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Northstar Engines and System Technical Discussion Discussion, Northstar exhaust in Cadillac Engine Technical Discussion; I have a 4.0 that was modified for the Shelby Series 1, the exhaust really helps it breathe during valve ...
  1. #16
    shelbyracing is offline Cadillac Owners Member
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    Re: Northstar exhaust

    I have a 4.0 that was modified for the Shelby Series 1, the exhaust really helps it breathe during valve over-lap.
    You can get it tuned as well. I plan on having mine dyno-tuned sometime this year. Check out Madtuner. He has tuned an Aurora in our club. Even Randy has a tuned PCM from him for his 4.6 swap. I need my shift points put at 7,200, I mainly did that no load pressure test to make sure I had enough exhaust flow not to build up pressure during higher rpms. But I am going to test it tomorrow under load.

  2. #17
    JoeTahoe is offline Cadillac Owners Fanatic
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    This is the worst mixing y pipe I have seen this is on a 2002 DTS codwize's car

    Attachment 107352



    ForumRunner_20130430_111835.png

  3. #18
    JoeTahoe is offline Cadillac Owners Fanatic
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    Sorry trying to add pics with my cell phone
    ForumRunner_20130430_112726.png

  4. #19
    JoeTahoe is offline Cadillac Owners Fanatic
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    As for the corsa exhaust I don't know if there is a hp gain ad I never drove my sts with out it but it truly is a awsome sounding exhaust

  5. #20
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Northstar exhaust

    Quote Originally Posted by shelbyracing View Post
    I have a 4.0 that was modified for the Shelby Series 1, the exhaust really helps it breathe during valve over-lap.
    You can get it tuned as well. I plan on having mine dyno-tuned sometime this year. Check out Madtuner. He has tuned an Aurora in our club. Even Randy has a tuned PCM from him for his 4.6 swap. I need my shift points put at 7,200, I mainly did that no load pressure test to make sure I had enough exhaust flow not to build up pressure during higher rpms. But I am going to test it tomorrow under load.
    All well and good - but the problem for the majority in this forum is that NONE of the above paragraph applies to a FWD PCM controlled Cadillac sedan from 1998 - 2004. We would all love to be able to tweak and mess with our fuel/air/ignition programs but it ain't gonna happen: AJxtcman (pcmcalibrators) has posted that he has quit trying on this series of OBD-II controlled cars. CHRFAB does some wonderful tuning work for the 4.6 Northstar - using a stand-alone drivetrain management system in a kit car or sand rail. Their website specifically says they do no work on standard Cadillac vehicles/engines. If I'm not mistaken, you said that your Aurora uses the 3.71 final drive, so anyone with a FWD Cadillac VIN Y drivetrain is handicapped by the lower rpm curve (3.11 final drive) from the get-go.

    CORSA used to publish this dyno run, but it disappeared a couple of years ago - You'll notice that the STS dyno run - WOT all the way - shows that essentially nothing positive happens until 70 mph WOT - about 10 - 15 mph below redline shift to 3rd - you can see the little hiccup at 80 in this graph.

    Redline in the stock PCM is about 6250, so the engine is already well up in its power curve. The 4.6 VIN 9 Northstar doesn't even try to make power until over 4,000 rpm, and that engine (VIN 9) shifts right at max horsepower in the curve - 300 hp, while the torque is holding well above the VIN Y curve, which is already dropping fast. (Power/torque curves - find the GM dyno runs for the two engines in my albums.) My STS shifts from 3rd to 4th at about 138 mph - WOT. (The posted dyno run is obviously done on a H-limiter car - FWD power delivery holds remarkably well from 105 mph to ~130.)

    Remember - unless you're running the car at absolute maximum power demand a modified exhaust system does essentially nothing - even at highway cruise - where it may add a hp or two, allowing you to depress the gas pedal by .020" less, saving you an ounce or two of gasoline a mile. Exhaust backpressure - a couple of pounds or less - means nothing at cruise rpm - but it means a lot at WOT redline.

    As Joe Tahoe posted, the "stock" CORSA sound up at redline is a thing of beauty - but I'll bet that a true dual CORSA system would be awe-inspiring.

    (EDIT: shelbyracing, have you ever hooked up with Mike Lawson, a Northstar engine rebuilder up in Lexington ??)

