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    Default open loop vs closed loop efi

    IF all of the tuning was done correctly is there a downside to running in open loop?

    The way I understand normal EFI operation in a car is: OPEN LOOP for warm up, acceleration and deceleration, and WOT... CLOSED LOOP for idle and cruise (mainly for emmissions).

    Is there much downside to running in open loop in a boat? The computer still adjusts for air temp and elevation right?

    I don't want o2 sensors in wet exhaust if it is not a MUST HAVE. Thanks.

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    I run closed loop 100% of the time.
    It is the best way to go IMO.
    It's always adjusting to optimise the A/F ratio.

    I set it so it isnt active below 1500 rpm or at low coolant temp (below 120 degrees)
    It is active at WOT.
    Last edited by Unchained; 09-14-2012 at 04:21 AM.

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    Closed loop is the way to go if possible...especially with computers like FAST XFI which use closed loop wideband O2s even at WOT.



    But, to answer your question, open loop is "fine". My boat runs open loop because of other issues the prevented using an O2 sensor...but the tuning is rarely as accurate, but can be close.
    Last edited by FormulaZR; 09-14-2012 at 10:32 AM.


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    Quote Originally Posted by Unchained View Post
    I run closed loop 100% of the time.
    It is the best way to go IMO.
    It's always adjusting to optimise the A/F ratio.

    I set it so it isnt active below 1500 rpm or at low coolant temp (below 120 degrees)
    It is active at WOT.
    Same here and only 20 percent correction

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    You won't get automatic correction for changing atmospheric conditions if you limit yourself to open loop. It's like putting a mechanical injection on and never changing the pills.
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    Quote Originally Posted by dnewps;1713532[B
    ]IF all of the tuning was done correctly is there a downside to running in open loop? [/B]

    The way I understand normal EFI operation in a car is: OPEN LOOP for warm up, acceleration and deceleration, and WOT... CLOSED LOOP for idle and cruise (mainly for emmissions).

    Is there much downside to running in open loop in a boat? The computer still adjusts for air temp and elevation right?

    I don't want o2 sensors in wet exhaust if it is not a MUST HAVE. Thanks.
    no
    Last edited by Hullshot; 09-14-2012 at 10:24 AM.

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    There is some info that isn't so clear in this thread...and some that just isn't so good.....

    Open loop and close loop ONLY refer to whether the PCM uses the O2 as a "reference" check against what target AFR should be AND has the authorization to make a set fuel change to correct any discrepancy between measured O2 and target O2.

    It has nothing to do with other sensors or how they operate. Closed loop is also different than what people hear of as "self learn tuning". It actually functions about the same, except closed loop has no ability to actually change the VE table. It can only deviate slightly (depending in how much authorization you give it) from the VE table. I use closed loop operation on almost all the tunes I build, but typically no more that 10% authorization. I have found that giving the PCM too much authorization or Increasing the speed and size the correction can be, just causes a "hunting" effect and it chases itself with the O2.

    Self learn and closed loop are different things. PCMs are absolutely stupid, they know nothing on their own and can only do what you tell them to. You program the VE table and you also program the AFR target table....you decide what BOTH tables should be! In theory, you would do everything in your power to tune the VE table to match your target AFR table and if you truly did your job tuning and got your VE table to closely matched you AFR target table then the result should be that the O2 in closed loop are doing very little correction at all. They would simply be correcting for discrepancies in sensors, lags, environmental differences, mechanical differences...very small unmetered changes the PCM cannot actually account for....that is ALL that closed loop does.

    Closed loop cannot account for you if you don't understand what the AFR should be at a given load and RPM since you decide what it should be! One of the biggest reasons I use closed loop is for error or fault detection. I know my tunes should have some correction in certain areas and move around a little in others, but if it's pegged on 10% correction all the time, I know something has changed or failed.

    All of this info is in regards to AFTERMARKET EFI. OEM functions slightly different than this because it essentially has 2 layers of authority which I'm not going to get into.



    Andrew
    Last edited by ap67et10; 09-14-2012 at 08:17 AM.

