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PCM Tuning Question

This is a discussion on PCM Tuning Question within the Computer & Tuning forums, part of the LSx Technical Help Section category; Is it possible to get my pcm tuned so I can run 87 octane? I have heard all of this ...

  1. #1
    SS Driver aerojt's Avatar
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    PCM Tuning Question

    Is it possible to get my pcm tuned so I can run 87 octane? I have heard all of this is in the PCM, but not really sure.

    I also noticed when I was head shopping, they offer a lower compression ratio option for the heads, would this have any affect on the octane or is it all in tuning? I have a 98 ss, just curious what could be done on the pcm, I am not really familiar with the options for it and how much it controls as far as fuel octanes. Thanks

    -JT

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    Moderator Firebirdjones's Avatar
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    You could possibly run 87 in the car as is but I wouldn't risk it and don't know why you would want to. I don't even run that stuff in my tractor.
    These cars tell you to at least run 91 or better in the owners manual. Here in Ohio we have 94 Sunoco which is all I have run in all my cars for the last 30 years.
    There is a high and low octane table in your tune and if the knock sensors pickup any knock it will revert to the low octane table, whether thats enough is hard to say.

    I have my car tuned to run on 94. I am sure you could de-tune it and run safely on 87 if you like, but gas mileage may suffer as a result.

    Price differences between 87-89-92-94 usually only differs 10 cents so the savings isn't worth it to me,,,quite frankly I just don't see the logic in it.

  3. #3
    SS Driver aerojt's Avatar
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    Just curious, i also have a 96 impala ss with the lt1 and it runs fine on 87 octane from the factory. It does not call for high octane. Just curious if I could get my LS1 to do that same thing. Thanks for the insight, anybody else have info on the pcm tuning? Thanks

    -JT

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    Quote Originally Posted by aerojt View Post
    Just curious, i also have a 96 impala ss with the lt1 and it runs fine on 87 octane from the factory. It does not call for high octane. Just curious if I could get my LS1 to do that same thing. Thanks for the insight, anybody else have info on the pcm tuning? Thanks

    -JT
    96 Impala

  5. #5
    Senior Member 35thAnniZ28's Avatar
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    eating bulldog
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    i regreted the day i had 89 in mine....

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    SS Driver aerojt's Avatar
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    Quote Originally Posted by 35thAnniZ28 View Post
    i regreted the day i had 89 in mine....
    Why is that? Would gas mileage suffer or performance? I have run 89 a couple times with no trouble. I know this is a debated issue, just curious more about the pcm tuning and timing adjustments.

  7. #7
    Racer/Tuner San Diego
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    I've done an 87 octane tune. Client wanted a performance tune.
    Turned out he was running 87 octane in his 99 ta.
    87 octane in these cars will knock like their is no tomorrow.
    This car knocked on start up and pretty much all the time.
    All this on the low octane table.
    So I built a low octane tune from the low octane table
    and loaded high octane improvements as well.
    So the answer is with a 87 octane specific tune yes
    but with the stock tune audible detonation will occur.

    Gary

  8. #8
    Senior Member 35thAnniZ28's Avatar
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    eating bulldog
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    well my mother borrowed the car for the day.....ended up putting regular.... when i got it back....it stumbled....knocked,pinged...all that stupid bullshit.....leave that shit for the hondas...

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    Mr. YUK BigBrian442's Avatar
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    Quote Originally Posted by Firebirdjones View Post

    Price differences between 87-89-92-94 usually only differs 10 cents so the savings isn't worth it to me,,,quite frankly I just don't see the logic in it.
    Hmmmmmm..... 30 cents or more difference here in Maryland. but still only a few bucks a tank.


    Brian

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    TunedbyFrost.com Tuner Frost's Avatar
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    buy another car if gas is that big of issue. Why take a giant ass step backwards like this?

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    Member jag42420's Avatar
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    You can detune for mileage over power, as long as you're willing to sacrifice some HP.

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