: Northstar exhaust



BlueAngel#07
04-06-13, 11:40 PM
HAVING A DEBATE ABOUT TRUE DUAL EXHAUST ( header to pipe straight back) and if the N* 4.6 WOULD HAVE BACK PRESSURE ISSUES AND CAUSE COMPUTER CONFLICTS.
WITH ONE PIPE PER HEADER. HOW TOUCHY ARE THESE CARS.

Submariner409
04-07-13, 10:17 AM
sOMETHING iS wRONG wITH yOUR cAPS lOCK.

If you can fit the piping, sensors, cats and mufflers to the car (lots of luck) it will run just fine............ no performance gain because the little Northstar has all the pipe it needs as-is.

Even fitting the larger CORSA cat-back to my STS made no difference in anything but sound except MAYBE, just maybe, up near WOT redline.

Let's move this to the proper forum: Northstar Performance. The Lounge is more for non-specific chit-chat.

BlueAngel#07
04-07-13, 12:27 PM
sOMETHING iS wRONG wITH yOUR cAPS lOCK.

If you can fit the piping, sensors, cats and mufflers to the car (lots of luck) it will run just fine............ no performance gain because the little Northstar has all the pipe it needs as-is.

Even fitting the larger CORSA cat-back to my STS made no difference in anything but sound except MAYBE, just maybe, up near WOT redline.

Let's move this to the proper forum: Northstar Performance. The Lounge is more for non-specific chit-chat.

Thanks for that....(I win:) ). The debate was chit chat, but will in the future.

basscatt
04-07-13, 09:24 PM
true duals on a Northstar powered Caddy has been tried since 1993 -

IF you could complete a true dual exhaust -
and have no problems -
YOU would be the FIRST -

BlueAngel#07
04-07-13, 09:58 PM
true duals on a Northstar powered Caddy has been tried since 1993 -

IF you could complete a true dual exhaust -
and have no problems -
YOU would be the FIRST -

What type of problems? Code producing? Performance robbing?

CadillacLuke24
04-07-13, 10:47 PM
What type of problems? Code producing? Performance robbing?

My guess would be room. There isn't a whole lot to work with on these cars.

pimpincaddystyle
04-16-13, 09:41 PM
imo it can be done. i just replaced the head gaskets on my 98 sts and while i had it apart i looked for a dual exhaust solution.. it looks tight but i think you could do it... furthermore the front bank pipe runs into the downpipe at about an 85 degree angle which is clearly not great for flow and adds turbulence to the flow of the rear bank exhaust. i think if you found a dual inlet/outlet cat converter it would be ok... i will attempt it at some point... the major problem i see would be actually welding the new downpipe off the front bank crossover(at the correct angle)

beyond the obvious 85 degree entrance of the crossover pipe, there is about 1 inch if pipe protruding into the exhaust stream of the downpipe... scroll down to see the pic
http://www.carrollcustomcadillac.com/Pages/HighPerformanceupgrades.aspx

RandyT.
04-20-13, 05:46 PM
There is a member on the Aurora club with a Shelby engine in his Aurora that has true dual exhaust, I will see if I can find a thread about it. He could tell you more about any back pressure issues if any exist. I think one of the biggest killers is the exhaust manifolds, they have like a dual wall in them that takes up a lot of space on the inside of the exhaust, I have been trying to figure out a way to remove it, I have been considering cutting the manifold open, removing the guts, and then welding it back together. I have already cleaned my y flex pipe, I am waiting to install it with my 4.6 into my Aurora, I also have a hallowed catalytic convertor, it throws a code, but that should be fixed with my Madtuner tuned pcm.

http://imageshack.us/a/img208/3429/46004c.jpg


http://imageshack.us/a/img16/2721/46015.jpg

stoveguyy
04-21-13, 12:12 PM
Shelby motor in FWD aurora? Shelby like ford?

RandyT.
04-22-13, 08:20 AM
No, it's from a Shelby Series 1, it's a car made by Shelby that used an Aurora V8.

stoveguyy
04-22-13, 10:24 AM
Did see a nice YouTube video of bare Shelby chassis. Had a ford motor though. Certainly not aurora style valve covers with center location plug wells.

shelbyracing
04-29-13, 11:15 AM
http://www.youtube.com/watch?v=dCN-3dRgWFE
http://www.youtube.com/watch?v=8I2CChWnQ-g
107337 107338

Submariner409
04-29-13, 11:29 AM
So you maintain that exhaust gas flow/pressure is the same under light load engine rev conditions as it is under maximum load WOT demands ?

Do the same pressure test on a full-tilt dyno run and it will mean something.

Sure wish the Seville had that much exhaust pipe tunnel width ...............

shelbyracing
04-29-13, 11:37 AM
So you maintain that exhaust gas flow/pressure is the same under light load engine rev conditions as it is under maximum load WOT demands ?

Do the same pressure test on a full-tilt dyno run and it will mean something.

Sure wish the Seville had that much exhaust pipe tunnel width ...............
That's a good idea, I may do that and get some copper to plumb it into the car. Seville's have different tunnel width in rear? I would've thought that to be the same.

Submariner409
04-29-13, 02:16 PM
Here's Joe Tahoe's CORSA install as of last year. Not much room to spread out. Even worse up toward the resonator and Y/flex coupling. When I did my CORSA the car was up on a 4-point at the local AMJ Automotive - we looked long and hard at the room to work with, the little (279 c.i) Northstar engine, and the pipe ID's. The extra weight, cat(s), sensor(s), and labor was not worth the minimal gains in a FWD car with a non-programable PCM (1998-on). We're also screwed by the "crossunder" pipe arrangement coupled with the low under-engine ground clearance.

Notice how Joe's Y-pipe area is off-center in the tunnel - that can be cured by using small screw band hose clamps on the muffler hanger rods: The front flex coupling allows you to move the entire system back and forth - center it, use a hose clamp against each side of the muffler hanger cookies, and BINGO ! - the exhaust system will not walk side-to-side.

shelbyracing
04-29-13, 09:47 PM
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.

JoeTahoe
04-30-13, 11:21 AM
This is the worst mixing y pipe I have seen this is on a 2002 DTS codwize's car

107352



107353

JoeTahoe
04-30-13, 11:28 AM
Sorry trying to add pics with my cell phone
107354

JoeTahoe
04-30-13, 11:43 AM
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 :)

Submariner409
04-30-13, 12:41 PM
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 ??)

vincentm
04-30-13, 12:45 PM
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

shelbyracing
04-30-13, 02:36 PM
"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 lbft (390 Nm) at 5000 rpm" <<The modified motor (Mine) has Vin 9 cams. I pulled valve cover to verify this. 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.

Submariner409
04-30-13, 04:17 PM
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.

shelbyracing
04-30-13, 04:29 PM
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.

Submariner409
04-30-13, 04:47 PM
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".

shelbyracing
04-30-13, 04:56 PM
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.

http://www.youtube.com/watch?v=9wWnqF_JeGY&feature=youtu.be
I'd also bet that gauge isn't nearly fast enough to catch the full range of the pulse too.