Cadillac Seville / Cadillac Eldorado Forum Discussion, Best exhaust combos for best HP and sound in Past Cadillac Vehicle Discussion; I have a 1996 STS and I was wondering what HP advantages I would see from a cat back system ...
Well, considering there's no room for anything other than a cat-back system, I've heard good result with custom 2.5 inch systems using mufflers such as Dynomax, Magnaflow,...ect. you might see anywhere from 5-10hp gain I guess. These cars do tend to wake up a little with a less restrictive exhaust system.
Completely useless. You might as well just stick a rubber plug in the TB and be done with it. All the K&N filter does for the Northstar is weaken it's bottom end torque, and eventually clog the MAF sensor with oil.
I have a 1996 STS and I was wondering what HP advantages I would see from a cat back system or a Down pipe back or headers back exhaust systems.
Here's what our insider once said:
Originally Posted by retired resident expert
In all honesty the real cork will ultimately be the production exhaust manifolds and the "cross through" pipe that goes from the front bank to the rear bank to route the front bank exhaust rearward. The production parts are packaging-constrained and designed for emissions performance to light the catalytic converter quickly. That being said, they are not THAT bad... But the real hotrod Northstars like CHRFAB is putting into sand rails and such run headers.
I would go with 2.5 to 3 inch pipe from the cat rearward. It will have to be a custom bent setup as I don't know of any avialable sources for the prebent parts. Several people have tried different brand mufflers for low backpressure. Flowmaster, Corsa, etc... You'll have to do some searching in the archives for their reports on sound quality and noise. They will definitely be louder but probably tolerable.
There's really no practical way to put real exhaust headers on the transverse mounted Northstar engines due to space, packaging and routing constraints. The idea of a "free flow" exhaust sytem is not lost on the engineers that designed the production car... but... packaging, lack of space, the cross-thru pipe design, emissions performance, durability of the exhaust manifolds and system, etc... All got in the way of real headers...
One thing that will help free up a few horse power is to get the exhaust manifolds off and have them extrude-honed. There are a lot of sharp edges and corners in the fabricated manifolds that can be ground, smoothed and radiused. Not a huge gain here and a lot of work to pull the manifolds and such but if you want the most power, the manifold rework with the low backpressure system will provide the most. I would say that the ultimate exhaust on a transverse passenger car with extrude-honed manifolds, large pipes and Flowmaster style muffler would probably provide 20-25 HP at peak power.
As danbuc stated, the cat-back is about as much as you can do. You can additionally get a high-flow catalitic converver, which will also increase the sound a bit. Magnaflow makes one that fits perfectly.
BTW, removing the resonator does nothing but make the exhaust louder.