What size exhaust is everyone running I had 2 1/4 now im up to 3" and I think it may be a lil too big any opinions? Should I go 2 1/2?

 

2.5" is best. For top end I have gone to a 2.75" once, It worked out well and got the car moving. When I went back to 2.5" I picked up alot of lowend loss that I didn't realize was there. With that 3.5L though, you could probably get away with a 2.75 to get a happy medium.

 

I think 3" is awfully big for no boost. 2.5" from header collector to muffler for me.

 

I think its going down to 2 1/2 this week

 

For NA, mandrel 2.5" is the absolute biggest you should go. There's a thread in General somewhere about it, 2 or 3 pages.

 

I noticed the 3" seems to cause starting problems. the 2 1/4 seemed to be a lil restrctive with the bigger disp. and high comp.

 

Well you gotta think about it, our stock size is 2.25" -- but that 1/4" opens it up a lot. 3/4" is WAY too big for NA. Even with cams and other NA motor work done.....there still isnt a significant amount of air flow into the motor. (As compared to boosting). Not only will NA 3" sound like hell, but it MAY also cause a big loss at low end....but at top end...thats different.

But what do I know..

 

I running all 2.5" on mine.

 

2.5...and I can atest to tilley's N/A's exhaust being LOUD......but worth it

I'm 2.5 from the cat-back

 

Would a full Cattman (headers to catback) system work with a setup similar to tilley's with a 3.5 in a 4th gen?

 

Thw apexi ws I have is 2 3/8 from the cat to where it bends over the axle, after that it's 2.5. I think that even 2.5 is a bit big for most n/a people on this board. Our stock size isn't 2.25. It's most likely 2" if you take all the bends and crushes into consideration. It becomes 2.25 near the muffler. Also y-pipes aren't 2.5 til they get past the flex, before that they are around 2".

 

so what would a good exhaust cat back (CALI) setup be for a STOCK vq30de-k be?
2.5?
Or y pipe and header's/collector's (can't afford yet)?

And... mildly off topic but not out of the thread heading... are the pre-cats restrictive and should I try and do the sensor bypass fed pipes for more balanced back pressure?

Or....... leave the setup the way it is and get custom headers?

HELP!!

 

Dude ^ all you would NEED just for "exhaust" would be a Y pipe and cat back...are you planning on boosting your car?

 

no, i am not looking to boost, just balance pressure, i was told it is unbalanced with the three precats in cali spec, and a little deeper/louder sound

just cat back, or y pipe too?

 

so you're saying its not neccessary to have a B- pipe?

 

So did they stop including those in cat-backs? Or.. maybe that they moved the cat further back?? What exactly do you think is included in a "cat-back" besides the muffler?