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Tuning a stock 420a question.

Posted by Ryan Pappalau, Apr 6, 2020

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  1. Ryan Pappalau

    Ryan Pappalau Probationary Member

    2
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    Joined Apr 6, 2020
    Ballston Spa, New York
    New to the car community and am having some troubles. I have a pretty much stock 420a on a 97 rs. It came with stage 2 Brian crower cams in the box still and since I work as a tech I’m able to install them. But what I have no clue how to do is tune the car. Do I need a stand alone? Can I reprogram and tune the stock ecu? I have the timing tag for the cams but still no idea why I’m going to do for a tune. And honestly? Do I even need one? Probably.
     
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  2. silvreclips

    silvreclips Proven Member

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    Joined Jul 19, 2005
    Greenville, South Carolina
    You can't tune the stock ECU. With just a set of cams, you probably won't have to make any changes anyways. What are your long term plans for the car?

    A wideband 02 sensor would be a good investment. That will tell you if you need to add additional fueling after the cams.
     

    Autocross Build 559  1

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  3. 609DSM

    609DSM Proven Member

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    Joined Aug 13, 2019
    Langhorne, Pennsylvania
    FWIW the research I did on this topic has been the following:

    Upgrade to wideband with a megasquirt system installed and then you can start to tune the 420a.

    Withought the megasquirt you are only able to look at your fuel trims and install the proper mods like bigger pump or bigger fuel injectors.

    I havent done any of this myself and I'm sure things get a lot more complicated. And iirc the bc stage 2 cams dont require anything to run properly, maybe slightly bigger injectors if your fuel trims is a little lean?
     

    Street Build 231  2

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM

    Street Build 352  1

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  4. Ryan Pappalau

    Ryan Pappalau Probationary Member

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    Joined Apr 6, 2020
    Ballston Spa, New York
    So you’re saying I could likely install the stage 2 cams and not need a tune? And plans, I would like to think of a turbo later down the road. But for now, the cams came with it when I bought it. Just never installed. So since their there I may as well put them in. I just didn’t know if I would need a tune.
     
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  5. 609DSM

    609DSM Proven Member

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    Joined Aug 13, 2019
    Langhorne, Pennsylvania
    Sorry I also forgot to mention you will need a spring and retainer kit as well for the stage 2. Check the part number on the cams, did it come with springs and what not? Dont want your stock spring to break, they are most likely tired and worn out. Here is a link for you.

    https://briancrower.com/makes/mitsubishi/420a.shtml
     

    Street Build 231  2

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM

    Street Build 352  1

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  6. Canadian_CD9A

    Canadian_CD9A Proven Member

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    Joined Feb 10, 2012
    Winnipeg, MB, Canada
    Cams are the one mod that I would want a tune for regardless of what they are. A cam change affects volumetric efficiency everywhere in the RPM curve, which may present driveability issues in the lower RPM band.
     
  7. BLACK'98DSM

    BLACK'98DSM Proven Member

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    Joined Feb 9, 2019
    Hoover, Alabama
    A 420a on the stock tune can be driveable with BC stage 2's. But some have experienced occasional "misfires" at idle.
     

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