So when I was running the stock 2.2, I was averaging at best, 21mpg mixed driving. Not even heavy footed; 67 on the freeway/cruise, shifting at 4k, easing into the pedal. I attributed it to the old engine, blowby, and the like. The BEST I had gotten was 25, all freeway around 70mph. Not really impressed. I hear of WRXs topping that mixed.

 

Now that I have the new engine in, it's more of the same. My suspicion lies in the cats. They have around 235k miles and are white was a sheet. When I had the exhaust out, I debated gutting out the cats since I live in a non emissions area, and could maybe pull a bit more powaaa since that's the restriction in my exhaust now. Couldn't bring myself to do it.

 

Now that I've researched more, I feel that the cats are the primary culprit in my sub 2500rpm stumble (I have a really wonky rear o2 reading under moderate acceleration), as well as my bad fuel economy. I can "mask" the rear o2 sensor with a spark plug non fouler to avoid the CEL. More power, better economy... why not?

 

Can anyone give me a good reason not to do this? Aside from the granolas who think I should hug a tree and leave the cats.

I did this a couple of time in years gone by. The result was no difference in power performance or gas millage. Granted, neither car was a Subaru, so it is not a precise comparison. IMHO, if you gut the cats, you are pretty much wasting your time.

IMHO, if you gut the cats, you are pretty much wasting your time.

 

I would agree.

Use a manometer (I think that's the right word) to check if they're clogged. If they're not, leave them alone.

I don't wear socks with my sandals, but if it's working, why tamper with it.

have cleaned cats before can be just washed out with hose strait water low preshure i whould not remove them cause the engine is tuned to have catts i have not seen any proof of power increase from removing catts on na cars and milage will go down cause o2s will not get hot enuff without catts

Have you ever replaced the Front O2sensor? The rear has nothing to do with fuel mixture, it's there to merely to check the efficiency of the cats. The front sensor does all the adjusting work. I'd try replacing that before gutting the cats.

If the cats are clogged, you'll lose power in the high rpm range first.

Have you ever replaced the Front O2sensor? The rear has nothing to do with fuel mixture, it's there to merely to check the efficiency of the cats. The front sensor does all the adjusting work. I'd try replacing that before gutting the cats.

If the cats are clogged, you'll lose power in the high rpm range first.

 

+1 to this.

 

The cat clogged in my dad's truck. It still had all the off idle torque it always had, but it got to the point where it would barely rev over 2k RPMs.

Still though, it would take off from idle fast as ever.

After more research, it seems that gutting the cats creates expansion chambers like on a 2 stroke dirtbike... which is a bad thing on a 4 stroke engine. Guess I'll just have to build a track pipe

Let me get this straight, you live in a place called grass pants AND in oregon, and you're making fun of granola eatin' tree huggers? Just TRY to tell me those pants aren't made with anythin but 100% hemp byproduct...

subaru cats are very high quality and do not go bad often [non turbo ] have seen cars with 400000+ kms on origanal cats not pluged or any problems they get ruined from running lean or antifreeze contamination