I've heard CARB cats are actually more free flowing. They cost quite a bit more. Are they better quality or just stamped with a CARB number?

08 Forester N/A Auto.

 

Edited January 28, 20233 yr by uniberp1

why do you need to replace the cat?

there are only 2 reasons I can think of for doing such a thing - one is the cat is clogged - in which case the reason for the clog needs to be addressed, the other is rust damage.

If you are thinking performance gains, forget it.

 

 

CARB converters are aftermarket converters intended to be equivalent to OEM and won’t give any performance gains for your engine. 

aftermarket converters are cheaper and not as emissions efficient as original converters installed at the factory (OEM).  They use less of the expensive catalysts to make them cheap - and that’s why they can cause check engine and emission compliance issues.

So CA requires CARB compliance which simply means aftermarket converters have to meet higher requirements, or are much closer to OEM specs. They’re more expensive because they have more expensive catalyst and ECON 101 supply and demand.  There’s less demand for them.

Ignoring all the converter stuff there’s practically zero gains to be had for performance efficiency in the exhaust of a *non turbo* engine. That 08 Forester will have unimpressive 0-60 times no matter what is done to it except forced induction. Entirely removing the converter will have zero practical performance gains. You can have a shop (or do it yourself, Ive done it) make a short section of straight pipe to bolt up to the exhaust. for that matter just unbolt it and run open LOUD exhaust one day to get “free flowing” exhaust and you’ll notice it doesn’t run any different.  Happens in the rust belt where exhausts rust off. Those options will result in a tiny performance difference from hoping and pressing the gas pedal more aggressively.

None of that is true for turbo engines. Completely different beasts. This can make it deceptive for those scouring online forums or listening to locals talk at work or Friday night at the bar. Just because Atticus installed a high flow exhaust and gained a bunch of power in his turbo doesn’t mean a non-turbo car owner can do the same. 

4 hours ago, heartless said:

why do you need to replace the cat?

there are only 2 reasons I can think of for doing such a thing - one is the cat is clogged - in which case the reason for the clog needs to be addressed, the other is rust damage.

If you are thinking performance gains, forget it.

 

 

Rear flange is rusted.

The only performance gain I would bother with is increased gas mileage.

 

Edited January 28, 20233 yr by uniberp1

21 hours ago, uniberp1 said:

Rear flange is rusted.

valid reason, then..

The major difference is in the catalyst material itself, as ido said above... and would be related more to emissions, not fuel consumption.

fwiw - slightly raising tire inflation will net you more in the way of fuel mileage than any cat would. I usually go with about halfway between recommended pressure (on the car's info tag) and max pressure listed on the tire.. and check it regularly..