Question about the Northstar PCM
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Northstar Engines and System Technical Discussion Discussion, Question about the Northstar PCM in Cadillac Engine Technical Discussion; This may be kind of dumb but am I correct that the PCM automatically adjusts fuel mix ratio, rpm, spark ...
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    weister42 is offline Cadillac Owners Enthusiast
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    Question about the Northstar PCM

    This may be kind of dumb but am I correct that the PCM automatically adjusts fuel mix ratio, rpm, spark timing, etc... to maintain a predetermined level of performance and economy? If yes then what if you just stick a supercharger on the engine and run it as-is, would the car run like it's about to die, run normal like nothing changed or will it run like it has a supercharger in it?

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Question about the Northstar PCM

    You are correct. The PCM adjusts the fuel and timing. I don't know what a supercharger would do to it, but you better have LOTS of money if you are going to try that.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Question about the Northstar PCM

    Quote Originally Posted by Ranger View Post
    You are correct. The PCM adjusts the fuel and timing. I don't know what a supercharger would do to it, but you better have LOTS of money if you are going to try that.
    For the FWD setup you would have to do some severe black magic with a stand-alone engine management system - the existing PCM programming would never support a supercharger/turbo. The car would not then be a daily driver, and the starting cost is now around $16,000.

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    weister42 is offline Cadillac Owners Enthusiast
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    Re: Question about the Northstar PCM

    So the stock PCM does not have the ability to deal with the suddenly large amounts of air intake and higher compression ratio from a blower-type supercharger, like the software is not capable or is it unable to deal with the change in all the input values from all the sensors? No one (except Top Gear UK) has ever just stick a turbo or a supercharger on a car and hope it works, mainly because it just doesn't make any sense. My hypothesis is that if GM thinks our PCM is so smart that they made it superhard to change it then maybe it's smart enough to deal with an increase in air and fuel intake?




    Just for a laugh... these guys stuck a gas leaf blower on two different vehicles and was able to get around 15 extra hp on the dyno.


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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Question about the Northstar PCM

    Good thoughts.........and this is a guess (AJXTCMAN will know).............the fuel/air/ignition maps in the FWD PCM series don't have the flexibility to make out-of-design-parameter "decisions". The PCM won't be able to adjust settings outside it's original program.

    Don't get sucked up in the hope and the hype - If the supercharger thing could be done, wouldn't it stand to reason that SOMEONE had done it since the end of the "2004" Seville run in 12/03 ? (Mark99's one-off turbo excluded).

    Any thoughts on what the hood would look like with a decent blower on top of a sidewinder Northstar - and how you would drive the blower anyway............

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    weister42 is offline Cadillac Owners Enthusiast
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    Re: Question about the Northstar PCM

    Quote Originally Posted by submariner409 View Post

    Any thoughts on what the hood would look like with a decent blower on top of a sidewinder Northstar - and how you would drive the blower anyway............

    Probably sumthin like this... no hood can contain that haha








    ^^^I should have asked the dude more about it

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    Re: Question about the Northstar PCM

    Quote Originally Posted by weister42 View Post
    This may be kind of dumb but am I correct that the PCM automatically adjusts fuel mix ratio, rpm, spark timing, etc... to maintain a predetermined level of performance and economy? If yes then what if you just stick a supercharger on the engine and run it as-is, would the car run like it's about to die, run normal like nothing changed or will it run like it has a supercharger in it?
    No it will not.

    That is so far off and sooooooooooooooo many people assume that is how it works and it is simply not true

    Wow I don't even know where to start -- maybe fuel first

    The PCM has many setting for fuel. 1 of the settings is the Stoich. This is set at 14.68 or 14.7 and if you have E10 in your tank it is not correct. This throws off the O2 sensors and the fuel strategy.
    You have a bunch of Power Enrichment (PE) settings and they in some part are user defined. Think of this as the Power valve or the secondary’s on a carb and they are very much setup for the end user, yes a base setting is ok. You have the ramp in and the ramp out of the PE and these setting the PCM cannot change. The PCM really corrects the fuel at cruise.

    The timing is soooooooooooooooooo far off on these it just a joke. Again some people think that the PCM runs the timing up until it pings and then it backs it down just a little until it stops. This is far from how it works. The PCM has a lot of spark setting and limits parameters and they are set up for all conditions including a case of bad gas.

    These calibrations were done a very long time ago and GM has learned a lot since that time. If you just think about what you did 20 years ago and how you would do it today if you could. The 1996 OBD II calibration was probably done around 20 years ago. These needed to be EPA certified and they had a lot of work to get then certified because the 95’s were OBD I

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    Quote Originally Posted by weister42 View Post
    Probably sumthin like this... no hood can contain that haha








    ^^^I should have asked the dude more about it
    My little bother texted me that picture a few years back

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