  6. #21
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    vincentm is offline Cadillac Owners Connoisseur
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    Re: Northstar exhaust

    Quote Originally Posted by Submariner409 View Post
    All well and good - but the problem for the majority in this forum is that NONE of the above paragraph applies to a FWD PCM controlled Cadillac sedan from 1998 - 2004. We would all love to be able to tweak and mess with our fuel/air/ignition programs but it ain't gonna happen: AJxtcman (pcmcalibrators) has posted that he has quit trying on this series of OBD-II controlled cars. CHRFAB does some wonderful tuning work for the 4.6 Northstar - using a stand-alone management system in a kit car or sand rail. Their website specifically says they do no work on standard Cadillac vehicles/engines. If I'm not mistaken, you said that your Aurora uses the 3.71 final drive, so anyone with a FWD Cadillac VIN Y drivetrain is handicapped by the lower rpm curve (3.11 final drive) from the get-go.

    CORSA used to publish this, but it disappeared a couple of years ago -
    /thread

  7. #22
    shelbyracing is offline Cadillac Owners Member
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    Re: Northstar exhaust

    "It (Shelby Series 1) was powered by Oldsmobile's 4.0 L L47 Aurora V8 DOHC engine. It has 320 hp (324 PS) at 6500 rpm, 290 lb·ft (390 N·m) at 5000 rpm" <<The modified motor (Mine) has Vin 9 cams. I pulled valve cover to verify this. Attachment 107369 Also the Oldsmobile Aerotech version that ran an Aurora motor was to prove it's durability in a long haul test and was at 7,200 rpms for several hours making a land speed record. I am not exactly sure where the actual shift point will be but making max power at 6,500 it will most likely be between 7,200-6,800.
    I will not speak ill of anyone but AJ failed to prove he could tune an Aurora. That said Madtuner has proved himself and here >

    EDIT: Links to non-vendor advertising deleted.

    That is an intense power increase wow. My exhaust is true dual 2" with X pipe and 2.5" Magnaflow (so it will move through even more easily as there is turbulence and back pressure in any muffler) there is nothing else. No real restrictions, I am off to the hardware now to get that copper as I am very curious what pressure will be at WOT with a load.
    And no never heard of Mike I don't think, but I am in Jamestown, Ky so not too far from Lex.

  8. #23
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Northstar exhaust

    Quote Originally Posted by shelbyracing View Post
    My exhaust is true dual 2" with X pipe and 2.5" Magnaflow (so it will move through even more easily as there is turbulence and back pressure in any muffler) there is nothing else.
    Take a flashlight and look through a CORSA resonator or muffler. Straight pipe; no baffles, no deflectors, no reverse flow chambers. Straight pipe. Before I put the system on the car I laid it out on the floor, slid together - a flashlight beam reflection could be seen through the entire length - resonator to tips.

    Look real hard - you can see the edges of the "tuning holes" cut into the resonator outer can and the red carpet at the outlet.. Nice head pipe - no kinks.

  9. #24
    shelbyracing is offline Cadillac Owners Member
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    Re: Northstar exhaust

    The "tuning holes" are made to baffle else wise they wouldn't quiet at all (and I had straight pipes while deciding what mufflers I was going to order and WOW, super loud. Sounded like a nascar haha). That looks just like my Magnaflow internals though, sweet. I did a load pressure test and it was 2.5 psi. I will upload video after a while, I have to transfer from phone, then upload.

  10. #25
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Northstar exhaust

    2.5 psi WOT is essentially zippo - you might even have been measuring "pressure" at a positive node of the exhaust pulses. Google the exhaust characteristics of a pulse jet - an analogy of the exhaust pulses in a multi-cylinder exhaust pipe - and a hint at why "circumcising" an exhaust pipe after the muffler will change the exhaust sound. The reason for the term "tuned header" - "tuned intake runner".

  11. #26
    shelbyracing is offline Cadillac Owners Member
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    Re: Northstar exhaust

    The pulses at 6k were between 2-3 (low-high pulse) I figured the static measurement was 2.5 I don't think it'd increase too much between that and the post tuned shift point. Prob 1 or 1.5 more would be my best guess. I'd love to have some shorty headers on her, but I don't feel the split cast stainless is a bad design at all.

    I'd also bet that gauge isn't nearly fast enough to catch the full range of the pulse too.

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