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Thread: F-body engine install to B-body

  1. #1
    Carb and Points!
    Join Date
    Jun 2015

    F-body engine install to B-body


    I have just intalled firebird LT1 engine to my 95 caprice 9c1. Stock. Everything works nice with stock b-body firmware, but I have uploaded an f-body tune due to cam/heads differences.
    The problem I got with this tune is that the a/c does not engage because of different climat system in f-body.
    What is the correct way to make the a/c working? Do I have to take a b-body tune as a base and import tables from f-body tune? Or some other way?
    And any other tuning advices according to my intall?

    Thanks in advance!

  2. #2
    Fuel Injected!
    Join Date
    Sep 2012
    I just used the difference tool in TunerPro and compared a 9C1 file with a TA file and didn't see anything that I thought would keep the a/c from working. Its possible the files you are using may have something a little different.
    Both of the files I used were for 94's and I downloaded them from

  3. #3
    Carb and Points!
    Join Date
    Jun 2015
    I have compared a/c control digrams for F and B.
    In B-body the a/c clutch engagement is controlled by pcm with pressure cycling switch signal. And F-body has another, a bit more complicated scheme. F-body PCM uses a/c refrigerant pressure signal input and evap. temp sensor for a/c clutch contol.
    So if I use F-body tune, the pcm will never engage a/c as it has no evap. temp sensor. I suppose it is programmed in a part of code that is not covered by .xdf.
    Now I`m going to make a tune of B-body firmware with tables for F-body (almost all of them). Correct me if I`m wrong.
    By the way, what is your opinion, is it really worth doing such a tune, or I`m just wasting time?

    A/C compressor control diagrams for F and B-bodies. I think gonna be useful for someone doing such kind of swap.
    Attachment 10975 Attachment 10976

  4. #4
    Fuel Injected! steveo's Avatar
    Join Date
    Aug 2013
    start with the bbody bin, use the spark tables from the fbody for aluminum heads, use the maf table from whichever maf you run (bbody maf table is different than the fbody one)

    everything should be re-tuned manually regardless, but that'll give you a good baseline?

    what are you doing for knock sensors? the b-body knock filter and dual sensors probably wont work with the aluminum heads very well, are you using the fbody setup?

    part of the difference with the a/c control is from fan control too, the fbody is dual electric fan and the bbody is a clutch fan with an electric fan just for a/c, isn't it? i'd probably use b-body code and just call it a day... but that said, i have a bit of a/c disassembled, if you want to use a static value for the evap temp sensor or something, would that work instead? (dont know much about a/c)

  5. #5
    Fuel Injected!
    Join Date
    Jan 2013
    Yes, Stevo, the MAF tables are different and the MAFs themselves are different diameters. The Caprice/Cadillac/Roadmaster(iron head LT1's) use a smaller MAF tan the Vettes/F-body alum heads do.


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