Mustang3GT07

As the title says. Which is better and why?

Full 3" as in longtubes, midpipe & catback.

RuffCat

Not too much difference on these cars.The s/c'ed cars do move a bit more air, but 2-1/2 is just fine. I would have to say that your better off going a 3" collector into a 2-1/2" all way back for clearance. Not much room on those irs cars!

spray175

I had the Stainless Works full 3" exhaust. Longtubes, X pipe and catback made more torque than 2.5" and stock manifolds. Plus it sounds better I think. Little louder and deeper and more choppy at idle.

Me and my buddy have the same exhaust set up now mines 3" his is 2.5" and you can tell the difference.

Mustang3GT07

Who all makes a 3" catback? I only know of 2. Thats mac and flowmaster. Any1 else make one?

spray175

I cant remember if Bassani makes one or not. Stainless works does but you cant buy just the catback.

RuffCat

I'll explain this plain and simple: Ther is no huge benefit from going 3" vs 2.5" You and me both have a tiny 281cu/in engine. They do not need that much cfm flow through the exhaust to reach peak power. These are not old school 454 big block muscle car engines. The downfalls of having 3" is far greater than just sticking to a 2.5" like everyone else. I belive factory is only 2-1/4" and simply flared at the ends. That's how my 97 was. Idle quality and driveability will suffer at lower rpms. Actully on a Naturally Aspirated 4.6L motor, you will LOSE torque output with a larger diameter exhaust. Bigger tubing causes a loss of low end torque unless you can fill up the given area and create pressure that would force the gases out faster. An example would be Supercharged or Big Block.
Clearance troubles. The IRS is very close as it is. It's simply a PIA to fit 3" exhaust in there. Not saying it cannot be done, but it's merely a PIA for what it's worth.
Ohh, sorry, but "seat of the pants" is not one that I call a dyno. Get that sucker up on a machine and see the diff. It could all be in the head. It could also be that your suffering from down low so much that when you do start to produce gain, it feels so much more significant than your buddies smooth power through out.

spray175

Lol I simply just stated it made more torque, never said it was a "seat in the pants difference" but thanks for that novel you wrote. I know nothing about Cobras.

I didnt have any problems at all with the 3" fitting either. Im refering to 03-04 Cobra.