Y Pipe, what size piping should I use??

[jmpSHO2nd]

I decided to have a custom y pipe made and I am going to put 2 Magnaflow cats back on the car, I currently have only one. What is a good size piping to use? Should I just stay with the stock size?

 

[lowc]

i use the dynomax and catlees y that is 2.25 i think thats a good size to use ive only heard of a couple people running single exhaust with a little bigger pipe

 

[SHO.fast]

i have a 2.25 from sho source and it seems to do just fine i dont think u want to go any bigger then 2.5

 

[SHOtime2511]

2.25 unless you plan to S/C or run huge cams.

 

[shomethe$$$]

I've got dual 2.5" into single 3" (should be 3.5"), i'm boosted, 2.25 is probably too big for a stock N/A, between 2-2.25 is fine.

what I found is that the rear bank can gain good midrange if the merge is pushed a lot further back, I moved the merge back to the pass. side of the shifter, I dented in the pass. floor well to make room for the merge, so now the distance from the outlet of the manifold (I have headers) is atleast 18-20" before the merge(should be longer with a stock manifold outlet), this will keep the velocity high enough and comparable with the front bank. Basically a similar concept to the the equal length y-pipe, mine are definately unequal but I didn't think I could get a dual 2.5" and keep them equal.

 

[Phoenix]

Same what these guys said

im running 2.5 into 3'' but I got big cams and modded to death.

Dont go overkill because you will loose torque if you do.

 

[illSHOyou]

Stock collector is 1.9 inch so a 2 inch would be a great start for a y-pipe merging into a 2.5-3 inch.

 

[NovaSS]

Stock collector is 1.9 inch so a 2 inch would be a great start for a y-pipe merging into a 2.5-3 inch.

I agree as long as you are using mandrel bent tubing. Maybe 2.25 MAX with krinkle pipe

 

[operdot]

what I found is that the rear bank can gain good midrange if the merge is pushed a lot further back, I moved the merge back to the pass. side of the shifterQUOTE]

I agree with this because that is what i did, and had good results. In my setup the read bank catolytic converter sits behind the subframe and the collector sits next to the shifter. I also used a 2.25" rear pipe that is equal in volume to the front pipe(2"); this all gets carries back to a 2.5" catback exhaust. This setup feels very strong, definitely stronger than any stock 3.2 mtx setup.

 

[jmpSHO2nd]

what I found is that the rear bank can gain good midrange if the merge is pushed a lot further back, I moved the merge back to the pass. side of the shifterQUOTE]

I agree with this because that is what i did, and had good results. In my setup the read bank catolytic converter sits behind the subframe and the collector sits next to the shifter. I also used a 2.25" rear pipe that is equal in volume to the front pipe(2"); this all gets carries back to a 2.5" catback exhaust. This setup feels very strong, definitely stronger than any stock 3.2 mtx setup.

How many cats do you have on there? My set-up right now is similar to this, I have one cat and it sits behind the sub-frame. I don't mind this but I thought I would benefit from having two cats instead of one.

 

[operdot]

I have two cats, a flex pipe, glasspack, and two mufflers. The sound is awesome, no rasp at all, just deeep base tone at lower rpm, and a formula one type sound at higher rpm.