Tobynine9

iTrader: (17)

Who all has done this? Is it worth it? I'm having trouble getting the Mac y to seal well with my Corsa cat-back. Right now the Mac y pipes are the stock 2.5" and they meet into a 2.5" collector which then goes to the Corsa which is necked down to 2.5" before opening up to 3". Seems silly to bottleneck it all down to 2.5" when I could put the Flowmaster Collector in and go straight from the 2.5" y pipes to the 3" Corsa pipe. If that's not normal for the Mac y-pipe, then the previous owner of headers/y-pipe did it that way, not me.

What I'm really concerned with is keeping costs down. It's Christmas time and, like the rest of you, I'm probably going to spend too much money on gifts. Will the Mac pipes fit into the Flowmaster collector without tons of rebending or fabbing? I don't want to end up needing a whole new y pipe fabricated (even though it would probably fit/flow better).

Also, will the Flowmaster collector lap/slip fit with the Corsa. I'm not sure which is I.D. 3" or O.D. 3"?

dug

iTrader: (10)

I used the flowmaster collector on mine. Fit ok but the muffler shop coulda done a better job.

If I were to do it over, Id use a 3.5" collector with a 3.5" bullet before a 3.5" cutout.

Tobynine9

iTrader: (17)

That would be nice and... loud. I'm not about to give up the Corsa. That's one of my favorite parts of the car.

lsx24

iTrader: (45)

Shouldn't be much of a problem to adapt the mac ypipe to the flowmaster collector. I'm sure any muffler shop could do it for under $100 or so. It's a good idea to run the FM collector 2.5" --> 3" because it will increase flow, but realistically speaking you're not giving up a whole lot transitioning down to 2.5" after the collector, so it remains to be seen if it would be worth it. It would be nice piece of mind knowing you aren't leaving any hp on the table from a poor collector, so I would do it. I doubt you are going to be able to slip fit after the collector so plan on having that connected by your muffler shop too.

Tobynine9

iTrader: (17)

That sucks. I want to be able to remove the headers/y-pipe w/o cutting up anything.

lsx24

iTrader: (45)

If they don't line up for the slip fit (they might--have to try) look into putting a flange there. That way you can connect and disconnect the system, without having to reweld anything on the system.

Tobynine9

iTrader: (17)

Thanks. I'm gonna go to what I've heard is a reputable custom exhaust shop here in Houston with the parts and ask for them to do what they can.

gillbot

iTrader: (27)

My MAC Y is 2.5" into a 3" -OD collector. Bolts up to my exhaust fine.

Tobynine9

iTrader: (17)

Yeah, I think the previous owner of my Mac y had the collector changed to fit a stock 2.5" cat-back.

NOBR8KSS

iTrader: (12)

The MAC y-pipe merges to 2 3/4" to mate to the stock intermediate pipe....I wanted it merged to 3", so I bought the 3" Flowmaster y-merge and a 2.5" 180 J-bend from Jegs or Summit for about $60.
I used the j-bend and y-merge to make a new "end" to replace the MAC y-pipe merge.
I then cut off the MAC merge and had a muffler shop weld the Flowmaster merge in place for $40.
It probably didn't add any power, but it was bothering me. The exhaust note is smoother now, but that may just be me.

Tobynine9

iTrader: (17)

Thanks. Exactly what I needed to know.

Tobynine9

iTrader: (17)

I got the flowmaster collector welded to the y with a nice 4" band clamp holding that to the cat-back. Sounds so nice w/o the leak.