supercharging a 4.6L Northstar
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Northstar Engines and System Technical Discussion Discussion, supercharging a 4.6L Northstar in Cadillac Engine Technical Discussion; can it be done?...
  1. #1
    samm is offline Cadillac Owners Fanatic
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    supercharging a 4.6L Northstar

    can it be done?

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    zonie77 is offline Cadillac Owners Connoisseur
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    Re: supercharging a 4.6L Northstar

    Anything can be done. Given time, manpower, money, etc...what a silly question without putting parameters on it!

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    Re: supercharging a 4.6L Northstar

    Yeah it can be done, it's not impossible, it's just *almost* impossible The actual mounting of a centrifugal supercharger isn't too hard, it requires running a drive-shaft over to near where the stock airbox is (where the S/C is mounted.) Then intake ducting... not hard at all.

    The hard thing is fuel management. The stock PCM isn't going to be able to handle boost, and anything 96 (OBDII) or newer can not be reprogrammed. 93-95s (OBDI) use a removable prom chip that can be reprogrammed, and I've heard it is possible to use an OBDI computer on a newer motor/car, however that's probably quite hard to do. Your other option for fuel management is a piggyback computer that only handles fuel requirements under boost.

    XMS was going to make a S/C kit for northstars, but they dropped that idea after building one test setup when they couldn't find any way to get into the OBDII PCM.

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    Re: supercharging a 4.6L Northstar

    Can't you send your pcm out for reprogramming? I know there was a company that would get like 50hp more out of the vw turbos and you had to send them the pcm, and that they did many other models as well. Is it just a case of a lack of aftermarket or is the cadillac pcm just so hard to modify? I remeber that some group was making a supercharger, they were even taking preorders, I wonder what happened to that.

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    Re: supercharging a 4.6L Northstar

    ^^ONLY 93-95s. They had a removable PROM chip. Newer PCMs have integrated memory that's nonremovable and as of now can only be tweaked with a tech 2, which nobody has and even then I'm told that can only upload new data packages (and no one has the capability to make new packages.)

    Remember when you could just rejet the carb and put it on top of the blower?

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    Re: supercharging a 4.6L Northstar

    Quote Originally Posted by davesdeville
    ^^ONLY 93-95s. They had a removable PROM chip. Newer PCMs have integrated memory that's nonremovable and as of now can only be tweaked with a tech 2, which nobody has and even then I'm told that can only upload new data packages (and no one has the capability to make new packages.)

    Remember when you could just rejet the carb and put it on top of the blower?

    Something doesn't sound right to me. But then again, that's just me.

    As for OBDII, I recall seeing company's that could indeed repogram it for better performance. Fastchip is one of them. Like stated earlier, they do require you to send in your PCM, and then in turn reprogram it, then ship it on back.

    They do list a few 2004 model years, too. So I know there were not a few grey area's where they can alter teh OBDII.

    www.fastchip.com

    Even JCWhitney sells handheld programmers for many newer model trucks that supposedly help your performance out. Many of them even have differetn programming packages for different purpose. Towing, cruising, racing, etc.

    Is there something I'm not understanding?

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    Re: supercharging a 4.6L Northstar

    Mark99STS seems to have been having some good results with that piggy back system he got. He's woking on a turbo setup now, but it would also work with that supercharger form XMS. This unit wasn't available when XMS developed their supercharger, so they were able to finish the project. If you could convince XMS to build you one, and then buy that piggy back setup, you could probably get it to work just fine.

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    Re: supercharging a 4.6L Northstar

    whats wrong with just buying a new high flow pump and adjustable FPR? also, would you have to alter the lines/rail at all to allow the increased flow/pressure? i really have no clue about the fuel supply capabilities in a caddy yet, so please input.
    Thanks,
    SAM

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    Re: supercharging a 4.6L Northstar

    Quote Originally Posted by Trench
    Even JCWhitney sells handheld programmers for many newer model trucks that supposedly help your performance out. Many of them even have differetn programming packages for different purpose. Towing, cruising, racing, etc.

    Is there something I'm not understanding?
    Let us know when JC Whitney comes out with something for us. Nobody's figured out how to do N* PCMs yet, and nobody to my knowlege is working on it anymore. Sure they'll figure out crap for high volume vehicles that a lot of people will mod... but how many Caddys are there compared to mainstream cars? And how many of those are owned by old people who will never ask it for more than stock performance?

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    Re: supercharging a 4.6L Northstar

    Ahh this would be a dream come true if it could be done on 96 on up caddys

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    Re: supercharging a 4.6L Northstar

    Ah, so it is not OBDII in general. Just the Northstar PCM?

    That is what I was missing.

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    Re: supercharging a 4.6L Northstar

    It's my understanding that low boost levels don't necessarilly need new chips. If the current program can handle the increase in flow you can run with the stock chip. You may be giving up some potential power but you'ld still have more than stock. An adjustable FPR might help.

    Adding 5lbs boost may be OK. That's usually the entry level kit's output and I think many of them use stock chips on various cars.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: supercharging a 4.6L Northstar

    FMUs (adjustable FPRs that increase fuel pressure in some ratio to boost, like 10:1) are typically a band aid for proper tuning. Yeah, you can probably get it done that way, but remember your injectors stop firing around 60-70psi. That means that using the stock injectors, you're good for around 3psi boost. Practically nothing... but it would be about an extra 50hp.

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    Re: supercharging a 4.6L Northstar

    This got me thinking. What would happen if I just ran a set of bigger injectors off a Megasquirt, and spliced all the connections to the stock PCM. The only thing I can think of is the MAP sensor... the PCM would still see everything and I don't think it would notice that it's not running injectors anymore. What would it do if there happened to be boost in the manifold? Or if I just applied a vacuum to the map sensor all the time?

    Would that make the PCM think there was either too much or too little load on the engine so tht it would shift too soon or too late? Or is that based on the TPS more than the MAP?

    Quote Originally Posted by Trench
    Ah, so it is not OBDII in general. Just the Northstar PCM?
    That is what I was missing.
    Well it's the OBDII N* PCM... since the OBDI N* PCM is relatively easily reprogrammed.

    Quote Originally Posted by eldorado1
    but remember your injectors stop firing around 60-70psi.
    Why is that, exactly?

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: supercharging a 4.6L Northstar

    Quote Originally Posted by davesdeville
    Why is that, exactly?
    Because it's a solenoid. The force to open the pintle given by the electricity is a constant... The fuel pressure wants to keep the solenoid closed, and the magnetic force has to overcome the fuel pressure to open the solenoid. So once you start upping the fuel pressure, eventually it won't open anymore. In my experience that's right around 65psi on the stock northstar injectors.

    I think the piggyback system is a possibility if you don't mind a few error codes and an SES light.

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