my cat is finally on its way out...rattles constantly and looks like its dead from removing and inspecting

i would rather jump ahead to the midpipe rather than replace the cat with an expensive high flow so my question is..

- i hav m2 3inch dp, and the stock catback piping with aftermarket welded on muffler (stock is 2.5inch right?)...so if i replace the cat w/ a 3inch midpipe will the stock catback piping provide enough backpressure to eliminate the boost problems on the stock ecu/wastegate????

and out of curiousity, would this provide more gains that adding a 3inch catback to the stock cat?

 

the stock catback is not enough IMO to take care of boost creep.

 

It likely depends on the type muffler you put in place of the stock one. The 2 1/2" tubing itself is not that much of a restriction. If you used a straight through type muffler, then it may not be enough; if it a chambered type, then it might work.

Believe it or not, the stock catback is actually more restrictive than the stock main cat. This was observed during flow testing that I did on each component. I wouldn't sweat it though, you can always add a restrictor plate at any flange. Or you could port your wastegate, which is a more elegant solution, if you want to get into that. I personally would keep the cat, as it makes the car more agreeable and easier to live with.

 

how fresh are your turbos?

only one way to find out, but be careful.....that boost gauge needle can move awful quick

 

Highly unlikely that it would be enough. Especially once it gets cold out.

 

Either find a used cat in better condition or spend the money on a good high flow cat. At your mod level there is no reason and almost no benefit to run a midpipe.

 

i dont see why not move to no-cat if i can control the boost, its MUCH cheaper, if i get a resonated pipe it will sound awesome, smell awesome to people around me and maybe shoot some flames..then when i do more modds i can remove the restriction and spool faster, plus i can ditch the airpump now and not worry about the piping to the cat

 

Do a search on 'boost creep.'

You didn't answer my question---how fresh are your turbos? if they are old tired originals you might be ok.

leaving the stock ic and airbox as restrictions, you might be ok, but you might not.

Hey, they're your apex seals, do with them what you feel is best

 

My 2 cents:

If you are running stock turbos (and thus will likely have boost creep issues with an open exhaust), then get yourself a high-flow cat. You'll much prefer not sucking fumes, these cars REAK without a cat.

I personally do not understand the folks that buy midpipes and then put restrictor plates in, or run stock intake/IC's or stock cat back's to add restriction back in.

First, the restrictors may actually make things worse... who knows what sort of back pressure and weird turbulence you might create with a plate in your exhaust. Might as well just run a high-fow that's been tested at least. It isn't likely to make LESS power.

There's also no way i'd leave the shitty factory airbox or IC on the car. I bet you make alot more power, and run cooler with an intake/IC/HiFlow combo than you will with a midpipe/stock intake/stock IC combo.

 

The unmodified stock catback is enough restriction. The stock piping with an aftermarket muffler (as in this case) is probably not.

Dave

 

turbos were either rebuilt (yikes) or replaced by mazda when i bought the car and they had 30k miles on them...ive added another 3k to them and only boost on occasion i do not drive the hell out of them...they tend to want to hit 11,12lbs on my defi d gauge when i floor it from 2k rpms on the primary

 

If they're already hitting 11-12 psi then you'll probably need a boost controller if you go with a mid pipe. I've never had an FD or an FC that didn't struggle to control boost in cold weather.

 

yea get a Boost controller deff iv been boosting 14 psi all of a sudden in hot and cold weather so i had to get off my lazy *** and install the controller i had for a year in a half lol

 

Guys, I feel like a broken record, so I'll put a spin on it this time:

A boost controller does jack **** when it comes to boost creep

 

i didnt mean it that it would stop boost creep i ment if the car was boosting more that it should like mine (with cat) just to lower it

 

I'm running a 3" down and mid pipe into a stock catback with NO problems. No creep and no overboosting. Maybe the aftermarket muffler is a problem if it doesn't have enough restriction in your case. There's always one way to find out.