2.5" vs. 3" exhaust?

[RobbyMartin]

On another message board I raised the question of whether the 2.5" exhaust tube is better for my '02 4.6L over the 3" tube. Opinions were about 60/40 in favor of 3". One guy suggested that the 2.5" provided the proper back pressure and scavenging affect, while others suggesting 3" failed to mention back pressure or scavenging in their opinion.
Now this question becomes even more valueable because I am intending to buy the Gryphon and I'm trying to gather all the info possible in order to have Bill write a tune that is best for my truck. I have a 3" tube installed after the "Y" on my truck, but it was done by an accessory shop, not by an exhaust specialist. Should I have 2.5" put in place of the 3" or should I leave it?
If anyone chiming can also give me opinions on these mods I would appreciate it: I own these already.
Airaid CAI or Gotts mods (I live in So Calif - hot climate)?
Stock or BBK 75mm TB?
U-Drive Pulleys?

I'm more of a daily driver with a heavy foot.

[Jackpine]

Originally Posted by RobbyMartin

On another message board I raised the question of whether the 2.5" exhaust tube is better for my '02 4.6L over the 3" tube. Opinions were about 60/40 in favor of 3". One guy suggested that the 2.5" provided the proper back pressure and scavenging affect, while others suggesting 3" failed to mention back pressure or scavenging in their opinion.
Now this question becomes even more valueable because I am intending to buy the Gryphon and I'm trying to gather all the info possible in order to have Bill write a tune that is best for my truck. I have a 3" tube installed after the "Y" on my truck, but it was done by an accessory shop, not by an exhaust specialist. Should I have 2.5" put in place of the 3" or should I leave it?
If anyone chiming can also give me opinions on these mods I would appreciate it: I own these already.
Airaid CAI or Gotts mods (I live in So Calif - hot climate)?
Stock or BBK 75mm TB?
U-Drive Pulleys?

I'm more of a daily driver with a heavy foot.

I think Lars and Bill are more expert on this than me, but I'm going out on a limb here and saying it probably doesn't matter if the modification is downstream of the cats. The reason I say this is your exhaust is already seeing the "stock" restrictions from the cats forward and what you do beyond them isn't going to do much (to engine performance that is).

But the bigger tubes look different and they probably effect the exhaust sound.

- Jack

[88Racing]

The pipe that is connected to the y pipe after the cats is called the intermediate pipe.
This pipe should remain stock or 3" and not exceed 3". If you decrease the size anymore than stock you may get to much back pressure.
In all my research the best exhaust system is the 3" si/3"so system or the 3" si/do 2.25 or 2.5.
Now if you want check out Banks they have a good one with a lot of r+d into it.

Lars

[JWBFX4]

Originally Posted by 88Racing

The pipe that is connected to the y pipe after the cats is called the intermediate pipe.
This pipe should remain stock or 3" and not exceed 3". If you decrease the size anymore than stock you may get to much back pressure.
In all my research the best exhaust system is the 3" si/3"so system or the 3" si/do 2.25 or 2.5.
Now if you want check out Banks they have a good one with a lot of r+d into it.

Lars

very well put, exactly what I would have said.

[88Racing]

One of the best tune needing kits out on the market right now is one from troyer. I think dynatech makes it. It does cost $$$$

One of the other mods I like is the high flow cats and cat back from magnaflow. No tune required.

But if you want the biggest bang for your buck. Get a magnaflow 12" si/so cut out the stock muffler and add a piece of pipe, put a nice 15" tip w/rolled edge on and wahlah! a nice sounding system for under a $150! Just need about 3 or 4 clamps and most of your stock piping and hagers.
Rockauto.com has all the parts.

So there are a few more suggestions.

Lars