I could have swore there was a thread about how a test pipe in place of the 3rd cat could lower torque. Well I can't find it now. Can anybody confirm this? Also would I gain any torque if I replaced the test pipe with my gutted
3rd cat?

 

FALSE... no way in hell if anything the stock cat in between your rv6 jpipe and stock exhaust would lower torque


ps. you must have not wired up ur rollup mod correctly

 

Well, I wouldn't gut your 3rd cat. Just get a test pipe, since it's not too expensive.

 

Why the hell would you even consider destroying a good catalytic converter?

 

Exactly what I say to people that do. Instead you can just weld a pipe with flanges in its place and it will flow better in the long run.

 

Especially considering how expensive they are

When I worked on exhausts I actually loved people like this - they would come in and tell me they wanted to gut the cat (couldn't do). But I would be more than happy to make them a 'test pipe' for tuning purposes. I'd either sell the OEM cat for a shit ton of money (relative to the price of a new one) or salvage it for 40-60 dollars. Such a waste to simply bang out the insides.

 

but by the sounds of it he already has the gutted 3rd cat. but like the others, destroying something that is so expensive to gain a few ponies is so not worth it. and then if and when you fail inspection and you have to replace it, you are now double boned!

 

A lot of people in the Subaru community used to gut the cats in their uppipes simply because it was free to do it. It makes an awful mess, the dust is extremely hazardous to breathe in and it's a pain in the ass to do. If you do it right though it was just as good as the catless versions of the uppipes you'd find on the aftermarket at 0 cost.

 

Ok to clarify I have the RV-6 test pipe installed. I removed the 3rd cat which is still in perfect shape. So there is no advantage to gutting the 3rd cat? It feels like I lost low end torque when I put the test pipe in. Maybe I'll just put the cat back in an see how it feels.

 

stupid to guy any stock cat. there is absolutely no need for it, since their are PCD's and race/test pipes available.

also, the stock 3rd cat bottlenecks anyways, 2 1/2 inlet, 1 7/8 so it can match the stock exhaust piping.

 

Audi People do it too. As I recall they call them piggies. We did it for my friend never will I do that again. So much dust and I assume there is some sort of fiberglass in there because I was itchy like a mofo afterwards.

 

the loss in tq you feel is probably from ur stock exhaust the gasses are hitting a wall

 

IMO test pipe would flow better than any gutted cat regardless of size.

 

Gutting the cat has a couple advantages.

It's free.
It's less likely to cause raspiness.
It will give the same power gains as a test pipe.
It will pass a visual inspection.

Like I've mentioned a hundred times before, I had a friend smog my car with the 3rd cat removed before I gutted it to make sure it would pass CA emissions. Since it passes, there is no need to ever run it again so there is no harm in destroying it.

The last thing you want is to get caught with a straight pipe in a communist state like CA.

Would I do it again? Probably not just because I felt no difference. My car is also bone stock power wise. Someone with precat deletes and full exhaust along with other engine mods might feel a difference. Mine was actually done to hopefully increase fuel economy since I was commuting a lot. It would also be a good idea to bore out the inlet and exit if you were serious about power. But the media is the largest restriction by a long shot. A 300 cell cat is almost high flow territory in iteslf so again, unless you have other mods you're not going to gain much by gutting it or running a test pipe.

 

I forgot, no way will removing the stock 3rd cat cause a loss in low end torque. It's hard to actually lose low end torque no matter how low the back pressure goes and the 3rd cat just doesn't cause much of a restriction in the first place.

 

I remember a few members saying that they lost a bit of low end torque when they took off the third cats... They also had the Pre-cat Deletes, J-Pipe and other exhaust mods, maybe a bit to free-flowing?

 

True i have rv6 pre cats, rv6 j pipe, thierd cat removed and a custom 2.5 exaust only one muffler connected for better flow, lost torque and i feel slowww as fuck, getting a new exaust already.

 

I wouldn't gut it unless the monoliths have clogged.. then it becomes cheaper than buying a new one, plus the minor performance gains.

I remember a thread with a dyno about precat deletes increasing top end & dropping low end.. I could be mistaken.