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    Senior Member Hullshot's Avatar
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    yes the O2 is the main part of a closed loop system so it can check itself.
    Last edited by Hullshot; 09-14-2012 at 09:40 AM.

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    [QUOTE=ap67et10;1713604 Closed loop is also different than what people hear of as "self learn tuning". It actually functions about the same, except closed loop has no ability to actually change the VE table.

    Andrew[/QUOTE]

    The FAST learning feature in the 2.0 program does change the numbers in the VE table.
    It changes the V/E table to progressively less correction but still is only as good as the target lambda or a/f table.

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    Quote Originally Posted by ap67et10 View Post
    There is some info that isn't so clear in this thread...and some that just isn't so good.....

    Open loop and close loop ONLY refer to whether the PCM uses the O2 as a "reference" check against what target AFR should be AND has the authorization to make a set fuel change to correct any discrepancy between measured O2 and target O2.

    It has nothing to do with other sensors or how they operate. Closed loop is also different than what people hear of as "self learn tuning". It actually functions about the same, except closed loop has no ability to actually change the VE table. It can only deviate slightly (depending in how much authorization you give it) from the VE table. I use closed loop operation on almost all the tunes I build, but typically no more that 10% authorization. I have found that giving the PCM too much authorization or Increasing the speed and size the correction can be, just causes a "hunting" effect and it chases itself with the O2.

    Self learn and closed loop are different things. PCMs are absolutely stupid, they know nothing on their own and can only do what you tell them to. You program the VE table and you also program the AFR target table....you decide what BOTH tables should be! In theory, you would do everything in your power to tune the VE table to match your target AFR table and if you truly did your job tuning and got your VE table to closely matched you AFR target table then the result should be that the O2 in closed loop are doing very little correction at all. They would simply be correcting for discrepancies in sensors, lags, environmental differences, mechanical differences...very small unmetered changes the PCM cannot actually account for....that is ALL that closed loop does.

    Closed loop cannot account for you if you don't understand what the AFR should be at a given load and RPM since you decide what it should be! One of the biggest reasons I use closed loop is for error or fault detection. I know my tunes should have some correction in certain areas and move around a little in others, but if it's pegged on 10% correction all the time, I know something has changed or failed.

    All of this info is in regards to AFTERMARKET EFI. OEM functions slightly different than this because it essentially has 2 layers of authority which I'm not going to get into.



    Andrew
    this guy knows what he is talking about

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    Quote Originally Posted by ap67et10 View Post



    Self learn and closed loop are different things.

    Closed loop cannot account for you if you don't understand what the AFR should be at a given load and RPM since you decide what it should be!

    All of this info is in regards to AFTERMARKET EFI. OEM functions slightly different than this because it essentially has 2 layers of authority which I'm not going to get into.



    Andrew
    I think all the misconceptions of closed loop can be summed up right there.

    I think much of the misconceptions come from things like the Flexfuel vehicles as well. Like Andrew said, OEM closed loop is a didfferent animal. The OEMs have the tools and means to map a powerplant within a nats ass. But an open loop cannot detect a bad plug or a shitty injector spary pattern from crud.
    A well tuned open loop in a boat will perform very well. They are not like road cars with varying loads, transmission gears, up hill, with loads, coasting down hill, A/C on/off, all while trying to maintain emmissions and milage.
    A open loop isn't going to turn on your "check engine light" because your plugs are toast, or your "guardian" because your idle air motor is taking a dinger.



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    will the closed loop sytem still adjust to elevation and temps? Will it adjust to havasu at 120 then be right for lake tahoe at 80 deg?

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    Temp and altitude are automatic corrections factored into the software algorithm it uses to calculate injector pulse width. this is the case whether it is in open loop, closed loop or self learn/self tune. Without those things factored in at all times in any mode, efi would suck.

    Andrew

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    Without those things open loop efi would be a slightly more specific CARB right? So if you run it in learning mode long enough for the computer to see every different circumstance...then switch to open loop...there would be little difference from closed loop since there would be no need to correct?? Am i on the right path?

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