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Thread: Who runs a COS on a NA setup? Pros/Cons???

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    Default Who runs a COS on a NA setup? Pros/Cons???

    I am thinking of switching to a Custom Operating System and I would like to hear about peoples different opinions... A couple of reasons I want to do this. First trying to dial in the MAF is a huge PIA.... Running in Open Loop with PE feels so much better than normal Closed loop MAF... Also I want to command 15.5 in the cruise regions for some better MPG...

  2. #2
    Lifetime Member Chevy366's Avatar
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    Quote Originally Posted by BlackGMC
    I am thinking of switching to a Custom Operating System and I would like to hear about peoples different opinions... A couple of reasons I want to do this. First trying to dial in the MAF is a huge PIA.... Running in Open Loop with PE feels so much better than normal Closed loop MAF... Also I want to command 15.5 in the cruise regions for some better MPG...
    Started with a OLSD tune to begin with , runs great (over a year now) , but no real gain over a MAF tune .
    I run OLSD with out PE use the [B3647] for PE , [A0014] and [A0008] can be tricky to set up .

    Try it nothing to lose , and quite easy to do .
    I am sure dc_justin will set you straight .
    Last edited by Chevy366; January 1st, 2008 at 06:45 AM.
    2005 1500 HD , Custom OS3 SD tune .
    2006 Trailblazer
    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

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    Quote Originally Posted by tunedbyGM
    I run OLSD with out PE use the [B3647] for PE , [A0014] and [A0008] can be tricky to set up .
    I don't have those 3 tables in my stock tune.... Are those added when you upgrade to a COS?

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    Oh and do you need to adjust your tune for the various seasons? Like summer and winter? Here in texas summer can be like 100* then in winter is it like 40*...

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    Lifetime Member TAQuickness's Avatar
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    I've been running OLSD for about 2 years, and COS5 for about a year of that. The Alpha-N VE found in COS5 was what I needed to acheive a level of drivability that resembles OEM.


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    Lifetime Member Chevy366's Avatar
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    Quote Originally Posted by BlackGMC
    I don't have those 3 tables in my stock tune.... Are those added when you upgrade to a COS?
    Yes .
    2005 1500 HD , Custom OS3 SD tune .
    2006 Trailblazer
    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

  7. #7
    Lifetime Member Chevy366's Avatar
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    Quote Originally Posted by BlackGMC
    Oh and do you need to adjust your tune for the various seasons? Like summer and winter? Here in texas summer can be like 100* then in winter is it like 40*...
    No , runs a shade better during the winter than the summer .
    IAT temps better during winter .
    2005 1500 HD , Custom OS3 SD tune .
    2006 Trailblazer
    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

  8. #8
    Joe (Moderator) joecar's Avatar
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    I'v been running COS5 in OLSD on my stock '01 TA (headers only)... I don't really need to run a COS or OLSD, but it has been a good educational exercise, and I have gone from 17 MPG to 22 MPG.

    It has been shown that SD and MAF produce the same TQ/HP... I don't disagree with that... TQ/HP depend on air, AFR and timing all of which can be made the same in SD or MAF modes.

    I have found that throttle response seems to be quicker with SD... i.e. engine responds quicker to throttle transitions (which also seems to make the trans respond in a postive manner).

    $0.02

  9. #9
    Lifetime Member Chevy366's Avatar
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    Quote Originally Posted by joecar
    I don't really need to run a COS or OLSD, but it has been a good educational exercise, and I have gone from 17 MPG to 22 MPG.

    It has been shown that SD and MAF produce the same TQ/HP... I don't disagree with that... TQ/HP depend on air, AFR and timing all of which can be made the same in SD or MAF modes.

    I have found that throttle response seems to be quicker with SD... i.e. engine responds quicker to throttle transitions (which also seems to make the trans respond in a postive manner).

    $0.02
    Very good summation (summarization ) !
    2005 1500 HD , Custom OS3 SD tune .
    2006 Trailblazer
    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

  10. #10
    Lifetime Member Biggsy's Avatar
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    Quote Originally Posted by joecar

    I have found that throttle response seems to be quicker with SD... i.e. engine responds quicker to throttle transitions

    I agree
    Dave.

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